Transplanted neuronal progenitor cells in a peripheral nerve gap promote nerve repair

Regenerative Strategies in Treatment of Peripheral Nerve Injuries in Different Animal Models

BACKGROUND

Peripheral nerve damage mainly resulted from traumatic or infectious causes; the main signs of a damaged nerve are the loss of sensory and/or motor functions. The injured nerve has limited regenerative capacity and is recovered by the body itself, the recovery process depends on the severity of damage to the nerve, nowadays the use of stem cells is one of the new and advanced methods for treatment of these problems.

METHOD

Following our review, data are collected from different databases "Google scholar, Springer, Elsevier, Egyptian Knowledge Bank, and PubMed" using different keywords such as Peripheral nerve damage, Radial Nerve, Sciatic Nerve, Animals, Nerve regeneration, and Stem cell to investigate the different methods taken in consideration for regeneration of PNI.

RESULT

This review contains tables illustrating all forms and types of regenerative medicine used in treatment of peripheral nerve injuries (PNI) including different types of stem cells " adipose-derived stem cells, bone marrow stem cells, Human umbilical cord stem cells, embryonic stem cells" and their effect on re-constitution and functional recovery of the damaged nerve which evaluated by physical, histological, Immuno-histochemical, biochemical evaluation, and the review illuminated the best regenerative strategies help in rapid peripheral nerve regeneration in different animal models included horse, dog, cat, sheep, monkey, pig, mice and rat.

CONCLUSION

Old surgical attempts such as neurorrhaphy, autogenic nerve transplantation, and Schwann cell implantation have a limited power of recovery in cases of large nerve defects. Stem cell therapy including mesenchymal stromal cells has a high potential differentiation capacity to renew and form a new nerve and also restore its function.

Mesenchymal Stem Cells in Nerve Tissue Engineering: Bridging Nerve Gap Injuries in Large Animals

Cell-therapy-based nerve repair strategies hold great promise. In the field, there is an extensive amount of evidence for better regenerative outcomes when using tissue-engineered nerve grafts for bridging severe gap injuries. Although a massive number of studies have been performed using rodents, only a limited number involving nerve injury models of large animals were reported. Nerve injury models mirroring the human nerve size and injury complexity are crucial to direct the further clinical development of advanced therapeutic interventions. Thus, there is a great need for the advancement of research using large animals, which will closely reflect human nerve repair outcomes. Within this context, this review highlights various stem cell-based nerve repair strategies involving large animal models such as pigs, rabbits, dogs, and monkeys, with an emphasis on the limitations and strengths of therapeutic strategy and outcome measurements. Finally, future directions in the field of nerve repair are discussed. Thus, the present review provides valuable knowledge, as well as the current state of information and insights into nerve repair strategies using cell therapies in large animals.

Endometrium Derived Stem Cells as Potential Candidates in Nervous System Repair

Limited cell division and lack of endogenous repair mechanisms in the central nervous system, hampers tissue repair following neurodegenerative diseases or tissue injuries. Unlike central nervous system; peripheral nervous system has some capacity to repair after injury, but in case of critical sized defects the use of supporting cells in the neural guidance channels seems inevitable to obtain a satisfactory functional recovery. Stem cell therapies have provided new frontiers in the repair of nervous system largely through paracrine secretion mechanisms. The therapeutic potential of stem cells differs according to their tissue of origin, mode of isolation, administration route, and passage number. During the past decades, studies have been focused on stem cells harvested from disposable tissues such as menstrual blood or biopsies from endometrium. These cells are characterized by their high differentiation and proliferation potential, ease of harvest, and lack of ethical concerns. In the current review, we will discuss the prospects and challenges of endometrial stem cells' application in nervous system repair.

Transplanted neural lineage cells derived from dental pulp stem cells promote peripheral nerve regeneration

Cell therapy for peripheral nerve injury is a promising strategy as regenerative medicine that restores neurological function. However, challenges remain in producing suitable and sufficient amounts of autologous cells for promoting nerve regeneration. This study aimed to identify the characteristics of neural lineage cells (NLCs) differentiated from dental pulp stem cells (DPSCs) and reveal their effect on functional recovery and nerve regeneration after cell transplantation into an immunodeficient rat using a nerve guide conduit. Here we report a protocol of neural induction in monolayer culture and characterize NLCs in vitro. Furthermore, NLCs were transplanted into an immunodeficient rat model with a 10-mm sciatic nerve defect, and cell survival and differentiation were investigated in vivo. Outcomes of nerve regeneration were also assessed using the remyelinated axon numbers, myelin sheath thickness, electrophysiological activities, and gastrocnemius muscle mass. NLCs comprised neuronal, astrocyte, oligodendrocyte, and neural crest lineage cells. NLCs enhanced the activities of endothelial cells, Schwann cells, and neurons in a paracrine-dependent manner in vitro. At 2 weeks post-transplantation, numerous transplanted NLCs differentiated into platelet-derived growth factor receptor alpha (PDGFRα) + oligodendrocyte progenitor cells (OPCs) and a few PDGFRα + /p75 neurotrophin receptor + Schwann cell-like cells derived from OPCs were observed. At 12 weeks post-transplantation, human Schwann cell-like cells survived, and axon growth, remyelination, electrophysiological activities, and muscle atrophy were improved. This study demonstrates the broad application of our protocol of neural induction of DPSCs and portrays the efficacy of transplantation of NLCs derived from human DPSCs as a promising strategy for peripheral nerve regeneration.

Tissue-engineered nerve guides with mesenchymal stem cells in the facial nerve regeneration

Nerve guides with mesenchymal stem cells have been investigated in the rat facial nerve defect model to promote peripheral nerve regeneration and shorten recovery time to improve patients' quality of life. A 7-mm facial nerve gap experimental rat model is frequently employed in facial nerve regeneration studies. Facial nerve regeneration with nerve guides is evaluated by (1) assessing myelinated fiber counts using toluidine blue staining, (2) immunohistological analysis, (3) determining the g-ratio (axon diameter/total outer diameter) of regenerated nerve on transmission electron microscopic images, (4) retrograde nerve tracing in the facial nucleus, (5) electrophysiological evaluations using compound muscle action potential, and (6) functional evaluations using rat facial palsy scores. Dental pulp and adipose-derived stem cells, easily harvested using a minimally invasive procedure, possess characteristics of mesenchymal tissue lineages and can differentiate into Schwann-like cells. Cultured dental pulp-derived cells can produce neurotrophic factors, including nerve growth factor, brain-derived neurotrophic factor, and glial cell line-derived neurotrophic factor. These neurotrophic factors promote peripheral nerve regeneration and afford protection against facial motor neuron death. Moreover, artificial nerve guides can maneuver axonal regrowth, and dental pulp-derived cells and adipose-derived Schwann cells may supply neurotrophic factors, promoting axonal regeneration. In the present review, the authors discuss facial nerve regeneration using nerve guides with mesenchymal stem cells.

