RNA sequencing of exosomes secreted by fibroblast and Schwann cells elucidates mechanisms underlying peripheral nerve regeneration

Exosomes exhibit complex biological functions and mediate a variety of biological processes,such as promoting axonal regeneration and functional recove ry after injury.Long non-coding RNAs(IncRNAs)have been reported to play a crucial role in axonal regeneration.Howeve r,the role of the IncRNA-microRNAmessenger RNA(mRNA)-competitive endogenous RNA(ceRNA)network in exosome-mediated axonal regeneration remains unclear.In this study,we performed RNA transcriptome sequencing analysis to assess mRNA expression patterns in exosomes produced by cultured fibroblasts(FC-EXOs)and Schwann cells(SCEXOs).Diffe rential gene expression analysis,Gene Ontology analysis,Kyoto Encyclopedia of Genes and Genomes analysis,and protein-protein intera ction network analysis were used to explo re the functions and related pathways of RNAs isolated from FC-EXOs and SC-EXOs.We found that the ribosome-related central gene Rps5 was enriched in FC-EXOs and SC-EXOs,which suggests that it may promote axonal regeneration.In addition,using the miRWalk and Starbase prediction databases,we constructed a regulatory network of ceRNAs targeting Rps5,including 27 microRNAs and five IncRNAs.The ceRNA regulatory network,which included Ftx and Miat,revealed that exsosome-derived Rps5 inhibits scar formation and promotes axonal regeneration and functional recovery after nerve injury.Our findings suggest that exosomes derived from fibro blast and Schwann cells could be used to treat injuries of peripheral nervous system.

Gp78 regulates PMP22 and causes ER stress and autophagy in EV71-VP1-overexpressing mouse Schwann cells

Background:During Enterovirus type 71(EV71)infection,the structural viral protein 1(VP1)activates endoplasmic reticulum(ER)stress associated with peripheral myelin protein 22(PMP22)accumulation and induces autophagy.However,the specific mechanism behind this process remains elusive.Methods:In this research,we used the VP1-overexpressing mouse Schwann cells(SCs)models co-transfected with a PMP22 silencing or Autocrine motility factor receptor(AMFR/gp78)overexpressing vector to explore the regulation of gp78 on PMP22 and its relationship with autophagy and apoptosis.Results:The activity of gp78 could be influenced by EV71-VP1,leading to a decrease in the ubiquitination and degradation of PMP22,resulting in PMP22 accumulation in ER.In VP1-overexpressing mouse SCs,all three ER stress sensors,including pancreatic endoplasmic reticulum kinase(PERK),activating transcription factor 6(ATF6)and inositol-requiring enzyme 1(IRE1)and the related downstream signals(C/EBP-homologous protein(CHOP)and Caspase 12)were activated,as well as the ER-resident chaperone Glucose-regulated protein 78(GRP78).In addition,VP1 upregulated the autophagy marker Microtubule-associated protein 1 light chain 3 beta(LC3B),while PMP22 silencing or gp78 overexpression reversed the phenomenon.Meanwhile,PMP22 silencing or gp78 overexpression increased proliferation of EV71-VP1-transfected mouse SCs.Conclusion:Gp78 could regulate PMP22 accumulation through ubiquitination degradation and cause ER stress and autophagy in EV71-VP1-overexpressing mouse SCs.Therefore,the gp78/PMP22/ER stress axis might emerge as a promising therapeutic target for myelin and neuronal damage induced by EV71 infection.

Long noncoding RNA Pvt1 promotes the proliferation and migration of Schwann cells by sponging microRNA-214 and targeting c-Jun following peripheral nerve injury

