Promotes Schwann Cell Proliferation Research Articles

Hyaluronic acid hybrid formulations optimised for 3D printing of nerve conduits and the delivery of the novel neurotrophic-like compound tyrosol to enhance peripheral nerve regeneration via Schwann cell proliferation

Peripheral nerve injuries, predominantly affecting individuals aged 20–40, pose significant healthcare challenges, with current surgical methods often failing to achieve complete functional recovery. This study focuses on the development of 3D printed hydrogel nerve conduits using modified hyaluronic acid (HA) for potentially enhancing peripheral nerve regeneration. Hyaluronic acid was chemically altered with cysteamine HCl and methacrylic anhydride to create thiolated HA (HA-SH) and methacrylated HA (HA-MA), achieving a modification degree of approximately 20 %. This modification was crucial to maintain the receptor interaction of HA. The modified HA was rigorously tested to ensure cytocompatibility in neuronal and glial cell lines. Subsequently, various 3D printed HA formulations were evaluated, focusing on improving HA’s inherent mechanical weaknesses. These formulations were assessed for cytotoxicity through direct contact and elution extract testing, confirming their safety over a 24-h period. Among the neurotrophic compounds tested, Tyrosol emerged as the most effective in promoting Schwann cell proliferation in vitro. The 3D printed HA system demonstrated proficiency in loading and releasing Tyrosol at physiological pH. The findings from this research highlight the promising role of 3D printed HA and Tyrosol in the field of nerve tissue engineering, offering a novel approach to peripheral nerve regeneration.

Dual-layer conduit containing VEGF-A – Transfected Schwann cells promotes peripheral nerve regeneration via angiogenesis

Peripheral nerve injuries (PNIs) can cause neuropathies and significantly affect the patient's quality of life. Autograft transplantation is the gold standard for conventional treatment; however, its application is limited by nerve unavailability, size mismatch, and local tissue adhesion. Tissue engineering, such as nerve guidance conduits, is an alternative and promising strategy to guide nerve regeneration for peripheral nerve repair; however, only a few conduits could reach the high repair efficiency of autografts. The healing process of PNI is frequently accompanied by not only axonal and myelination regeneration but also angiogenesis, which initializes nerve regeneration through vascular endothelial growth factor A (VEGF-A). In this study, a composite nerve conduit with a poly (lactic-co-glycolic acid) (PLGA) hollow tube as the outer layer and gelatin methacryloyl (GelMA) encapsulated with VEGF-A transfected Schwann cells (SCs) as the inner layer was established to evaluate its promising ability for peripheral nerve repair. A rat model of peripheral nerve defect was used to examine the efficiency of PLGA/GelMA-SC (VA) conduits, whereas autograft, PLGA, PLGA/GelMA, and PLGA/GelMA-SC (NC) were used as controls. VEGF-A-transfected SCs can provide a stable source for VEGF-A secretion. Furthermore, encapsulation in GelMA cannot only promote proliferation and tube formation of human umbilical vein endothelial cells but also enhance dorsal root ganglia and neuronal cell extension. Previous animal studies have demonstrated that the regenerative effects of PLGA/GelMA-SC (VA) nerve conduit were similar to those of autografts and much better than those of other conduits. These findings indicate that combination of VEGF-A-overexpressing SCs and PLGA/GelMA conduit-guided peripheral nerve repair provides a promising method that enhances angiogenesis and regeneration during nerve repair. Statement of significanceNerve guidance conduits shows promise for peripheral nerve repair, while achieving the repair efficiency of autografts remains a challenge. In this study, a composite nerve conduit with a PLGA hollow tube as the outer layer and gelatin methacryloyl (GelMA) encapsulated with vascular endothelial growth factor A (VEGF-A)-transfected Schwann cells (SCs) as the inner layer was established to evaluate its potential ability for peripheral nerve repair.This approach preserves growth factor bioactivity and enhances material properties. GelMA insertion promotes Schwann cell proliferation and morphology extension. Moreover, transfected SCs serve as a stable VEGF-A source and fostering angiogenesis. This study offers a method preserving growth factor efficacy and safeguarding SCs, providing a comprehensive solution for enhanced angiogenesis and nerve regeneration.