Minimally Invasive Injection to the Phrenic Nerve in a Porcine Hemidiaphragmatic Paralysis Model: A Pilot Study

BACKGROUND

Neurodegenerative diseases and spinal cord injury can affect respiratory function often through motor neuron loss innervating the diaphragm. To reinnervate this muscle, new motor neurons could be transplanted into the phrenic nerve (PN), allowing them to extend axons to the diaphragm. These neurons could then be driven by an optogenetics approach to regulate breathing. This type of approach has already been demonstrated in the peripheral nerves of mice. However, there is no established thoracoscopic approach to PN injection. Also, there is currently a lack of preclinical large animal models of diaphragmatic dysfunction in order to evaluate the efficacy of potential treatments.

OBJECTIVE

To evaluate the feasibility of thoracoscopic drug delivery into the PN and to assess the viability of hemidiaphragmatic paralysis in a porcine model.

METHODS

Two Landrace farm pigs underwent a novel procedure for thoracoscopic PN injections, including 1 nonsurvival and 1 survival surgery. Nonsurvival surgery involved bilateral PN injections and ligation. Survival surgery included a right PN injection and transection proximal to the injection site to induce hemidiaphragmatic paralysis.

RESULTS

PN injections were successfully performed in both procedures. The animal that underwent survival surgery recovered postoperatively with an established right hemidiaphragmatic paralysis. Over the 5-d postoperative period, the animal displayed stable vital signs and oxygenation saturation on room air with voluntary breathing.

CONCLUSION

Thoracoscopic targeting of the porcine PN is a feasible approach to administer therapeutic agents. A swine model of hemidiaphragmatic paralysis induced by unilateral PN ligation or transection may be potentially used to study diaphragmatic reinnervation following delivery of therapeutics.

Tissue Engineering and Regenerative Medicine in Craniofacial Reconstruction and Facial Aesthetics

The craniofacial region is anatomically complex and is of critical functional and cosmetic importance, making reconstruction challenging. The limitations of current surgical options highlight the importance of developing new strategies to restore the form, function, and esthetics of missing or damaged soft tissue and skeletal tissue in the face and cranium. Regenerative medicine (RM) is an expanding field which combines the principles of tissue engineering (TE) and self-healing in the regeneration of cells, tissues, and organs, to restore their impaired function. RM offers many advantages over current treatments as tissue can be engineered for specific defects, using an unlimited supply of bioengineered resources, and does not require immunosuppression. In the craniofacial region, TE and RM are being increasingly used in preclinical and clinical studies to reconstruct bone, cartilage, soft tissue, nerves, and blood vessels. This review outlines the current progress that has been made toward the engineering of these tissues for craniofacial reconstruction and facial esthetics.

Regenerative Effects and Development Patterns of Solid Neural Tissue Grafts Located in Gelatin Hydrogel Conduit for Treatment of Peripheral Nerve Injury

Supplemental Digital Content is available in the text.

Background:

The regeneration of the peripheral nerves after injuries is still a challenging fundamental and clinical problem. The cell therapy and nerve guide conduit construction are promising modern approaches. Nowadays, different sources of cells for transplantation are available. But it is little known about the interaction between fetal central nervous system cells and peripheral nerve tissue. In this study, we analyzed the development of the fetal neocortex and spinal cord solid grafts injected into the gelatin hydrogel conduits and their effects on sciatic nerve regeneration after cut injury.

Methods:

Frontal neocortex tissue was obtained from E19.5 and spinal cord tissue was obtained from E14.5 fetuses harvested from transgenic EGFP mice. The grafts were injected into the hydrogel conduits which were connected to the nerve stumps after cut injury. The recovery of motor function was estimated with walking track analysis at 2, 5, and 8 weeks after surgery. Then immunohistochemical study was performed.

Results:

The histological examination showed that only fetal neocortex solid graft cells had survived after implantation. Immunostaining revealed that some of the transplanted cells expressed neural markers such as neurofilament protein and NeuN. But the cells mostly differentiated in glial lineage, which was confirmed with immunostaining for GFAP and S100β. The walking-track analysis has shown that 8 weeks after surgery bioengineered conduit differed significantly from the control.

Conclusions:

We revealed that the hydrogel conduit is suitable for nerve re-growth and that the fetal neocortex grafted cells can survive and differentiate. Bioengineered conduit can stimulate functional recovery after the nerve injury.

Adult tissue-derived neural crest-like stem cells: Sources, regulatory networks, and translational potential

Neural crest (NC) cells are a multipotent stem cell population that give rise to a diverse array of cell types in the body, including peripheral neurons, Schwann cells (SC), craniofacial cartilage and bone, smooth muscle cells, and melanocytes. NC formation and differentiation into specific lineages takes place in response to a set of highly regulated signaling and transcriptional events within the neural plate border. Premigratory NC cells initially are contained within the dorsal neural tube from which they subsequently emigrate, migrating to often distant sites in the periphery. Following their migration and differentiation, some NC‐like cells persist in adult tissues in a nascent multipotent state, making them potential candidates for autologous cell therapy. This review discusses the gene regulatory network responsible for NC development and maintenance of multipotency. We summarize the genes and signaling pathways that have been implicated in the differentiation of a postmigratory NC into mature myelinating SC. We elaborate on the signals and transcription factors involved in the acquisition of immature SC fate, axonal sorting of unmyelinated neuronal axons, and finally the path toward mature myelinating SC, which envelope axons within myelin sheaths, facilitating electrical signal propagation. The gene regulatory events guiding development of SC in vivo provides insights into means for differentiating NC‐like cells from adult human tissues into functional SC, which have the potential to provide autologous cell sources for the treatment of demyelinating and neurodegenerative disorders.

In Vivo Survival of Mesenchymal Stromal Cell-Enhanced Decellularized Nerve Grafts for Segmental Peripheral Nerve Reconstruction

PURPOSE

Adipose-derived mesenchymal stromal cells (MSCs) have emerged as promising tools for peripheral nerve reconstruction. There is a paucity of information regarding the ultimate survivorship of implanted MSCs or whether these cells remain where they are placed. The aim of the present study was to track the in vivo distribution and survival of MSCs seeded on a decellularized nerve allograft reconstruction of a peripheral nerve defect using luciferase-based bioluminescence imaging (BLI).