Research has shown that long-chain noncoding RNAs(lncRNAs) are involved in the regulation of a variety of biological processes, including peripheral nerve regeneration, in part by acting as competing endogenous RNAs. c-Jun plays a key role in the repair of peripheral nerve injury. However, the precise underlying mechanism of c-Jun remains unclear. In this study, we performed microarray and bioinformatics analysis of mouse crush-injured sciatic nerves and found that the lncRNA Pvt1 was overexpressed in Schwann cells after peripheral nerve injury. Mechanistic studies revealed that Pvt1 increased c-Jun expression through sponging miRNA-214. We overexpressed Pvt1 in Schwann cells cultured in vitro and found that the proliferation and migration of Schwann cells were enhanced, and overexpression of miRNA-214 counteracted the effects of Pvt1 overexpression on Schwann cell proliferation and migration. We conducted in vivo analyses and injected Schwann cells overexpressing Pvt1 into injured sciatic nerves of mice. Schwann cells overexpressing Pvt1 enhanced the regeneration of injured sciatic nerves following peripheral nerve injury and the locomotor function of mice was improved. Our findings reveal the role of lncRNAs in the repair of peripheral nerve injury and highlight lncRNA Pvt1 as a novel potential treatment target for peripheral nerve injury.

Artificial nerve graft constructed by coculture of activated Schwann cells and human hair keratin for repair of peripheral nerve defects

Studies have shown that human hair keratin(HHK) has no antigenicity and excellent mechanical properties. Schwann cells, as unique glial cells in the peripheral nervous system, can be induced by interleukin-1β to secrete nerve growth factor, which promotes neural regeneration. Therefore, HHK with Schwann cells may be a more effective approach to repair nerve defects than HHK without Schwann cells. In this study, we established an artificial nerve graft by loading an HHK skeleton with activated Schwann cells. We found that the longitudinal HHK microfilament structure provided adhesion medium, space and direction for Schwann cells, and promoted Schwann cell growth and nerve fiber regeneration. In addition, interleukin-1β not only activates Schwann cells, but also strengthens their activity and increases the expression of nerve growth factors. Activated Schwann cells activate macrophages, and activated macrophages secrete interleukin-1β, which maintains the activity of Schwann cells. Thus, a beneficial cycle forms and promotes nerve repair. Furthermore, our studies have found that the newly constructed artificial nerve graft promotes the improvements in nerve conduction function and motor function in rats with sciatic nerve injury, and increases the expression of nerve injury repair factors fibroblast growth factor 2 and human transforming growth factor B receptor 2. These findings suggest that this artificial nerve graft effectively repairs peripheral nerve injury.

Sequential expression of miR-221-3p and miR-338-3p in Schwann cells as a therapeutic strategy to promote nerve regeneration and functional recovery

The functional properties of endogenous Schwann cells(SCs)during nerve repair are dynamic.Optimizing the functional properties of SCs at different stages of nerve repair may have therapeutic benefit in improving the repair of damaged nerves.Previous studies showed that miR-221-3p promotes the proliferation and migration of SCs,and miR-338-3p promotes the myelination of SCs.In this study,we established rat models of sciatic nerve injury by bridging the transected sciatic nerve with a silicone tube.We injected a miR-221 lentiviral vector system together with a doxycycline-inducible Tet-On miR-338 lentiviral vector system into the cavity of nerve conduits of nerve stumps to sequentially regulate the biological function of endogenous SCs at different stages of nerve regeneration.We found that the biological function of SCs was sequentially regulated,the diameter and density of myelinated axons were increased,the expression levels of NF200 and myelin basic protein were increased,and the function of injured peripheral nerve was improved using this system.miRNA Target Prediction Database prediction,Nanopore whole transcriptome sequencing,quantitative PCR,and dual luciferase reporter gene assay results predicted and verified Cdkn1b and Nrp1 as target genes of miR-221-3p and miR-338-3p,respectively,and their regulatory effects on SCs were confirmed in vitro.In conclusion,here we established a new method to enhance nerve regeneration through sequential regulation of biological functions of endogenous SCs,which establishes a new concept and model for the treatment of peripheral nerve injury.The findings from this study will provide direct guiding significance for clinical treatment of sciatic nerve injury.