MiR-132-3p negatively regulates CAMTA1 to promote Schwann cell proliferation and migration and alleviates I-125 seeds-induced exacerbation of facial nerve injury in rats

To investigate the regulatory effect of miR-132-3p on calmodulin-binding transcription activator 1 (CAMTA1) and Schwann cell activity in rats with facial nerve injury (FNI) treated with I-125 seeds. Rat Schwann cells were irradiated with I-125 seeds and transfected with miR-132-3p mimic, miR-132-3p inhibitor or sh-CAMTA1. The expressions of S100B and β-tubulin Ⅲ in the cells were detected with immunofluorescence assay, and the expressions of miR-132-3p and CAMTA1 protein were determined using RT-qPCR and Western blotting, respectively. EdU staining and Transwell assay were used to evaluate the changes in cell proliferation and migration ability. In a rat model of FNI, I-125 seeds were implanted into the facial tissues near the facial nerve 2 weeks before modeling, and miR-132-3p mimic was injected subcutaneously in the face after modeling. The pathologies of the facial nerve was assessed by HE, LFB and immunofluorescence staining. The targeting relationship between miR-132-3p and CAMTA1 was verified using StarBase v2.0 database and dual-luciferase reporter assay. Rat Schwann cells showed high expressions of S100B and β-tubulin Ⅲ. I-125 seeds radiation significantly decreased miR-132-3p expression and repressed proliferation and migration of the cells (P < 0.001). Overexpression of miR-132-3p or CAMTA1 knockdown obviously enhanced proliferation and migration of the Schwann cells, while miR-132-3p knockdown produced the opposite effect. MiR-132-3p negatively regulated CAMTA1 expression. In the rat models of FNI, miR-132-3p injection significantly inhibited CAMTA1 expression and attenuated I-125 seeds-induced exacerbation of FNI. Overexpression of miR-132-3p suppresses CAMTA1 expression and promotes Schwann cell proliferation and migration to alleviate I-125 seeds-induced exacerbation of FNI in rats.

Electrospun Composite PLLA-PPSB Nanofiber Nerve Conduits for Peripheral Nerve Defects Repair and Regeneration.

Peripheral nerve injury (PNI) is a common clinical problem and regenerating peripheral nerve defects remain a significant challenge. Poly(polyol sebacate) (PPS) polymers are developed as promising materials for biomedical applications due to their biodegradability, biocompatibility, elastomeric properties, and ease of production. However, the application of PPS-based biomaterials in nerve tissue engineering, especially in PNI repair, is limited. In this study, PPS-based composite nanofibers poly(l-lactic acid)-poly(polycaprolactone triol-co-sebacic acid-co-N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid sodium salt) (PLLA-PPSB) are aimed to construct through electrospinning and assess their in vitro biocompatibility with Schwann cells (SCs) and in vivo repair capabilities for peripheral nerve defects. For the first time, the biocompatibility and bioactivity of PPS-based nanomaterial are examined at the molecular, cellular, and animal levels for PNI repair. Electrospun PLLA-PPSB nanofibers display favorable physicochemical properties and biocompatibility, providing an effective interface for the proliferation, glial expression, and adhesion of SCs in vitro. In vivo experiments using a 10-mm rat sciatic nerve defect model show that PLLA-PPSB nanofiber nerve conduits enhance myelin formation, axonal regeneration, angiogenesis, and functional recovery. Transcriptome analysis and biological validation indicate that PLLA-PPSB nanofibers may promote SC proliferation by activating the PI3K/Akt signaling pathway. This suggests the promising potential of PLLA-PPSB nanomaterial for PNI repair.

Combining PLGA microspheres loaded with Liver X receptor agonist GW3965 with a chitosan nerve conduit can promote the healing and regeneration of the wounded sciatic nerve.