METHODS

To determine the in vivo survivability of MSCs, autologous Lewis rat MSCs were stably labeled with luciferase by lentiviral particles. Labeled cells were dynamically seeded onto a Sprague Dawley decellularized rat nerve allograft and used to bridge a 10-mm sciatic nerve defect. The MSC survival was determined by performing in vivo BLI to detect living cells. Twelve animals were examined at 24 hours after implantation, 3, 7, 9, 11, and 14 days, and at daily intervals thereafter if signals were still present.

RESULTS

Labeled MSCs could be detected for up to 29 days. Gradually diminishing BLI signals were observed within the first week following implantation. Implanted MSCs were not detected anywhere other than the site of surgery.

CONCLUSIONS

The MSCs seeded on decellularized nerve allografts can survive in vivo but have finite survival after implantation. There was no evidence of migration of MSCs to surrounding tissues.

CLINICAL RELEVANCE

The findings support a therapeutic approach that combines MSCs with a biological scaffold for peripheral nerve surgery. It provides understanding of the viability and distribution of implanted MSCs, which is a prerequisite before clinical translation can be considered.

Transplantation effects of dental pulp-derived cells on peripheral nerve regeneration in crushed sciatic nerve injury

The effects of transplanted human dental pulp-derived cells (DPCs) on peripheral nerve regeneration were studied in a rat model of sciatic nerve crush injury. In one group, DPCs were transplanted into the compression site (cell transplantation group); the control group underwent no transplantation (crushed group). Sciatic nerve regeneration was determined based on the recovery of motor function and histological and immunohistochemical analyses. The cell transplantation group showed improved motor function compared with the crushed group using the CatWalk XT system, which corresponded to a higher ratio of tibialis to anterior muscle weight 14 days after surgery. Histological analysis revealed a smaller interspace area and few vacuoles in the sciatic nerve after cell transplantation compared with the crushed group. The myelin sheath was visualized with Luxol Fast Blue (LFB) staining and anti-myelin basic protein (anti-MBP) antibody labeling; the percentages of LFB- and MBP-positive areas were higher in the cell transplantation group than in the crushed group. Human mitochondria-positive cells were also identified in the sciatic nerve at the transplantation site 14 days after surgery. Taken together, the observed correlation between morphological findings and functional outcomes following DPC transplantation indicates that DPCs promote peripheral nerve regeneration in rats.

Adipose-Derived Mesenchymal Stem Cells Applied in Fibrin Glue Stimulate Peripheral Nerve Regeneration

Mesenchymal stem cells (MSCs) hold a great promise for cell therapy. To date, they represent one of the best choices for the treatment of post-traumatic injuries of the peripheral nervous system. Although autologous can be easily transplanted in the injured area, clinical advances in this filed have been impaired by lack of preservation of graft cells into the injury area after transplantation. Indeed, cell viability is not retained after injection into the blood stream, and cells injected directly into the area of injury either are washed off or inhibit regeneration through scar formation and neuroma development. This study proposes a new way of MSCs delivery to the area of traumatic injury by using fibrin glue, which not only fixes cells at the site of application but also provides extracellular matrix support. Using a sciatic nerve injury model, MSC derived from adipose tissue embedded in fibrin glue were able to enter the nerve and migrate mainly retrogradely after transplantation. They also demonstrated a neuroprotective effect on DRG L5 sensory neurons and stimulated axon growth and myelination. Post-traumatic changes of the sensory neuron phenotype were also improved. Importantly, MSCs stimulated nerve angiogenesis and motor function recovery. Therefore, our data suggest that MSC therapy using fibrin glue is a safe and efficient method of cell transplantation in cases of sciatic nerve injury, and that this method of delivery of regeneration stimulants could be beneficial for the successful treatment of other central and peripheral nervous system conditions.

Adipose-derived stem cells and the stromal vascular fraction in polyglycolic acid-collagen nerve conduits promote rat facial nerve regeneration

Adipose-derived stem cells (ADSCs) and the stromal vascular fraction (SVF) promote nerve regeneration. Biodegradable nerve conduits are used to treat peripheral nerve injuries, but their efficiencies are lower than those of autologous nerve grafts. This study developed biodegradable nerve conduits containing ADSCs and SVF and evaluated their facial nerve regenerating abilities in a rat model with a 7-mm nerve defect. SVF and ADSCs were individually poured into nerve conduits with polyglycolic acid-type I collagen as a scaffold (ADSCs and SVF groups). The conduits were grafted on to the nerve defects. As the control, the defect was bridged with polyglycolic acid-collagen nerve conduits without cells. At 13 weeks, after transplantation, the regenerated nerves were evaluated physiologically and histologically. The compound muscle action potential of the SVF group was significantly higher in amplitude than that of the control group. Electron microscopy showed that the axon diameter of the SVF group was the largest, followed by the ADSC group and control group with significant differences among them. The SVF group had the largest fiber diameter, followed by the ADSC group and control group with significant differences among them. The ADSC group had the highest myelin thickness, followed by the SVF group and control group with significant differences among them. Identical excellent promoting effects on nerve regeneration were observed in both the ADSC and SVF groups. Using SVF in conduits was more practical than using ADSCs because only the enzymatic process was required to prepare SVF, indicating that SVF could be more suitable to induce nerve regeneration.

Matrices, scaffolds & carriers for cell delivery in nerve regeneration

Nerve injuries can be life-long debilitating traumas that severely impact patients' quality of life. While many acellular neural scaffolds have been developed to aid the process of nerve regeneration, complete functional recovery is still very difficult to achieve, especially for long-gap peripheral nerve injury and most cases of spinal cord injury. Cell-based therapies have shown many promising results for improving nerve regeneration. With recent advances in neural tissue engineering, the integration of biomaterial scaffolds and cell transplantation are emerging as a more promising approach to enhance nerve regeneration. This review provides an overview of important considerations for designing cell-carrier biomaterial scaffolds. It also discusses current biomaterials used for scaffolds that provide permissive and instructive microenvironments for improved cell transplantation.

Vascularization of the Damaged Nerve under the Effect of Experimental Cell Therapy

Quantitative analysis of blood vessels in the distal segment of rat sciatic nerve after its ligation for 40 sec and subperineurial administration of mesenchymal stem cells or dissociated cells of rat embryonic spinal cord was carried our by immunohistochemical tracing of von Willebrand factor, a marker of endothelial cells of blood vessels. It was found that the number of blood vessels per unit area of the nerve trunk in 21 days after injury and administration of mesenchymal stem cells increased by more than 1.5 times in comparison with the control (damaged nerve). After administration of dissociated cells of the embryonic spinal cord, this effect was not observed. It is assumed that mesenchymal stem cells stimulate the growth of vessels of the damaged nerve via production of angiogenic factors.