Glial cell line-derived neurotrophic factor and brain-derived neurotrophic factor regulate the interaction between astrocytes and Schwann cells at the trigeminal root entry zone

The trigeminal root entry zone is the zone at which the myelination switches from peripheral Schwann cells to central oligodendrocytes.Its special anatomical and physiological structure renders it susceptible to nerve injury.The etiology of most primary trigeminal neuralgia is closely related to microvascular compression of the trigeminal root entry zone.This study aimed to develop an efficient in vitro model mimicking the glial environment of trigeminal root entry zone as a tool to investigate the effects of glial cell line-derived neurotrophic factor and brain-derived neurotrophic factor on the structural and functional integrity of trigeminal root entry zone and modulation of cellular interactions.Primary astrocytes and Schwann cells isolated from trigeminal root entry zone of postnatal rats were inoculated into a two-well silicon culture insert to mimic the trigeminal root entry zone microenvironment and treated with glial cell line-derived neurotrophic factor and brain-derived neurotrophic factor.In monoculture,glial cell line-derived neurotrophic factor promoted the migration of Schwann cells,but it did not have effects on the migration of astrocytes.In the co-culture system,glial cell line-derived neurotrophic factor promoted the bidirectional migration of astrocytes and Schwann cells.Brain-derived neurotrophic factor markedly promoted the activation and migration of astrocytes.However,in the co-culture system,brain-derived neurotrophic factor inhibited the migration of astrocytes and Schwann cells to a certain degree.These findings suggest that glial cell line-derived neurotrophic factor and brain-derived neurotrophic factor are involved in the regulation of the astrocyte-Schwann cell interaction in the co-culture system derived from the trigeminal root entry zone.This system can be used as a cell model to study the mechanism of glial dysregulation associated with trigeminal nerve injury and possible therapeutic interventions.

Induction of Functional Recovery by Co-transplantation of Neural Stem Cells and Schwann Cells in a Rat Spinal Cord Contusion Injury Model

Objective To study the transplantation efficacy of neural stem cells （NSCs） and Schwann cells （SC） in a rat model of spinal cord contusion injury. Methods Multipotent neural stem cells （NSCs） and Schwann cells were harvested from the spinal cords of embryonic rats at 16 days post coitus and sciatic nerves of newborn rats, respectively. The differential characteristics of NSCs in vitro induced by either serum-based culture or co-culture with SC were analyzed by immunofluorescence. NSCs and SCs were co-transplanted into adult rats having undergone spinal cord contusion at T9 level. The animals were weekly monitored using the Basso-Beattie-Bresnahan locomotor rating system to evaluate functional recovery from contusion-induced spinal cord injury. Migration and differentiation of transplanted NSCs were studied in tissue sections using immunohistochemical staining. Results Embryonic spinal cord-derived NSCs differentiated into a large number of oligodendrocytes in serum-based culture upon the withdrawal of mitogens. In cocultures with SCs, NSCs differentiated into neuron more readily. Rats with spinal cord contusion injury which had undergone transplantation of NSCs and SCs into the intraspinal cavity demonstrated a moderate improvement in motor functions. Conclusions SC may contribute to neuronal differentiation of NSCs in vitro and in vivo. Transplantation of NSCs and SCs into the affected area may be a feasible approach to promoting motor recovery in patients after spinal cord injury.

Effects of cotransplantated Schwann cells and neural stem cells in a rat model of Alzheimer's disease

Schwann cells （SCs） are significantly better at promoting neural stem cell （NSCs） proliferation, differentiation and synaptic formation when cocultured with NSCs in vitro, compared with cultured in a single nerve growth factor. The present study transplanted NSCs and SCs into the brain of a rat model of Alzheimer＇s disease to investigate the effect of cotransplantation. Results show transplantation of both NSCs alone and NSCs ＋ SCs significantly promoted learning and memory functions in Alzheimer＇s disease rats, decreased glial fibrillary acidic protein and calcium binding protein S100β expression, but increased expression of the cholinergic neuron marker choline acetyl transferase mRNA. The effect of NSCs ＋ SCs cotransplantation was, however, more significant. NSCs and SCs cotransplantation significantly reduced the number of astrocytes and increased cholinergic neurons, facilitating the recovery of learning and memory function, compared with NSCs transplantation alone.