Globally, peripheral nerve injury (PNI) is a common clinical issue. Successfully repairing severe PNIs has posed a major challenge for clinicians. GW3965 is a highly selective LXR agonist, and previous studies have demonstrated its positive protective effects in both central and peripheral nerve diseases. In this work, we examined the potential reparative effects of GW3965-loaded polylactic acid co-glycolic acid microspheres in conjunction with a chitosan nerve conduit for peripheral nerve damage. The experiment revealed that GW3965 promoted Schwann cell proliferation and neurotrophic factor release in vitro. In vivo experiments conducted on rats showed that GW3965 facilitated the restoration of motor function, promoted axon and myelin regeneration in the sciatic nerve, and enhanced the microenvironment of nerve regeneration. These results offer a novel therapeutic approach for the healing of nerve damage. Overall, this work provides valuable insights and presents a promising therapeutic strategy for addressing PNI.

Hypoxic Bone Mesenchymal Stem Cell-Derived Exosomes Direct Schwann Cells Proliferation, Migration, and Paracrine to Accelerate Facial Nerve Regeneration via circRNA_Nkd2/miR-214-3p/MED19 Axis.

Facial nerves have the potential for regeneration following injury, but this process is often challenging and slow. Schwann cells (SCs) are pivotal in this process. Bone mesenchymal stem cells (BMSC)-derived exosomes promote tissue repair through paracrine action, with hypoxic preconditioning enhancing their effects. The main purpose of this study was to determine whether hypoxia-preconditioned BMSC-derived exosomes (Hypo-Exos) exhibit a greater therapeutic effect on facial nerve repair/regeneration and reveal the mechanism. CCK-8, EdU, Transwell, and ELISA assays were used to evaluate the functions of Hypo-Exos in SCs. Histological analysis and Vibrissae Movements (VMs) recovery were used to evaluate the therapeutic effects of Hypo-Exos in rat model. circRNA array was used to identify the significantly differentially expressed exosomal circRNAs between normoxia-preconditioned BMSC-derived exosomes (Nor-Exos) and Hypo-Exos. miRDB, TargetScan, double luciferase assay, qRT-PCR and WB were used to predict and identify potential exosomal cirRNA_Nkd2-complementary miRNAs and its target gene. The function of exosomal circRNA_Nkd2 in facial nerve repair/regeneration was evaluated by cell and animal experiments. This study confirmed that Hypo-Exos more effectively promote SCs proliferation, migration, and paracrine function, accelerating facial nerve repair following facial nerve injury (FNI) compared with Nor-Exos. Furthermore, circRNA analysis identified significant enrichment of circRNA_Nkd2 in Hypo-Exos compared with Nor-Exos. Exosomal circRNA_Nkd2 positively regulates mediator complex subunit 19 (MED19) expression by sponging rno-miR-214-3p. Our results demonstrated a mechanism by which Hypo-Exos enhanced SCs proliferation, migration, and paracrine function and facial nerve repair and regeneration following FNI through the circRNA_Nkd2/miR-214-3p/Med19 axis. Hypoxic preconditioning is an effective and promising method for optimizing the therapeutic action of BMSC-derived exosomes in FNI.

Platelet-rich plasma-derived exosomes boost mesenchymal stem cells to promote peripheral nerve regeneration

Peripheral nerve injury (PNI) remains a severe clinical problem with debilitating consequences. Mesenchymal stem cell (MSC)-based therapy is promising, but the problems of poor engraftment and insufficient neurotrophic effects need to be overcome. Herein, we isolated platelet-rich plasma-derived exosomes (PRP-Exos), which contain abundant bioactive molecules, and investigated their potential to increase the regenerative capacity of MSCs. We observed that PRP-Exos significantly increased MSC proliferation, viability, and mobility, decreased MSC apoptosis under stress, maintained MSC stemness, and attenuated MSC senescence. In vivo, PRP-Exo-treated MSCs (pExo-MSCs) exhibited an increased retention rate and heightened therapeutic efficacy, as indicated by increased axonal regeneration, remyelination, and recovery of neurological function in a PNI model. In vitro, pExo-MSCs coculture promoted Schwann cell proliferation and dorsal root ganglion axon growth. Moreover, the increased neurotrophic behaviour of pExo-MSCs was mediated by trophic factors, particularly glia-derived neurotrophic factor (GDNF), and PRP-Exos activated the PI3K/Akt signalling pathway in MSCs, leading to the observed phenotypes. These findings demonstrate that PRP-Exos may be novel agents for increasing the ability of MSCs to promote neural repair and regeneration in patients with PNI.

