Transdifferentiated mesenchymal stem cells as alternative therapy in supporting nerve regeneration and myelination

Overview of emerging therapies for demyelinating diseases

This paper provides an overview of autoimmune disorders of the central nervous system, specifically those caused by demyelination. We explore new research regarding potential therapeutic interventions, particularly those aimed at inducing remyelination. Remyelination is a detailed process, involving many cell types-oligodendrocyte precursor cells (OPCs), astrocytes, and microglia-and both the innate and adaptive immune systems. Our discussion of this process includes the differentiation potential of neural stem cells, the function of adult OPCs, and the impact of molecular mediators on myelin repair. Emerging therapies are also explored, with mechanisms of action including the induction of OPC differentiation, the transplantation of mesenchymal stem cells, and the use of molecular mediators. Further, we discuss current medical advancements in relation to many myelin-related disorders, including multiple sclerosis, optic neuritis, neuromyelitis optica spectrum disorder, myelin oligodendrocyte glycoprotein antibody-associated disease, transverse myelitis, and acute disseminated encephalomyelitis. Beyond these emerging systemic therapies, we also introduce the dimethyl fumarate/silk fibroin nerve conduit and its potential role in the treatment of peripheral nerve injuries. Despite these aforementioned scientific advancements, this paper maintains the need for ongoing research to deepen our understanding of demyelinating diseases and advance therapeutic strategies that enhance affected patients' quality of life.

Human umbilical cord mesenchymal stem cells prevent glucocorticoid-induced osteonecrosis of the femoral head by promoting angiogenesis

The impairment of angiogenesis is an outstanding pathogenic characteristic of glucocorticoid (GC)-induced osteonecrosis of the femoral head (ONFH). Human umbilical cord mesenchymal stem cells (hUC-MSCs) have been used in several diseases models, which were reported to be involved in the angiogenesis. However, whether hUC-MSCs suppress the GC-induced ONFH via promoting angiogenesis is still unclear. hUC-MSCs were isolated from the Wharton's jelly using the explant culture method. A GC-induced ONFH model was established in vitro and in vivo. The angiogenesis, proliferation and migration ability of HMECs were determined using the tube-forming, CCK-8, transwell and scratching assays in vitro. The protective role of hUC-MSCs in GC-induced ONFH was evaluated using micro-CT scanning and histological, immunohistochemical (IHC) and Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) assays in vivo. The results showed that hUC-MSCs treatment improved the tube-forming, proliferation and migration ability of HMECs in vitro. Moreover, hUC-MSCs treatment enhanced the integrity of trabecular bone of the femoral head, and the tube-forming ability in vivo. hUC-MSCs prevent the femoral head against necrosis and damage caused by GCs though promoting angiogenesis.

The Efficacy of Schwann-Like Differentiated Muscle-Derived Stem Cells in Treating Rodent Upper Extremity Peripheral Nerve Injury

BACKGROUND

There is a pressing need to identify alternative mesenchymal stem cell sources for Schwann cell cellular replacement therapy, to improve peripheral nerve regeneration. This study assessed the efficacy of Schwann cell-like cells (induced muscle-derived stem cells) differentiated from muscle-derived stem cells (MDSCs) in augmenting nerve regeneration and improving muscle function after nerve trauma.

METHODS

The Schwann cell-like nature of induced MDSCs was characterized in vitro using immunofluorescence, flow cytometry, microarray, and reverse-transcription polymerase chain reaction. In vivo, four groups (n = 5 per group) of rats with median nerve injuries were examined: group 1 animals were treated with intraneural phosphate-buffered saline after cold and crush axonotmesis (negative control); group 2 animals were no-injury controls; group 3 animals were treated with intraneural green fluorescent protein-positive MDSCs; and group 4 animals were treated with green fluorescent protein-positive induced MDSCs. All animals underwent weekly upper extremity functional testing. Rats were euthanized 5 weeks after treatment. The median nerve and extrinsic finger flexors were harvested for nerve histomorphometry, myelination, muscle weight, and atrophy analyses.

RESULTS

In vitro, induced MDSCs recapitulated native Schwann cell gene expression patterns and up-regulated pathways involved in neuronal growth/signaling. In vivo, green fluorescent protein-positive induced MDSCs remained stably transformed 5 weeks after injection. Induced MDSC therapy decreased muscle atrophy after median nerve injury (p = 0.0143). Induced MDSC- and MDSC-treated animals demonstrated greater functional muscle recovery when compared to untreated controls (hand grip after induced MDSC treatment: group 1, 0.91 N; group 4, 3.38 N); p < 0.0001) at 5 weeks after treatment. This may demonstrate the potential beneficial effects of MDSC therapy, regardless of differentiation stage.

CONCLUSION

Both MDSCs and induced MDSCs decrease denervation muscle atrophy and improve subsequent functional outcomes after upper extremity nerve trauma in rodents.

An In Vitro Comparison of Anti-Tumoral Potential of Wharton's Jelly and Bone Marrow Mesenchymal Stem Cells Exhibited by Cell Cycle Arrest in Glioma Cells (U87MG)

The therapeutic potential of mesenchymal stem cells (MSCs) for various malignancies is currently under investigation due to their unique properties. However, many discrepancies regarding their anti-tumoral or pro-tumoral properties have raised uncertainty about their application for anti-cancer therapies. To investigate, if the anti-tumoral or pro-tumoral properties are subjective to the type of MSCs under different experimental conditions we set out these experiments. Three treatments namely cell lysates (CL), serum-free conditioned media and FBS conditioned media (FBSCM) from each of Wharton’s Jelly MSCs and Bone Marrow-MSCs were applied to evaluate the anti-tumoral or pro-tumoral effect on the glioma cells (U87MG). The functional analysis included; Morphological evaluation, proliferation and migration potential, cell cycle analysis, and apoptosis for glioma cells. The fibroblast cell line was added to investigate the stimulatory or inhibitory effect of treatments on the proliferation of the normal cell. We found that cell lysates induced a generalized inhibitory effect on the proliferation of the glioma cells and the fibroblasts from both types of MSCs. Similarly, both types of conditioned media from two types of MSCs exerted the same inhibitory effect on the proliferation of the glioma cells. However, the effect of two types of conditioned media on the proliferation of fibroblasts was stimulatory from BM-MSCs and variable from WJ-MSCs. Moreover, all three treatments exerted a likewise inhibitory effect on the migration potential of the glioma cells. Furthermore, we found that the cell cycle was arrested significantly at the G1 phase after treating cells with conditioned media which may have led to inhibit the proliferative and migratory abilities of the glioma cells (U87MG). We conclude that cell extracts of MSCs in the form of secretome can induce specific anti-tumoral properties in serum-free conditions for the glioma cells particularly the WJ-MSCs and the effect is mediated by the cell cycle arrest at the G1 phase.