Transplantation of a Peripheral Nerve with Neural Stem Cells Plus Lithium Chloride Injection Promote the Recovery of Rat Spinal Cord Injury

Transplantation of neural stem cells (NSCs) holds great potential for the treatment of spinal cord injury (SCI). However, transplanted NSCs poorly survive in the SCI environment. We injected NSCs into tibial nerve and transplanted tibial nerve into a hemisected spinal cord and investigated the effects of lithium chloride (LiCl) on the survival of spinal neurons, axonal regeneration, and functional recovery. Our results show that most of the transplanted NSCs expressed glial fibrillary acidic protein, while there was no obvious expression of nestin, neuronal nuclei, or acetyltransferase found in NSCs. LiCl treatment produced less macrosialin (ED1) expression and axonal degeneration in tibial nerve after NSC injection. Our results also show that a regimen of LiCl treatment promoted NSC differentiation into NF200-positive neurons with neurite extension into the host spinal cord. The combination of tibial nerve transplantation with NSCs and LiCl injection resulted in more host motoneurons surviving in the spinal cord, more regenerated axons in tibial nerve, less glial scar area, and decreased ED1 expression. We conclude that lithium may have therapeutic potential in cell replacement strategies for central nervous system injury due to its ability to promote survival and neuronal generation of grafted NSCs and reduced host immune reaction.

Bioabsorbable nerve conduits coated with induced pluripotent stem cell-derived neurospheres enhance axonal regeneration in sciatic nerve defects in aged mice

Aging influences peripheral nerve regeneration. Nevertheless, most basic research of bioabsorbable nerve conduits including commercial products have been performed in very young animals. Results from these studies may not provide information about axonal regeneration in aged tissue, because young nerve tissue holds sufficient endogenous potential for axonal regeneration. The clinical target age for nerve conduit application is most likely going to increase with a rapidly growing elderly population. In the present study, we examined axonal regeneration after sciatic nerve defects in aged and young mice. 5-mm sciatic nerve defects in young (6 weeks old) and aged (92 weeks old) mice were reconstructed using nerve conduits (composed of a poly lactide and caprolactone) or autografts. In addition, in aged mice, sciatic nerve defects were reconstructed using nerve conduits coated with mouse induced pluripotent stem cell (iPSc)-derived neurospheres. Using electrophysiological and histological techniques, we demonstrated axonal regeneration was significantly less effective in aged than in young mice both for nerve conduits and for nerve autografts. However, despite the low regenerative capacity of the peripheral nerve in aged mice, axonal regeneration significantly increased when nerve conduits coated with iPSc-derived neurospheres, rather than nerve conduits alone, were used. The present study shows that aging negatively affects peripheral nerve regeneration based on nerve conduits in mice. However, axonal regeneration using nerve conduits was improved when supportive iPSc-derived neurospheres were added in the aged mice. We propose that tissue-engineered bioabsorbable nerve conduits in combination with iPSc-derived neurospheres hold therapeutic potential both in young and elderly patients. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1752-1758, 2018.

Capacity of Human Dental Follicle Cells to Differentiate into Neural Cells In Vitro

The dental follicle is an ectomesenchymal tissue surrounding the developing tooth germ. Human dental follicle cells (hDFCs) have the capacity to commit to differentiation into multiple cell types. Here we investigated the capacity of hDFCs to differentiate into neural cells and the efficiency of a two-step strategy involving floating neurosphere-like bodies for neural differentiation. Undifferentiated hDFCs showed a spindle-like morphology and were positive for neural markers such as nestin, β-III-tubulin, and S100β. The cellular morphology of several cells was neuronal-like including branched dendrite-like processes and neurites. Next, hDFCs were used for neurosphere formation in serum-free medium containing basic fibroblast growth factor, epidermal growth factor, and B27 supplement. The number of cells with neuronal-like morphology and that were strongly positive for neural markers increased with sphere formation. Gene expression of neural markers also increased in hDFCs with sphere formation. Next, gene expression of neural markers was examined in hDFCs during neuronal differentiation after sphere formation. Expression of Musashi-1 and Musashi-2, MAP2, GFAP, MBP, and SOX10 was upregulated in hDFCs undergoing neuronal differentiation via neurospheres, whereas expression of nestin and β-III-tubulin was downregulated. In conclusion, hDFCs may be another optimal source of neural/glial cells for cell-based therapies to treat neurological diseases.

Advances in Nerve Guidance Conduit-Based Therapeutics for Peripheral Nerve Repair

Peripheral nerve injuries have high incidence rates, limited treatment options and poor clinical outcomes, rendering a significant socioeconomic burden. For effective peripheral nerve repair, the gap or site of injury must be structurally bridged to promote correct reinnervation and functional regeneration. However, effective repair becomes progressively more difficult with larger gaps. Autologous nerve grafting remains the best clinical option for the repair of large gaps (20-80 mm) despite being associated with numerous limitations including permanent donor site morbidity, a lack of available tissue and the formation of neuromas. To meet the clinical demand of large gap repair and overcome these limitations, tissue engineering has led to the development of nerve guidance conduit-based therapeutics. This review focuses on the advances of nerve guidance conduit-based therapeutics in terms of their structural properties including biomimetic composition, permeability, architecture, and surface modifications. Associated biochemical properties, pertaining to the incorporation of cells and neurotrophic factors, are also reviewed. After reviewing the progress in the field, we conclude by presenting an outlook on their clinical translatability and the next generation of therapeutics.

Poly(l-lysine) modified zein nanofibrous membranes as efficient scaffold for adhesion, proliferation, and differentiation of neural stem cells

Cell viability, adhesion, proliferation, and differentiation of neural stem cells (NSCs) on zein nanofibrous membranes could be improved by poly(l-lysine) modification.

Scaffoldless tissue-engineered nerve conduit promotes peripheral nerve regeneration and functional recovery after tibial nerve injury in rats

Damage to peripheral nerve tissue may cause loss of function in both the nerve and the targeted muscles it innervates. This study compared the repair capability of engineered nerve conduit (ENC), engineered fibroblast conduit (EFC), and autograft in a 10-mm tibial nerve gap. ENCs were fabricated utilizing primary fibroblasts and the nerve cells of rats on embryonic day 15 (E15). EFCs were fabricated utilizing primary fibroblasts only. Following a 12-week recovery, nerve repair was assessed by measuring contractile properties in the medial gastrocnemius muscle, distal motor nerve conduction velocity in the lateral gastrocnemius, and histology of muscle and nerve. The autografts, ENCs and EFCs reestablished 96%, 87% and 84% of native distal motor nerve conduction velocity in the lateral gastrocnemius, 100%, 44% and 44% of native specific force of medical gastrocnemius, and 63%, 61% and 67% of native medial gastrocnemius mass, respectively. Histology of the repaired nerve revealed large axons in the autograft, larger but fewer axons in the ENC repair, and many smaller axons in the EFC repair. Muscle histology revealed similar muscle fiber cross-sectional areas among autograft, ENC and EFC repairs. In conclusion, both ENCs and EFCs promoted nerve regeneration in a 10-mm tibial nerve gap repair, suggesting that the E15 rat nerve cells may not be necessary for nerve regeneration, and EFC alone can suffice for peripheral nerve injury repair.