Chitosan nerve conduit filled with ZIF-8-functionalized guide microfibres enhances nerve regeneration and sensory function recovery in sciatic nerve defects

Nerve conduits have shown promise as alternatives to autologous nerves, but their repair effects need to be improved. The topographical guidance and functionalization of scaffolds are crucial in nerve repair. In this work, a chitosan-based nerve graft filled with guiding fibres modified by ZIF-8 nanoparticles (CS@ZIF-8) was fabricated for defective nerve repair. An in vitro study demonstrated that CS@ZIF-8 exhibited excellent cytocompatibility and could significantly promote Schwann cell proliferation. In vivo, nerve conduits filled with CS@ZIF-8 were observed to guide stronger axonal longitudinal elongation. Rats bridged with the conduit filled with CS@ZIF-8 showed significant morphological and functional improvements in terms of regenerated nerve density, the number of myelinated nerve fibres, the number of myelin layers, the thickness of myelin sheath, target muscle recovery and sensory function compared to those transplanted with the hollow conduit and the conduit filled with pure chitosan fibres. The repair effects achieved by using the conduit filled with CS@ZIF-8 were similar to those of autografts. Altogether, the data here show that nerve conduits filled with ZIF-8-loaded guide fibres provide a promising approach for repairing nerve defects.

CDK5R1 promotes Schwann cell proliferation, migration, and production of neurotrophic factors via CDK5/BDNF/TrkB after sciatic nerve injury

Cyclin-dependent kinase 5 regulatory subunit 1 (CDK5R1) is necessary for central nervous system development and neuronal migration. At present, there are few reports about the role of CDK5R1 in peripheral nerve injury, and these need to be further explored. The CCK-8 and EdU assay was performed to examine cell proliferation. The migration ability of Schwann cells was tested by the cell scratch test. The apoptosis of Schwann cells was detected by flow cytometry. Sciatic nerve injury model in rats was established by crush injury. The sciatic function index (SFI) and the paw withdrawal mechanical threshold (PWMT) were measured at different time points. The results revealed that overexpression of CDK5R1 promoted the proliferation and migration of Schwann cells, and inhibited the apoptosis. Further studies found that pcDNA3.1-CDK5R1 significantly upregulated the expression of CDK5, BDNF and TrkB. More importantly, CDK5R1 promoted the recovery of nerve injury in rats. In addition, the CDK5 mediated BDNF/TrkB pathway was involved in the molecular mechanism of CDK5R1 on Schwann cells. It is suggested that the mechanism by which CDK5R1 promotes functional recovery after sciatic nerve injury is by CDK5 mediated activation of BDNF/TrkB signaling pathways.

Fully Biodegradable and Long-Term Operational Primary Zinc Batteries as Power Sources for Electronic Medicine.

Given the advantages of high energy density and easy deployment, biodegradable primary battery systems remain as a promising power source to achieve bioresorbable electronic medicine, eliminating secondary surgeries for device retrieval. However, currently available biobatteries are constrained by operational lifetime, biocompatibility, and biodegradability, limiting potential therapeutic outcomes as temporary implants. Herein, we propose a fully biodegradable primary zinc-molybdenum (Zn-Mo) battery with a prolonged functional lifetime of up to 19 days and desirable energy capacity and output voltage compared with reported primary Zn biobatteries. The Zn-Mo battery system is shown to have excellent biocompatibility and biodegradability and can significantly promote Schwann cell proliferation and the axonal growth of dorsal root ganglia. The biodegradable battery module with 4 Zn-Mo cells in series using gelatin electrolyte accomplishes electrochemical generation of signaling molecules (nitric oxide, NO) that can modulate the behavior of the cellular network, with efficacy comparable with that of conventional power sources. This work sheds light on materials strategies and fabrication schemes to develop high-performance biodegradable primary batteries to achieve a fully bioresorbable electronic platform for innovative medical treatments that could be beneficial for health care.

LncRNA HAGLR promotes the proliferation, migration, and neurotrophic factor production of Schwann cells via miR-204/CDK5R1 after sciatic nerve injury.