Tissue Engineered Axon Tracts Serve as Living Scaffolds to Accelerate Axonal Regeneration and Functional Recovery Following Peripheral Nerve Injury in Rats

Strategies to accelerate the rate of axon regeneration would improve functional recovery following peripheral nerve injury, in particular for cases involving segmental nerve defects. We are advancing tissue engineered nerve grafts (TENGs) comprised of long, aligned, centimeter-scale axon tracts developed by the controlled process of axon "stretch-growth" in custom mechanobioreactors. The current study used a rat sciatic nerve model to investigate the mechanisms of axon regeneration across nerve gaps bridged by TENGs as well as the extent of functional recovery compared to nerve guidance tubes (NGT) or autografts. We established that host axon growth occurred directly along TENG axons, which mimicked the action of "pioneer" axons during development by providing directed cues for accelerated outgrowth. Indeed, axon regeneration rates across TENGs were 3-4 fold faster than NGTs and equivalent to autografts. The infiltration of host Schwann cells - traditional drivers of peripheral axon regeneration - was also accelerated and progressed directly along TENG axons. Moreover, TENG repairs resulted in functional recovery levels equivalent to autografts, with both several-fold superior to NGTs. These findings demonstrate that engineered axon tracts serve as "living scaffolds" to guide host axon outgrowth by a new mechanism - which we term "axon-facilitated axon regeneration" - that leads to enhanced functional recovery.

Stammzellen in der Regenerativen Medizin – Translationale Hürden und Möglichkeiten zur Überwindung

Der Einsatz von mesenchymalen Stammzellen in der regenerativen Medizin wird immer populärer. Nichtsdestotrotz ist ihre Anwendung im klinischen Alltag noch immer limitiert. Zahlreiche ethische, rechtliche und translationale Probleme sowie Ungewissheit bzgl. der Sicherheit hemmen noch immer die Entstehung von entsprechenden Therapien aus vielversprechenden wissenschaftlichen Ansätzen.

Diese Arbeit soll die Hauptprobleme bei der Translation von stammzellbasierten Therapien aus der Grundlagenforschung und Präklinik in den klinischen Alltag darstellen, sowie Ansätze aufzeigen, diese zu überwinden.

Mesenchymal stem cells in chemotherapy-induced peripheral neuropathy: A new challenging approach that requires further investigations

Chemotherapeutic drugs may disrupt the nervous system and cause chemotherapy-induced peripheral neuropathy (CIPN) as side effects. There are no completely successful medications for the prevention or treatment of CIPN. Many drugs such as tricyclic antidepressants and anticonvulsants have been used for symptomatic treatment of CIPN. Unfortunately, these drugs often give only partial relief or have dose-limiting side effects. Thus, the treatment of CIPN becomes a challenge because of failure to regenerate and repair the injured neurons. Mesenchymal stem cell (MSC) therapy is a new attractive approach for CIPN. Evidence has demonstrated that MSCs play important roles in reducing oxidative stress, neuroinflammation, and apoptosis, as well as mediating axon regeneration after nerve damage in several experimental studies and some clinical trials. We will briefly review the pathogenesis of CIPN, traditional therapies used and their drawbacks as well as therapeutic effects of MSCs, their related mechanisms, future challenges for their clinical application, and the additional benefit of their combination with pharmacological agents. MSCs-based therapies may provide a new therapeutic strategy for patients suffering from CIPN where further investigations are required for studying their exact mechanisms. Combined therapy with pharmacological agents can provide another promising option for enhancing MSC therapy success while limiting its adverse effects.

Peripheral nerve injury and myelination: Potential therapeutic strategies

Traumatic peripheral nerve injury represents a major clinical and public health problem that often leads to significant functional impairment and permanent disability. Despite modern diagnostic procedures and advanced microsurgical techniques, functional recovery after peripheral nerve repair is often unsatisfactory. Therefore, there is an unmet need for new therapeutic or adjunctive strategies to promote the functional recovery in nerve injury patients. In contrast to the central nervous system, Schwann cells in the peripheral nervous system play a pivotal role in several aspects of nerve repair such as degeneration, remyelination, and axonal growth. Several non-surgical approaches, including pharmacological, electrical, cell-based, and laser therapies, have been employed to promote myelination and enhance functional recovery after peripheral nerve injury. This review will succinctly discuss the potential therapeutic strategies in the context of myelination following peripheral neurotrauma.

Human mesenchymal stem cell sheets in xeno-free media for possible allogenic applications

Cell-based therapies are increasingly focused on allogeneic stem cell sources because of several advantages in eliminating donor variability (e.g., aging and disease pathophysiology) affecting stem cell quality and in cell-banked sourcing of healthy donors to enable “off-the-shelf” products. However, allogeneic cell therapy is limited by host patient immunologic competence and inconsistent performance due to cell delivery methods. To address allogeneic cell therapy limitations, this study developed a new allogeneic stem cell sheet using human umbilical cord mesenchymal stem cells (hUC-MSC) that present low antigenicity (i.e., major histocompatibility complex, MHC). Optimal conditions including cell density, passage number, and culture time were examined to fabricate reliable hUC-MSC sheets. MHC II antigens correlated to alloimmune rejection were barely expressed in hUC-MSC sheets compared to other comparator MSC sheets (hBMSC and hADSC). hUC-MSC sheets easily graft spontaneously onto subcutaneous tissue in immune-deficient mice within 10 minutes of placement. No sutures are required to secure sheets to tissue because sheet extracellular matrix (ECM) actively facilitates cell-target tissue adhesion. At 10 days post-transplantation, hUC-MSC sheets remain on ectopic target tissue sites and exhibit new blood vessel formation. Furthermore, implanted hUC-MSC sheets secrete human HGF continuously to the murine target tissue. hUC-MSC sheets described here should provide new insights for improving allogenic cell-based therapies.

Combination of Chemical and Neurotrophin Stimulation Modulates Neurotransmitter Receptor Expression and Activity in Transdifferentiating Human Adipose Stromal Cells

Adipose stromal cells are promising tools for clinical applications in regeneration therapies, due to their ease of isolation from tissue and its high yield; however, their ability to transdifferentiate into neural phenotypes is still a matter of controversy. Here, we show that combined chemical and neurotrophin stimulation resulted in neuron-like morphology and regulated expression and activity of several genes involved in neurogenesis and neurotransmission as well as ion currents mediated by NMDA and GABA receptors. Among them, expression patterns of genes coding for kinin-B1 and B2, α7 nicotinic, M1, M3 and M4 muscarinic acetylcholine, glutamatergic (AMPA2 and mGlu2), purinergic P2Y1 and P2Y4 and GABAergic (GABA-A, β3-subunit) receptors and neuronal nitric oxide synthase were up-regulated compared to levels of undifferentiated cells. Simultaneously, expression levels of P2X1, P2X4, P2X7 and P2Y6 purinergic and M5 muscarinic acetylcholine receptors were down-regulated. Agonist-induced activity levels of the studied receptor classes also augmented during neuronal transdifferentiation. Transdifferentiated cells expressed high levels of neuronal β3-tubulin, NF-H, NeuN and MAP-2 proteins as well as increased ASCL1, MYT1 and POU3F2 gene expression known to drive neuronal fate determination. The presented work contributes to a better understanding of transdifferentiation induced by neurotrophins for a prospective broad spectrum of medical applications.

