Article Reviews
BRIDGING THE GAP BETWEEN OSTEOCYTES; PDGF-AA PROMOTES GAP JUNCTION FORMATION THROUGH PI3K/AKT SIGNALLING PATHWAY
Osteocytes play an essential role in bone remodeling in many organisms. As a mechanical-sensory regulator, they maintain calcification of the bone matrix and transmit information such as the amount of mechanical pressure upon the bone. Originating from osteoblasts, osteocytes lie within the lacunae of bone and form interconnected cellular networks. Osteocytes contact each other via gap junctions on their dendritic processes that pass through canaliculi. Gap junctions are composed of connexins which allow the transportation of nutrients and molecules between the cytoplasm of adjacent cells. Connexin 43 (Cx43) is abundant in osteocytes. Osteocytes also contain platelet-derived growth factors (PDGF). The roles and responsibilities of PDGF range from wound repair and embryo development, to regulating chemotactic and mitotic activity in undifferentiated cells. PDGF-AA, a member of the PDGF family, is abundantly expressed within osteocytes. Previous studies have explored the relationship between PDGF and Cx43 and displayed inconsistent results between different cell types. Liu et al. (2021) sought to explore and verify the relationship between PDGF-AA and Cx43 in osteocytes.
To investigate the relationship between PDGF-AA and osteocytes, Liu et al. (2021) first performed a wound closure assay. To observe the migration of cells, a pipette tip was used to make a scratch in a Petri dish. If osteocyte migration is observed, the osteocytes must be in communication. At specific PDGF-AA concentrations, the wound closure assay showed an increase in migration rates of osteocytes. A scanning electron microscope also displayed that PDGF-AA increased the number and length of dendritic processes of osteocytes, meaning more connections formed between adjacent osteocytes cells. To further confirm these results, the cells were treated with LY, a small molecule dye, that can pass through gap junctions. PDGF-AA treated cells showed more transmission of LY than the control cells, thus exhibiting more cell-to-cell communication.
To explore how PDGF-AA enhanced cell to cell communication in osteocytes, Liu et al. (2021) performed a Western blot analysis with increasing concentrations of PDGF-AA and observed increased expression of Cx43. In addition, immunostaining displayed greater clusters of Cx43 at the gap junctions in PDGF-AA treated cells compared to control. The number of gap junctions observed also increased in PDGF-AA treated cells compared to control cells.
To confirm which cell signalling pathways play a role in how PDGF regulates expression of Cx43, a western blot analysis was performed. Liu et al. (2021) found that phosphorylated Akt (p-Akt) expression was high in cells treated with PDGF-AA, indicating that p-Akt plays a role in Cx43 expression induced by PDGF-AA. Additional imaging showed the enhanced expression of p-Akt was found in the nucleus of osteocytes.
Liu et al. (2021) further established the role of PI3K/Akt signalling in Cx43 expression by treating osteocytes with LY294002, a PI3K/Akt inhibitor. Focusing endogenously first, the inhibitor was found to decrease expression of p-Akt and Cx43. Reduced lengths of dendritic processes were also observed via immunofluorescence imaging. Next, the osteocytes were exposed to exogenous PDGF-AA and treated with LY294002. Western blot results displayed a decreased expression of Cx43 and p-Akt, indicating that LY294002 can block the PI3K/Akt pathway and thus decrease Cx43 expression when cells are induced with PDGF-AA. Imaging was used to explain this result and showed how PDGF-AA could promote p-Akt entry into the nucleus but when LY294002 was added, the p-Akt content was greatly decreased. Subsequently, imaging showed vastly reduced Cx43 expression. Shortened dendritic processes and fewer gap junctions were again observed after inhibitor treatment.
The effect of PDGF on Cx43 has always been inconsistent between cell types, and there was limited knowledge on this relationship in osteocytes. In this study, PDGF-AA enhanced Cx43 expression and dendritic process formation, thus promoting gap junctional communication in osteocytes. Since PDGF-AA increased Cx43 expression via the PI3K/Akt signalling pathway, the authors inferred that p-Akt phosphorylates CERB, a transcription factor for the Gja1 gene that encodes Cx43. A key point to note is that connexins, specifically Cx43, are not directly associated with the formation of the dendritic process, and this study does not indicate this as such. As mentioned, osteocyte communication plays a significant role in bone-associated activities. Mineral balance in bone, bone remodelling and response to the mechanical load on bones all rely on osteocyte communication. Previous studies have demonstrated that mice with Cx43 deficiencies show impaired bone fracture healing, whereas overexpression of Cx43 can reduce cell apoptosis and preserve bone quality. Establishing a connection between PDGF, Cx43 and enhanced osteocyte communication provides a further understanding of osteocyte signalling involved in bone growth regulation and fracture healing.
Article Citation:
Liu, Y., Duan, M., Guo, D., Kan, S., Zhang, L., Aili, M., Zhang, D., Du, W., and Xie, J. (2021). PDGF-AA promotes cell to cell communication in osteocytes through PI3K/Akt signaling pathway. Acta Biochem Biophys Sin. 0, 1–10.
To investigate the relationship between PDGF-AA and osteocytes, Liu et al. (2021) first performed a wound closure assay. To observe the migration of cells, a pipette tip was used to make a scratch in a Petri dish. If osteocyte migration is observed, the osteocytes must be in communication. At specific PDGF-AA concentrations, the wound closure assay showed an increase in migration rates of osteocytes. A scanning electron microscope also displayed that PDGF-AA increased the number and length of dendritic processes of osteocytes, meaning more connections formed between adjacent osteocytes cells. To further confirm these results, the cells were treated with LY, a small molecule dye, that can pass through gap junctions. PDGF-AA treated cells showed more transmission of LY than the control cells, thus exhibiting more cell-to-cell communication.
To explore how PDGF-AA enhanced cell to cell communication in osteocytes, Liu et al. (2021) performed a Western blot analysis with increasing concentrations of PDGF-AA and observed increased expression of Cx43. In addition, immunostaining displayed greater clusters of Cx43 at the gap junctions in PDGF-AA treated cells compared to control. The number of gap junctions observed also increased in PDGF-AA treated cells compared to control cells.
To confirm which cell signalling pathways play a role in how PDGF regulates expression of Cx43, a western blot analysis was performed. Liu et al. (2021) found that phosphorylated Akt (p-Akt) expression was high in cells treated with PDGF-AA, indicating that p-Akt plays a role in Cx43 expression induced by PDGF-AA. Additional imaging showed the enhanced expression of p-Akt was found in the nucleus of osteocytes.
Liu et al. (2021) further established the role of PI3K/Akt signalling in Cx43 expression by treating osteocytes with LY294002, a PI3K/Akt inhibitor. Focusing endogenously first, the inhibitor was found to decrease expression of p-Akt and Cx43. Reduced lengths of dendritic processes were also observed via immunofluorescence imaging. Next, the osteocytes were exposed to exogenous PDGF-AA and treated with LY294002. Western blot results displayed a decreased expression of Cx43 and p-Akt, indicating that LY294002 can block the PI3K/Akt pathway and thus decrease Cx43 expression when cells are induced with PDGF-AA. Imaging was used to explain this result and showed how PDGF-AA could promote p-Akt entry into the nucleus but when LY294002 was added, the p-Akt content was greatly decreased. Subsequently, imaging showed vastly reduced Cx43 expression. Shortened dendritic processes and fewer gap junctions were again observed after inhibitor treatment.