Peripheral nerve injury induces motor and sensory defects and has serious impacts on patients' quality of life. Schwann cells (SCs) are the major glial cells in the peripheral nervous system and play important roles in the repair and regeneration of peripheral nerves. Long noncoding RNA HAGLR has been reported to be highly expressed in neurons and to promote neuronal differentiation but its expression decreases after nerve injury, suggesting that HAGLR may be involved in the process of nerve injury repair. This study aimed to investigate the role and mechanism of HAGLR in neural repair functions of SCs. We found that HAGLR promoted SC proliferation and migration and facilitated the secretion of neurotrophic factors. Furthermore, HAGLR functions as a competing endogenous RNA to regulate CDK5R1 expression via sponging miR-204. Overexpression of miR-204 or silencing of CDK5R1 partially abolished the promoting effect of HAGLR on SCs. Moreover, overexpression of HAGLR promoted the functional recovery of sciatic nerve crush (SNC) model rats. In summary, HAGLR promoted SC proliferation, migration, neurotrophic factor production, and facilitated functional recovery of SNC rats via miR-204/CDK5R1. Therefore, it may provide a potential therapeutic target for peripheral nerve repair and regeneration.

Low-intensity pulsed ultrasound ameliorates erectile dysfunction induced by bilateral cavernous nerve injury through enhancing Schwann cell-mediated cavernous nerve regeneration.

Cavernous nerve injury-induced erectile dysfunction caused by pelvic surgery or trauma is refractory to conventional medications and required an alternative treatment. Low-intensity pulsed ultrasound is a noninvasive mechanical therapy that promotes nerve regeneration. To investigate the therapeutic effect and potential mechanism of low-intensity pulsed ultrasound in the treatment of neurogenic erectile dysfunction. Thirty rats were randomly divided into the sham-operated group, bilateral cavernous nerve injury group, and bilateral cavernous nerve injury + low-intensity pulsed ultrasound group. The erectile function was assessed 3weeks after daily low-intensity pulsed ultrasound treatment. The penile tissues and cavernous nerve tissues were harvested and subjected to histologic analysis. Primary Schwann cells and explants were extracted from adult rats. The effects of low-intensity pulsed ultrasound on proliferation, migration, and nerve growth factor expression of Schwann cells and axonal elongation were examined in vitro. RNA sequencing and western blot assay were applied to predict and verify the molecular mechanism of low-intensity pulsed ultrasound-induced Schwann cell activation. Our study showed that low-intensity pulsed ultrasound promoted Schwann cells proliferation, migration, and neurotrophic factor nerve growth factor expression. Meanwhile, low-intensity pulsed ultrasound exhibits a stronger ability to enhance Schwann cells-mediated neurite outgrowth of major pelvic ganglion neurons and major pelvic ganglion/cavernous nerve explants in vitro. In vivo experiments demonstrated that the erectile function of the rats in the bilateral cavernous nerve injury + low-intensity pulsed ultrasound group was significantly higher than those in the bilateral cavernous nerve injury groups. Moreover, the expression levels of smooth muscle and cavernous endothelium also increased significantly in the bilateral cavernous nerve injury + low-intensity pulsed ultrasound group. In addition, we observed the higher density and number of cavernous nerve regenerating axons in the bilateral cavernous nerve injury + low-intensity pulsed ultrasound group, indicating that low-intensity pulsed ultrasound promotes axonal regeneration following cavernous nerve injury in vivo. RNA sequencing analysis and bioinformatic analysis suggested that low-intensity pulsed ultrasound might trigger the activation of the PI3K/Akt pathway. Western blot assay confirmed that low-intensity pulsed ultrasound activated Schwann cells through TrkB/Akt/CREB signaling. Low-intensity pulsed ultrasound promoted nerve regeneration and ameliorated erectile function by enhancing Schwann cells proliferation, migration, and neurotrophic factor nerve growth factor expression. The TrkB/Akt/CREB axis is the possible mechanism of low-intensity pulsed ultrasound-mediated Schwann cell activation. Low-intensity pulsed ultrasound-based therapy could be a novel potential treatment strategy for cavernous nerve injury-induced neurogenic erectile dysfunction.