Human bone marrow-derived MSCs spontaneously express specific Schwann cell markers

In peripheral nerve injuries, Schwann cells (SC) play pivotal roles in regenerating damaged nerve. However, the use of SC in clinical cell-based therapy is hampered due to its limited availability. In this study, we aim to evaluate the effectiveness of using an established induction protocol for human bone marrow derived-MSC (hBM-MSCs) transdifferentiation into a SC lineage. A relatively homogenous culture of hBM-MSCs was first established after serial passaging (P3), with profiles conforming to the minimal criteria set by International Society for Cellular Therapy (ISCT). The cultures (n = 3) were then subjected to a series of induction media containing β-mercaptoethanol, retinoic acid, and growth factors. Quantitative RT-PCR, flow cytometry, and immunocytochemistry analyses were performed to quantify the expression of specific SC markers, that is, S100, GFAP, MPZ and p75 NGFR, in both undifferentiated and transdifferentiated hBM-MSCs. Based on these analyses, all markers were expressed in undifferentiated hBM-MSCs and MPZ expression (mRNA transcripts) was consistently detected before and after transdifferentiation across all samples. There was upregulation at the transcript level of more than twofolds for NGF, MPB, GDNF, p75 NGFR post-transdifferentiation. This study highlights the existence of spontaneous expression of specific SC markers in cultured hBM-MSCs, inter-donor variability and that MSC transdifferentiation is a heterogenous process. These findings strongly oppose the use of a single marker to indicate SC fate. The heterogenous nature of MSC may influence the efficiency of SC transdifferentiation protocols. Therefore, there is an urgent need to re-define the MSC subpopulations and revise the minimal criteria for MSC identification.

Egr2 overexpression in Schwann cells increases myelination frequency in vitro

Schwann cells are key players in peripheral nerve regeneration, and are uniquely capable of remyelinating axons in this context. Schwann cells orchestrate this process via a set of transcription factors. While it has been shown that overexpression of specific genes, e.g. Egr2, upregulates myelin-related transcripts, it remains unknown if such manipulation can functionalize the cells and enhance their myelination frequency. The ability to do so could have implications in the use of human stem cell-derived Schwann cells, where myelination is hard to achieve. After screening four candidate transcription factors (Sox10, Oct6, Brn2 and Egr2), we found that overexpression of Egr2 in rat Schwann cells co-cultured with sensory neurons enhanced myelination frequency and reduced cell proliferation. However, in a mouse model of sciatic nerve repair with cells engrafted within a nerve guide, myelination frequency in the engrafted cells was reduced upon Egr2 overexpression. Our results show that while overexpression of Egr2 can enhance the myelination frequency in vitro, it is context-dependent, potentially influenced by the microenvironment, timing of association with axons, expression level, species differences, or other factors.

DPSCs seeded in acellular nerve grafts processed by Myroilysin improve nerve regeneration

Since synthetic nerve conduits do not exhibit ideal regeneration characteristics, they are generally inadequate substitutes for autologous nerve grafts in the repair of long peripheral nerve defects. To resolve this problem, in this study, a nerve regeneration acellular nerve graft (ANG) with homologous dental pulp stem cells (DPSCs) was constructed. Xenogeneic ANG was processed by Myroilysin to completely remove cells and myelin sheath, while preserving extracellular matrix (ECM) microstructure of the natural nerve. The study revealed that ANG could support cell attachment and proliferation and did not stimulate a vigorous host rejection response. After inoculation of rabbit DPSCs (r-DPSCs) onto ANG, cells were observed to align along the longitudinal axis of the acellular nerve matrix (ANM) and persistently express NGF and BDNF. Undifferentiated r-DPSCs also presented glial cell characteristics and promoted nerve regeneration after transplantation in vivo. We repaired 1 cm purebred New Zealand White Rabbits sciatic nerve defects using this nerve graft construction, and nerve gap regeneration was indicated by electrophysiological and histological analysis. Therefore, we conclude that the combination of an ANG processed by Myroilysin with DPSCs providing a microenvironment that increases nerve regeneration for repairing peripheral nerve defects.

Is Regenerative Medicine Ready for Prime Time in Diabetic Polyneuropathy?

PURPOSE OF REVIEW

After a prolonged warm-up period of basic research, several modalities of cell replacement therapies are under development for diseases with no available cure. Diabetic polyneuropathy (DPN) is one of the most prevalent chronic diabetes complications that causes sensorimotor dysfunction, subsequent high risks for lower limb amputations, and high mortality. Currently, no disease modifying therapy exists for DPN.

RECENT FINDINGS

Several types of well-documented stem/progenitor cells have been utilized for cell transplantation therapies in DPN model rodents: mesenchymal stromal cells (MSCs), endothelial progenitor cells (EPCs), and cells with similar characteristics of MSCs or EPCs derived from embryonic stem cells or induced pluripotent stem cells. Some recent experimental studies reported that these immature cells may have beneficial effects on DPN. Although the role of nerve regeneration in the pathology of DPN has not been sufficiently elucidated, many intervention studies attempting regenerative therapy of DPN have been reported. Further studies are needed to better evaluate the potential of regeneration in reversing the pathology of DPN.

Neurotrophically Induced Mesenchymal Progenitor Cells Derived from Induced Pluripotent Stem Cells Enhance Neuritogenesis via Neurotrophin and Cytokine Production

Adult tissue‐derived mesenchymal stem cells (MSCs) are known to produce a number of bioactive factors, including neurotrophic growth factors, capable of supporting and improving nerve regeneration. However, with a finite culture expansion capacity, MSCs are inherently limited in their lifespan and use. We examined here the potential utility of an alternative, mesenchymal‐like cell source, derived from induced pluripotent stem cells, termed induced mesenchymal progenitor cells (MiMPCs). We found that several genes were upregulated and proteins were produced in MiMPCs that matched those previously reported for MSCs. Like MSCs, the MiMPCs secreted various neurotrophic and neuroprotective factors, including brain‐derived neurotrophic factor (BDNF), interleukin‐6 (IL‐6), leukemia inhibitory factor (LIF), osteopontin, and osteonectin, and promoted neurite outgrowth in chick embryonic dorsal root ganglia (DRG) cultures compared with control cultures. Cotreatment with a pharmacological Trk‐receptor inhibitor did not result in significant decrease in MiMPC‐induced neurite outgrowth, which was however inhibited upon Jak/STAT3 blockade. These findings suggest that the MiMPC induction of DRG neurite outgrowth is unlikely to be solely dependent on BDNF, but instead Jak/STAT3 activation by IL‐6 and/or LIF is likely to be critical neurotrophic signaling pathways of the MiMPC secretome. Taken together, these findings suggest MiMPCs as a renewable, candidate source of therapeutic cells and a potential alternative to MSCs for peripheral nerve repair, in view of their ability to promote nerve growth by producing many of the same growth factors and cytokines as Schwann cells and signaling through critical neurotrophic pathways. stemcellstranslational Medicine2018;7:45–58

Stem cell therapy for nerve injury

Peripheral nerve injury has remained a substantial clinical complication with no satisfactory treatment options. Despite the great development in the field of microsurgery, some severe types of neural injuries cannot be treated without causing tension to the injured nerve. Thus, current studies have focused on the new approaches for the treatment of peripheral nerve injuries. Stem cells with the ability to differentiate into a variety of cell types have brought a new perspective to this matter. In this review, we will discuss the use of three main sources of mesenchymal stem cells in the treatment of peripheral nerve injuries.