The effect of PDGF on Cx43 has always been inconsistent between cell types, and there was limited knowledge on this relationship in osteocytes. In this study, PDGF-AA enhanced Cx43 expression and dendritic process formation, thus promoting gap junctional communication in osteocytes. Since PDGF-AA increased Cx43 expression via the PI3K/Akt signalling pathway, the authors inferred that p-Akt phosphorylates CERB, a transcription factor for the Gja1 gene that encodes Cx43. A key point to note is that connexins, specifically Cx43, are not directly associated with the formation of the dendritic process, and this study does not indicate this as such. As mentioned, osteocyte communication plays a significant role in bone-associated activities. Mineral balance in bone, bone remodelling and response to the mechanical load on bones all rely on osteocyte communication. Previous studies have demonstrated that mice with Cx43 deficiencies show impaired bone fracture healing, whereas overexpression of Cx43 can reduce cell apoptosis and preserve bone quality. Establishing a connection between PDGF, Cx43 and enhanced osteocyte communication provides a further understanding of osteocyte signalling involved in bone growth regulation and fracture healing.
Article Citation:
Liu, Y., Duan, M., Guo, D., Kan, S., Zhang, L., Aili, M., Zhang, D., Du, W., and Xie, J. (2021). PDGF-AA promotes cell to cell communication in osteocytes through PI3K/Akt signaling pathway. Acta Biochem Biophys Sin. 0, 1–10.
A more accurate way to study alzheimer's disease
Alzheimer’s disease (AD) is a progressive neurodegenerative disorder, clinically displayed by cognitive deficits and pathologically characterized by neurofibrillary tangles and amyloid-β (Aβ) aggregates. Alzheimer’s disease is the leading cause of dementia, and its etiology is both genetically and environmentally rooted. Previous in vivo and in vitro models have highlighted the consequences of mutated amyloid precursor protein (APP), namely the cytotoxic effects of Aβ accumulation. It is unclear whether the Aβ plaques result in the hyperphosphorylation of Tau, but ultimately, helical and straight filaments of hyperphosphorylated Tau proteins form hallmark tangles. Although some previous in vivo and in vitro models have been successful in mimicking Aβ plaques via the overexpression of known commonly mutated genes, they fail to represent the additive effect of both the plaques and neurofibrillary tangles together.
This article by Frederica Cordella et al. (2022) studies the usage of stem-cell based 3D brain organoids to investigate the proteinopathies related to Alzheimer’s Disease. Organoids refer to in vitro multicellular structures used to mimic a corresponding organ. They aim to review methods which create more pathologically-accurate models using patient-specific induced pluripotent stem cells (iPSC) derived from neurons. They referred to some studies that demonstrated that 2D cell culture models, even with exaggerated mutations, were unable to reproduce sufficient Aβ accumulation. The research team attributed this to the lack of an in vivo-like cytoarchitectural organization and the brain’s synaptic connections, both of which are necessary to replicate AD-like conditions. The problem with the current technology involved in Alzheimer’s research was well-defined and appropriately set the stage for 3D models’ introduction.
The use of iPSCs in the generation of brain organoids is described as being the solution to the issues encountered by the use of 2D models. It is intended to model the interplay between the brain’s main cell types – neurons, astrocytes, microglia – and the neurovascular system. The authors highlight the ability of the iPSCs to take on key genetic mutations which are paramount to an accurate display of the disease. Further, iPSC-derived neurons would be genetically encoded to express the needed ions and sensors for efficient functional high throughput analysis of neuronal degeneration. Ultimately, the team makes a compelling case for the replacement of 2D models for 3D models in AD research with the goal of increasing accuracy. That said, there is a lack of critique of the method in that the authors fail to provide limitations to this approach. There is no information about this new technology’s financial burden nor how readily available it is to be implemented.
Overall, the authors provide an efficient and comprehensive overview of the use of 3D stem-cell based models in Alzheimer’s research. It appears to be a promising and interesting advancement within the research community and could likely reduce the use of animal models in disease-related studies.
This article by Frederica Cordella et al. (2022) studies the usage of stem-cell based 3D brain organoids to investigate the proteinopathies related to Alzheimer’s Disease. Organoids refer to in vitro multicellular structures used to mimic a corresponding organ. They aim to review methods which create more pathologically-accurate models using patient-specific induced pluripotent stem cells (iPSC) derived from neurons. They referred to some studies that demonstrated that 2D cell culture models, even with exaggerated mutations, were unable to reproduce sufficient Aβ accumulation. The research team attributed this to the lack of an in vivo-like cytoarchitectural organization and the brain’s synaptic connections, both of which are necessary to replicate AD-like conditions. The problem with the current technology involved in Alzheimer’s research was well-defined and appropriately set the stage for 3D models’ introduction.
The use of iPSCs in the generation of brain organoids is described as being the solution to the issues encountered by the use of 2D models. It is intended to model the interplay between the brain’s main cell types – neurons, astrocytes, microglia – and the neurovascular system. The authors highlight the ability of the iPSCs to take on key genetic mutations which are paramount to an accurate display of the disease. Further, iPSC-derived neurons would be genetically encoded to express the needed ions and sensors for efficient functional high throughput analysis of neuronal degeneration. Ultimately, the team makes a compelling case for the replacement of 2D models for 3D models in AD research with the goal of increasing accuracy. That said, there is a lack of critique of the method in that the authors fail to provide limitations to this approach. There is no information about this new technology’s financial burden nor how readily available it is to be implemented.
Overall, the authors provide an efficient and comprehensive overview of the use of 3D stem-cell based models in Alzheimer’s research. It appears to be a promising and interesting advancement within the research community and could likely reduce the use of animal models in disease-related studies.
Gene therapy with lentiglobin for sickle cell disease
Sickle cell disease is a genetic disease caused by a point mutation in the beta-globin gene, HBB, resulting in sickle hemoglobin production. This painful, lifelong disease interferes with the proper function of red blood cells. In addition, it is associated with recurrences of vaso-occlusive events, characterized by blockages of blood flow due to the abnormal sickle-shaped blood cells getting stuck in blood vessels. Previous methods of treating sickle cell disease use allogeneic hematopoietic stem-cell transplantation with human leukocyte antigen (HLA)-matched siblings. However, this method mainly targets younger patients and risks graft-versus-host disease, which may develop after allogeneic transplantation where the donated cells or bone marrow attacks the recipient’s body. In addition, not many patients have HLA-matched sibling donors, making this treatment option unavailable for many patients with sickle cell disease.
As a result, this led researchers Julie Kanter, et al. (2021) to test the biological and clinical efficacy of a new gene therapy with LentiGlobin, a possible solution for sickle cell disease, while avoiding the complications that come with allogeneic hematopoietic stem-cell transplantation. LentiGlobin allows for autologous transplantation, where the patient’s own hematopoietic stem cells and progenitor cells are used for their treatment; this eliminates risks of rejection from the host’s body. The cells are transduced with lentiviruses vectors which encode a different version of the beta-globin gene and produce HbAT87Q, an antisickling hemoglobin designed to inhibit the sickled hemoglobin from coming together. After the modified beta-globin gets delivered to the stem cells (taken from the patient), the cells are reintroduced into the patient. The outcome is the eventual production of healthy new red blood cells.
For this study, there were three groups of patients (Group A, B, and C). However, this paper focuses its report on group C’s interim analysis. In Group C, there was the transplant population group (all patients treated with LentiGlobin infusion) and the transplant population with vaso-occlusive events (TPVOE) (patients that have had at least four severe vaso-occlusive events within 24 months before enrollment). The follow-up from patients in the TPVOE group from Group C that was treated with LentiGlobin showed no severe vaso-occlusive events after treatment. In addition, the LentiGlobin treatment only required a single dosage for stable production of HbAT87Q, where 85% of red cells had HbAT87Q expressed, effectively reducing sickled hemoglobin levels. Therefore, the researchers concluded a complete resolution of severe vaso-occlusive events could be obtained using the LentiGlobin one-time treatment.