Platelet-rich plasma gel in combination with Schwann cells for repair of sciatic nerve injury

Bone marrow mesenchymal stem cells were isolated from New Zealand white rabbits, culture-expanded and differentiated into Schwann cell-like cells. Autologous platelet-dch plasma and Schwann cell-like cells were mixed in suspension at a density of 1 x 106 cells/mL, prior to introduction into a poly （lactic-co-glycolic acid） conduit. Fabricated tissue-engineered nerves were implanted into rabbits to bridge 10 mm sciatic nerve defects （platelet-rich plasma group）. Controls were established using fibrin as the seeding matrix for Schwann cell-like cells at identical density to construct tissue-engineered nerves （fibrin group）. Twelve weeks after implantation, toluidine blue staining and scanning electron microscopy were used to demonstrate an increase in the number of regenerating nerve fibers and thickness of the myelin sheath in the platelet-rich plasma group compared with the fibrin group. Fluoro-gold retrograde labeling revealed that the number of Fluoro-gold-positive neurons in the dorsal root ganglion and the spinal cord anterior horn was greater in the platelet-rich plasma group than in the fibrin group. Electrophysiological examination confirmed that compound muscle action potential and nerve conduction velocity were superior in the platelet-rich plasma group compared with the fibrin group. These results indicate that autologous platelet-rich plasma gel can effectively serve as a seeding matrix for Schwann cell-like cells to construct tissue-engineered nerves to promote perJpheral nerve regeneration.

Mild hypothermia combined with a scaffold of Ng Rsilenced neural stem cells/Schwann cells to treat spinal cord injury

Because the inhibition of Nogo proteins can promote neurite growth and nerve cell differentiation, a cell-scaffold complex seeded with Nogo receptor （NgR）-silenced neural stem cells and Schwann cells may be able to improve the microenvironment for spinal cord injury repair. Previous studies have found that mild hypothermia helps to attenuate secondary damage in the spinal cord and exerts a neuroprotective effect. Here, we constructed a cell-scaffold complex consisting of a poly（D,L-lactide-co-glycolic acid） （PLGA） scaffold seeded with NgR-silenced neural stem cells and Schwann cells, and determined the effects of mild hypothermia combined with the cell-scaffold complexes on the spinal cord hemi-transection injury in the T9 segment in rats. Compared with the PLGA group and the NgR-silencing cells ＋ PLGA group, hindlimb motor function and nerve electrophysiological function were dearly improved, pathological changes in the injured spinal cord were attenuated, and the number of surviving cells and nerve fibers were increased in the group treated with the NgR-silenced cell scaffold ＋ mild hypothermia at 34℃ for 6 hours. Furthermore, fewer pathological changes to the injured spinal cord and more surviving cells and nerve fibers were found after mild hypothermia therapy than in injuries not treated with mild hypothermia. These experimental results indicate that mild hypothermia combined with NgR gene-silenced cells in a PLGA scaffold may be an effective therapy for treating spinal cord injury.

miR-21 promotes the differentiation of hair folliclederived neural crest stem cells into Schwann cells

Hair follicle-derived neural crest stem cells can be induced to differentiate into Schwann cells in vivo and in vitro. However, the underlying regulatory mechanism during cell differentiation remains poorly understood. This study isolated neural crest stem cells from human hair folli-cles and induced them to differentiate into Schwann cells. Quantitative RT-PCR showed that microRNA （miR）-21 expression was gradually increased during the differentiation of neural crest stem cells into Schwann cells. After transfection with the miR-21 agonist （agomir-21）, the differentiation capacity of neural crest stem cells was enhanced. By contrast, after transfection with the miR-21 antagonist （antagomir-21）, the differentiation capacity was attenuated. Further study results showed that SOX-2 was an effective target of miR-21. Without compromising SOX2 mRNA expression, miR-21 can down-regulate SOX protein expression by binding to the 3′-UTR of miR-21 mRNA. Knocking out the SOX2 gene from the neural crest stem cells significantly reversed the antagomir-21 inhibition of neural crest stem cells differentiating into Schwann cells. The results suggest that miR-21 expression was increased during the differentiation of neural crest stem cells into Schwann cells and miR-21 promoted the differentiation through down-regu-lating SOX protein expression by binding to the 3′-UTR of SOX2 mRNA.

