Biological conduits combining bone marrow mesenchymal stem cells and extracellular matrix to treat long-segment sciatic nerve defects

Bone marrow mesenchymal stem cells in treatment of peripheral nerve injury

Peripheral nerve injury (PNI) is a common neurological disorder and complete functional recovery is difficult to achieve. In recent years, bone marrow mesenchymal stem cells (BMSCs) have emerged as ideal seed cells for PNI treatment due to their strong differentiation potential and autologous transplantation ability. This review aims to summarize the molecular mechanisms by which BMSCs mediate nerve repair in PNI. The key mechanisms discussed include the differentiation of BMSCs into multiple types of nerve cells to promote repair of nerve injury. BMSCs also create a microenvironment suitable for neuronal survival and regeneration through the secretion of neurotrophic factors, extracellular matrix molecules, and adhesion molecules. Additionally, BMSCs release pro-angiogenic factors to promote the formation of new blood vessels. They modulate cytokine expression and regulate macrophage polarization, leading to immunomodulation. Furthermore, BMSCs synthesize and release proteins related to myelin sheath formation and axonal regeneration, thereby promoting neuronal repair and regeneration. Moreover, this review explores methods of applying BMSCs in PNI treatment, including direct cell transplantation into the injured neural tissue, implantation of BMSCs into nerve conduits providing support, and the application of genetically modified BMSCs, among others. These findings confirm the potential of BMSCs in treating PNI. However, with the development of this field, it is crucial to address issues related to BMSC therapy, including establishing standards for extracting, identifying, and cultivating BMSCs, as well as selecting application methods for BMSCs in PNI such as direct transplantation, tissue engineering, and genetic engineering. Addressing these issues will help translate current preclinical research results into clinical practice, providing new and effective treatment strategies for patients with PNI.

Mesenchymal stem cells derived from bone marrow and adipose tissue for repairing acute sciatic nerve injury in a rabbit model

Peripheral nerve injury is one of the common disabling clinical conditions and around 50% of the cases end up in permanent impairment. Due to the lack of effective treatment options regenerative medicine employing stem cells is being evaluated. The presented study evaluated and compared regeneration potential of mesenchymal stem cells (MSCs) derived from bone marrow (BM) and adipose tissue (AD) in acute rabbit sciatic nerve injury (axonotmesis) model. A total of n = 54 grey giant rabbits were made subject of the study and divided equally into 3 groups: Control, BM-MSCs in Collagen I and AD-MSCs in Collagen I as per the treatment given. Iliac crest BM and omental AD was harvested from the same donor for isolation and culture of MSCs. The repair of sciatic nerve injury was evaluated on days 60 and 90. The clinical and histopathological scores and SEM morphology was better in cell treated groups as compared to the control. Morphology and histological studies revealed injured nerve in different levels of regenerative process. Gene expression was more than double for N-Cadherin in cell treated groups as compared to the control, especially at day 60. Between cell treated groups, BM-MSCs group showed better response as compared to the AD-MSCs, although statistically non-significant (p > 0.05). Incomplete nerve regeneration observed under various diagnostic parameters was in compliance to the incomplete clinical recovery at day 90. It was concluded that MSCs may improve sciatic nerve healing but fall short of complete regeneration at day 90, although BM-MSCs may have an edge over AD-MSCs.

A sciatic nerve gap-injury model in the rabbit

There has been an increased number of studies of nerve transection injuries with the sciatic nerve gap-injury model in the rabbit in the past 2 years. We wanted to define in greater detail what is needed to test artificial nerve guides in a sciatic nerve gap-injury model in the rabbit. We hope that this will help investigators to fully exploit the robust translational potential of the rabbit sciatic nerve gap-injury model in its capacity to test devices whose diameter and length are in the range of those commonly applied in hand and wrist surgery (diameter ranging between 2 and 4 mm; length up to 30 mm). We suggest that the rabbit model should replace the less translational rat model in nerve regeneration research. The rabbit sciatic model, however, requires an effective strategy to prevent and control self-mutilation of the foot in the postoperative period, and to prevent pressure ulcers.