Although this treatment is promising, the researchers emphasize the need for additional long-term evaluations to ensure safety and long-term efficacy since it is still undetermined if LentiGlobin has lifelong effects for treating sickle cell disease. Nevertheless, this paper’s interim results showcase this new gene therapy using LentiGlobin as new hope in treating patients with sickle cell disease.
Kanter J, Walters MC, Krishnamurti L, Mapara MY, Kwiatkowski JL, Rifkin-Zenenberg S, Aygun B, Kasow KA, Pierciey FJ, Bonner M, et al (2021) Biologic and clinical efficacy of lentiglobin for sickle cell disease. N England J of Med. doi:10.1056/nejmoa2117175
As a result, this led researchers Julie Kanter, et al. (2021) to test the biological and clinical efficacy of a new gene therapy with LentiGlobin, a possible solution for sickle cell disease, while avoiding the complications that come with allogeneic hematopoietic stem-cell transplantation. LentiGlobin allows for autologous transplantation, where the patient’s own hematopoietic stem cells and progenitor cells are used for their treatment; this eliminates risks of rejection from the host’s body. The cells are transduced with lentiviruses vectors which encode a different version of the beta-globin gene and produce HbAT87Q, an antisickling hemoglobin designed to inhibit the sickled hemoglobin from coming together. After the modified beta-globin gets delivered to the stem cells (taken from the patient), the cells are reintroduced into the patient. The outcome is the eventual production of healthy new red blood cells.
For this study, there were three groups of patients (Group A, B, and C). However, this paper focuses its report on group C’s interim analysis. In Group C, there was the transplant population group (all patients treated with LentiGlobin infusion) and the transplant population with vaso-occlusive events (TPVOE) (patients that have had at least four severe vaso-occlusive events within 24 months before enrollment). The follow-up from patients in the TPVOE group from Group C that was treated with LentiGlobin showed no severe vaso-occlusive events after treatment. In addition, the LentiGlobin treatment only required a single dosage for stable production of HbAT87Q, where 85% of red cells had HbAT87Q expressed, effectively reducing sickled hemoglobin levels. Therefore, the researchers concluded a complete resolution of severe vaso-occlusive events could be obtained using the LentiGlobin one-time treatment.
Although this treatment is promising, the researchers emphasize the need for additional long-term evaluations to ensure safety and long-term efficacy since it is still undetermined if LentiGlobin has lifelong effects for treating sickle cell disease. Nevertheless, this paper’s interim results showcase this new gene therapy using LentiGlobin as new hope in treating patients with sickle cell disease.
Kanter J, Walters MC, Krishnamurti L, Mapara MY, Kwiatkowski JL, Rifkin-Zenenberg S, Aygun B, Kasow KA, Pierciey FJ, Bonner M, et al (2021) Biologic and clinical efficacy of lentiglobin for sickle cell disease. N England J of Med. doi:10.1056/nejmoa2117175
Malaria protection due to sickle hemoglobin depends on parasite genotype
Malaria is a severe and sometimes fatal disease caused by a parasite. Plasmodium falciparum is the most prevalent species in Gambia and Kenya. These parasites infect mosquitoes, which then take their blood meals from humans while causing infection. Those who suffer from malaria will typically experience high fevers, chills, and flu-like symptoms. There has been a strong association between sickle hemoglobin (HbS) in the host and regions of the parasite genome. Humans in Africa have acquired a high frequency of sickle hemoglobin (HbS), which provides protection to those at high risk of the parasitic disease.
This article by Band et al., (2021) determines if there are genetic forms of P. falciparum present that can overcome human variants providing resistance to the malarial parasite. Band et al., analyzed the host and parasitic genome variation in samples from children living in Gambia and Kenya experiencing severe symptoms due to P. falciparum. They conducted the sequencing of these genomes using Illumina sequencing and found that there are three Pfloci associated with HbS, meaning there are three separate regions in the P. falciparum genome (Pfsa1, Pfsa2, Pfsa3). The researchers' data shows little evidence of protective effects against malaria with parasites of Pfsa1+, Pfsa2+, and Pfsa3+ genotype. However, they found that there is a strong correlation with a decreased risk of disease caused by parasites of Pfsa1-, Pfsa2- and Pfsa3- genotype. Therefore, the protective effects of HbS against severe malarial diseases caused by P. falciparum are dependent on the genotype at the Pfsa loci of the parasite.
The evidence provided in this article clearly signifies that the genetic makeup of infections is determined by the genotype of the host. They provide proof of a strong correlation between HbS in the host and the three loci in different regions of the parasite genome. Although there is a strong correlation present, further studies must be conducted to include the asymptomatic and milder cases of malaria to achieve a higher level of understanding of the interaction between HbS and the parasite loci.
Band, G., Leffler, E.M., Jallow, M. et al., Malaria protection due to sickle hemoglobin depends on parasite genotype. Nature (2021). https://doi.org/10.1038/s41586-021-04288-3
This article by Band et al., (2021) determines if there are genetic forms of P. falciparum present that can overcome human variants providing resistance to the malarial parasite. Band et al., analyzed the host and parasitic genome variation in samples from children living in Gambia and Kenya experiencing severe symptoms due to P. falciparum. They conducted the sequencing of these genomes using Illumina sequencing and found that there are three Pfloci associated with HbS, meaning there are three separate regions in the P. falciparum genome (Pfsa1, Pfsa2, Pfsa3). The researchers' data shows little evidence of protective effects against malaria with parasites of Pfsa1+, Pfsa2+, and Pfsa3+ genotype. However, they found that there is a strong correlation with a decreased risk of disease caused by parasites of Pfsa1-, Pfsa2- and Pfsa3- genotype. Therefore, the protective effects of HbS against severe malarial diseases caused by P. falciparum are dependent on the genotype at the Pfsa loci of the parasite.
The evidence provided in this article clearly signifies that the genetic makeup of infections is determined by the genotype of the host. They provide proof of a strong correlation between HbS in the host and the three loci in different regions of the parasite genome. Although there is a strong correlation present, further studies must be conducted to include the asymptomatic and milder cases of malaria to achieve a higher level of understanding of the interaction between HbS and the parasite loci.
Band, G., Leffler, E.M., Jallow, M. et al., Malaria protection due to sickle hemoglobin depends on parasite genotype. Nature (2021). https://doi.org/10.1038/s41586-021-04288-3
Roles of Interaction between CCN2 and Rab14 in Aggrecan Production by Chondrocytes
The connective tissue growth factor, cellular communication network factor 2 (CCN2), is expressed in multiple types of cells such as chondrocytes. CCN2 manages adhesion, differentiation of various cells, migration, and plays a role in chondrocyte proliferation, stimulation of cartilage-specific ECM, and chondrocyte maturation. In addition, CCN2 binds to extracellular proteins like fibronectin through the CT domain and aggrecan through the N-terminal half. While composed of four characteristic modules, each domain has interactive proteins in which CNN2 modulates the activity of binding partners. Previous studies have indicated that CCN2 may have intracellular functions by interacting with intracellular proteins since it was reported that CCN2 interacted with Rab14 GTPase. Activated Rab protein is involved in intracellular membrane trafficking, working to recruit proteins to the vesicle membrane. Rab14 specifically works in membrane trafficking between the Golgi complex and endosomes, and regulates apical targeting in polarized epithelial cells. This study displayed the interactions of Rab14 with CCN2 for the first time and showed evidence that the complex manages intracellular membrane trafficking within chondrocytes. In the methodology, the researchers performed a GAL-4-based yeast two-hybrid screening utilizing a cDNA library from chondrocytic cell line HCS-2/9. An in situ proximity ligation assay confirmed the interaction between CCN2 and Rab14 and positive signals were detected in the chondrocytic cells using a combination of the anti-CCN2 and anti-RAB14 antibodies.