Transdifferentiation of brain-derived neurotrophic factor (BDNF)-secreting mesenchymal stem cells significantly enhance BDNF secretion and Schwann cell marker proteins

The use of genetically modified mesenchymal stem cells (MSCs) is a rapidly growing area of research targeting delivery of therapeutic factors for neuro-repair. Cells can be programmed to hypersecrete various growth/trophic factors such as brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF), and nerve growth factor (NGF) to promote regenerative neurite outgrowth. In addition to genetic modifications, MSCs can be subjected to transdifferentiation protocols to generate neural cell types to physically and biologically support nerve regeneration. In this study, we have taken a novel approach by combining these two unique strategies and evaluated the impact of transdifferentiating genetically modified MSCs into a Schwann cell-like phenotype. After 8 days in transdifferentiation media, approximately 30-50% of transdifferentiated BDNF-secreting cells immunolabeled for Schwann cell markers such as S100β, S100, and p75^NTR. An enhancement was observed 20 days after inducing transdifferentiation with minimal decreases in expression levels. BDNF production was quantified by ELISA, and its biological activity tested via the PC12-TrkB cell assay. Importantly, the bioactivity of secreted BDNF was verified by the increased neurite outgrowth of PC12-TrkB cells. These findings demonstrate that not only is BDNF actively secreted by the transdifferentiated BDNF-MSCs, but also that it has the capacity to promote neurite sprouting and regeneration. Given the fact that BDNF production remained stable for over 20 days, we believe that these cells have the capacity to produce sustainable, effective, BDNF concentrations over prolonged time periods and should be tested within an in vivo system for future experiments.

Preconditioning of adipose tissue-derived mesenchymal stem cells with deferoxamine increases the production of pro-angiogenic, neuroprotective and anti-inflammatory factors: Potential application in the treatment of diabetic neuropathy

Diabetic neuropathy (DN) is one of the most frequent and troublesome complications of diabetes mellitus. Evidence from diabetic animal models and diabetic patients suggests that reduced availability of neuroprotective and pro-angiogenic factors in the nerves in combination with a chronic pro-inflammatory microenvironment and high level of oxidative stress, contribute to the pathogenesis of DN. Mesenchymal stem cells (MSCs) are of great interest as therapeutic agents for regenerative purposes, since they can secrete a broad range of cytoprotective and anti-inflammatory factors. Therefore, the use of the MSC secretome may represent a promising approach for DN treatment. Recent data indicate that the paracrine potential of MSCs could be boosted by preconditioning these cells with an environmental or pharmacological stimulus, enhancing their therapeutic efficacy. In the present study, we observed that the preconditioning of human adipose tissue-derived MSCs (AD-MSCs) with 150μM or 400μM of the iron chelator deferoxamine (DFX) for 48 hours, increased the abundance of the hypoxia inducible factor 1 alpha (HIF-1α) in a concentration dependent manner, without affecting MSC morphology and survival. Activation of HIF-1α led to the up-regulation of the mRNA levels of pro-angiogenic factors like vascular endothelial growth factor alpha and angiopoietin 1. Furthermore this preconditioning increased the expression of potent neuroprotective factors, including nerve growth factor, glial cell-derived neurotrophic factor and neurotrophin-3, and cytokines with anti-inflammatory activity like IL4 and IL5. Additionally, we observed that these molecules, which could also be used as therapeutics, were also increased in the secretome of MSCs preconditioned with DFX compared to the secretome obtained from non-preconditioned cells. Moreover, DFX preconditioning significantly increased the total antioxidant capacity of the MSC secretome and they showed neuroprotective effects when evaluated in an in vitro model of DN. Altogether, our findings suggest that DFX preconditioning of AD-MSCs improves their therapeutic potential and should be considered as a potential strategy for the generation of new alternatives for DN treatment.

Electrical Differentiation of Mesenchymal Stem Cells into Schwann-Cell-Like Phenotypes Using Inkjet-Printed Graphene Circuits

Graphene-based materials (GBMs) have displayed tremendous promise for use as neurointerfacial substrates as they enable favorable adhesion, growth, proliferation, spreading, and migration of immobilized cells. This study reports the first case of the differentiation of mesenchymal stem cells (MSCs) into Schwann cell (SC)-like phenotypes through the application of electrical stimuli from a graphene-based electrode. Electrical differentiation of MSCs into SC-like phenotypes is carried out on a flexible, inkjet-printed graphene interdigitated electrode (IDE) circuit that is made highly conductive (sheet resistance < 1 kΩ/sq) via a postprint pulse-laser annealing process. MSCs immobilized on the graphene printed IDEs and electrically stimulated/treated (etMSCs) display significant enhanced cellular differentiation and paracrine activity above conventional chemical treatment strategies [≈85% of the etMSCs differentiated into SC-like phenotypes with ≈80 ng mL^-1 of nerve growth factor (NGF) secretion vs. 75% and ≈55 ng mL^-1 for chemically treated MSCs (ctMSCs)]. These results help pave the way for in vivo peripheral nerve regeneration where the flexible graphene electrodes could conform to the injury site and provide intimate electrical simulation for nerve cell regrowth.

From transplanting Schwann cells in experimental rat spinal cord injury to their transplantation into human injured spinal cord in clinical trials

Among the potential therapies designed to repair the injured spinal cord is cell transplantation, notably the use of autologous adult human Schwann cells (SCs). Here, we detail some of the critical research accomplished over the last four decades to establish a foundation that enables these cells to be tested in clinical trials. New culture systems allowed novel information to be gained about SCs, including discovering ways to stimulate their proliferation to acquire adequately large numbers for transplantation into the injured human spinal cord. Transplantation of rat SCs into rat models of spinal cord injury has demonstrated that SCs promote repair of injured spinal cord. Additional work required to gain approval from the Food and Drug Administration for the first SC trial in the Miami Project is disclosed. This trial and a second one now underway are described.

In vitro differentiated hepatic oval-like cells enhance hepatic regeneration in CCl4 -induced hepatic injury

Hepatic oval cells are likely to be activated during advanced stage of liver fibrosis to reconstruct damaged hepatic tissue. However, their scarcity, difficulties in isolation, and in vitro expansion hampered their transplantation in fibrotic liver. This study was aimed to investigate the repair potential of in vitro differentiated hepatic oval-like cells in CCl₄ -induced liver fibrosis. BMSCs and oval cells were isolated and characterized from C57BL/6 GFP⁺ mice. BMSCs were differentiated into oval cells by preconditioning with HGF, EGF, SCF, and LIF and analyzed for the oval cells-specific genes. Efficiency of oval cells to reduce hepatocyte injury was studied by determining cell viability, release of LDH, and biochemical tests in a co-culture system. Further, in vivo repair potential of differentiated oval cells was determined in CCl₄ -induced fibrotic model by gene expression analysis, biochemical tests, mason trichrome, and Sirius red staining. Differentiated oval cells expressed hepatic oval cells-specific markers AFP, ALB, CK8, CK18, CK19. These differentiated cells when co-cultured with injured hepatocytes showed significant hepato-protection as measured by reduction in apoptosis, LDH release, and improvement in liver functions. Transplantation of differentiated oval cells like cells in fibrotic livers exhibited enhanced homing, reduced liver fibrosis, and improved liver functions by augmenting hepatic microenvironment by improved liver functions. This preconditioning strategy to differentiate BMSCs into oval cell leads to improved survival and homing of transplanted cells. In addition, reduction in fibrosis and functional improvement in mice with CCl₄ -induced liver fibrosis was achieved.