A Rabbit Model for Peripheral Nerve Reconstruction Studies Avoiding Automutilation Behavior

Background  The rabbit sciatic nerve injury model may represent a valuable alternative for critical gap distance seen in humans but often leads to automutilation. In this study, we modified the complete sciatic nerve injury model for avoiding autophagy.

Materials and Methods  In 20 adult female New Zealand White rabbits, instead of transecting the complete sciatic nerve, we unilaterally transected the tibial portion and preserved the peroneal portion. Thereby loss of sensation in the dorsal aspect of the paw was avoided. The tibial portion was repaired in a reversed autograft approach in a length of 2.6 cm. In an alternative repair approach, a gap of 2.6 cm in length was repaired with a chitosan-based nerve guide.

Results  During the 6-month follow-up period, there were no incidents of autotomy. Nerve regeneration of the tibial portion of the sciatic nerve was evaluated histologically and morphometrically. A clear difference between the distal segments of the healthy contralateral and the repaired tibial portion of the sciatic nerve was detectable, validating the model.

Conclusion  By transecting the isolated tibial portion of the rabbit sciatic nerve and leaving the peroneal portion intact, it was possible to eliminate automutilation behavior.

Stem Cell Therapy Enhances Motor Activity of Triceps Surae Muscle in Mice with Hereditary Peripheral Neuropathy

Impaired motor and sensory functions are the main features of Charcot-Marie-Tooth disease. Mesenchymal stem cell (MSCs) therapy is one of the possible treatments for this disease. It was assumed that MSCs therapy can improve the contractile properties of the triceps surae (TS) muscles in mice with hereditary peripheral neuropathy. Murine adipose-derived mesenchymal stromal cells (AD-MSCs) were obtained for transplantation into TS muscles of FVB-C-Tg(GFPU)5Nagy/J mice. Three months after AD-MSCs transplantation, animals were subjected to electrophysiological investigations. Parameters of TS muscle tension after intermittent high frequency electrical sciatic nerve stimulations were analyzed. It was found that force of TS muscle tension contraction in animals after AD-MSCs treatment was two-time higher than in untreated mice. Normalized values of force muscle contraction in different phases of electrical stimulation were 0.3 ± 0.01 vs. 0.18 ± 0.01 and 0.26 ± 0.03 vs. 0.13 ± 0.03 for treated and untreated animals, respectively. It is assumed that the two-fold increase in TS muscle strength was caused by stem cell therapy. Apparently, AD-MSCs therapy can promote nerve regeneration and partial restoration of muscle function, and thus can be a potential therapeutic agent for the treatment of peripheral neuropathies.

Small molecules efficiently reprogram apical papilla stem cells into neuron-like cells

Stem cell-based therapy may provide a novel approach for neural tissue regeneration. A small molecule cocktail-based culture protocol was previously shown to enhance neurogenic differentiation of stem cells from dental tissues. The present study aimed to investigate the early phase of small molecule-induced neurogenic differentiation of stem cells from the apical papilla (SCAP). SCAP were cultured in neural-induction medium or neural-induction medium with small molecules (NIMS-SCAP) and examined for their cell morphologies. Expression levels of neural progenitor cell-related markers, including Nestin, paired-box gene 6 (Pax6) and Sry-related HMG box 2 (Sox2), were examined using western blotting and immunocytofluorescence. Expression of differentiated neuron-related markers, including neurofilament protein (NFM), neuron-specific nuclear protein (NeuN) and microtubule-associated protein (MAP)-2, were also examined using western blotting, while NFM and MAP2 gene expression and cell proliferation were assessed using reverse transcription-quantitative (RT-q)PCR and Cell Counting Kit (CCK)-8 assays, respectively. SCAP morphology was affected by small molecules after as little as 30 min. Specifically, Nestin, Pax6 and Sox2 expression detected using western blotting was increased by day 3 but then decreased over the course of 7 days with neural induction, while immunocytofluorescence revealed expression of all three markers in NIMS-SCAP. The protein levels of NFM, NeuN and MAP2 on day 7 were significantly upregulated in NIMS-SCAP, as detected using western blotting, while NFM and MAP2 gene expression levels detected using RT-qPCR were significantly increased on days 5 and 7. Proliferation of NIMS-SCAP ceased after 5 days. Electrophysiological analysis showed that only SCAP cultured in NIMS had the functional activity of neuronal cells. Thus, small molecules reprogrammed SCAP into neural progenitor cells within the first 3 days, followed by further differentiation into neuron-like cells.