The results showed that they interact in the chondrocyte and the IGFBP-like domain works in their interaction. The participation of Rab14 in trafficking between the Golgi complex and early endosomes had been reported in previous studies. Rab14 and CCN2 were co-expressed and results displayed that they colocalized and were distributed as dots within the cytosol. The findings demonstrated that intracellular CCN2 enhances the accumulation of Rab14 on vesicles through the IGFBP-like domain of CCN2 during their transport within the cytosol, and CCN2 might cooperatively regulate endocytic trafficking with Rab14 as an effector protein. Furthermore, the overexpression of Rab14DN (dominant deletion form) revealed that extracellular proteoglycan was decreased compared to the overexpression of Rab14WT/CA (constituent active form) in the chondrocytic cells. The researchers also silenced RAB14 or CCN2 mRNA, which promoted ER or Golgi stress-related genes in chondrocytic cells. This suggested that a reduction in RAB14 or CCN2 activity may lead to ER or Golgi stress, alongside failure of intracellular trafficking. Based on the results of the paper, the researchers proposed the way CCN2 and Rab14 regulate vesicle trafficking is through the activation of Rab14 in the cytoplasm to allow for it to interact with the effector protein, CCN2. This results in Rab14 working with proteoglycan-containing vesicles to promote vesicle trafficking stimulating the secretion of proteoglycan into the extracellular space. Without this, ER and Golgi stress occur, giving the impression that CCN2 and Rab14 have a necessary role in chondrocytic function.
Hoshijima, M., Hattori, T., Aoyama, E., Nishida, T., Kubota, S., Kamioka, H., & Takigawa, M. (2020). Roles of Interaction between CCN2 and Rab14 in Aggrecan Production by Chondrocytes. International Journal of Molecular Sciences, 21(8), 2769. https://doi.org/10.3390/ijms21082769
The results showed that they interact in the chondrocyte and the IGFBP-like domain works in their interaction. The participation of Rab14 in trafficking between the Golgi complex and early endosomes had been reported in previous studies. Rab14 and CCN2 were co-expressed and results displayed that they colocalized and were distributed as dots within the cytosol. The findings demonstrated that intracellular CCN2 enhances the accumulation of Rab14 on vesicles through the IGFBP-like domain of CCN2 during their transport within the cytosol, and CCN2 might cooperatively regulate endocytic trafficking with Rab14 as an effector protein. Furthermore, the overexpression of Rab14DN (dominant deletion form) revealed that extracellular proteoglycan was decreased compared to the overexpression of Rab14WT/CA (constituent active form) in the chondrocytic cells. The researchers also silenced RAB14 or CCN2 mRNA, which promoted ER or Golgi stress-related genes in chondrocytic cells. This suggested that a reduction in RAB14 or CCN2 activity may lead to ER or Golgi stress, alongside failure of intracellular trafficking. Based on the results of the paper, the researchers proposed the way CCN2 and Rab14 regulate vesicle trafficking is through the activation of Rab14 in the cytoplasm to allow for it to interact with the effector protein, CCN2. This results in Rab14 working with proteoglycan-containing vesicles to promote vesicle trafficking stimulating the secretion of proteoglycan into the extracellular space. Without this, ER and Golgi stress occur, giving the impression that CCN2 and Rab14 have a necessary role in chondrocytic function.
Hoshijima, M., Hattori, T., Aoyama, E., Nishida, T., Kubota, S., Kamioka, H., & Takigawa, M. (2020). Roles of Interaction between CCN2 and Rab14 in Aggrecan Production by Chondrocytes. International Journal of Molecular Sciences, 21(8), 2769. https://doi.org/10.3390/ijms21082769
Using nanoparticles for the targeted delivery of chemotherapeutics to choriocarcinomA
Choriocarcinoma is a gestational trophoblastic cancer that arises from the aggressive over-proliferation of placental trophoblast cells, which can further metastasize to the brain, kidney, liver, and lung. Choriocarcinoma that develops during or after pregnancy is termed gestational choriocarcinoma and occurs in approximately one in every 50,000 pregnancies. The primary line of treatment is systemic chemotherapy; however, this type of treatment can result in non-selective drug distribution and severe toxicity.
The emerging topic of nanomedicine is beginning to show to be advantageous over traditional therapeutics due to its ability to target drugs to specific affected sites, thus increasing drug efficacy, and reducing adverse reactions. Previous studies have found that syncytiotrophoblast, a differentiated cell type of trophoblasts, exclusively produce chondroitin sulfate A (CSA). CSA is believed to be a strong binding target for nanoparticles. In addition, previous studies conducted by the same authors of the present study showed that loading doxorubicin (DOX), a chemotherapeutic, into lipid-polymer nanoparticles proved to be highly effective for targeting to and treating breast cancer in mice. Thus, the authors hypothesized in the present study that a synthetic CSA binding peptide (CSA-BP) could be used to target doxorubicin loaded nanoparticles to placental trophoblast cells to treat choriocarcinoma. The authors tested their hypothesis by investigating the targeting efficacy of CSA-targeted nanoparticles in vitro, in vivo, and ex vivo. They also investigated if doxorubicin loaded CSA-targeted nanoparticles (CSA-DNPs) can alleviate choriocarcinoma primary tumor growth and inhibit metastasis.
By using a single step sonication method, DNPs spontaneously self-assembled from lipids, polymers, and free DOX. CSA-BP was then conjugated to the surface of DNPs to form CSA-DNPs. It was found that JEG3 cells, a human choriocarcinoma derived cell line, were able to uptake the CSA-DNPs at a significantly higher capacity compared to the non-targeted nanoparticle control, and that internalization of the nanoparticles is mediated by lysosomes. Next, the CSA-DNPs displayed strong growth inhibition and apoptotic effects on JEG3 cells. A CCK-8 and quantitative apoptotic assay was used to evaluate cell viability and apoptosis respectively. Next, the authors were able to show that CSA-targeted nanoparticles can localize to the tumor region in vivo by visualizing fluorescently tagged nanoparticles in JEG3 tumor bearing nude mice. Additional in vivo imaging showed that CSA-DNPs can effectively inhibit primary tumor choriocarcinoma growth in mice. Tumor bearing mice treated with CSA-DNPs showed no macroscopic tumor growth after 18 days, and remarkably, two of the five treated mice showed no detection of fluorescent JEG3 tumor cells. Consequently, CSA-DNP treated mice had a 100% survival rate, which was significantly greater than non-targeted nanoparticle treatment groups which died 18 days after tumor implantation. Lastly, CSA-DNPs were shown to inhibit human choriocarcinoma metastasis in mice.
Overall, this study showed that CSA-DNPs could specifically bind to JEG3 choriocarcinoma cells both in vitro, and in vivo. Using a CSA-BP on the surface of DOX-loaded nanoparticles enhanced nanoparticle uptake by JEG3 cells and resulted in decreased cell viability and increased apoptosis. Finally, CSA-DNPs were able to rapidly localize to the tumor region in mice and effectively kill JEG3 tumor cells and inhibit metastasis. This study outlines a novel trophoblast targeted nanoparticle system for delivery of chemotherapeutics to choriocarcinoma cells and presents alternative therapy options for traditional systemic administration of drugs.