Synaptic development in the injured spinal cord cavity following co-transplantation of fetal spinal cord cells and autologous activated Schwann cells

Transplantation of activated transgenic Schwann cells or a fetal spinal cord cell suspension has been widely used to treat spinal cord injury. However, little is known regarding the effects of co-transplantation. In the present study, autologous Schwann cells in combination with a fetal spinal cord cell suspension were transplanted into adult Wistar rats with spinal cord injury, and newly generated axonal connections were observed ultrastructurally. Transmission electron microscopic observations showed that the neuroblast first presented cytoplasmic processes, followed by pre- and postsynaptic membranes with low electron density forming a dense projection. The number and types of synaptic vesicles were increased. Synaptic connections developed from single cell body-dendritic synapses into multiple cell body-dendritic and dendrite-dendritic synapses. In addition, the cell organs of the transplanted neuroblast, oligodendroblast and astroblast matured gradually. The blood-brain barrier appeared subsequently. Moreover, neurofilament, histamine, calcitonin-gene-related peptides, and glial fibrillary acidic protein positive fibers were observed in the transplant region. These findings demonstrate that fetal spinal cord cells in the presence of autologous activated Schwann cells can develop into mature synapses in the cavity of injured spinal cords, suggesting the possibility of information exchange through the reconstructed synapse between fetal spinal cord cells and the host.

Transplantation of human telomerase reverse transcriptase gene-transfected Schwann cells for repairing spinal cord injury

Transfection of the human telomerase reverse transcriptase（h TERT）gene has been shown to increase cell proliferation and enhance tissue repair.In the present study,h TERT was transfected into rat Schwann cells.A rat model of acute spinal cord injury was established by the modified free-falling method.Retrovirus PLXSN was injected at the site of spinal cord injury as a vector to mediate h TERT gene-transfected Schwann cells（1×10^（10）/L;10μL）or Schwann cells（1×10^（10）/L;10μL）without h TERT gene transfection.Between 1 and 4 weeks after model establishment,motor function of the lower limb improved in the h TERT-transfected group compared with the group with non-transfected Schwann cells.Terminal deoxynucleotidyl transferase-mediated d UTP nick-end labeling and reverse transcription-polymerase chain reaction results revealed that the number of apoptotic cells,and gene expression of aquaporin 4/9 and matrix metalloproteinase 9/2decreased at the site of injury in both groups;however,the effect improved in the h TERT-transfected group compared with the Schwann cells without h TERT transfection group.Hematoxylin and eosin staining,PKH26 fluorescent labeling,and electrophysiological testing demonstrated that compared with the non-transfected group,spinal cord cavity and motor and sensory evoked potential latencies were reduced,while the number of PKH26-positive cells and the motor and sensory evoked potential amplitude increased at the site of injury in the h TERT-transfected group.These findings suggest that transplantation of h TERT gene-transfected Schwann cells repairs the structure and function of the injured spinal cord.

Dorsal root ganglion-derived Schwann cells combined with poly(lactic-co-glycolic acid)/chitosan conduits for the repair of sciatic nerve defects in rats

Schwann cells, nerve regeneration promoters in peripheral nerve tissue engineering, can be used to repair both the peripheral and central nervous systems. However, isolation and puriifcation of Schwann cells are complicated by contamination with ifbroblasts. Current reported measures are mainly limited by either high cost or complicated procedures with low cell yields or purity. In this study, we collected dorsal root ganglia from neonatal rats from which we obtained highly puriifed Schwann cells using serum-free melanocyte culture medium. The purity of Schwann cells （〉95%） using our method was higher than that using standard medium containing fetal bovine serum. The obtained Schwann cells were implanted into poly（lactic-co-glycolic acid）/chi-tosan conduits to repair 10-mm sciatic nerve defects in rats. Results showed that axonal diameter and area were signiifcantly increased and motor functions were obviously improved in the rat sciatic nerve tissue. Experimental ifndings suggest that serum-free melanocyte culture medium is conducive to purify Schwann cells and poly（lactic-co-glycolic acid）/chitosan nerve conduits combined with Schwann cells contribute to restore sciatic nerve defects.