A Novel Model for Acute Peripheral Nerve Injury in the Horse and Evaluation of the Effect of Mesenchymal Stromal Cells Applied In Situ on Nerve Regeneration: A Preliminary Study

Transplantation of mesenchymal stromal cells (MSCs) to sites of experimentally created nerve injury in laboratory animals has shown promising results in restoring nerve function. This approach for nerve regeneration has not been reported in horses. In this study, we first evaluated the in vitro ability of equine bone marrow-derived MSCs (EBM-MSCs) to trans-differentiate into Schwann-like cells and subsequently tested the MSCs in vivo for their potential to regenerate a transected nerve after implantation. The EBM-MSCs from three equine donors were differentiated into SCLs for 7 days, in vitro, in the presence of specialized differentiation medium and evaluated for morphological characteristics, by using confocal microscopy, and for protein characteristics, by using selected Schwann cell markers (GFAP and S100b). The EBM-MSCs were then implanted into the fascia surrounding the ramus communicans of one fore limb of three healthy horses after a portion of this nerve was excised. The excised portion of the nerve was examined histologically at the time of transection, and stumps of the nerve were examined histologically at day 45 after transplantation. The EBM-MSCs from all donors demonstrated morphological and protein characteristics of those of Schwann cells 7 days after differentiation. Nerves implanted with EBM-MSCs after nerve transection did not show evidence of nerve regeneration at day 45. Examination of peripheral nerves collected 45 days after injury and stem cell treatment revealed no histological differences between nerves treated with MSCs and those treated with isotonic saline solution (controls). The optimal delivery of MSCs and the model suitable to study the efficacy of MSCs in nerve regeneration should be investigated.

Effect of Laminin on Neurotrophic Factors Expression in Schwann-Like Cells Induced from Human Adipose-Derived Stem Cells In Vitro

The Schwann-like cells can be considered as promising in stem cell therapies, at least in experimental models. Human adipose-derived stem cells (ADSCs) are induced into Schwann-like cells (SC-like cells) and are cultured on either a plastic surface or laminin-coated plates. The findings here reveal that laminin is a critical component in extracellular matrix (ECM) of SC-like cells at in vitro. The survival rate of SC-like cells on a laminin matrix are measured through MTT assay and it is found that this rate is significantly higher than that of the cells grown on a plastic surface (P < 0.05). Schwann cell markers and the myelinogenic ability of SC-like cells at the presence versus absence of laminin are assessed through immunocytochemistry. The analysis of GFAP/S100β and S100β/MBP markers indicate that laminin can increase the differentiated rate and myelinogenic potential of SC-like cells. The expression levels of SCs markers, myelin basic proteins (MBP), and neurotrophic factors in two conditions are analyzed by real-time reverse transcription polymerase chain reaction (RT-PCR). The findings here demonstrated that gene expression of SCs markers, MBP, and brain-derived neurotrophic factors (BDNF) increase significantly on laminin compared to plastic surface (P < 0.01). In contrast, the nerve growth factor (NGF) expression is downregulated significantly on laminin-coated plates (P < 0.05). The obtained data suggest that production of neurotrophic factors in SC-like cell in presence of laminin can induce appropriate microenvironment for nerve repair in neurodegenerative diseases.

The migration and differentiation of hUC-MSCs(CXCR4/GFP) encapsulated in BDNF/chitosan scaffolds for brain tissue engineering

We previously developed a biomaterial scaffold that could effectively provide seed cells to a lesion cavity resulting from traumatic brain injury. However, we subsequently found that few transplanted human umbilical cord mesenchymal stem cells (hUC-MSCs) are able to migrate from the scaffold to the lesion boundary. Stromal derived-cell factor-1α and its receptor chemokine (C-X-C motif) receptor (CXCR)4 are chemotactic factors that control cell migration and stem cell recruitment to target areas. Given the low expression level of CXCR4 on the hUC-MSC membrane, lentiviral vectors were used to generate hUC-MSCs stably expressing CXCR4 fused to green fluorescent protein (GFP) (hUC-MSCs(CXCR4/GFP)). We constructed a scaffold in which recombinant human brain-derived neurotrophic factor (BDNF) was linked to chitosan scaffolds with the crosslinking agent genipin (CGB scaffold). The scaffold containing hUC-MSCs(CXCR4/GFP) was transplanted into the lesion cavity of a rat brain, providing exogenous hUC-MSCs to both lesion boundary and cavity. These results demonstrate a novel strategy for inducing tissue regeneration after traumatic brain injury.

Regenerative cellular therapies for neurologic diseases

The promise of stem cell regeneration has been the hope of many neurologic patients with permanent damage to the central nervous system. There are hundreds of stem cell trials worldwide intending to test the regenerative capacity of stem cells in various neurological conditions from Parkinson's disease to multiple sclerosis. Although no stem cell therapy is clinically approved for use in any human disease indication, patients are seeking out trials and asking clinicians for guidance. This review summarizes the current state of regenerative stem cell transplantation divided into seven conditions for which trials are currently active: demyelinating diseases/spinal cord injury, amyotrophic lateral sclerosis, stroke, Parkinson's disease, Huntington's disease, macular degeneration and peripheral nerve diseases. This article is part of a Special Issue entitled SI: PSC and the brain.

Using Stem Cells to Grow Artificial Tissue for Peripheral Nerve Repair

Peripheral nerve injury continues to pose a clinical hurdle despite its frequency and advances in treatment. Unlike the central nervous system, neurons of the peripheral nervous system have a greater ability to regenerate. However, due to a number of confounding factors, this is often both incomplete and inadequate. The lack of supportive Schwann cells or their inability to maintain a regenerative phenotype is a major factor. Advances in nervous system tissue engineering technology have led to efforts to build Schwann cell scaffolds to overcome this and enhance the regenerative capacity of neurons following injury. Stem cells that can differentiate along a neural lineage represent an essential resource and starting material for this process. In this review, we discuss the different stem cell types that are showing promise for nervous system tissue engineering in the context of peripheral nerve injury. We also discuss some of the biological, practical, ethical, and commercial considerations in using these different stem cells for future clinical application.