The emerging topic of nanomedicine is beginning to show to be advantageous over traditional therapeutics due to its ability to target drugs to specific affected sites, thus increasing drug efficacy, and reducing adverse reactions. Previous studies have found that syncytiotrophoblast, a differentiated cell type of trophoblasts, exclusively produce chondroitin sulfate A (CSA). CSA is believed to be a strong binding target for nanoparticles. In addition, previous studies conducted by the same authors of the present study showed that loading doxorubicin (DOX), a chemotherapeutic, into lipid-polymer nanoparticles proved to be highly effective for targeting to and treating breast cancer in mice. Thus, the authors hypothesized in the present study that a synthetic CSA binding peptide (CSA-BP) could be used to target doxorubicin loaded nanoparticles to placental trophoblast cells to treat choriocarcinoma. The authors tested their hypothesis by investigating the targeting efficacy of CSA-targeted nanoparticles in vitro, in vivo, and ex vivo. They also investigated if doxorubicin loaded CSA-targeted nanoparticles (CSA-DNPs) can alleviate choriocarcinoma primary tumor growth and inhibit metastasis.
By using a single step sonication method, DNPs spontaneously self-assembled from lipids, polymers, and free DOX. CSA-BP was then conjugated to the surface of DNPs to form CSA-DNPs. It was found that JEG3 cells, a human choriocarcinoma derived cell line, were able to uptake the CSA-DNPs at a significantly higher capacity compared to the non-targeted nanoparticle control, and that internalization of the nanoparticles is mediated by lysosomes. Next, the CSA-DNPs displayed strong growth inhibition and apoptotic effects on JEG3 cells. A CCK-8 and quantitative apoptotic assay was used to evaluate cell viability and apoptosis respectively. Next, the authors were able to show that CSA-targeted nanoparticles can localize to the tumor region in vivo by visualizing fluorescently tagged nanoparticles in JEG3 tumor bearing nude mice. Additional in vivo imaging showed that CSA-DNPs can effectively inhibit primary tumor choriocarcinoma growth in mice. Tumor bearing mice treated with CSA-DNPs showed no macroscopic tumor growth after 18 days, and remarkably, two of the five treated mice showed no detection of fluorescent JEG3 tumor cells. Consequently, CSA-DNP treated mice had a 100% survival rate, which was significantly greater than non-targeted nanoparticle treatment groups which died 18 days after tumor implantation. Lastly, CSA-DNPs were shown to inhibit human choriocarcinoma metastasis in mice.
Overall, this study showed that CSA-DNPs could specifically bind to JEG3 choriocarcinoma cells both in vitro, and in vivo. Using a CSA-BP on the surface of DOX-loaded nanoparticles enhanced nanoparticle uptake by JEG3 cells and resulted in decreased cell viability and increased apoptosis. Finally, CSA-DNPs were able to rapidly localize to the tumor region in mice and effectively kill JEG3 tumor cells and inhibit metastasis. This study outlines a novel trophoblast targeted nanoparticle system for delivery of chemotherapeutics to choriocarcinoma cells and presents alternative therapy options for traditional systemic administration of drugs.
High-dose vitamin B1 therapy prevents the development of experimental fatty liver driven by overnutrition
The prevalence of hepatic steatosis, defined as a metabolic condition where intrahepatic fat comprises over 5.5% of liver weight, has grown over recent years due to an increase in sedentary lifestyles and overeating. Although this has subsequently led to a rise in the need for transplantations due to chronic liver disease, there is currently no available drug therapy to treat hepatic steatosis. Kalyesubula et al. (2020) conducted a study on thiamine—more commonly referred to as vitamin B1—as a possible treatment, since it plays a critical role in the catabolism of carbohydrates and fatty acids. For instance, it is an essential coenzyme for the production of acetyl coenzyme A from pyruvate. Thiamine levels can decrease due to consumption of simple carbohydrates, which are abundant in most western diets, and a deficit in this vitamin is associated with obesity and diabetes. Thus, it was hypothesized that an excess in thiamine could increase the efficiency of certain metabolic enzymes and consequently reduce the rate of fat accumulation in the liver. Lambs were raised for 135 days under one of three randomly assigned treatments: a low-calorie diet, a high-calorie diet, or a thiamine treatment in addition to a high-calorie diet. Those in the latter were injected with thiamine hydrochloride thrice weekly from days 50 to 93 and five times a week following that (the increased dosage was to account for the increase in body weight). Lambs in the other two groups were injected with an equivalent volume of saline solution as a control.
Predictably, the low-calorie diet was associated with a much lower body weight and less fat in comparison to the high-calorie diet. The group that received the thiamine treatment was found to weigh less than the high-calorie diet control group, had a liver-fat content that was less than 5.5%, and was statistically similar to the low-calorie diet group. The experimental group was found to have lower blood glucose levels than the overnourished control group, indicating a higher rate in carbohydrate catabolism in the thiamine-treated lambs. However, hepatic glycogen levels were observed to increase. This is known to happen when plasma insulin and glucose act as a substrate for glycogen, suggesting that thiamine may improve hepatic sensitivity to insulin. However, no effect was observed on whole-body insulin sensitivity. On a genetic level, the experimental group also had a greater abundance of mRNA transcripts coding for microsomal triglyceride transfer proteins and fewer perilipin 2 transcripts relative to the high-calorie diet group. The expression of these proteins are associated with the inhibition of adipose storage.
The results of this study suggest that thiamine is a promising potential pharmacological treatment for diet-induced hepatic steatosis. Increased levels of thiamine result in a higher efficiency of carbohydrate metabolism and prevent accumulation of hepatic fat. Most notably, thiamine’s lack of an effect on whole-body insulin sensitivity indicates a possible ability to target the liver for treatments. These findings are exciting and increasingly necessary as hepatic steatosis becomes more abundant as a consequence of modern societal habits.
Kalyesubula, M., Mopuri, R., Asiku, J., Rosov, A., Yosefi, S., Edery, N., Bocobza, S., Moallem, U. and Hay Dvir. (2021). High-dose vitamin B1 therapy prevents the development of experimental fatty liver driven by overnutrition. Dis Model Mech. 14 (3): dmm048355. doi: https://doi.org/10.1242/dmm.048355
Predictably, the low-calorie diet was associated with a much lower body weight and less fat in comparison to the high-calorie diet. The group that received the thiamine treatment was found to weigh less than the high-calorie diet control group, had a liver-fat content that was less than 5.5%, and was statistically similar to the low-calorie diet group. The experimental group was found to have lower blood glucose levels than the overnourished control group, indicating a higher rate in carbohydrate catabolism in the thiamine-treated lambs. However, hepatic glycogen levels were observed to increase. This is known to happen when plasma insulin and glucose act as a substrate for glycogen, suggesting that thiamine may improve hepatic sensitivity to insulin. However, no effect was observed on whole-body insulin sensitivity. On a genetic level, the experimental group also had a greater abundance of mRNA transcripts coding for microsomal triglyceride transfer proteins and fewer perilipin 2 transcripts relative to the high-calorie diet group. The expression of these proteins are associated with the inhibition of adipose storage.
The results of this study suggest that thiamine is a promising potential pharmacological treatment for diet-induced hepatic steatosis. Increased levels of thiamine result in a higher efficiency of carbohydrate metabolism and prevent accumulation of hepatic fat. Most notably, thiamine’s lack of an effect on whole-body insulin sensitivity indicates a possible ability to target the liver for treatments. These findings are exciting and increasingly necessary as hepatic steatosis becomes more abundant as a consequence of modern societal habits.