Roles of neural stem cells in the repair of peripheral nerve injury

Currently, researchers are using neural stem cell transplantation to promote regeneration after peripheral nerve injury, as neural stem cells play an important role in peripheral nerve injury repair. This article reviews recent research progress of the role of neural stem cells in the repair of peripheral nerve injury. Neural stem cells can not only differentiate into neurons, astrocytes and oligodendrocytes, but can also differentiate into Schwann-like cells, which promote neurite outgrowth around the injury. Transplanted neural stem cells can differentiate into motor neurons that innervate muscles and promote the recovery of neurological function. To promote the repair of peripheral nerve injury, neural stem cells secrete various neurotrophic factors, including brain-derived neurotrophic factor, fibroblast growth factor, nerve growth factor, insulin-like growth factor and hepatocyte growth factor. In addition, neural stem cells also promote regeneration of the axonal myelin sheath, angiogenesis, and immune regulation. It can be concluded that neural stem cells promote the repair of peripheral nerve injury through a variety of ways.

Approaches to Peripheral Nerve Repair: Generations of Biomaterial Conduits Yielding to Replacing Autologous Nerve Grafts in Craniomaxillofacial Surgery

Peripheral nerve injury is a common clinical entity, which may arise due to traumatic, tumorous, or even iatrogenic injury in craniomaxillofacial surgery. Despite advances in biomaterials and techniques over the past several decades, reconstruction of nerve gaps remains a challenge. Autografts are the gold standard for nerve reconstruction. Using autografts, there is donor site morbidity, subsequent sensory deficit, and potential for neuroma development and infection. Moreover, the need for a second surgical site and limited availability of donor nerves remain a challenge. Thus, increasing efforts have been directed to develop artificial nerve guidance conduits (ANCs) as new methods to replace autografts in the future. Various synthetic conduit materials have been tested in vitro and in vivo, and several first- and second-generation conduits are FDA approved and available for purchase, while third-generation conduits still remain in experimental stages. This paper reviews the current treatment options, summarizes the published literature, and assesses future prospects for the repair of peripheral nerve injury in craniomaxillofacial surgery with a particular focus on facial nerve regeneration.

Regeneration of rat corpora cavernosa tissue by transplantation of CD133+ cells derived from human bone marrow and placement of biodegradable gel sponge sheet

The objective is to develop an easier technique for regenerating corpora cavernosa tissue through transplantation of human bone marrow-derived CD133 + cells into a rat corpora cavernosa defect model. We excised 2 mm × 2 mm squares of the right corpora cavernosa of twenty-three 8-week-old male nude rats. Alginate gel sponge sheets supplemented with 1 × 10 4 CD133 + cells were then placed over the excised area of nine rats. Functional and histological evaluations were carried out 8 weeks later. The mean intracavernous pressure/mean arterial pressure ratio for the nine rats (0.34258 ± 0.0831) was significantly higher than that for eight rats with only the excision (0.0580 ± 0.0831, P = 0.0238) and similar to that for five rats for which the penis was exposed, and there was no excision (0.37228 ± 0.1051, P = 0.8266). Immunohistochemical analysis revealed that the nine fully treated rats had venous sinus-like structures and quantitative reverse transcription polymerase chain reaction analysis of extracts from their alginate gel sponge sheets revealed that the amounts of mRNA encoding the nerve growth factor (NGF), and vascular endothelial growth factor (VEGF) were significantly higher than those for rats treated with alginate gel sheets without cell supplementation (NGF: P = 0.0309; VEGF: P < 0.0001). These findings show that transplantation of CD133 + cells accelerates functional and histological recovery in the corpora cavernosa defect model.

A Silk Fibroin/Collagen Nerve Scaffold Seeded with a Co-Culture of Schwann Cells and Adipose-Derived Stem Cells for Sciatic Nerve Regeneration

As a promising alternative to autologous nerve grafts, tissue-engineered nerve grafts have been extensively studied as a way to bridge peripheral nerve defects and guide nerve regeneration. The main difference between autogenous nerve grafts and tissue-engineered nerve grafts is the regenerative microenvironment formed by the grafts. If an appropriate regenerative microenvironment is provided, the repair of a peripheral nerve is feasible. In this study, to mimic the body's natural regenerative microenvironment closely, we co-cultured Schwann cells (SCs) and adipose-derived stem cells (ADSCs) as seed cells and introduced them into a silk fibroin (SF)/collagen scaffold to construct a tissue-engineered nerve conduit (TENC). Twelve weeks after the three different grafts (plain SF/collagen scaffold, TENC, and autograft) were transplanted to bridge 1-cm long sciatic nerve defects in rats, a series of electrophysiological examinations and morphological analyses were performed to evaluate the effect of the tissue-engineered nerve grafts on peripheral nerve regeneration. The regenerative outcomes showed that the effect of treatment with TENCs was similar to that with autologous nerve grafts but superior to that with plain SF/collagen scaffolds. Meanwhile, no experimental animals had inflammation around the grafts. Based on this evidence, our findings suggest that the TENC we developed could improve the regenerative microenvironment and accelerate nerve regeneration compared to plain SF/collagen and may serve as a promising strategy for peripheral nerve repair.

Histological Study of Bone Marrow and Umbilical Cord Stromal Cell Transplantation in Regenerating Rat Peripheral Nerve

Objective

Bone marrow and umbilical cord stromal cells are multipotential stem cells that have the ability to produce growth factors that play an important role in survival and generation of axons. The goal of this study was to evaluate the effects of the two different mesenchymal stem cells on peripheral nerve regeneration.

Materials and Methods

In this experimental study, a 10 mm segment of the left sciatic nerve of male Wistar rats (250-300 g) was removed with a silicone tube interposed into this nerve gap. Bone marrow stromal cells (BMSCs) and human umbilical cord stromal cells (HUCSCs) were respectively obtained from rat and human. The cells were sepa- rately cultured and transplanted into the nerve gap. The sciatic nerve regeneration was evaluated by immunohistochemistry, and light and electron microscopy. Moreover, histo- morphology of the gastrocnemius muscle was observed.