Inter-microcarrier transfer and phenotypic stability of stem cell-derived Schwann cells in stirred suspension bioreactor culture

Emerging bioreactor technologies offer an effective way for scaled-up production of large numbers of cells for cell therapy applications. One of the clinical paradigms where cell therapy can be an asset is restorative neurosciences. Nerve repair can benefit from the injections of stem cells and/or Schwann cells, acting as a source for axon myelination, myelin debris clearance, and trophic support. We have adapted microcarrier-based suspension bioreactor culture for Schwann cells (SCs) differentiated from a new stem cell source - skin-derived precursors (SKPs). SKP-derived SCs attach and grow on different types of microcarriers in both static and stirred culture, with Cytodex 3 and CultiSpher-S found most effective. Inter-microcarrier migration of SKP-SCs represents a key mechanism for rapid expansion and colonization in stirred suspension culture. We have shown that microcarrier-expanded SKP-SCs cells express Schwann cell markers p75-NTR, GFAP and S100 and retain their key ability to myelinate axons both in vitro and in vivo. Scaled-up microcarrier-based production of SKP-SCs in suspension bioreactors appears feasible for timely generation of sufficient cell numbers for nerve repair strategies.

Bone-tissue engineering: complex tunable structural and biological responses to injury, drug delivery, and cell-based therapies

Bone loss and failure of proper bone healing continues to be a significant medical condition in need of solutions that can be implemented successfully both in human and veterinary medicine. This is particularly true when large segmental defects are present, the bone has failed to return to normal form or function, or the healing process is extremely prolonged. Given the inherent complexity of bone tissue - its unique structural, mechanical, and compositional properties, as well as its ability to support various cells - it is difficult to find ideal candidate materials that could be used as the foundation for tissue regeneration from technological platforms. Recently, important developments have been made in the implementation of complex structures built both at the macro- and the nano-level that have been shown to positively impact bone formation and to have the ability to deliver active biological molecules (drugs, growth factors, proteins, cells) for controlled tissue regeneration and the prevention of infection. These materials are diverse, ranging from polymers to ceramics and various composites. This review presents developments in this area with a focus on the role of scaffold structure and chemistry on the biologic processes that influence bone physiology and regeneration.

Rat Nasal Respiratory Mucosa-Derived Ectomesenchymal Stem Cells Differentiate into Schwann-Like Cells Promoting the Differentiation of PC12 Cells and Forming Myelin In Vitro

Schwann cell (SC) transplantation as a cell-based therapy can enhance peripheral and central nerve repair experimentally, but it is limited by the donor site morbidity for clinical application. We investigated weather respiratory mucosa stem cells (REMSCs), a kind of ectomesenchymal stem cells (EMSCs), isolated from rat nasal septum can differentiate into functional Schwann-like cells (SC-like cells). REMSCs proliferated quickly in vitro and expressed the neural crest markers (nestin, vimentin, SOX10, and CD44). Treated with a mixture of glial growth factors for 7 days, REMSCs differentiated into SC-like cells. The differentiated REMSCs (dREMSCs) exhibited a spindle-like morphology similar to SC cells. Immunocytochemical staining and Western blotting indicated that SC-like cells expressed the glial markers (GFAP, S100β, Galc, and P75) and CNPase. When cocultured with dREMSCs for 5 days, PC12 cells differentiated into mature neuron-like cells with long neurites. More importantly, dREMSCs could form myelin structures with the neurites of PC12 cells at 21 days in vitro. Our data indicated that REMSCs, a kind of EMSCs, could differentiate into SC-like cells and have the ability to promote the differentiation of PC12 cells and form myelin in vitro.

Bone Marrow-Derived Mesenchymal Stem Cells Improve Diabetic Neuropathy by Direct Modulation of Both Angiogenesis and Myelination in Peripheral Nerves

Recent evidence has suggested that diabetic neuropathy (DN) is pathophysiologically related to both impaired angiogenesis and a deficiency of neurotrophic factors in the nerves. It is widely known that vascular and neural growths are intimately associated. Mesenchymal stem cells (MSCs) promote angiogenesis in ischemic diseases and have neuroprotective effects, particularly on Schwann cells. Accordingly, we investigated whether DN could be improved by local transplantation of MSCs by augmenting angiogenesis and neural regeneration such as remyelination. In sciatic nerves of streptozotocin (STZ)-induced diabetic rats, motor and sensory nerve conduction velocities (NCVs) and capillary density were reduced, and axonal atrophy and demyelination were observed. After injection of bone marrow-derived MSCs (BM-MSCs) into hindlimb muscles, NCVs were restored to near-normal levels. Histological examination demonstrated that injected MSCs were preferentially and durably engrafted in the sciatic nerves, and a portion of the engrafted MSCs were distinctively localized close to vasa nervora of sciatic nerves. Furthermore, vasa nervora increased in density, and the ultrastructure of myelinated fibers in nerves was observed to be restored. Real-time RT-PCR experiments showed that gene expression of multiple factors involved in angiogenesis, neural function, and myelination were increased in the MSC-injected nerves. These findings suggest that MSC transplantation improved DN through direct peripheral nerve angiogenesis, neurotrophic effects, and restoration of myelination.

Grafted Activated Schwann Cells Support Survival of Injured Rat Spinal Cord White Matter

BACKGROUND AND OBJECTIVE

The influence of cultured Schwann cells on injured spinal cord in rats is examined.

METHODS

Focal injury of spinal cord white matter at the T10 level was produced using our original non-laminectomy method with a high-pressure air stream. Schwann cells from 7-day predegenerated rat sciatic nerves were cultured, transducted with green fluorescent protein and injected into the cisterna magna (experimental group) 3 times: immediately after spinal cord injury and 3 and 7 days later. Neurons in the brainstem and motor cortex were labeled with FluoroGold (FG) delivered caudally from the injury site a week before the end of the experiment. The functional outcome and morphologic features of neuronal survival were analyzed during a 12-week follow-up. The lesions were visualized and analyzed using magnetic resonance imaging. The maximal distance of expansion of implanted cells in the spinal cord was measured and the number of FG-positive neurons in the brain was counted.

RESULTS

Rats treated with Schwann cells presented significant improvement of locomotor performance and spinal cord morphology compared with the control group. The distance covered by Schwann cells was 7 mm from the epicenter of the injury. The number of brainstem and motor cortex FG-positive neurons in the experimental group was significantly higher than in the control group.

CONCLUSIONS

The data show that activated Schwann cells are able to induce the repair of injured spinal cord white matter. The route of application of cells via the cisterna magna seemed to be useful for their delivery in spinal cord injury therapy.

Plasticity of mesenchymal stem cells from mouse bone marrow in the presence of conditioned medium of the facial nerve and fibroblast growth factor-2

A number of evidences show the influence of the growth of injured nerve fibers in peripheral nervous system as well as potential implant stem cells (SCs). The SCs implementation in the clinical field is promising and the understanding of proliferation and differentiation is essential. This study aimed to evaluate the plasticity of mesenchymal SCs from bone marrow of mice in the presence of culture medium conditioned with facial nerve explants and fibroblast growth factor-2 (FGF-2). The growth and morphology were assessed for over 72 hours. Quantitative phenotypic analysis was taken from the immunocytochemistry for glial fibrillary acidic protein (GFAP), protein OX-42 (OX-42), protein associated with microtubule MAP-2 (MAP-2), protein β-tubulin III (β-tubulin III), neuronal nuclear protein (NeuN), and neurofilament 200 (NF-200). Cells cultured with conditioned medium alone or combined with FGF-2 showed morphological features apparently similar at certain times to neurons and glia and a significant proliferative activity in groups 2 and 4. Cells cultivated only with conditioned medium acquired a glial phenotype. Cells cultured with FGF-2 and conditioned medium expressed GFAP, OX-42, MAP-2, β-tubulin III, NeuN, and NF-200. This study improves our understanding of the plasticity of mesenchymal cells and allows the search for better techniques with SCs.

