Characterization of Nerve Conduits Seeded with Neurons and Schwann Cells Derived from Hair Follicle Neural Crest Stem Cells

Predicting in vivo therapeutic efficacy of CelTrac1000-labeled hair follicle epidermal neural crest stem cells in models of repairing rat facial nerve defects via second near-infrared fluorescence imaging

AIMS

To detect the therapeutic efficacy of CelTrac1000-labeled hair follicle epidermal neural crest stem cells (EPI-NCSCs) on repairing facial nerve defects by second near-infrared (NIR-II) fluorescence imaging.

MATERIALS AND METHODS

Firstly, CelTrac1000-labeled EPI-NCSCs were microinjected into the acellular nerve allografts (ANAs) to bridge a 10-mm-long gap in the buccal branch of facial nerve in adult rats. Then, Celtrac1000-labeled EPI-NCSCs were detected by NIR-II fluorescence imaging system to visualize the behavior of the transplanted cells in vivo. Additionally, the effect of the transplanted EPI-NCSCs on repairing facial nerve defect was examined.

KEY FINDINGS

Through 14 weeks of dynamic observation, the transplanted EPI-NCSCs survived in the ANAs in vivo after surgery. Meanwhile, the region of the NIR-II fluorescence signals was gradually limited to be consistent with the direction of the regenerative nerve segment. Furthermore, the results of functional and morphological analysis showed that the transplanted EPI-NCSCs could promote the recovery of facial paralysis and neural regeneration after injury.

SIGNIFICANCE

Our research provides a novel way to track the transplanted cells in preclinical studies of cell therapy for facial paralysis, and demonstrates the therapeutic potential of EPI-NCSCs combined with ANAs in bridging rat facial nerve defects.

The phenotypic changes of Schwann cells promote the functional repair of nerve injury

Functional recovery after nerve injury is a significant challenge due to the complex nature of nerve injury repair and the non-regeneration of neurons. Schwann cells (SCs), play a crucial role in the nerve injury repair process because of their high plasticity, secretion, and migration abilities. Upon nerve injury, SCs undergo a phenotypic change and redifferentiate into a repair phenotype, which helps in healing by recruiting phagocytes, removing myelin fragments, promoting axon regeneration, and facilitating myelin formation. However, the repair phenotype can be unstable, limiting the effectiveness of the repair. Recent research has found that transplantation of SCs can be an effective treatment option, therefore, it is essential to comprehend the phenotypic changes of SCs and clarify the related mechanisms to develop the transplantation therapy further.

The Effect of Schwann Cells/Schwann Cell-Like Cells on Cell Therapy for Peripheral Neuropathy

Peripheral neuropathy is a common neurological issue that leads to sensory and motor disorders. Over time, the treatment for peripheral neuropathy has primarily focused on medications for specific symptoms and surgical techniques. Despite the different advantages of these treatments, functional recovery remains less than ideal. Schwann cells, as the primary glial cells in the peripheral nervous system, play crucial roles in physiological and pathological conditions by maintaining nerve structure and functions and secreting various signaling molecules and neurotrophic factors to support both axonal growth and myelination. In addition, stem cells, including mesenchymal stromal cells, skin precursor cells and neural stem cells, have the potential to differentiate into Schwann-like cells to perform similar functions as Schwann cells. Therefore, accumulating evidence indicates that Schwann cell transplantation plays a crucial role in the resolution of peripheral neuropathy. In this review, we summarize the literature regarding the use of Schwann cell/Schwann cell-like cell transplantation for different peripheral neuropathies and the potential role of promoting nerve repair and functional recovery. Finally, we discuss the limitations and challenges of Schwann cell/Schwann cell-like cell transplantation in future clinical applications. Together, these studies provide insights into the effect of Schwann cells/Schwann cell-like cells on cell therapy and uncover prospective therapeutic strategies for peripheral neuropathy.