A bio-orthogonally functionalized chitosan scaffold with esterase-activatable release for nerve regeneration

Developing nerve conduits with biological cues is a promising approach for repairing peripheral nerve injuries. Although most biological cues incorporated into conduits generally exert their biological functions at the surface, they could not be released into the on-demand regeneration sites under physiological conditions. Herein, we firstly report a bio-orthogonally functionalized chitosan scaffold with esterase-activatable release for peripheral nerve regeneration. In this study, biological cues are not only selectively conjugated into nerve conduits by bio-orthogonal reaction, but also precisely released in on-demand regeneration sites via esterase-activatable cleavage for peripheral nerve repair. Moreover, this nerve scaffold with esterase-activatable release could promote Schwann cells proliferation. In a rat sciatic nerve defect model, the bio-orthogonally functionalized scaffold with esterase-activatable release significantly increased sciatic nerve function recovery and improved target muscles weight. This strategy of incorporating esterase-activatable bioactive cues into peripheral nerve conduits offers great potential in preclinical studies.

Surface Modification of Titanium by Micro-Arc Oxidation in Promoting Schwann Cell Proliferation and Secretion of Neurotrophic Factors

Titanium and its alloys have been widely used in the field of oral implants over the past few decades. However, the effect of micro-arc oxidation modified titanium surface on Schwann cells has not been studied, which is of great significance for nerve regeneration around implants and improvement of osseoperception. In this study, the characterization of the titanium surface modified by micro-arc oxidation (MAO) was detected by scanning electron microscope (SEM), XPS and a contact angle measurement system. Schwann cells (SCs) were cultured on titanium surfaces of micro-arc oxidation (MAO) and pure titanium (Ti). At different time points, the morphology and adhesion of SCs on the titanium surfaces were observed by SEM. Cell proliferation activity was detected by the CCK-8 method. The expression levels of mRNA and proteins of nerve growth factor (NGF) and glial-derived neurotrophic factor (GDNF) were detected by RT-PCR, immunofluorescence and western blot. The results of this in vitro study revealed that micro-arc-oxidation-modified titanium surfaces promoted Schwann cell proliferation and secretion of neurotrophic factors compared with pure titanium. CCK-8 results showed that the number of Schwann cells on MAO surfaces was significantly higher than that of the Ti group on day 7. The mRNA expressions of Ngf and Gdnf were up-regulated in both groups from day 1 to day 7. On day 3 and day 7, the gene expression of Ngf in the MAO group was significantly higher than that of the Ti group. On day 7, the MAO group appeared significantly up-regulated in gene expression level of Gdnf. The results of western blot were consistent. Micro-arc oxidation modification provides an accurate and effective method for promoting nerve regeneration of titanium microtopography coatings, which have potential significance for promoting patients’ osseoperception ability in clinical practice.

Exosomes Derived from Adipose Mesenchymal Stem Cells Carrying miRNA-22-3p Promote Schwann Cells Proliferation and Migration through Downregulation of PTEN.

Peripheral nerve injury (PNI) is often resulting from trauma, which leads to severe and permanently disability. Schwann cells are critical for facilitating the regeneration process after PNI. Adipose-derived mesenchymal stem cells (ADSCs) exosomes have been used as a novel treatment for peripheral nerve injury. However, the underlying mechanism remains unclear. In this study, we isolated ADSCs and extracted exosomes, which were verified by transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA), and western blot (WB). Cocultured with Dorsal Root Ganglion (DRG) and Schwann cells (SCs) to evaluate the effect of exosomes on the growth of DRG axons by immunofluorescence, and the proliferation and migration of SCs by CCK8 and Transwell assays, respectively. Through exosomal miRNA sequencing and bioinformatic analysis, the related miRNAs and target gene were predicted and identified by dual luciferase assay. Related miRNAs were overexpressed and inhibited, respectively, to clarify their effects; the downstream pathway through the target gene was determined by real-time fluorescence quantitative polymerase chain reaction (RT-qPCR) and WB. Results found that ADSC-exosomes could promote the proliferation and migration of SCs and the growth of DRG axons, respectively. Exosomal miRNA-22-3p from ADSCs directly inhibited the expression of Phosphatase and Tensin Homolog deleted on Chromosome 10 (PTEN), activated phosphorylation of the AKT/mTOR axis, and enhanced SCs proliferation and migration. In conclusion, our findings suggest that ADSC-exosomes could promote SCs function through exosomal miRNA-22-3p, which could be used as a therapeutic target for peripheral nerve injury.