Stem cell-based approaches to improve nerve regeneration: potential implications for reconstructive transplantation?

Reconstructive transplantation has become a viable option to restore form and function after devastating tissue loss. Functional recovery is a key determinant of overall success and critically depends on the quality and pace of nerve regeneration. Several molecular and cell-based therapies have been postulated and tested in pre-clinical animal models to enhance nerve regeneration. Schwann cells remain the mainstay of research focus providing neurotrophic support and signaling cues for regenerating axons. Alternative cell sources such as mesenchymal stem cells and adipose-derived stromal cells have also been tested in pre-clinical animal models and in clinical trials due to their relative ease of harvest, rapid expansion in vitro, minimal immunogenicity, and capacity to integrate and survive within host tissues, thereby overcoming many of the challenges faced by culturing of human Schwann cells and nerve allografting. Induced pluripotent stem cell-derived Schwann cells are of particular interest since they can provide abundant, patient-specific autologous Schwann cells. The majority of experimental evidence on cell-based therapies, however, has been generated using stem cell-seeded nerve guides that were developed to enhance nerve regeneration across "gaps" in neural repair. Although primary end-to-end repair is the preferred method of neurorrhaphy in reconstructive transplantation, mechanistic studies elucidating the principles of cell-based therapies from nerve guidance conduits will form the foundation of further research employing stem cells in end-to-end repair of donor and recipient nerves. This review presents key components of nerve regeneration in reconstructive transplantation and highlights the pre-clinical studies that utilize stem cells to enhance nerve regeneration.

Differentiation of equine mesenchymal stromal cells into cells of neural lineage: potential for clinical applications

Mesenchymal stromal cells (MSCs) are able to differentiate into extramesodermal lineages, including neurons. Positive outcomes were obtained after transplantation of neurally induced MSCs in laboratory animals after nerve injury, but this is unknown in horses. Our objectives were to test the ability of equine MSCs to differentiate into cells of neural lineage in vitro, to assess differences in morphology and lineage-specific protein expression, and to investigate if horse age and cell passage number affected the ability to achieve differentiation. Bone marrow-derived MSCs were obtained from young and adult horses. Following demonstration of stemness, MSCs were neurally induced and microscopically assessed at different time points. Results showed that commercially available nitrogen-coated tissue culture plates supported proliferation and differentiation. Morphological changes were immediate and all the cells displayed a neural crest-like cell phenotype. Expression of neural progenitor proteins, was assessed via western blot or immunofluorescence. In our study, MSCs generated from young and middle-aged horses did not show differences in their ability to undergo differentiation. The effect of cell passage number, however, is inconsistent and further experiments are needed. Ongoing work is aimed at transdifferentiating these cells into Schwann cells for transplantation into a peripheral nerve injury model in horses.

Sensory recovery after cell therapy in peripheral nerve repair: effects of naïve and skin precursor-derived Schwann cells

Object

Cell therapy is a promising candidate among biological or technological innovations sought to augment microsurgical techniques in peripheral nerve repair. This report describes long-term functional regenerative effects of cell therapy in the rat injury model with a focus on sensory recovery.

Methods

Schwann cells were derived from isogenic nerve or skin precursor cells and injected into the transected and immediately repaired sciatic nerve distal to the injury site. Sensory recovery was assessed at weeks 4, 7, and 10. Axonal regeneration was assessed at Week 11.

Results

By Week 10, thermal sensitivity in cell therapy groups returned to a level indistinguishable from the baseline (p > 0.05). Immunohistochemistry at 11 weeks after injury showed improved regeneration of NF+ and IB4+ axons.

Conclusions:

The results of this study show that cell therapy significantly improves thermal sensation and the number of regenerated sensory neurons at 11 weeks after injury. These findings contribute to the view of skin-derived stem cells as a reliable source of Schwann cells with therapeutic potential for functional recovery in damaged peripheral nerve.

Transplanted hUCB-MSCs migrated to the damaged area by SDF-1/CXCR4 signaling to promote functional recovery after traumatic brain injury in rats

Transplanted human umbilical cord mesenchymal stem cells (hUC-MSCs) have exhibited considerable therapeutic potential for traumatic brain injury (TBI). However, how hUC-MSCs migrating to the injury region and the mechanism of hUC-MSCs promoting functional recovery after TBI are still unclear. In this study, we investigated whether stromal cell-derived factor-1 (SDF-1) was involved in the hUC-MSCs migration and the possible mechanisms that might be involved in the beneficial effect on functional recovery. In vitro experiments demonstrated that SDF-1 induces a concentration-dependent migration of hUC-MSCs. Furthermore, pre-treatment with the CXCR4-specific antagonist AMD3100 significantly prevented the migration of hUC-MSCs in vitro. We found that the expression of SDF-1 increased significantly around the damaged area. Transplanted hUC-MSCs were localized to regions where SDF-1 was highly expressed. Additionally, our results showed that hUC-MSCs-treated animals showed significantly improved functional recovery compared with controls. In hUC-MSCs-transplanted group, terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL)-positive cells were decreased and BrdU-positive cells were significantly increased compared with control group, more of BrdU-positive cells co-localized with GFAP. These suggest that SDF-1 plays an important role in the migration of hUC-MSCs to the damaged area and hUC-MSCs are beneficial for functional recovery after TBI.

Schwann-like cells seeded in acellular nerve grafts improve nerve regeneration

BACKGROUND

This study evaluated whether Schwann-like cells (SLCs) induced from bone marrow-derived mesenchymal stem cells (BM-MSCs) transplanted into acellular nerve grafts (ANGs) could repair nerve defects compared with nerve isografts and ANGs with BM-MSCs.

METHODS

BM-MSCs extracted, separated and purified from the bone marrow of rats, and some of the BM-MSCs were cultured with mixed induction agents that could induce BM-MSCs into SLCs. Either SLCs or BM-MSCs were seeded onto 10-mm ANGs, and the isografts were chosen as the control. The walking-track test, tibialis anterior muscle weight measurement, electrophysiological examination, toluidine blue staining, transmission electron micrographs and immunostaining of S-100 and VEGF in these three groups were evaluated in a 10-mm rat sciatic injury-repair model.

RESULTS

The walking-track test, tibialis anterior muscle weight measurement and electrophysiological examination of the sciatic nerve suggested the groups of ANGs with SLCs and isografts obtained better results than the BM-MSC group (P<0.05). Meanwhile, the results of the SLCs and isograft groups were similar (P>0.05). All the histomorphometric analyses (toluidine blue staining, transmission electron micrographs and immunostaining of S-100 and VEGF) showed that there were more regenerating nerve fibers in the group of ANGs with SLCs than the BM-MSCs (P<0.05), but there was no significant difference between the SLC and isograft groups (P>0.05).