Olig2 positive cells derived from hair follicle neural crest stem cells in rats

Motor neuron disease (MND) is a kind of common clinical nervous system disease with typical characteristic of progressive motor neurons degeneration or death. Motor neuron derived from stem cells or motor neuron progenitor cells will be a good choice to be used for treatment of the disease. In this study, we used the combination of 5 small molecular including CHIR99021 (CHIR), SB431542 (SB), DMH1 (DMH), retinoic acid (RA) and Purmorphamine (Pur) to induce hair follicles neural crest stem cells (hfNCSCs) to motor neurons progenitors (MNPs). Valproic acid (VPA) was used to make MNPs proliferation. RA and Pur were used to try to induce MNPs toward motor neurons (MNs) and CpdE was tried for MNs maturation. Nestin, β-tubulin Ш (Tuj1), microtubule associated protein 2 (MAP2), Olig2, choline acetyltransferase (ChAT)and TUBB3 were examined at protein and mRNA levels by immunofluoresence cytochemistry, western blot and real time PCR at 6, 16 and 22 days. Our data showed cells changed into bipolar or multipolar shape forming the cell clusters like scattered rosettes. Nestin expression decreased significantly at 22 days. Compared to 6 days, percentage of Olig2 + MNPs was higher, (88.53 ± 6.67)%, and Olig2 expression at protein and gene level was lower at 22 days. Percentage of MAP2 positive cells increased to (90.62 ± 2.31) % and ChAT positive cells increased to (83.29 ± 6.62) % at 22 days. But no expression of ChAT was examined by western blot and real time PCR. It indicates that these 5 molecular can differentiate hfNCSCs into Olig2 positive cells with a unipotent differentiation toward motor neurons.

Advances in stem cell treatment for sciatic nerve injury

INTRODUCTION

The sciatic nerve is one of the peripheral nerves that is most prone to injuries. After injury, the connection between the nervous system and the distal organs is disrupted, and delayed treatment results in distal organ atrophy and total disability. Regardless of great advances in the fields of neurosurgery, biological sciences, and regenerative medicine, total functional recovery is yet to be achieved.

AREAS COVERED

Cell-based therapy for the treatment of peripheral nerve injuries (PNIs) has brought a new perspective to the field of regenerative medicine. Having the ability to differentiate into neural and glial cells, stem cells enhance neural regeneration after PNIs. Augmenting axonal regeneration, remyelination, and muscle mass preservation are the main mechanisms underlying stem cells' beneficial effects on neural regeneration.

EXPERT OPINION

Despite the usefulness of employing stem cells for the treatment of PNIs in pre-clinical settings, further assessments are still needed in order to translate this approach into clinical settings. Mesenchymal stem cells, especially adipose-derived stem cells, with the ability of autologous transplantation, as well as easy harvesting procedures, are speculated to be the most promising source to be used in the treatment of PNIs.

Stem cells purified from human induced pluripotent stem cell-derived neural crest-like cells promote peripheral nerve regeneration

Strategies for therapeutic cell transplantation have been assessed for use in the treatment of massive peripheral nerve defects. To support safe and efficient cell transplantation, we have focused on the purification of cells using cell surface markers. Our group previously reported low-affinity nerve growth factor receptor (LNGFR)- and thymocyte antigen-1 (THY-1)-positive neural crest-like cells (LT-NCLCs), generated from human induced pluripotent stem cells (hiPSCs). In the present study, we investigated the efficacy of transplantation of hiPSC-derived LT-NCLCs in a murine massive peripheral nerve defect model. Animals with a sciatic nerve defect were treated with a bridging silicone tube prefilled with LT-NCLCs or medium in the transplantation (TP) and negative control (NC) groups, respectively. The grafted LT-NCLCs survived and enhanced myelination and angiogenesis, as compared to the NC group. Behavioral analysis indicated that motor functional recovery in the TP group was superior to that in the NC group, and similar to that in the autograft (Auto) group. LT-NCLCs promoted axonal regrowth and remyelination by Schwann cells. Transplantation of LT-NCLCs is a promising approach for nerve regeneration treatment of massive peripheral nerve defects.