Kalyesubula, M., Mopuri, R., Asiku, J., Rosov, A., Yosefi, S., Edery, N., Bocobza, S., Moallem, U. and Hay Dvir. (2021). High-dose vitamin B1 therapy prevents the development of experimental fatty liver driven by overnutrition. Dis Model Mech. 14 (3): dmm048355. doi: https://doi.org/10.1242/dmm.048355
Targeting Pin1 renders pancreatic cancer eradicable by synergizing with immunochemotherapy
Pancreatic ductal adenocarcinoma (PDAC) is one of the most common types of pancreatic cancer. It is a highly aggressive solid malignancy, predicted to be the second leading cause of cancer death by 2030. Characteristics of PDAC include intratumor heterogeneity and a highly desmoplastic and immunosuppressive tumour microenvironment (TME). Intratumor heterogeneity contains multiple, distinct subpopulations of cells within a single tumour. The highly desmoplastic TME is a dense layer that surrounds and supports the tumour, making it especially difficult for immune cells to penetrate and attack the tumour. An immunosuppressive TME is essentially an environment where the immune system has difficulty combating cancer cells effectively. These specific features make PDACs notorious for being resistant to chemotherapy, targeted therapies, and immunotherapies.
One of the methods of cell regulation is a proline-directed phosphorylated signalling mechanism. After this phosphorylation event, a unique phosphor-specific proline isomerase called Pin1 will further regulate the protein by changing the protein’s conformation. However, if Pin1 is hyperactive, it can promote tumorigenesis through over-activating protooncogenes, turning them into oncogenes (involved in the growth and division of cancer cells), and inactivating tumour suppressor genes (involved in regulating the cell cycle). Therefore, targeting Pin1 may be helpful in patients with PDAC, as inhibition of Pin1 may block multiple oncogenic signalling pathways. However, Pin1’s role in the TME and immunotherapy was unclear in previous research, and it was unknown whether solid malignancies were curable using Pin1 inhibitors.
Koikawa et al. (2021) reported that Pin1 drives the desmoplastic and immunosuppressive TME in PDAC, which consequently induces endocytosis followed by the degradation of response markers, PD-L1 and ENT1, found at the surface of PDAC cells. They also reported Pin1’s involvement in activating various oncogenic pathways. This supported the findings that Pin1 was overexpressed in cancer cells and CAFs in human PDAC, which correlated with poor prognosis. Furthermore, Pin1 can promote oncogenic signalling pathways and reduce PD-L1 and ENT1 cell surface expression of PDAC cells. In addition to activating multiple cancer pathways, Pin1 acts on cancer-associated fibroblasts, which drives tumour malignancy and drug resistance. Therefore, targeting Pin1 disrupts the TME and renders tumours of PDACs curable using immunochemotherapy. Specifically, with immunochemotherapy, the general, nonspecific chemotherapeutic gemcitabine (GEM) treatment is often used. However, for GEM to be transported into the cells, it requires the ENT1 transporter. Thus, inhibiting Pin1 allows for an increase in ENT1 transporters, allowing more GEM to be bioavailable.
These results suggest using Pin1 paired with immunochemotherapy using GEM can render aggressive PDAC eradicable, as this would upregulate PD-L1 and ENT1, block various cancer pathways, and disrupt the desmoplastic and immunosuppressive TME. Furthermore, evidence suggests there should be little concern over toxicity in the Pin1 inhibitor-immunochemotherapy combination. To conclude, the researchers discovered a unique therapeutic strategy that addresses the underlying mechanisms in aggressive PDAC, providing evidence for further clinical trials using Pin1 inhibitors.
Citation
Koikawa, K., Kibe, S., Suizu, F., Sekino, N., Kim, N., Manz, T. D., Pinch, B. J., Akshinthala, D., Verma, A., Gaglia, G., Nezu, Y., Ke, S., Qiu, C., Ohuchida, K., Oda, Y., Lee, T. H., Wegiel, B., Clohessy, J. G., London, N., … Lu, K. P. (2021). Targeting Pin1 renders pancreatic cancer eradicable by synergizing with immunochemotherapy. Cell, 184(18), 4753-4771.e27. https://doi.org/10.1016/j.cell.2021.07.020
One of the methods of cell regulation is a proline-directed phosphorylated signalling mechanism. After this phosphorylation event, a unique phosphor-specific proline isomerase called Pin1 will further regulate the protein by changing the protein’s conformation. However, if Pin1 is hyperactive, it can promote tumorigenesis through over-activating protooncogenes, turning them into oncogenes (involved in the growth and division of cancer cells), and inactivating tumour suppressor genes (involved in regulating the cell cycle). Therefore, targeting Pin1 may be helpful in patients with PDAC, as inhibition of Pin1 may block multiple oncogenic signalling pathways. However, Pin1’s role in the TME and immunotherapy was unclear in previous research, and it was unknown whether solid malignancies were curable using Pin1 inhibitors.
Koikawa et al. (2021) reported that Pin1 drives the desmoplastic and immunosuppressive TME in PDAC, which consequently induces endocytosis followed by the degradation of response markers, PD-L1 and ENT1, found at the surface of PDAC cells. They also reported Pin1’s involvement in activating various oncogenic pathways. This supported the findings that Pin1 was overexpressed in cancer cells and CAFs in human PDAC, which correlated with poor prognosis. Furthermore, Pin1 can promote oncogenic signalling pathways and reduce PD-L1 and ENT1 cell surface expression of PDAC cells. In addition to activating multiple cancer pathways, Pin1 acts on cancer-associated fibroblasts, which drives tumour malignancy and drug resistance. Therefore, targeting Pin1 disrupts the TME and renders tumours of PDACs curable using immunochemotherapy. Specifically, with immunochemotherapy, the general, nonspecific chemotherapeutic gemcitabine (GEM) treatment is often used. However, for GEM to be transported into the cells, it requires the ENT1 transporter. Thus, inhibiting Pin1 allows for an increase in ENT1 transporters, allowing more GEM to be bioavailable.
These results suggest using Pin1 paired with immunochemotherapy using GEM can render aggressive PDAC eradicable, as this would upregulate PD-L1 and ENT1, block various cancer pathways, and disrupt the desmoplastic and immunosuppressive TME. Furthermore, evidence suggests there should be little concern over toxicity in the Pin1 inhibitor-immunochemotherapy combination. To conclude, the researchers discovered a unique therapeutic strategy that addresses the underlying mechanisms in aggressive PDAC, providing evidence for further clinical trials using Pin1 inhibitors.
Citation
Koikawa, K., Kibe, S., Suizu, F., Sekino, N., Kim, N., Manz, T. D., Pinch, B. J., Akshinthala, D., Verma, A., Gaglia, G., Nezu, Y., Ke, S., Qiu, C., Ohuchida, K., Oda, Y., Lee, T. H., Wegiel, B., Clohessy, J. G., London, N., … Lu, K. P. (2021). Targeting Pin1 renders pancreatic cancer eradicable by synergizing with immunochemotherapy. Cell, 184(18), 4753-4771.e27. https://doi.org/10.1016/j.cell.2021.07.020
Expression Profiles of the Genes Associated with Zinc Homeostasis in Normal and Cancerous Breast and Prostate Cells
Zinc is the most abundant element in the body following iron, and is required for numerous functions as a cofactor and structural element in the body. As a result, to ensure homeostasis, a normally functioning cell must have tight control over zinc transport. The cell performs this with two transporters called ZRT/Irt-like proteins (ZIP) which import zinc into the cytosol from the subcellular organelles or the extracellular space, and Zn transporters (ZnT), which do the opposite. In addition, a protein called MT preferentially binds to metals such as zinc to sequester it from the cytoplasm as another layer of control in the cell. Interestingly, healthy breast epithelial cells have a lower concentration of zinc compared to breast cancer epithelial cells, and the opposite is true in the prostate, where the cancerous prostate epithelial cells have a lower concentration of zinc compared to the healthy prostate. To better understand this occurrence, the researchers wanted to study the change in gene expression in zinc transporter proteins that causes this phenomenon.