The interaction of stem cells and vascularity in peripheral nerve regeneration

The degree of nerve regeneration after peripheral nerve injury can be altered by the microenvironment at the site of injury. Stem cells and vascularity are postulated to be a part of a complex pathway that enhances peripheral nerve regeneration; however, their interaction remains unexplored. This review aims to summarize current knowledge on this interaction, including various mechanisms through which trophic factors are promoted by stem cells and angiogenesis. Angiogenesis after nerve injury is stimulated by hypoxia, mediated by vascular endothelial growth factor, resulting in the growth of pre-existing vessels into new areas. Modulation of distinct signaling pathways in stem cells can promote angiogenesis by the secretion of various angiogenic factors. Simultaneously, the importance of stem cells in peripheral nerve regeneration relies on their ability to promote myelin formation and their capacity to be influenced by the microenvironment to differentiate into Schwann-like cells. Stem cells can be acquired through various sources that correlate to their differentiation potential, including embryonic stem cells, neural stem cells, and mesenchymal stem cells. Each source of stem cells serves its particular differentiation potential and properties associated with the promotion of revascularization and nerve regeneration. Exosomes are a subtype of extracellular vesicles released from cell types and play an important role in cell-to-cell communication. Exosomes hold promise for future transplantation applications, as these vesicles contain fewer membrane-bound proteins, resulting in lower immunogenicity. This review presents pre-clinical and clinical studies that focus on selecting the ideal type of stem cell and optimizing stem cell delivery methods for potential translation to clinical practice. Future studies integrating stem cell-based therapies with the promotion of angiogenesis may elucidate the synergistic pathways and ultimately enhance nerve regeneration.

Advances and clinical challenges for translating nerve conduit technology from bench to bed side for peripheral nerve repair

Injuries to the peripheral nervous system remain a large-scale clinical problem. These injuries often lead to loss of motor and/or sensory function that significantly affects patients' quality of life. The current neurosurgical approach for peripheral nerve repair involves autologous nerve transplantation, which often leads to clinical complications. The most pressing need is to increase the regenerative capacity of existing tubular constructs in the repair of large nerve gaps through development of tissue-engineered approaches that can surpass the performance of autografts. To fully realize the clinical potential of nerve conduit technology, there is a need to reconsider design strategies, biomaterial selection, fabrication techniques and the various potential modifications to optimize a conduit microenvironment that can best mimic the natural process of regeneration. In recent years, a significant progress has been made in the designing and functionality of bioengineered nerve conduits to bridge long peripheral nerve gaps in various animal models. However, translation of this work from lab to commercial scale has not been achieve. The current review summarizes recent advances in the development of tissue engineered nerve guidance conduits (NGCs) with regard to choice of material, novel fabrication methods, surface modifications and regenerative cues such as stem cells and growth factors to improve regeneration performance. Also, the current clinical potential and future perspectives to achieve therapeutic benefits of NGCs will be discussed in context of peripheral nerve regeneration.

Mechanism of Peripheral Nerve Regeneration Using a Bio 3D Conduit Derived from Normal Human Dermal Fibroblasts

BACKGROUND

 We previously reported the development of a scaffold-free Bio three-dimensional (3D) nerve conduit from normal human dermal fibroblasts (NHDFs). The aim of this study was to investigate the regenerative mechanism of peripheral nerve cells using a Bio 3D conduit in a rat sciatic nerve defect model.

METHODS

 Bio 3D conduits composed of NHDFs were developed, and cell viability was evaluated using a LIVE/DEAD cell viability assay immediately before transplantation and 1-week post-surgery. Tracking analysis using PKH26-labeled NHDFs was performed to assess the distribution of NHDFs within the regenerated nerve and the differentiation of NHDFs into functional Schwann cells (SCs).