Regenerative effects of human embryonic stem cell-derived neural crest cells for treatment of peripheral nerve injury

Surgical intervention is the current gold standard treatment following peripheral nerve injury. However, this approach has limitations, and full recovery of both motor and sensory modalities often remains incomplete. The development of artificial nerve grafts that either complement or replace current surgical procedures is therefore of paramount importance. An essential component of artificial grafts is biodegradable conduits and transplanted cells that provide trophic support during the regenerative process. Neural crest cells are promising support cell candidates because they are the parent population to many peripheral nervous system lineages. In this study, neural crest cells were differentiated from human embryonic stem cells. The differentiated cells exhibited typical stellate morphology and protein expression signatures that were comparable with native neural crest. Conditioned media harvested from the differentiated cells contained a range of biologically active trophic factors and was able to stimulate in vitro neurite outgrowth. Differentiated neural crest cells were seeded into a biodegradable nerve conduit, and their regeneration potential was assessed in a rat sciatic nerve injury model. A robust regeneration front was observed across the entire width of the conduit seeded with the differentiated neural crest cells. Moreover, the up-regulation of several regeneration-related genes was observed within the dorsal root ganglion and spinal cord segments harvested from transplanted animals. Our results demonstrate that the differentiated neural crest cells are biologically active and provide trophic support to stimulate peripheral nerve regeneration. Differentiated neural crest cells are therefore promising supporting cell candidates to aid in peripheral nerve repair.

Sciatic nerve regeneration by transplantation of in vitro differentiated nucleus pulposus progenitor cells

Aim: To assess the applicability of mouse intervertebral disc-derived nucleus pulposus (NP) progenitor cells as a cell source for sciatic nerve regeneration. Materials & methods: P0-Cre/Floxed-EGFP-transgenic mouse-derived NP progenitor cells were differentiated to Schwann-like cells in conventional induction medium. Schwann-like cells were subsequently transplanted into a mouse model of sciatic nerve transection, and nerve regeneration assessed by immunohistochemistry, electron microscopy and functional walking track analysis and heat stimulus reflex. Results & conclusion: NP progenitor cells differentiated into Schwann-like cells. Transplantation of these cells promoted myelinated axon formation, morphology restoration and nerve function improvement. NP progenitor cells have the capacity to differentiate into neuronal cells and are candidates for peripheral nerve regeneration therapy.

Engineering of the human vessel wall with hair follicle stem cells in vitro

Hair follicle stem cells (HFSCs) are increasingly used as a stem cell paradigm in vascular tissue engineering due to the fact that they are a rich source of easily accessible multipotent adult stem cells. Promising results have been demonstrated with small diameter (less than 6 mm) tissue engineered blood vessels under low blood pressure, however engineering large vessels (>6 mm in diameter) remains a challenge due to the fact it demands a higher number of seed cells and higher quality biomechanical properties. The aim of the current study was to engineer a large vessel (6 mm in diameter) with differentiated smooth muscle cells (SMCs) induced from human (h)HFSCs using transforming growth factor‑β1 and platelet‑derived growth factor BB in combination with low‑serum culture medium. The cells were seeded onto polyglycolic acid and then wrapped around a silicone tube and further cultured in vitro. A round vessel wall was formed subsequent to 8 weeks of culture. Histological examination indicated that layers of smooth muscle‑like cells and collagenous fibres were oriented in the induced group. In contrast, disorganised cells and collagenous fibres were apparent in the undifferentiated group. The approach developed in the current study demonstrated potential for constructing large muscular vessels with differentiated SMCs induced from hHFSCs.

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.

Construction of Tissue-Engineered Nerve Conduits Seeded with Neurons Derived from Hair-Follicle Neural Crest Stem Cells

Tissue-engineered nerve conduits are widely used for the study of peripheral nerve injury repair. With regard to repairing long nerve defects, stem-cell-derived neurons are recommended as seed cells. As hair-follicle neural crest stem cells (hfNCSCs) are easily to be harvested from patients and have the potential to differentiate into neuronal cells, hfNCSCs-derived neurons are an ideal candidate choice. Acellular nerve grafts, a type of biological material scaffold, with intact collagen structure, with biocompatibility and less toxicity are obtained through removing live cells with 1 % lysolecithin, are also an ideal choice. In the present report, we describe a tissue-engineered nerve conduit seeded with rat hfNCSCs-derived neurons into the beagle acellular sciatic nerve scaffold. Our goal is to provide a novel engineered therapeutic for repairing peripheral nerve injury with long distance defects.