Schwann cells differentiated from skin-derived precursors provide neuroprotection via autophagy inhibition in a cellular model of Parkinson’s disease

Autophagy has been shown to play an important role in Parkinson’s disease.We hypothesized that skin-derived precursor cells exhibit neuroprotective effects in Parkinson’s disease through affecting autophagy.In this study,6-hydroxydopamine-damaged SH-SY5Y cells were pretreated with a culture medium containing skin-derived precursors differentiated into Schwann cells(SKP-SCs).The results showed that the SKP-SC culture medium remarkably enhanced the activity of SH-SY5Y cells damaged by 6-hydroxydopamine,reduced excessive autophagy,increased tyrosine hydroxylase expression,reducedα-synuclein expression,reduced the autophagosome number,and activated the PI3K/AKT/mTOR pathway.Autophagy activator rapamycin inhibited the effects of SKP-SCs,and autophagy inhibitor 3-methyladenine had the opposite effect.These findings confirm that SKP-SCs modulate the PI3K/AKT/mTOR pathway to inhibit autophagy,thereby exhibiting a neuroprotective effect in a cellular model of Parkinson’s disease.This study was approved by the Animal Ethics Committee of Laboratory Animal Center of Nantong University(approval No.S20181009-205)on October 9,2018.

Pannexin 1,a large-pore membrane channel,contributes to hypotonicity-induced ATP release in Schwann cells

Pannexin 1(Panx 1),as a large-pore membrane channel,is highly permeable to ATP and other signaling molecules.Previous studies have demonstrated the expression of Panx 1 in the nervous system,including astrocytes,microglia,and neurons.However,the distribution and function of Panx 1 in the peripheral nervous system are not clear.Blocking the function of Panx 1 pharmacologically(carbenoxolone and probenecid)or with small interfering RNA targeting pannexins can greatly reduce hypotonicity-induced ATP release.Treatment of Schwann cells with a Ras homolog family member(Rho)GTPase inhibitor and small interfering RNA targeting Rho or cytoskeleton disrupting agents,such as nocodazole or cytochalasin D,revealed that hypotonicity-induced ATP release depended on intracellular RhoA and the cytoskeleton.These findings suggest that Panx 1 participates in ATP release in Schwann cells by regulating RhoA and the cytoskeleton arrangement.This study was approved by the Animal Ethics Committee of Nantong University,China(No.S20180806-002)on August 5,2018.

Co-transplantation of Schwann cells and bone marrow stromal cells versus single cell transplantation on repairing hemisected spinal cord injury of rats

BACKGROUND： Bone marrow stromal cells （BMSCs） or Schwann cells （SCs） transplantation alone can treat spinal cord injury. However, the transplantation either cell-type alone has disadvantages. The co-transplantation of both cells may benefit structural reconstruction and functional recovery of spinal nerves. OBJECTIVE： To verify spinal cord repair and related mechanisms after co-transplantation of BMSCs and SCs in a rat model of hemisected spinal cord injury. DESIGN, TIME AND SETTING： A randomized, controlled, animal experiment was performed at the Department of Histology and Embryology, Mudanjiang Medical College from January 2008 to May 2009. MATERIALS： Rabbit anti-S-100, glial fibrillary acidic protein, neuron specific enolase and neurofilament-200 monoclonal antibodies were purchased from Sigma, USA. METHODS： A total of 100 Wistar rats were used in a model of hemisected spinal cord injury. The rats were randomly assigned to vehicle control, SCs transplantation, BMSCs transplantation, and co-transplantation groups; 25 rats per group. At 1 week after modeling, SCs or BMSCs cultured in vitro were labeled and injected separately into the hemisected spinal segment of SCs and BMSCs transplantation groups through three injection points [5 μL （1 x 107 cells/mL）] cell suspension in each point）. In addition, a 15 μL 1 × 10^7 cells/mL SCs suspension and a 15 μL 1 × 10^7 cells/mL BMSC suspension were injected into co-transplantation group by the above method. MAIN OUTCOME MEASURES： The Basso-Beattie-Bresnahan （BBB） locomotor rating scale and somatosensory evoked potential （SEP） tests were used to assess the functional recovery of rat hind limbs following operation. Structural repair of injured nerve tissue was observed by light microscopy, electron microscopy, immunohistochemistry, and magnetic resonance imaging （MRI）. In vivo differentiation, survival and migration of BMSCs were evaluated by immunofluorescence. RESULTS： BBB scores were significantly greater in all three transplantation groups compared with vehicle control group 8 weeks after transplantation. In particular, the co-transplantation group displayed the highest scores among the groups （P 〈 0.05）. Moreover, recovery of SEP latency and amplitude was observed in all the transplantation groups, particularly after 8 weeks. Again, the co-transplantation group exhibited the greatest improvement （P 〈 0.05）. In the co-transplantation group, imaging showed a smooth surface and intact inner structure at the injury site, with no scar formation, and a large number of orderly cells at the injured site. Axonal regeneration, new myelination, and a large amount of cell division were detected in the co-transplantation group by electron microscopy. Neuron specific enolase （NSE）- and glial fibriilary acidic protein （GFAP）-positive cells were observed in the spinal cord sections 1 week following co-transplantation by immunofluorescence staining. CONCLUSION： Co-transplantation of SCs and BMSCs effectively promoted functional recovery of injured spinal cord in rats compared with SCs or BMSCs transplantation alone. This repair effect is probably achieved because of neuronal-like cells derived from BMSCs to supplement dead neurons in vivo.