The gene expression of each protein was studied in MCF-7 and MDA-MB-231 breast cancer cells and PC-3 and DU145 prostate cancer cells and were compared to the healthy cell line. The authors first performed a cell viability test where each cell line was treated with zinc sulfate at different time points. To determine the expression levels of the genes, three heat maps were made. The first heat map looked at the changes in gene expression in healthy epithelial cells and cancerous epithelial cells before zinc treatment. The second heat map studied the differences in gene expression following zinc treatment, and the final map looked at just breast cells that were treated with a non-cytotoxic dose of zinc sulfate.
The authors found that only in the healthy and cancerous breast epithelial cells, the protein ZIP1 and ZIP2 were upregulated compared to the prostate cells in which they were downregulated. This led the authors to hypothesize that these proteins must be housekeeping genes as the changes in expression are minimal. One protein that was significantly upregulated in only prostate cancer cells was ZnT1 which has normal functions as a zinc exporter. Due to the abnormally low zinc concentration in prostate cells, the authors concluded that this protein may be involved in an unknown mechanism where zinc leaks out of the cell. Throughout the study, MT overexpression was consistent in both cancer cell lines, suggesting an important role of MT in carcinogenesis. ZIP4 was highly upregulated in both cancer cell lines compared to their healthy counterparts; in addition, it was not commonly expressed in other healthy tissues. The authors concluded that ZIP4 could be an attractive anti-cancer therapeutic target and suggested that this would be an area of research to explore further.
Barman, S. K., Zaman, M. S., Veljanoski, F., Malladi, C. S., Mahns, D. A., & Wu, M. J. (2022). Expression profiles of the genes associated with zinc homeostasis in normal and cancerous breast and prostate cells. Metallomics, 14(8). https://doi.org/10.1093/mtomcs/mfac038
The gene expression of each protein was studied in MCF-7 and MDA-MB-231 breast cancer cells and PC-3 and DU145 prostate cancer cells and were compared to the healthy cell line. The authors first performed a cell viability test where each cell line was treated with zinc sulfate at different time points. To determine the expression levels of the genes, three heat maps were made. The first heat map looked at the changes in gene expression in healthy epithelial cells and cancerous epithelial cells before zinc treatment. The second heat map studied the differences in gene expression following zinc treatment, and the final map looked at just breast cells that were treated with a non-cytotoxic dose of zinc sulfate.
The authors found that only in the healthy and cancerous breast epithelial cells, the protein ZIP1 and ZIP2 were upregulated compared to the prostate cells in which they were downregulated. This led the authors to hypothesize that these proteins must be housekeeping genes as the changes in expression are minimal. One protein that was significantly upregulated in only prostate cancer cells was ZnT1 which has normal functions as a zinc exporter. Due to the abnormally low zinc concentration in prostate cells, the authors concluded that this protein may be involved in an unknown mechanism where zinc leaks out of the cell. Throughout the study, MT overexpression was consistent in both cancer cell lines, suggesting an important role of MT in carcinogenesis. ZIP4 was highly upregulated in both cancer cell lines compared to their healthy counterparts; in addition, it was not commonly expressed in other healthy tissues. The authors concluded that ZIP4 could be an attractive anti-cancer therapeutic target and suggested that this would be an area of research to explore further.
Barman, S. K., Zaman, M. S., Veljanoski, F., Malladi, C. S., Mahns, D. A., & Wu, M. J. (2022). Expression profiles of the genes associated with zinc homeostasis in normal and cancerous breast and prostate cells. Metallomics, 14(8). https://doi.org/10.1093/mtomcs/mfac038
Maresin 1 as an Alternative Treatment for Peripheral Nerve Injuries (PNI)
Peripheral nerve injuries (PNI) often occur from sudden crushing, compression, lacerations, and extreme wounds occurring near the spinal cord or limbs. This type of injury often leads to impairment of sensory and motor capabilities as well as neuropathic pain. While experimental treatments such as nerve grafts, nerve transfers, nerve conduits, cell-based therapy, and gene therapy have been researched and are being used in modern-day treatment, they all lead to the same side effect: increased neuropathic pain.
Out of these treatments, researchers have focused on studying anti-NGF therapy and finding possible alternatives to this type of treatment without increasing the occurrence of neuropathic pain. Nerve growth factor (NGF), is a cytokine that protects damaged neurons while promoting neuronal survival, growth, and maintenance. However, NGF carries a double-edged effect in treating PNI; while it may improve nerve regeneration capabilities, it also accelerates the development of neuropathic pain. Researchers believe that Maresin 1 may be an alternative therapeutic to NGF that is able to exert anti-inflammatory effects and accelerate nerve regeneration while alleviating neuropathic pain. Previous studies have found that Maresin 1 (MaR1) is an anti-inflammatory product produced by human macrophages and has shown promise in treating other diseases/conditions such as pneumonia, colitis, airway inflammation, and wound healing through the reduction of pain hypersensitivity and protecting neurons.
To study the effects of MaR1, a mouse sciatic nerve crush injury model was used by researchers to possibly replicate and examine the nerve regeneration process. The motor and sensory functions, as well as pain behavior after the nerve injury, was assessed and their recovery wastracked after surgical procedures or therapeutic targeting. Four different control conditions of non-injured mice were first established: normal/non-injured mice, non-injured mice with surgery performed (sham mice), sham mice with MaR1, and sham mice with MaR1 in a vehicle such as saline. By establishing these control conditions, the researchers confirmed that MaR1 had no negative effects on a system at homeostasis. MaR1 was then tested on fetal mouse nerve cell cultures and it was found that MaR1 induced the extension of nerve fibers in a dose-dependent manner. MaR1 in a saline vehicle was then tested on injured mice after surgery by coating the vehicle solution on the damaged nerves. As expected from previous literature, it was found from this experiment that MaR1 was able to reduce neuronal damage, inhibit muscle atrophy, and promote the regeneration of the neurons in these mice compared to when MaR1 was not used to treat the mice after surgery. In addition, MaR1 was compared to treatment with NGF and was found that MaR1 produced better neuronal regeneration products than NGF at lower dosages; MaR1 was also able to alleviate neuropathic pain unlike NGF and the preceding treatment methods on their own.
In summary, this study was able to show that, in the post-surgery time frame, MaR1 could be a promising alternative rather than using NGF. With MaR1 inducing better effects of neuronal regeneration at lower dosages, as well as being able to reduce the issue of neuropathic pain after treatment, the researchers present a new and promising method for treating peripheral nerve injuries.
Wei, J., Su, W., Zhao, Y., Wei, Z., Hua, Y., Xue, P., Zhu, X., Chen, Y., & Chen, G. (2022). Maresin 1 promotes nerve regeneration and alleviates neuropathic pain after nerve injury. Journal of neuroinflammation, 19(1), 32.
Out of these treatments, researchers have focused on studying anti-NGF therapy and finding possible alternatives to this type of treatment without increasing the occurrence of neuropathic pain. Nerve growth factor (NGF), is a cytokine that protects damaged neurons while promoting neuronal survival, growth, and maintenance. However, NGF carries a double-edged effect in treating PNI; while it may improve nerve regeneration capabilities, it also accelerates the development of neuropathic pain. Researchers believe that Maresin 1 may be an alternative therapeutic to NGF that is able to exert anti-inflammatory effects and accelerate nerve regeneration while alleviating neuropathic pain. Previous studies have found that Maresin 1 (MaR1) is an anti-inflammatory product produced by human macrophages and has shown promise in treating other diseases/conditions such as pneumonia, colitis, airway inflammation, and wound healing through the reduction of pain hypersensitivity and protecting neurons.