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

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

Effects of low-intensity pulsed ultrasound on cell viability, proliferation and neural differentiation of induced pluripotent stem cells-derived neural crest stem cells

Low-intensity pulsed ultrasound (LIPUS) acting on induced pluripotent stem cells-derived neural crest stem cells (iPSCs-NCSCs) is considered a promising therapy to improve the efficacy of injured peripheral nerve regeneration. Effects of LIPUS on cell viability, proliferation and neural differentiation of iPSCs-NCSCs were examined respectively in this study. LIPUS at 500 mW cm(-2) enhanced the viability and proliferation of iPSCs-NCSCs after 2 days and, after 4 days, up-regulated gene and protein expressions of NF-M, Tuj1, S100β and GFAP in iPSCs-NCSCs whereas after 7 days expression of only NF-M, S100β and GFAP were up-regulated. LIPUS treatment at an appropriate intensity can, therefore, be an efficient and cost-effective method to enhance cell viability, proliferation and neural differentiation of iPSCs-NCSCs in vitro for peripheral nerve tissue engineering.

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

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

Differentiation of human hair follicle stem cells into endothelial cells induced by vascular endothelial and basic fibroblast growth factors

Hair follicle stem cells (HFSCs) possess powerful expansion and multi‑differentiation potential, properties that place them at the forefront of the field of tissue engineering and stem cell‑based therapy. The aim of the present study was to investigate the differentiation of human HFSCs (hHFSCs) into cells of an endothelial lineage. hHFSCs were expanded to the second passage in vitro and then induced by the addition of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) to the culture medium. The expression levels of endothelial cell (EC)‑related markers, including von Willebrand factor (vWF), vascular endothelial cadherin (VE)‑cadherin and cluster of differentiation (CD)31, were detected by immunofluorescence staining, flow cytometric analysis and reverse transcription‑polymerase chain reaction. The hHFSCs expressed vWF, VE‑cadherin and CD31 when exposed to a differentiation medium, similar to the markers expressed by the human umbilical vein ECs. More significantly, differentiated cells were also able to take up low‑density lipoprotein. The data of the present study demonstrated that an efficient strategy may be developed for differentiating hHFSCs into ECs by stimulation with VEGF and bFGF. Thus, hHFSCs represent a novel cell source for vascular tissue engineering and studies regarding the treatment of various forms of ischaemic vascular disease.

Human hair follicle stem cell differentiation into contractile smooth muscle cells is induced by transforming growth factor-β1 and platelet-derived growth factor BB

Smooth muscle cells (SMCs) are important in vascular homeostasis and disease and thus, are critical elements in vascular tissue engineering. Although adult SMCs have been used as seed cells, such mature differentiated cells suffer from limited proliferation potential and cultural senescence, particularly when originating from older donors. By comparison, human hair follicle stem cells (hHFSCs) are a reliable source of stem cells with multi-differentiation potential. The aim of the present study, was to develop an efficient strategy to derive functional SMCs from hHFSCs. hHFSCs were obtained from scalp tissues of healthy adult patients undergoing cosmetic plastic surgery. The hHFSCs were expanded to passage 2 and induced by the administration of transforming growth factor-β1 (TGF-β1) and platelet-derived growth factor BB (PDGF-BB) in combination with culture medium. Expression levels of SMC-related markers, including α-smooth muscle actin (α-SMA), α-calponin and smooth muscle myosin heavy chain (SM-MHC), were detected by immunofluorescence staining, flow cytometry analysis and reverse transcription-polymerase chain reaction (RT-PCR). When exposed to differentiation medium, hHFSCs expressed early, mid and late markers (α-SMA, α-calponin and SM-MHC, respectively) that were similar to the markers expressed by human umbilical artery SMCs. Notably, when entrapped inside a collagen matrix lattice, these SM differentiated cells showed a contractile function. Therefore, the present study developed an efficient strategy for differentiating hHFSCs into contractile SMCs by stimulation with TGF-β1 and PDGF-BB. The high yield of derivation suggests that this strategy facilitates the acquisition of the large numbers of cells that are required for blood vessel engineering and the study of vascular disease pathophysiology.