Neuritin Promotes Bone Marrow-Derived Mesenchymal Stem Cell Migration to Treat Diabetic Peripheral Neuropathy.

The purpose of this study is to explore the effect and mechanism of neuritin overexpression in the bone marrow on peripheral neuropathy in type 2 diabetic (db/db) mice. We analyzed the impact of bone marrow neuritin overexpression on diabetic peripheral neuropathy and migration of bone marrow mesenchymal stem cells in db/db mice. Antagonists were used to inhibit the stromal cell-derived factor (SDF)-1α/C-X-C chemokine receptor type 4 (CXCR4)-phosphoinositide 3-kinase (PI3K)/Akt signaling pathway in primary cultured bone marrow mesenchymal stem cells. Immunofluorescence, transmission electron microscopy, Oil Red O staining, and transwell migration assays were used. Bone marrow-specific overexpression of neuritin in db/db mice was successfully established. Overexpression of neuritin in the bone marrow ameliorated hyperglycemia, prevented diabetic peripheral neuropathy, protected the ultrastructure of the sciatic nerve and intra-epidermal nerve fiber density, and promoted Schwann cell proliferation and remyelination in the sciatic nerve. Moreover, it ameliorated fat accumulation, adipocyte number, and vascular and nerve densities; decreased glutamate content in serum and bone marrow; restored gradient SDF-1α contents between bone marrow, blood, and sciatic nerve; and promoted impaired diabetic bone marrow mesenchymal stem cell migration. Neuritin improves bone marrow mesenchymal stem cell migration via the SDF-1α/CXCR4-PI3K/Akt signaling pathway in vitro. Overexpression of neuritin in the bone marrow can locally ameliorate neuropathy in the bone marrow. This improves the migration capability of bone marrow mesenchymal stem cells and repairs diabetic peripheral neuropathy, at least partly by activating the PI3K/Akt pathway through the SDF-1α/CXCR4 axis.

Activin A Secreted From Peripheral Nerve Fibroblasts Promotes Proliferation and Migration of Schwann Cells

The peripheral nervous system has remarkable regenerative capabilities. Schwann cells and fibroblasts are known to play crucial roles in these processes. In this study, we delineated the differential effects of peripheral nerve fibroblasts and cardiac fibroblasts on Schwann cells. We found that peripheral nerve fibroblasts significantly promoted Schwann cell proliferation and migration compared with cardiac fibroblasts. The cytokine array results identified 32 of 67 proteins that were considered differentially expressed in peripheral nerve fibroblasts versus cardiac fibroblasts. Among them, 25 were significantly upregulated in peripheral nerve fibroblasts compared with cardiac fibroblasts. Activin A, the protein with the greatest differential expression, clearly co-localized with fibroblasts in the in vivo sciatic never injury rat model. In vitro experiments proved that activin A secreted from nerve fibroblasts is the key factor responsible for boosting proliferation and migration of Schwann cells through ALK4, ALK5, and ALK7. Overall, these findings suggest that peripheral nerve fibroblasts and cardiac fibroblasts exhibit different patterns of cytokine secretion and activin A secreted from peripheral nerve fibroblasts can promote the proliferation and migration of Schwann cells.

Transcriptome Analysis of Schwann Cells at Various Stages of Myelination Implicates Chromatin Regulator Sin3A in Control of Myelination Identity.