RESULTS

 The assessment of the viability of cells within the Bio 3D conduit showed high cell viability both immediately before transplantation and 1-week post-surgery (88.56 ± 1.70 and 87.58 ± 9.11, respectively). A modified Masson's trichrome staining of the Bio 3D conduit revealed the formation of a prominent extracellular matrix (ECM) in between the cells. We observed, via tracking analysis, that the tube-like distribution of the NHDFs remained stable, the majority of the regenerated axons had penetrated this structure and PKH26-labeled cells were also positive for S-100.

CONCLUSION

 Abundant ECM formation resulted in a stable tube-like structure of the Bio 3D conduit with high cell viability. NHDFs in the Bio 3D conduit have the potential to differentiate into SCs-like cells.

Mechanical properties of the sciatic nerve following combined transplantation of analytically extracted acellular allogeneic nerve and adipose-derived mesenchymal stem cells

Purpose

To investigate the effects of Chemically Extracted Acellular Nerves (CEANs) when combined with Adipose-Derived mesenchymal Stem Cell (ADSC) transplantation on the repair of sciatic nerve defects in rabbits.

Methods

A total of 71 six-month-old Japanese rabbit were used in this study. Twenty rabbits served as sciatic nerve donors, while the other 51 rabbits were randomly divided into Autologous Nerve Transplantation Group (ANT, n=17), CEAN group (n=17) and CEAN-ADSCs group (n=17). In all these groups, the rabbit’s left sciatic nerves were injured before the experiment, and the uninjured sciatic nerves on their right side were used as the control (CON). Electrophysiological tests were carried out and sciatic nerves were prepared for histomorphology and stretch testing at 24 weeks post-transplant.

Results

There were significant differences between ANT and Con groups in amplitude (AMP): P=0.031; motor nerve conduction velocity (MNCV): P=0.029; Maximum stress: P=0.029; and Maximum strain P=0.027. There were also differences between the CEAN and CEAN+ADSCs groups in AMP: P=0.026, MNCV: P=0.024; Maximum stress: P=0.025 and Maximum strain: P=0.030. No significant differences in these parameters were observed when comparing the ANT and CEAN+SACN groups (MNCV: P=0.071) or the CEAN and ANT groups (Maximum stress: P=0.069; Maximum strain P=0.077).

Conclusion

Addition of ADSCs has a significant impact on the recovery of nerve function, morphology, and tensile mechanical properties following sciatic nerve injury.

Comparison of bone biomechanical properties after bone marrow mesenchymal stem cell or alendronate treatment in an osteoporotic animal model

The aim of this study was to explore the effects of bone marrow mesenchymal stem cells (BMMSCs) and alendronate sodium (ALN) intervention on osteoporosis (OP). Sixty-eight 6-month-old healthy female Sprague Dawley (SD) rats were used to generate an OP model by removal of the ovaries. After 12 weeks, rats were treated with BMMSCs (BMMSC group) or ALN (ALN group) for 5 weeks. Serum type I collagen C terminal peptide (CTX_1), procollagen type I N-terminal propeptide (PINP), and bone alkaline phosphatase (BALP) were tested along with the femur bone density and other properties, including bone mineral density (BMD), BALP, percent trabecular area (BV/TV), trabecular thickness (Tb.Th), trabecular number (TbN), maximum load, maximum stress, maximum strain, and elastic modulus. BMD, BALP, BV/TV, Tb.Th, TbN, maximum load, maximum stress, maximum strain, and elastic modulus values were higher in the BMMSC group versus the ALN group relative to the control group (p < 0.05); CTX_1, PINP, trabecular separation (Tb.Sp), and osteoclast number (OC.N) were lowest in the BMMSC group versus the ALN group relative to the control group (p < 0.05). Both BMMSCs and ALN could improve the metabolic function and bone quality in osteoporotic mice while restoring the strength and toughness of bones. The intervention effects of BMMSCs are better than ALN in this model.