Acceleration of peripheral nerve regeneration using nerve conduits in combination with induced pluripotent stem cell technology and a basic fibroblast growth factor drug delivery system

Various modifications including addition of Schwann cells or incorporation of growth factors with bioabsorbable nerve conduits have been explored as options for peripheral nerve repair. However, no reports of nerve conduits containing both supportive cells and growth factors have been published as a regenerative therapy for peripheral nerves. In the present study, sciatic nerve gaps in mice were reconstructed in the following groups: nerve conduit alone (control group), nerve conduit coated with induced pluripotent stem cell (iPSc)-derived neurospheres (iPSc group), nerve conduit coated with iPSc-derived neurospheres and basic fibroblast growth factor (bFGF)-incorporated gelatin microspheres (iPSc + bFGF group), and autograft. The fastest functional recovery and the greatest axon regeneration occurred in the autograft group, followed in order by the iPSc + bFGF group, iPSc group, and control group until 12 weeks after reconstruction. Thus, peripheral nerve regeneration using nerve conduits and functional recovery in mice was accelerated by a combination of iPSc-derived neurospheres and a bFGF drug delivery system. The combination of all three fundamental methodologies, iPSc technology for supportive cells, bioabsorbable nerve conduits for scaffolds, and a bFGF drug delivery system for growth factors, was essential for peripheral nerve regenerative therapy.

Epidermal stem cells in orthopaedic regenerative medicine

In the last decade, great advances have been made in epidermal stem cell studies at the cellular and molecular level. These studies reported various subpopulations and differentiations existing in the epidermal stem cell. Although controversies and unknown issues remain, epidermal stem cells possess an immune-privileged property in transplantation together with easy accessibility, which is favorable for future clinical application. In this review, we will summarize the biological characteristics of epidermal stem cells, and their potential in orthopedic regenerative medicine. Epidermal stem cells play a critical role via cell replacement, and demonstrate significant translational potential in the treatment of orthopedic injuries and diseases, including treatment for wound healing, peripheral nerve and spinal cord injury, and even muscle and bone remodeling.

Hair follicle: a novel source of multipotent stem cells for tissue engineering and regenerative medicine

The adult body harbors powerful reservoirs of stem cells that enable tissue regeneration under homeostatic conditions or in response to disease or injury. The hair follicle (HF) is a readily accessible mini organ within the skin and contains stem cells from diverse developmental origins that were shown to have surprisingly broad differentiation potential. In this review, we discuss the biology of the HF with particular emphasis on the various stem cell populations residing within the tissue. We summarize the existing knowledge on putative HF stem cell markers, the differentiation potential, and technologies to isolate and expand distinct stem cell populations. We also discuss the potential of HF stem cells for drug and gene delivery, tissue engineering, and regenerative medicine. We propose that the abundance of stem cells with broad differentiation potential and the ease of accessibility makes the HF an ideal source of stem cells for gene and cell therapies.

Comparison of Schwann cells and olfactory ensheathing cells for peripheral nerve gap bridging

INTRODUCTION

Previously, we introduced the biogenic conduit (BC) as a novel autologous nerve conduit for bridging peripheral nerve defects and tested its regenerative capacity in a short- and long-term setting. The aim of the present study was to clarify whether intraluminal application of regeneration-promoting glial cells, including Schwann cells (SC) and olfactory ensheathing cells (OEC), displayed differential effects after sciatic nerve gap bridging.

MATERIAL AND METHODS

BCs were generated as previously described. The conduits filled with fibrin/SC (n = 8) and fibrin/OEC (n = 8) were compared to autologous nerve transplants (NT; n = 8) in the 15-mm sciatic nerve gap lesion model of the rat. The sciatic functional index was evaluated every 4 weeks. After 16 weeks, histological evaluation followed regarding nerve area, axon number, myelination index and N ratio.

RESULTS

Common to all groups was a continual improvement in motor function during the observation period. Recovery was significantly better after SC transplantation compared to OEC (p < 0.01). Both cell transplantation groups showed significantly worse function than the NT group (p < 0.01). Whereas nerve area and axon number were correlated to function, being significantly lowest in the OEC group (p < 0.001), both cell groups showed lowered myelination (p < 0.001) and lower N ratio compared to the NT group.

DISCUSSION

SC-filled BCs led to improved regeneration compared to OEC-filled BCs in a 15-mm-long nerve gap model of the rat.