To study the effects of MaR1, a mouse sciatic nerve crush injury model was used by researchers to possibly replicate and examine the nerve regeneration process. The motor and sensory functions, as well as pain behavior after the nerve injury, was assessed and their recovery wastracked after surgical procedures or therapeutic targeting. Four different control conditions of non-injured mice were first established: normal/non-injured mice, non-injured mice with surgery performed (sham mice), sham mice with MaR1, and sham mice with MaR1 in a vehicle such as saline. By establishing these control conditions, the researchers confirmed that MaR1 had no negative effects on a system at homeostasis. MaR1 was then tested on fetal mouse nerve cell cultures and it was found that MaR1 induced the extension of nerve fibers in a dose-dependent manner. MaR1 in a saline vehicle was then tested on injured mice after surgery by coating the vehicle solution on the damaged nerves. As expected from previous literature, it was found from this experiment that MaR1 was able to reduce neuronal damage, inhibit muscle atrophy, and promote the regeneration of the neurons in these mice compared to when MaR1 was not used to treat the mice after surgery. In addition, MaR1 was compared to treatment with NGF and was found that MaR1 produced better neuronal regeneration products than NGF at lower dosages; MaR1 was also able to alleviate neuropathic pain unlike NGF and the preceding treatment methods on their own.
In summary, this study was able to show that, in the post-surgery time frame, MaR1 could be a promising alternative rather than using NGF. With MaR1 inducing better effects of neuronal regeneration at lower dosages, as well as being able to reduce the issue of neuropathic pain after treatment, the researchers present a new and promising method for treating peripheral nerve injuries.
Wei, J., Su, W., Zhao, Y., Wei, Z., Hua, Y., Xue, P., Zhu, X., Chen, Y., & Chen, G. (2022). Maresin 1 promotes nerve regeneration and alleviates neuropathic pain after nerve injury. Journal of neuroinflammation, 19(1), 32.
Cellular senescence: from physiology to pathology
Cellular senescence is a process primarily designed to eliminate cells that are no longer needed. This process may occur by inducing tissue remodelling. Senescent cells will arrest their own proliferation, recruit inflammatory cells and promote tissue renewal. An accumulation of senescent cells may arise if the previously stated events , followed by clearance and regeneration, are not efficiently completed in aged tissues or in pathological situations. Various therapies may be useful for this accumulation, including pro-senescent and antisenescene therapies. Pro-senescent therapies may contribute to the minimization of damage in cancer and active tissue repair by limiting proliferation and fibrosis. Whereas antisenescent therapies may help to eliminate accumulated senescent cells and recover tissue function.
This article focuses on the important molecular mechanisms involved in cellular senescence and the implications of senescence in normal physiology and in pathological disorders. Furthermore, the authors propose a model for senescence as a tissue remodelling mechanism and review pro-senescent and antisenescent therapies for cancer, chronic disorders, and aging.
The mechanism of senescence includes many downstream signaling pathways that are complex and well organized. There is an increasing number of stimuli that will induce senescence and the mechanisms are constantly under revision. Many stimuli activate the p53 molecule, in which most pathways will converge in activating cyclin-dependent kinase inhibitors. This inhibition of the cyclin-dependent kinase complexes will result in proliferation arrest. In addition to this pathway, multiple triggers to senescence depend on the cell type and the cellular conditions.
Senescence plays a crucial role in development and physiology, generally in the context of cellular damage or stress. There are many senescence-positive structures in the developmental process across vertebrates. These include mesonephric tubules during mesonephros involution, the endolymphatic sac of the inner ear, the apical ectodermal ridge (AER) of the limbs, the regressing interdigital webs and the closing of the neural tube. The studies of these structures and their senescence indicate that developmentally programmed senescence is characterized by developmental cues that converge on the p21 molecule.
The absence of senescence may produce morphological defects but there are beneficial effects of senescence present in diseases. Senescence has been associated with multiple pathological processes leading to either beneficial or detrimental effects depending on the cell type and the cellular environment. These beneficial effects include protection against atherosclerosis, mitigation of renal fibrosis, counteraction against cancer progression, etc. The detrimental effects include emerging diseases associated with senescence, such as contribution to type 2 diabetes, association with obesity, and pulmonary fibrosis.
Senescence may be used as a therapeutic target depending on the therapeutic context. For example, the promotion of senescence can be beneficial by limiting the fibrotic response, and may also be beneficial in treating many human cancer cell lines. However, the senescent cells sustain high levels of proteotoxicity and therefore require high lysosomal activity which may be a disadvantage for these types of treatments.
Pro-senescent therapies can be useful for the treatment of cancer and for ongoing tissue repair processes and antisenescent therapies may be advantageous for eliminating senescence and fibrosis in injuries or to rejuvenate aged muscle.
A more comprehensive analysis is necessary to reveal even more developmental processes associated with senescence. Although there are benefits associated with senescence-based therapies for cancer treatment and ongoing tissue repair processes, there are consequences that may lead to other diseases.
Muñoz-Espín, D., & Serrano, M. (2014, June 23). Cellular senescence: From physiology to pathology. Nature News. Retrieved January 4, 2023, from https://www.nature.com/articles/nrm3823
This article focuses on the important molecular mechanisms involved in cellular senescence and the implications of senescence in normal physiology and in pathological disorders. Furthermore, the authors propose a model for senescence as a tissue remodelling mechanism and review pro-senescent and antisenescent therapies for cancer, chronic disorders, and aging.
The mechanism of senescence includes many downstream signaling pathways that are complex and well organized. There is an increasing number of stimuli that will induce senescence and the mechanisms are constantly under revision. Many stimuli activate the p53 molecule, in which most pathways will converge in activating cyclin-dependent kinase inhibitors. This inhibition of the cyclin-dependent kinase complexes will result in proliferation arrest. In addition to this pathway, multiple triggers to senescence depend on the cell type and the cellular conditions.
Senescence plays a crucial role in development and physiology, generally in the context of cellular damage or stress. There are many senescence-positive structures in the developmental process across vertebrates. These include mesonephric tubules during mesonephros involution, the endolymphatic sac of the inner ear, the apical ectodermal ridge (AER) of the limbs, the regressing interdigital webs and the closing of the neural tube. The studies of these structures and their senescence indicate that developmentally programmed senescence is characterized by developmental cues that converge on the p21 molecule.
The absence of senescence may produce morphological defects but there are beneficial effects of senescence present in diseases. Senescence has been associated with multiple pathological processes leading to either beneficial or detrimental effects depending on the cell type and the cellular environment. These beneficial effects include protection against atherosclerosis, mitigation of renal fibrosis, counteraction against cancer progression, etc. The detrimental effects include emerging diseases associated with senescence, such as contribution to type 2 diabetes, association with obesity, and pulmonary fibrosis.
Senescence may be used as a therapeutic target depending on the therapeutic context. For example, the promotion of senescence can be beneficial by limiting the fibrotic response, and may also be beneficial in treating many human cancer cell lines. However, the senescent cells sustain high levels of proteotoxicity and therefore require high lysosomal activity which may be a disadvantage for these types of treatments.
Pro-senescent therapies can be useful for the treatment of cancer and for ongoing tissue repair processes and antisenescent therapies may be advantageous for eliminating senescence and fibrosis in injuries or to rejuvenate aged muscle.
A more comprehensive analysis is necessary to reveal even more developmental processes associated with senescence. Although there are benefits associated with senescence-based therapies for cancer treatment and ongoing tissue repair processes, there are consequences that may lead to other diseases.
Muñoz-Espín, D., & Serrano, M. (2014, June 23). Cellular senescence: From physiology to pathology. Nature News. Retrieved January 4, 2023, from https://www.nature.com/articles/nrm3823