Stem-cell-based therapies to enhance peripheral nerve regeneration

Peripheral nerve injury remains a major cause of morbidity in trauma patients. Despite advances in microsurgical techniques and improved understanding of nerve regeneration, obtaining satisfactory outcomes after peripheral nerve injury remains a difficult clinical problem. There is a growing body of evidence in preclinical animal studies demonstrating the supportive role of stem cells in peripheral nerve regeneration after injury. The characteristics of both mesoderm-derived and ectoderm-derived stem cell types and their role in peripheral nerve regeneration are discussed, specifically focusing on the presentation of both foundational laboratory studies and translational applications. The current state of clinical translation is presented, with an emphasis on both ethical considerations of using stems cells in humans and current governmental regulatory policies. Current advancements in cell-based therapies represent a promising future with regard to supporting nerve regeneration and achieving significant functional recovery after debilitating nerve injuries.

[Significance of the composition of conduit internal environment for the activation of axon growth in patients with extended peripheral nerve defects]

The recovery of peripheral nerves after injury is an urgent medical problem. Despite the advances in microsurgery techniques, it is still not possible to achieve complete holistic and functional recovery. It is more difficult to repair neural tissue after injury if there is a diastasis between the injured ends nerves. In this case, neurorraphy can not be carried out due to the eruption of the filaments in tension and convergence of proximal and distal ends of the axon. Modern tactics of restoration of extended defects of nerves involves the use of conduits - cylindrical conductors, overlapping posttraumatic diastasis, in order to create a vector of regeneration from the proximal part of the nerve to the distal. An ideal conduit should contain an internal environment that stimulates the recovery processes of nerve fibers. At present, there is no unified approach involving the use of a certain natural or artificial conduit environment. The review analyzes the regenerative potential of the internal environments of conduits as the most promising in modern biotechnologies for the reconstruction of extended peripheral nerve defects.

Novel approaches using mesenchymal stem cells for curing peripheral nerve injuries

Peripheral nerve injury (PNI) is a common life-changing disability of peripheral nervous system with significant socioeconomic consequences. Conventional therapeutic approaches for PNI have several drawbacks such as need to autologous nerve scarifying, surplus surgery, and difficult accessibility to donor nerve; therefore, other therapeutic strategies such as mesenchymal stem cells (MSCs) therapy are getting more interesting. MSCs have been proved to be safe and efficient in numerous degenerative diseases of central and peripheral nervous systems. In this paper, we review novel biotechnological advancements in treating PNI using MSCs.

Analysis of BMSCs-intervened viscoelasticity of sciatic nerve in rats with chronic alcoholic intoxication 1

PURPOSE

To investigate the impact of bone mesenchymal stem cells (BMSCs) intervention on the viscoelasticity of sciatic nerve in rats with chronic alcohol intoxication (CAI).

METHODS

The CAI rat models were prepared, divided into model groups, and treated with either BMSCs or basic fibroblast growth factor (bFGF). Then the rats underwent electrophysiological test and the serum levels of malondialdehyde (MDA), superoxide dismutase (SOD), and metallothionein (MT) were measured. Histological observation, stress relaxation test, and creep test were performed for the sciatic nerve of the CAI model in each group.

RESULTS

The MDA level of group BMSC was significantly lower (p<0.05) than that of groups MOD (the CIA model) and bFGF. The SOD and MT levels were higher in group BMSC than in groups MOD and bFGF (p<0.05). The motor nerve conduction velocity and amplitude were higher in group BMSC than in groups MOD and bFGF (p<0.05). The amounts of 7200s stress reduction and 7200 s strain increase of the sciatic nerve in group BMSC were greater than those in groups bFGF and MOD (p<0.05).

CONCLUSION

Bone mesenchymal stem cells can improve the metabolism of free radicals, restore the tissue morphology and viscoelasticity of the chronic alcohol intoxication animal model, and positively affect the repairing of the injured sciatic nerve.