Results

The nerve regeneration in the BMSCs and HUCSCs groups that had received the stem cells was significantly more favorable than the control group. In addition, the BM- SCs group was significantly more favorable than the HUCSCs group (P<0.05).

Conclusion

The results of this study suggest that both homograft BMSCs and het- erograft HUCSCs may have the potential to regenerate peripheral nerve injury and transplantation of BMSCs may be more effective than HUCSCs in rat.

Pluripotent stem cells for Schwann cell engineering

Tissue engineering of Schwann cells (SCs) can serve a number of purposes, such as in vitro SC-related disease modeling, treatment of peripheral nerve diseases or peripheral nerve injury, and, potentially, treatment of CNS diseases. SCs can be generated from autologous stem cells in vitro by recapitulating the various stages of in vivo neural crest formation and SC differentiation. In this review, we survey the cellular and molecular mechanisms underlying these in vivo processes. We then focus on the current in vitro strategies for generating SCs from two sources of pluripotent stem cells, namely embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs). Different methods for SC engineering from ESCs and iPSCs are reviewed and suggestions are proposed for optimizing the existing protocols. Potential safety issues regarding the clinical application of iPSC-derived SCs are discussed as well. Lastly, we will address future aspects of SC engineering.

Differentiation of Cholinergic Neurons in Rat Spinal Cord Under Conditions of Allotransplantation into a Peripheral Nerve and In Situ Development

The method of ectopic transplantation of embryonic anlages of CNS allows studying histoblastic potencies of progenitor cells developing under conditions of changed microenvironment. Some progenitor cells in the transplants of rat embryonic spinal cord retained their ability to express choline acetyltransferase after transplantation into the sciatic nerve of adult animals. Comparative analysis of cholinergic neurons in the neurotransplants and neurons formed in rat spinal cord during normal ontogeny showed that choline acetyltransferase-positive cells after transplantation into the nerve reached morphological differentiation of motor neurons at later terms than cells developing in situ. They were scattered one by one and did not form nuclear nerve centers. We did not fi nd structures similar to presynaptic cholinergic buds typical of intact spinal cord near these cells throughout the observation period. Solitary cholinergic neurons survived in the transplants for 19 months.

Dental pulp stem cells as a multifaceted tool for bioengineering and the regeneration of craniomaxillofacial tissues

Dental pulp stem cells, or DPSC, are neural crest-derived cells with an outstanding capacity to differentiate along multiple cell lineages of interest for cell therapy. In particular, highly efficient osteo/dentinogenic differentiation of DPSC can be achieved using simple in vitro protocols, making these cells a very attractive and promising tool for the future treatment of dental and periodontal diseases. Among craniomaxillofacial organs, the tooth and salivary gland are two such cases in which complete regeneration by tissue engineering using DPSC appears to be possible, as research over the last decade has made substantial progress in experimental models of partial or total regeneration of both organs, by cell recombination technology. Moreover, DPSC seem to be a particularly good choice for the regeneration of nerve tissues, including injured or transected cranial nerves. In this context, the oral cavity appears to be an excellent testing ground for new regenerative therapies using DPSC. However, many issues and challenges need yet to be addressed before these cells can be employed in clinical therapy. In this review, we point out some important aspects on the biology of DPSC with regard to their use for the reconstruction of different craniomaxillofacial tissues and organs, with special emphasis on cranial bones, nerves, teeth, and salivary glands. We suggest new ideas and strategies to fully exploit the capacities of DPSC for bioengineering of the aforementioned tissues.

Evaluation of biodegradable polymer conduits--poly(L-lactic acid)--for guiding sciatic nerve regeneration in mice

Polymeric biomaterials are often used for stimulating nerve regeneration. Among different conduits, poly(lactide acid) - PLA polymer is considered to be a good substrate due to its biocompatibility and resorbable characteristics. This polymer is an aliphatic polyester which has been mostly used in biomedical application. It is an organic compound with low allergenic potential, low toxicity, high biocompatibility and predictable kinetics of degradation. In this study we fabricated and evaluated a PLA microporous hollow fiber as a conduit for its ability to bridge a nerve gap in a mouse sciatic nerve injury model. The PLA conduit was prepared from a polymer solution, throughout extrusion technique. The left sciatic nerve of C57BL/6 mouse was transected and the nerve stumps were placed into a resorbable PLA (PLA group) or a PCL conduit (PCL group), n=5 each group. We have also used another group in which the nerves were repaired by autograft (autograft group, n=5). Motor function was analyzed according to sciatic functional index (SFI). After 56days, the regenerated nerves were processed for light and electron microscopy and morphometric analyses were performed. A quantitative analysis of regenerated nerves showed significant increase in the number of myelinated fibers and blood vessels in animals that received PLA conduit. The PLA group exhibited better overall tissue organization compared to other groups. Presenting well-organized bundles, many regenerating clusters composed of preserved nerve fibers surrounded by layers of compacted perineurium-like cells. Also the SFI revealed a significant improvement in functional recovery. This work suggests that PLA conduits are suitable substrate for cell survival and it provides an effective strategy to be used to support axonal growth becoming a potential alternative to autograft.

Effect of an Epineurial-Like Biohybrid Nerve Conduit on Nerve Regeneration

A novel approach of making a biomimetic nerve conduit was established by seeding adipose-derived adult stem cells (ADSCs) on the external wall of porous poly(d,l-lactic acid) (PLA) nerve conduits. The PLA conduits were fabricated using gas foaming salt and solvent-nonsolvent phase conversion. We examined the effect of two different porous structures (GS and GL) on ADSC growth and proliferation. The GS conduits had better structural stability, permeability, and porosity, as well as better cell viability at 4, 7, and 10 days. The epineurial-like tissue was grown from ADSC-seeded conduits cultured for 7 days in vitro and then implanted into 10-mm rat sciatic nerve defects for evaluation. The regeneration capacity and functional recovery were evaluated by histological staining, electrophysiology, walking track, and functional gait analysis after 6 weeks of implantation. Experimental data indicated that the autograft and ADSC-seeded GS conduits had better functional recovery than the blank conduits and ADSC-seeded GL conduits. The area of regenerated nerve and number of myelinated axons quantified based on the histology also indicated that the autograft and AGS groups performed better than the other two groups. We suggested that ADSCs may interact with endogenous Schwann cells and release neurotrophic factors to promote peripheral nerve regeneration. The design of the conduit may be critical for producing a biohybrid nerve conduit and to provide an epineurial-like support.