A comparison between neurally induced bone marrow derived mesenchymal stem cells and olfactory ensheathing glial cells to repair spinal cord injuries in rat

Cell therapy has proven to be a highly promising method in clinical applications, raising so much hope for the treatment of injured tissues with low, if any, self regeneration potential such as central and peripheral nervous system. Neurally induced bone marrow derived mesenchymal stem cells (NIMSCs) as well as olfactory ensheathing cells (OECs) were transplanted in a rat model of sub-acute spinal cord injury and the behavioral and histological analyses were conducted. A balloon-compression technique was used to produce an injury at T8-T9 level of spinal cord. After a week post injury, rats were injected with either NIMSCs or OECs at the center of developing lesion cavity, 3mm cranial and 3mm caudal to the cavity. Weekly behavioral assessment using BBB score was done over five-week period post transplantation and finally histological assessment was performed to locate labeled cells in the tissue in order to evaluate the reduction of cavity formation and axonal regeneration. Evaluation of locomotor performance showed significant behavioral improvement in NIMSC group over OEC and control groups. The histological analyses revealed the presence of transplanted cells in the spinal cord parenchyma. Volume of injured area that was occupied with syrinx cavity in NIMSC group was significantly less than control group. In addition, meanwhile neurofilament-positive axons significantly showed higher expression in rats receiving NIMSC compared to the other two groups. In conclusion NIMSC caused both behavioral and histological improvement that potentially makes them a promising candidate for cell therapy approaches of spinal cord injuries.

Nerve regeneration with aid of nanotechnology and cellular engineering

Repairing nerve defects with large gaps remains one of the most operative challenges for surgeons. Incomplete recovery from peripheral nerve injuries can produce a diversity of negative outcomes, including numbness, impairment of sensory or motor function, possibility of developing chronic pain, and devastating permanent disability. In the last few years, numerous microsurgical techniques, such as coaptation, nerve autograft, and different biological or polymeric nerve conduits, have been developed to reconstruct a long segment of damaged peripheral nerve. A few of these techniques are promising and have become popular among surgeons. Advancements in the field of tissue engineering have led to development of synthetic nerve conduits as an alternative for the nerve autograft technique, which is the current practice to bridge nerve defects with gaps larger than 30 mm. However, to date, despite significant progress in this field, no material has been found to be an ideal alternative to the nerve autograft. This article briefly reviews major up-to-date published studies using different materials as an alternative to the nerve autograft to bridge peripheral nerve gaps in an attempt to assess their ability to support and enhance nerve regeneration and their prospective drawbacks, and also highlights the promising hope for nerve regeneration with the next generation of nerve conduits, which has been significantly enhanced with the tissue engineering approach, especially with the aid of nanotechnology in development of the three-dimensional scaffold. The goal is to determine potential alternatives for nerve regeneration and repair that are simply and directly applicable in clinical conditions.

Transplantation of induced pluripotent stem cell-derived neurospheres for peripheral nerve repair

In spite of the extensive research using induced pluripotent stem (iPS) cells, the therapeutic potential of iPS cells in the treatment of peripheral nerve injury is largely unknown. In this study, we repaired peripheral nerve gaps in mice using tissue-engineered bioabsorbable nerve conduits coated with iPS cell-derived neurospheres. The secondary neurospheres derived from mouse iPS cells were suspended in each conduit (4000,000 cells per conduit) and cultured in the conduit in three-dimensional (3D) culture for 14 days. We then implanted them in the mouse sciatic nerve gaps (5 mm) (iPS group; n=10). The nerve conduit alone was implanted in the control group (n=10). After 4, 8 and 12 weeks, motor and sensory functional recovery in mice were significantly better in the iPS group. At 12 weeks, all the nerve conduits remained structurally stable without any collapse and histological analysis indicated axonal regeneration in the nerve conduits of both groups. However, the iPS group showed significantly more vigorous axonal regeneration. The bioabsorbable nerve conduits created by 3D-culture of iPS cell-derived neurospheres promoted regeneration of peripheral nerves and functional recovery in vivo. The combination of iPS cell technology and bioabsorbable nerve conduits shows potential as a future tool for the treatment of peripheral nerve defects.