Differentiation of Human Tonsil-Derived Mesenchymal Stem Cells into Schwann-Like Cells Improves Neuromuscular Function in a Mouse Model of Charcot-Marie-Tooth Disease Type 1A

Charcot-Marie-Tooth disease type 1A (CMT1A) is the most common inherited motor and sensory neuropathy, and is caused by duplication of PMP22, alterations of which are a characteristic feature of demyelination. The clinical phenotype of CMT1A is determined by the degree of axonal loss, and patients suffer from progressive muscle weakness and impaired sensation. Therefore, we investigated the potential of Schwann-like cells differentiated from human tonsil-derived stem cells (T-MSCs) for use in neuromuscular regeneration in trembler-J (Tr-J) mice, a model of CMT1A. After differentiation, we confirmed the increased expression of Schwann cell (SC) markers, including glial fibrillary acidic protein (GFAP), nerve growth factor receptor (NGFR), S100 calcium-binding protein B (S100B), glial cell-derived neurotrophic factor (GDNF), and brain-derived neurotrophic factor (BDNF), which suggests the differentiation of T-MSCs into SCs (T-MSC-SCs). To test their functional efficiency, the T-MSC-SCs were transplanted into the caudal thigh muscle of Tr-J mice. Recipients’ improved locomotive activity on a rotarod test, and their sciatic function index, which suggests that transplanted T-MSC-SCs ameliorated demyelination and atrophy of nerve and muscle in Tr-J mice. Histological and molecular analyses showed the possibility of in situ remyelination by T-MSC-SCs transplantation. These findings demonstrate that the transplantation of heterologous T-MSC-SCs induced neuromuscular regeneration in mice and suggest they could be useful for the therapeutic treatment of patients with CMT1A disease.

Schwann cells and mesenchymal stem cells in laminin- or fibronectin-aligned matrices and regeneration across a critical size defect of 15 mm in the rat sciatic nerve

OBJECTIVE

Artificial nerve guides are being developed to substitute for autograft repair after peripheral nerve injuries. However, the use of conduits is limited by the length of the gap that needs to be bridged, with the success of regeneration highly compromised in long gaps. Addition of aligned proregenerative cells and extracellular matrix (ECM) components inside the conduit can be a good strategy to achieve artificial grafts that recreate the natural environment offered by a nerve graft. The purpose of this study was to functionalize chitosan devices with different cell types to support regeneration in limiting gaps in the rat peripheral nerve.

METHODS

The authors used chitosan devices combined with proteins of the ECM and cells in a rat model of sciatic nerve injury. Combinations of fibronectin and laminin with mesenchymal stem cells (MSCs) or Schwann cells (SCs) were aligned within tethered collagen-based gels, which were placed inside chitosan tubes that were then used to repair a critical-size gap of 15 mm in the rat sciatic nerve. Electrophysiology and algesimetry tests were performed to analyze functional recovery during the 4 months after injury and repair. Histological analysis was performed at the midlevel and distal level of the tubes to assess the number of regenerated myelinated fibers.

RESULTS

Functional analysis demonstrated that SC-aligned scaffolds resulted in 100% regeneration success in a 15-mm nerve defect in this rat model. In contrast, animals that underwent repair with MSC-aligned constructs had only 90% regeneration success, and those implanted with acellular bridges had only 75% regeneration success.

CONCLUSIONS

These results indicate that the combination of chitosan conduits with ECM-enriched cellular gels represents a good alternative to the use of autografts for repairing long nerve gaps.

Establishing a reliable gait evaluation method for rodent studies

BACKGROUND

CatWalk is one of the most popular tools for evaluating gait recovery in preclinical research, however, there is currently no consensus on which of the many gait parameters captured by CatWalk can reliably model recovery. There are conflicting interpretations of results, along with many common but seldom reported problems such as heel walking and poor compliance.

NEW METHOD

We developed a systematic manual classification method that overcomes common problems such as heel walking and poor compliance. By correcting automation errors and removing inconsistent gait cycles, we isolated stretches of recordings that are more reliable for analysis. Recovery outcome was also assessed by quantitative histomorphometric analysis of myelinated axons.

RESULTS

While 40-60% of runs were erroneously classified without manual intervention, we corrected all errors with our new method, and showed that Stand Time, Duty Cycle, and Swing Speed are able to track significant differences over time and between experimental groups (all p<0.05). The usability of print area and intensity parameters requires further validation beyond the capabilities of CatWalk.

COMPARISON WITH EXISTING METHOD(S)

There is currently no strategy that addresses problems such as heel walking and poor compliance, and therefore no standard set of parameters that researchers can rely on to report their findings.