Recent advances in stem cell-mediated peripheral nerve repair

A major advance in the field of peripheral nerve repair has been the advent of stem and progenitor cell use to supplement the regenerative environment in animal models of nerve injury. As Schwann cell replacements, stem cells may be even better suited to promoting regeneration in these scenarios. We review the recent literature detailing the search for the definitive Schwann cell replacement cell, including a look at genetic modification of transplanted cells for nerve injury repair.

Electrophysiologic and functional evaluations of regenerated facial nerve defects with a tube containing dental pulp cells in rats

BACKGROUND

Dental pulp tissue contains Schwann and neural progenitor cells. Tissue-engineered nerve conduits with dental pulp cells promote facial nerve regeneration in rats. However, no nerve functional or electrophysiologic evaluations were performed. This study investigated the compound muscle action potential recordings and facial functional analysis of dental pulp cell regenerated nerve in rats.

METHODS

A silicone tube containing rat dental pulp cells in type I collagen gel was transplanted into a 7-mm gap of the buccal branch of the facial nerve in Lewis rats; the same defect was created in the marginal mandibular branch, which was ligatured. Compound muscle action potential recordings of vibrissal muscles and facial functional analysis with facial palsy score of the nerve were performed.

RESULTS

Tubulation with dental pulp cells showed significantly lower facial palsy scores than the autograft group between 3 and 10 weeks postoperatively. However, the dental pulp cell facial palsy scores showed no significant difference from those of autograft after 11 weeks. Amplitude and duration of compound muscle action potentials in the dental pulp cell group showed no significant difference from those of the intact and autograft groups, and there was no significant difference in the latency of compound muscle action potentials between the groups at 13 weeks postoperatively. However, the latency in the dental pulp cell group was prolonged more than that of the intact group.

CONCLUSION

Tubulation with dental pulp cells could recover facial nerve defects functionally and electrophysiologically, and the recovery became comparable to that of nerve autografting in rats.

Augmenting peripheral nerve regeneration using stem cells: A review of current opinion

Outcomes following peripheral nerve injury remain frustratingly poor. The reasons for this are multifactorial, although maintaining a growth permissive environment in the distal nerve stump following repair is arguably the most important. The optimal environment for axonal regeneration relies on the synthesis and release of many biochemical mediators that are temporally and spatially regulated with a high level of incompletely understood complexity. The Schwann cell (SC) has emerged as a key player in this process. Prolonged periods of distal nerve stump denervation, characteristic of large gaps and proximal injuries, have been associated with a reduction in SC number and ability to support regenerating axons. Cell based therapy offers a potential therapy for the improvement of outcomes following peripheral nerve reconstruction. Stem cells have the potential to increase the number of SCs and prolong their ability to support regeneration. They may also have the ability to rescue and replenish populations of chromatolytic and apoptotic neurons following axotomy. Finally, they can be used in non-physiologic ways to preserve injured tissues such as denervated muscle while neuronal ingrowth has not yet occurred. Aside from stem cell type, careful consideration must be given to differentiation status, how stem cells are supported following transplantation and how they will be delivered to the site of injury. It is the aim of this article to review current opinions on the strategies of stem cell based therapy for the augmentation of peripheral nerve regeneration.

Effect of allotransplants containing dissociated cells of rat embryonic spinal cord on nerve fiber regeneration in a recipient

Regeneration of nerve fibers in rat sciatic nerve was quantitatively assessed after injury (ligation) and injection of dissociated cells derived from embryonic spinal cord. A suspension of dissociated spinal cord cells from rat embryos was transplanted under the perineurium of a nerve trunk. After transplantation, bromodeoxyuridine-labeled precursor cells survived and retained the label for more than 2 months; some of these cells differentiated into NeuNpositive neurons. Analysis of semithin sections of the distal nerve segment from the recipient taken at a distance of 0.5 cm from the site of injury showed that transplantation of dissociated cells of embryonic spinal cord led to an increase in the number of myelinated nerve fibers in the recipient nerve.

Human periodontal ligament stem cells repair mental nerve injury

Human periodontal ligament stem cells are easily accessible and can differentiate into Schwann cells. We hypothesized that human periodontal ligament stem cells can be used as an alternative source for the autologous Schwann cells in promoting the regeneration of injured peripheral nerve. To validate this hypothesis, human periodontal ligament stem cells (1 × 10⁶) were injected into the crush-injured left mental nerve in rats. Simultaneously, autologous Schwann cells (1 × 10⁶) and PBS were also injected as controls. Real-time reverse transcriptase polymerase chain reaction showed that at 5 days after injection, mRNA expression of low affinity nerve growth factor receptor was significantaly increased in the left trigeminal ganglion of rats with mental nerve injury. Sensory tests, histomorphometric evaluation and retrograde labeling demonstrated that at 2 and 4 weeks after injection, sensory function was significantly improved, the numbers of retrograde labeled sensory neurons and myelinated axons were significantly increased, and human periodontal ligament stem cells and autologous Schwann cells exhibited similar therapeutic effects. These findings suggest that transplantation of human periodontal ligament stem cells show a potential value in repair of mental nerve injury.

Carriers in cell-based therapies for neurological disorders

There is a pressing need for long-term neuroprotective and neuroregenerative therapies to promote full function recovery of injuries in the human nervous system resulting from trauma, stroke or degenerative diseases. Although cell-based therapies are promising in supporting repair and regeneration, direct introduction to the injury site is plagued by problems such as low transplanted cell survival rate, limited graft integration, immunorejection, and tumor formation. Neural tissue engineering offers an integrative and multifaceted approach to tackle these complex neurological disorders. Synergistic therapeutic effects can be obtained from combining customized biomaterial scaffolds with cell-based therapies. Current scaffold-facilitated cell transplantation strategies aim to achieve structural and functional rescue via offering a three-dimensional permissive and instructive environment for sustainable neuroactive factor production for prolonged periods and/or cell replacement at the target site. In this review, we intend to highlight important considerations in biomaterial selection and to review major biodegradable or non-biodegradable scaffolds used for cell transplantation to the central and peripheral nervous system in preclinical and clinical trials. Expanded knowledge in biomaterial properties and their prolonged interaction with transplanted and host cells have greatly expanded the possibilities for designing suitable carrier systems and the potential of cell therapies in the nervous system.