CONCLUSIONS

SLCs seeded in ANGs and isografts show better functional regeneration compared with BM-MSCs seeded in ANGs. Additionally, SLCs combined with ANGs present almost the same outcome as the isografts. Therefore, SLCs with ANGs can be a good choice in nerve defect repairs.

Transplantation of bone marrow mesenchymal stem cells decreases oxidative stress, apoptosis, and hippocampal damage in brain of a spontaneous stroke model

Stroke is the most common cause of motor disabilities and is a major cause of mortality worldwide. Adult stem cells have been shown to be effective against neuronal degeneration through mechanisms that include both the recovery of neurotransmitter activity and a decrease in apoptosis and oxidative stress. We chose the lineage stroke-prone spontaneously hypertensive rat (SHRSP) as a model for stem cell therapy. SHRSP rats can develop such severe hypertension that they generally suffer a stroke at approximately 1 year of age. The aim of this study was to evaluate whether mesenchymal stem cells (MSCs) decrease apoptotic death and oxidative stress in existing SHRSP brain tissue. The results of qRT-PCR assays showed higher levels of the antiapoptotic Bcl-2 gene in the MSC-treated animals, compared with untreated. Our study also showed that superoxide, apoptotic cells, and by-products of lipid peroxidation decreased in MSC-treated SHRSP to levels similar those found in the animal controls, Wistar Kyoto rats. In addition, we saw a repair of morphological damage at the hippocampal region after MSC transplantation. These data suggest that MSCs have neuroprotective and antioxidant potential in stroke-prone spontaneously hypertensive rats.

Grafted bone marrow stromal cells: a contributor to glial repair after spinal cord injury

In the CNS, astrocytes, oligodendrocytes and microglias are involved in not only development but also pathology such as spinal cord injury (SCI). Glial cells play dual roles (negative vs. positive effects) in these processes. After SCI, detrimental effects usually dominate and significantly retard functional recovery, and curbing these effects is critical for promoting neurological improvement. Bone marrow stromal cells (BMSCs) represent a new therapeutic approach for SCI by enabling improved sensory and motor functions in animal models. Although transdifferentiation to spinal neurons was poor, because of their pleiotropic nature, the protective effects of BMSCs are broad and are primarily mediated through modulation of transdifferentiation into host spinal glial components. Transplantation of BMSCs can positively alter the spinal microenvironment and enhance recovery. The objective of this review is to discuss these and other related mechanisms. Since BMSCs transplantation has been applied in other clinical fields, we hope to provide useful clues for the clinical application of BMSCs to treat the SCI in the near future.

Cell-based reparative therapies for multiple sclerosis

The strong rationale for cell-based therapy in multiple sclerosis is based on the ability of stem and precursor cells of neural and mesenchymal origin to attenuate neuroinflammation, to facilitate endogenous repair processes, and to participate directly in remyelination, if directed towards a myelin-forming fate. However, there are still major gaps in knowledge regarding induction of repair in chronic multiple sclerosis lesions, and whether transplanted cells can overcome the multiple environmental inhibitory factors which underlie the failure of endogenous repair. Major challenges in clinical translation include the determination of the optimal cellular platform, the route of cell delivery, and candidate patients for treatment.

Stem cell salvage of injured peripheral nerve

We previously developed a collagen tube filled with autologous skin-derived stem cells (SDSCs) for bridging long rat sciatic nerve gaps. Here we present a case report describing a compassionate use of this graft for repairing the polyinjured motor and sensory nerves of the upper arms of a patient. Preclinical assessment was performed with collagen/SDSC implantation in rats after sectioning the sciatic nerve. For the patient, during the 3-year follow-up period, functional recovery of injured median and ulnar nerves was assessed by pinch gauge test and static two-point discrimination and touch test with monofilaments, along with electrophysiological and MRI examinations. Preclinical experiments in rats revealed rescue of sciatic nerve and no side effects of patient-derived SDSC transplantation (30 and 180 days of treatment). In the patient treatment, motor and sensory functions of the median nerve demonstrated ongoing recovery postimplantation during the follow-up period. The results indicate that the collagen/SDSC artificial nerve graft could be used for surgical repair of larger defects in major lesions of peripheral nerves, increasing patient quality of life by saving the upper arms from amputation.

In toto differentiation of human amniotic membrane towards the Schwann cell lineage

Human amniotic membrane (hAM) is a tissue containing cells with proven stem cell properties. In its decellularized form it has been successfully applied as nerve conduit biomaterial to improve peripheral nerve regeneration in injury models. We hypothesize that viable hAM without prior cell isolation can be differentiated towards the Schwann cell lineage to generate a possible alternative to commonly applied tissue engineering materials for nerve regeneration. For in vitro Schwann cell differentiation, biopsies of hAM of 8 mm diameter were incubated with a sequential order of neuronal induction and growth factors for 21 days and characterized for cellular viability and the typical glial markers glial fibrillary acidic protein (GFAP), S100β, p75 and neurotrophic tyrosine kinase receptor (NTRK) using immunohistology. The secretion of the neurotrophic factors brain-derived neurotrophic factor (BDNF) and glial cell-derived neurotrophic factor (GDNF) was quantified by ELISA. The hAM maintained high viability, especially under differentiation conditions (90.2 % ± 41.6 day 14; 80.0 % ± 44.5 day 21 compared to day 0). Both, BDNF and GDNF secretion was up-regulated upon differentiation. The fresh membrane stained positive for GFAP and p75 and NTRK, which was strongly increased after culture in differentiation conditions. Especially the epithelial layer within the membrane exhibited a change in morphology upon differentiation forming a multi-layered epithelium with intense accumulations of the marker proteins. However, S100β was expressed at equal levels and equal distribution in fresh and cultured hAM conditions. Viable hAM may be a promising alternative to present formulations used for peripheral nerve regeneration.

Tissue engineered constructs for peripheral nerve surgery

BACKGROUND

Tissue engineering has been defined as "an interdisciplinary field that applies the principles of engineering and life sciences toward the development of biological substitutes that restore, maintain, or improve tissue function or a whole organ". Traumatic peripheral nerve injury resulting in significant tissue loss at the zone of injury necessitates the need for a bridge or scaffold for regenerating axons from the proximal stump to reach the distal stump.

METHODS

A review of the literature was used to provide information on the components necessary for the development of a tissue engineered peripheral nerve substitute. Then, a comprehensive review of the literature is presented composed of the studies devoted to this goal.

RESULTS

Extensive research has been directed toward the development of a tissue engineered peripheral nerve substitute to act as a bridge for regenerating axons from the proximal nerve stump seeking the distal nerve. Ideally this nerve substitute would consist of a scaffold component that mimics the extracellular matrix of the peripheral nerve and a cellular component that serves to stimulate and support regenerating peripheral nerve axons.

CONCLUSIONS

The field of tissue engineering should consider its challenge to not only meet the autograft "gold standard" but also to understand what drives and inhibits nerve regeneration in order to surpass the results of an autograft.