CONCLUSION

Manual classification is a crucial step to generate reliable CatWalk data, and Stand Time, Duty Cycle, and Swing Speed are suitable parameters for evaluating gait recovery. Static parameters such as print area and intensity should be used with extreme caution.

The efficacy of a scaffold-free Bio 3D conduit developed from human fibroblasts on peripheral nerve regeneration in a rat sciatic nerve model

BACKGROUND

Although autologous nerve grafting is the gold standard treatment of peripheral nerve injuries, several alternative methods have been developed, including nerve conduits that use supportive cells. However, the seeding efficacy and viability of supportive cells injected in nerve grafts remain unclear. Here, we focused on a novel completely biological, tissue-engineered, scaffold-free conduit.

METHODS

We developed six scaffold-free conduits from human normal dermal fibroblasts using a Bio 3D Printer. Twelve adult male rats with immune deficiency underwent mid-thigh-level transection of the right sciatic nerve. The resulting 5-mm nerve gap was bridged using 8-mm Bio 3D conduits (Bio 3D group, n = 6) and silicone tube (silicone group, n = 6). Several assessments were conducted to examine nerve regeneration eight weeks post-surgery.

RESULTS

Kinematic analysis revealed that the toe angle to the metatarsal bone at the final segment of the swing phase was significantly higher in the Bio 3D group than the silicone group (-35.78 ± 10.68 versus -62.48 ± 6.15, respectively; p < 0.01). Electrophysiological studies revealed significantly higher compound muscle action potential in the Bio 3D group than the silicone group (53.60 ± 26.36% versus 2.93 ± 1.84%; p < 0.01). Histological and morphological studies revealed neural cell expression in all regions of the regenerated nerves and the presence of many well-myelinated axons in the Bio 3D group. The wet muscle weight of the tibialis anterior muscle was significantly higher in the Bio 3D group than the silicone group (0.544 ± 0.063 versus 0.396 ± 0.031, respectively; p < 0.01).

CONCLUSIONS

We confirmed that scaffold-free Bio 3D conduits composed entirely of fibroblast cells promote nerve regeneration in a rat sciatic nerve model.

Stem Cell Transplantation for Peripheral Nerve Regeneration: Current Options and Opportunities

Peripheral nerve regeneration is a complicated process highlighted by Wallerian degeneration, axonal sprouting, and remyelination. Schwann cells play an integral role in multiple facets of nerve regeneration but obtaining Schwann cells for cell-based therapy is limited by the invasive nature of harvesting and donor site morbidity. Stem cell transplantation for peripheral nerve regeneration offers an alternative cell-based therapy with several regenerative benefits. Stem cells have the potential to differentiate into Schwann-like cells that recruit macrophages for removal of cellular debris. They also can secrete neurotrophic factors to promote axonal growth, and remyelination. Currently, various types of stem cell sources are being investigated for their application to peripheral nerve regeneration. This review highlights studies involving the stem cell types, the mechanisms of their action, methods of delivery to the injury site, and relevant pre-clinical or clinical data. The purpose of this article is to review the current point of view on the application of stem cell based strategy for peripheral nerve regeneration.

Biological and biomechanical analysis of two types of mesenchymal stem cells for intervention in chemotherapy-induced ovarian dysfunction

PURPOSE

The study aim was to investigate the biological and biomechanical features of a chemotherapy-induced ovarian dysfunction (CIOD) rat model after intervention with human umbilical cord mesenchymal stem cells (UC-MSCs) and human amniotic mesenchymal stem cells (h-AMSCs), thus providing a biological and biomechanical research basis for clinical treatment.

METHODS

The serum levels of estradiol (E2), follicle-stimulating hormone (FSH), luteinizing hormone (LH), and vascular endothelial growth factor (VEGF) in the rat CIOD models were evaluated on the 14th, 30th, 60th, and 90th day of intervention with h-AMSCs and UC-MSCs. In addition, the ovaries in each group were sampled on the 14th and 90th day of intervention for tissue morphology and tensile testing.