Undifferentiated and differentiated adipose-derived stem cells improve nerve regeneration in a rat model of facial nerve defect

Autologous nerve grafting is the current procedure used for repairing facial nerve gaps. As an alternative to this method, tissue engineering cell-based therapy using induced pluripotent stem cells, Schwann cells and bone marrow-derived mesenchymal stem cells has been proposed. However, these cells have major problems, including tumorigenesis in induced pluripotent stem cells and invasiveness and limited tissue associated with harvesting for the other cells. Here, we investigated the therapeutic potential of adipose-derived stem cells (ASCs), which can be harvested easily and repeatedly by a minimally invasive liposuction procedure. The ASCs had characteristics of mesenchymal tissue lineages and could differentiate into Schwann-like cells that were relatively simple to isolate and expand in culture. In an in vivo study, a silicone conduit containing undifferentiated ASCs, differentiated ASCs or Schwann cells were transplanted, embedded in a collagen gel and the efficacy of repair of a 7 mm-gap in the rat facial nerve examined. Morphometric quantification analysis of regenerated facial nerves after a regeneration period of 13 weeks showed that undifferentiated ASCs, differentiated ASCs, and Schwann cells had similar potential for nerve regeneration. Furthermore, the functional recovery of facial nerve regeneration using a rat facial palsy scoring system in the three groups was close to that in autologous nerve graft positive controls. These findings suggest that undifferentiated and differentiated ASCs may both have therapeutic potential in facial nerve regeneration as a source of Schwann cells in cell-based therapy performed as an alternative to autologous nerve grafts. Copyright © 2014 John Wiley & Sons, Ltd.

Sciatic nerve regeneration induced by transplantation of in vitro bone marrow stromal cells into an inside-out artery graft in rat

Traumatic injury to peripheral nerves results in considerable motor and sensory disability. Several research groups have tried to improve the regeneration of traumatized nerves by invention of favorable microsurgery. Effect of undifferentiated bone marrow stromal cells (BMSCs) combined with artery graft on peripheral nerve regeneration was studied using a rat sciatic nerve regeneration model. A 10-mm sciatic nerve defect was bridged using an artery graft (IOAG) filled with undifferentiated BMSCs (2 × 10(7) cells/mL). In control group, the graft was filled with phosphated buffer saline alone. The regenerated fibers were studied 4, 8 and 12 weeks after surgery. Assessment of nerve regeneration was based on behavioral, functional (Walking Track Analysis), electrophysiological, histomorphometric and immuohistochemical (Schwann cell detection by S-100 expression) criteria. The behavioral, functional and electrophysiological studies confirmed significant recovery of regenerated axons in IOAG/BMSC group (P < 0.05). Quantitative morphometric analyses of regenerated fibers showed the number and diameter of myelinated fibers in IOAG/BMSC group were significantly higher than in the control group (P < 0.05). This demonstrates the potential of using undifferentiated BMSCs combined with artery graft in peripheral nerve regeneration without limitations of donor-site morbidity associated with isolation of Schwann cells. It is also cost saving due to reduction in interval from tissue collection until cell injection, simplicity of laboratory procedures compared to differentiated BMSCs and may have clinical implications for the surgical management of patients after facial nerve transection.

Nestin-expressing stem cells from the hair follicle can differentiate into motor neurons and reduce muscle atrophy after transplantation to injured nerves

We have previously shown that nestin-expressing hair follicle stem cells from the mouse and human are multipotent and can differentiate into many cell types, including neurons and glial cells. The nestin-expressing hair follicle stem cells can effect nerve and spinal cord repair upon transplantation in mouse models. In the present study, nestin-expressing hair follicle stem cells expressing red fluorescent protein (RFP) were induced by retinoic acid and fetal bovine serum to differentiate and then transplanted together with Matrigel into the transected distal sciatic or tibial nerve stump of transgenic nude mice ubiquitously expressing green fluorescent protein (GFP). Control mice were transplanted with Matrigel only. The transplanted cells appeared neuron like, with large round nuclei and long extensions. Immunofluorescence staining showed that some of the transplanted cells in the distal nerve stump expressed the neuron marker Tuj1 as well as motor neuron markers Isl 1/2 and EN1. These transplanted cells contacted each other as well as host nerve fibers. Two weeks post-transplantation, nerve fibers in the distal sciatic nerve stump of the transplanted mice had greater expression of motor neuron markers and neurotrophic factor-3 than those in the Matrigel-only transplanted mice. Muscle fiber areas in the nestin-expressing stem cell plus Matrigel-transplanted animals were much bigger than that in the Matrigel-only transplanted animals after 4 weeks. The present results suggest that transplanted nestin-expressing hair follicle stem cells can differentiate into motor neurons and reduce muscle atrophy after sciatic nerve transection. This study demonstrates a new and accessible neuron source to reduce muscle atrophy after nerve injury.

The role of neural precursor cells and self assembling peptides in nerve regeneration

OBJECTIVE

Cranial nerve injury involves loss of central neural cells in the brain stem and surrounding support matrix, leading to severe functional impairment. Therapeutically targeting cellular replacement and enhancing structural support may promote neural regeneration. We examined the combinatorial effect of neural precursor cells (NPC) and self assembling peptide (SAP) administration on nerve regeneration.

METHODS

Nerve injury was induced by clip compression of the rodent spinal cord. SAPs were injected immediately into the injured cord and NPCs at 2 weeks post-injury. Behavioral analysis was done weekly and rats were sacrificed at 11 weeks post injury. LFB-H&E staining was done on cord tissue to assess cavitation volume. Motor evoked potentials (MEP) were measured at week 11 to assess nerve conduction and Kaplan Meier curves were created to compare survival estimates.

RESULTS

NPCs and SAPs were distributed both caudal and rostral to the injury site. Behavioral analysis showed that SAP + NPC transplantation significantly improved locomotor score p <0.03) and enhanced survival (log rank test, p = 0.008) compared to control. SAP + NPC treatment also improved nerve conduction velocity (p = 0.008) but did not affect cavitation volume (p = 0.73).

CONCLUSION

Combinatorial NPC and SAP injection into injured nerve tissue may enhance neural repair and regeneration.

Schwann cells differentiated from adipose‑derived stem cells for the treatment of brain contusion

Rapid development of tissue engineering techniques has led to the possibility of treating central nervous injuries with Schwann cells (SCs). However, certain characteristics of SCs, such as a low proliferation ability, greatly restrict their use. The aim of the present study was to investigate whether SCs differentiated from adipose‑derived stem cells (ADSC‑SCs) could used to promote functional recovery in brain contusion in rat. ADSCs were isolated and expanded from the groin of Sprague‑Dawley rats and differentiated into SCs. The ADSC‑SCs were transplanted into the contused rat brain and the locomotor function of the rats was assessed. Significant locomotor function recovery was observed in hemiparalyzed rats treated with ADSCs‑SCs. In conclusion, transplantation of ADSC‑SCs significantly promoted functional recovery following brain contusion.