Macrophage polarization in nerve injury： do Schwann cells play a role？

In response to peripheral nerve injury, the inflammatory response is almost entirely comprised of infiltrating macrophages. Macrophages are a highly plastic, heterogenic immune cell, playing an indispensable role in peripheral nerve injury, clearing debris and regulating the microenvironment to allow for efficient regeneration. There are several cells within the microenvironment that likely interact with macrophages to support their function – most notably the Schwann cell, the glial cell of the peripheral nervous system. Schwann cells express several ligands that are known to interact with receptors expressed by macrophages, yet the effects of Schwann cells in regulating macrophage phenotype remains largely unexplored. This review discusses macrophages in peripheral nerve injury and how Schwann cells may regulate their behavior.

Synergistic Effect of Schwann Cells and Retinoic Acid on Differentiation and Synaptogenesis of Hippocampal Neural Stem Cells in vitro

Objective To investigate the synergistic effect of Schwann cells （SCs） and retinoic acid （R.A） on differentiation and synaptogenesis of neural stem cells （NSCs） derived from hippocampus of neonatal rats. Methods The classical method for 2×2 factorial analysis experiment was used to assess synergistic action of SCs and RA. NSCs were treated with R.A, SCs, and SCs ＋ RA in DMEM/F12 with 0.5% fetal bovine serum for six days, respectively. Double immunofluorescent staining was used to detect the differentiation of NSCs including nestin, glial fibrillary acidic protein （GFAP） and Map2. The expression of PSD95 was used to demonstrate synaptogenesis. Results After NSCs were treated with RA or SCs, the expression of nestin and GFAP was significantly decreased while the expression of Map2 and PSD95 was significantly increased in comparison with the control. Factorial ANOVA showed that interactions between SCs and RA could induce the expression of Map2 and PSD95. Conclusion SCs and RA could promote synergistically the neuronal differentiation and synaptogenesis of hippocampal neural stem cells in vitro while they decreased the astrocytes and nestin positive NSCs.

Role of endogenous Schwann cells in tissue repair after spinal cord injury

Schwann cells are glial cells of peripheral nervous system, responsible for axonal myelination and ensheathing, as well as tissue repair following a peripheral nervous system injury. They are one of several cell types that are widely studied and most commonly used for cell transplantation to treat spinal cord injury, due to their intrinsic characteristics including the ability to secrete a variety of neurotrophic factors. This mini review summarizes the recent findings of endogenous Schwann cells after spinal cord injury and discusses their role in tissue repair and axonal regeneration. After spinal cord injury, numerous endogenous Schwann cells migrate into the lesion site from the nerve roots, involving in the construction of newly formed repaired tissue and axonal myelination. These invading Schwann cells also can move a long distance away from the injury site both rostrally and caudally. In addition, Schwann cells can be induced to migrate by minimal insults （such as scar ablation） within the spinal cord and integrate with astrocytes under certain circumstances. More importantly, the host Schwann cells can be induced to migrate into spinal cord by transplantation of different cell types, such as exogenous Schwann cells, olfactory ensheathing cells, and bone marrow-derived stromal stem cells. Migration of endogenous Schwann cells following spinal cord injury is a common natural phenomenon found both in animal and human, and the myelination by Schwann cells has been examined effective in signal conduction electrophysiologically. Therefore, if the inherent properties of endogenous Schwann cells could be developed and utilized, it would offer a new avenue for the restoration of injured spinal cord.