Enhancing remyelination after injury is of utmost importance for optimizing the recovery of nerve function. While the formation of myelin by Schwann cells (SCs) is critical for the function of the peripheral nervous system, the temporal dynamics and regulatory mechanisms that control the progress of the SC lineage through myelination require further elucidation. Here, using in vitro co-culture models, gene expression profiling of laser capture-microdissected SCs at various stages of myelination, and multilevel bioinformatic analysis, we demonstrated that SCs exhibit three distinct transcriptional characteristics during myelination: the immature, promyelinating, and myelinating states. We showed that suppressor interacting 3a (Sin3A) and 16 other transcription factors and chromatin regulators play important roles in the progress of myelination. Sin3A knockdown in the sciatic nerve or specifically in SCs reduced or delayed the myelination of regenerating axons in a rat crushed sciatic nerve model, while overexpression of Sin3A greatly promoted the remyelination of axons. Further, in vitro experiments revealed that Sin3A silencing inhibited SC migration and differentiation at the promyelination stage and promoted SC proliferation at the immature stage. In addition, SC differentiation and maturation may be regulated by the Sin3A/histone deacetylase2 (HDAC2) complex functionally cooperating with Sox10, as demonstrated by rescue assays. Together, these results complement the recent genome and proteome analyses of SCs during peripheral nerve myelin formation. The results also reveal a key role of Sin3A-dependent chromatin organization in promoting myelinogenic programs and SC differentiation to control peripheral myelination and repair. These findings may inform new treatments for enhancing remyelination and nerve regeneration.

Melatonin Induced Schwann Cell Proliferation and Dedifferentiation Through NF-ĸB, FAK-Dependent but Src-Independent Pathways.

Peripheral nerve injury (PNI) is a common condition that compromises motor and sensory functions. Peripheral nerves are known to have regenerative capability and the pineal hormone, melatonin, is known to aid nerve regeneration. However, the role of Schwann cells and the pathways involved remain unclear. Thus, the aim of this study is to identify the effects of melatonin on Schwann cell proliferation, dedifferentiation, and the involvement of nuclear factor kappa light chain enhancer of activated B cells (NF-ĸB), focal adhesion kinase (FAK) and proto-oncogene tyrosine-protein kinase, Src pathways in this process. Schwann cells was treated with melatonin and its proliferation and dedifferentiation were identified using MTT assay and immunofluorescence staining for SRY (sex determining region Y)-box 2 (SOX2). Next, the protein expressions of NF-ĸB, FAK and Src pathways were identified by Western blot. MTT results confirmed increased proliferation of Schwann cells with melatonin treatment, and it was highest at 10 μM melatonin. Immunofluorescent staining revealed an increase in the green fluorescence staining for SOX2 in melatonin-treated cells, showing enhanced dedifferentiation. Western blot assay revealed melatonin increased phospho-NF-ĸB (PNF-ĸB), IKK-α, FAK (D2R2E), phospho-FAK (Tyr 576/577 and Tyr 397) protein expressions as compared with control. However, Src (32G6), Lyn (C13F9), Fyn, Csk (C74C1) protein expressions were not increased as compared with control. Melatonin promotes Schwann cell proliferation and dedifferentiation via NF-ĸB, FAK-dependent but Src-independent pathways.

Regulation of Schwann Cell and DRG Neurite Behaviors within Decellularized Peripheral Nerve Matrix.

Decellularized nerve hydrogels (dNHs) containing bioactive molecules are promising biomaterials for peripheral nerve injury (PNI) treatment and have been extensively applied in clinical and preclinical practice. However, most previous research projects studied their influences on nerve-related cellular behaviors in two dimensions (2D) without taking hydrogel biomechanics into consideration. The molecular mechanisms underlying the beneficial microenvironment provided by dNHs also remain unclear. In this study, dNHs from rat sciatic nerves were prepared, and their effects on Schwann cell (SC) and dorsal root ganglion (DRG) neurite behaviors were evaluated and compared to commercial rat tail type I collagen (Col) hydrogels in three-dimensional (3D) environments. We found that dNHs could promote SC proliferation and neurite outgrowth, and both the hydrogel mechanics and components contributed to the dNH functionalization. Through proteomics analysis, we found that laminin (LAM) and type V collagen (COLV) exclusively and abundantly existed in dNHs. By adding exogenous LAM and COLV into Col hydrogels, we demonstrated that they regulated SC gene expression and that LAM could promote SC spreading and neurite outgrowth, while COLV improved SC proliferation. Lastly, dNHs were fabricated into paper-like, aligned nerve scaffolds through unidirectional freezing to expand the dNH applications in PNI treatment.