RESULTS

The serum levels of E2, LH, and VEGF in the h-AMSC and UC-MSC groups were greater than in the model group, but the serum FSH level was less than in the model group, and the differences were significant (P < 0.05); the maximum tensile stress and maximum strain in h-AMSC and UC-MSC groups were significantly greater than in the model group (P < 0.05).

CONCLUSIONS

UC-MSC and h-AMSC intervention restored damaged ovarian morphology, elasticity, and toughness to a certain extent, and ovarian function showed some recovery.

Preparation of polypyrrole-embedded electrospun poly(lactic acid) nanofibrous scaffolds for nerve tissue engineering

Polypyrrole (PPy) is a biocompatible polymer with good conductivity. Studies combining PPy with electrospinning have been reported; however, the associated decrease in PPy conductivity has not yet been resolved. We embedded PPy into poly(lactic acid) (PLA) nanofibers via electrospinning and fabricated a PLA/PPy nanofibrous scaffold containing 15% PPy with sustained conductivity and aligned topography. There was good biocompatibility between the scaffold and human umbilical cord mesenchymal stem cells as well as Schwann cells. Additionally, the direction of cell elongation on the scaffold was parallel to the direction of fibers. Our findings suggest that the aligned PLA/PPy nanofibrous scaffold is a promising biomaterial for peripheral nerve regeneration.

Acellular allogeneic nerve grafting combined with bone marrow mesenchymal stem cell transplantation for the repair of long-segment sciatic nerve defects: biomechanics and validation of mathematical models

We hypothesized that a chemically extracted acellular allogeneic nerve graft used in combination with bone marrow mesenchymal stem cell transplantation would be an effective treatment for long-segment sciatic nerve defects. To test this, we established rabbit models of 30 mm sciatic nerve defects, and treated them using either an autograft or a chemically decellularized allogeneic nerve graft with or without simultaneous transplantation of bone marrow mesenchymal stem cells. We compared the tensile properties, electrophysiological function and morphology of the damaged nerve in each group. Sciatic nerves repaired by the allogeneic nerve graft combined with stem cell transplantation showed better recovery than those repaired by the acellular allogeneic nerve graft alone, and produced similar results to those observed with the autograft. These findings confirm that a chemically extracted acellular allogeneic nerve graft combined with transplantation of bone marrow mesenchymal stem cells is an effective method of repairing long-segment sciatic nerve defects.

Neural Progenitor-Like Cells Induced from Human Gingiva-Derived Mesenchymal Stem Cells Regulate Myelination of Schwann Cells in Rat Sciatic Nerve Regeneration

Regeneration of peripheral nerve injury remains a major clinical challenge. Recently, mesenchymal stem cells (MSCs) have been considered as potential candidates for peripheral nerve regeneration; however, the underlying mechanisms remain elusive. Here, we show that human gingiva‐derived MSCs (GMSCs) could be directly induced into multipotent NPCs (iNPCs) under minimally manipulated conditions without the introduction of exogenous genes. Using a crush‐injury model of rat sciatic nerve, we demonstrate that GMSCs transplanted to the injury site could differentiate into neuronal cells, whereas iNPCs could differentiate into both neuronal and Schwann cells. After crush injury, iNPCs, compared with GMSCs, displayed superior therapeutic effects on axonal regeneration at both the injury site and the distal segment of the injured sciatic nerve. Mechanistically, transplantation of GMSCs, especially iNPCs, significantly attenuated injury‐triggered increase in the expression of c‐Jun, a transcription factor that functions as a major negative regulator of myelination and plays a central role in dedifferentiation/reprogramming of Schwann cells into a progenitor‐like state. Meanwhile, our results also demonstrate that transplantation of GMSCs and iNPCs consistently increased the expression of Krox‐20/EGR2, a transcription factor that governs the expression of myelin proteins and facilitates myelination. Altogether, our findings suggest that transplantation of GMSCs and iNPCs promotes peripheral nerve repair/regeneration, possibly by promoting remyelination of Schwann cells mediated via the regulation of the antagonistic myelination regulators, c‐Jun and Krox‐20/EGR2. Stem Cells Translational Medicine2017;6:458–470