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

Regenerative Medicine: A New Horizon in Peripheral Nerve Injury and Repair

A peripheral nerve injury is a great burden for the patient and a challenge for the clinician. In a complete injury (axonotmesis or neurotmesis), the slow nature of nerve regeneration after repair or reconstruction hardly catches up to the target organ's degeneration rate, leading to a poor prognosis. The current advance in regenerative medicine has shown the potency of stem cells and their products for healing many human body structures, including the nerve. A comprehensive literature search was conducted using an internet-based search engine for current advances in regenerative medicine to augment peripheral nerve repair or reconstruction. Stem cells can differentiate into nerve cells and have paracrine and immunomodulatory effects. Its products, such as the secretome and exosome, have also been studied, and they have many benefits for the regeneration process. This novel treatment possesses significant potential to accelerate nerve healing after nerve reconstruction and potentially postpone the degenerative process in the target organ, allowing it to respond to the new signal once nerve regeneration is complete. The aim of this article is to summarized the application of stem cells and its products for nerve healing.

Nerve guidance conduit development for primary treatment of peripheral nerve transection injuries: A commercial perspective

Commercial nerve guidance conduits (NGCs) for repair of peripheral nerve discontinuities are of little use in gaps larger than 30 mm, and for smaller gaps they often fail to compete with the autografts that they are designed to replace. While recent research to develop new technologies for use in NGCs has produced many advanced designs with seemingly positive functional outcomes in animal models, these advances have not been translated into viable clinical products. While there have been many detailed reviews of the technologies available for creating NGCs, none of these have focussed on the requirements of the commercialisation process which are vital to ensure the translation of a technology from bench to clinic. Consideration of the factors essential for commercial viability, including regulatory clearance, reimbursement processes, manufacturability and scale up, and quality management early in the design process is vital in giving new technologies the best chance at achieving real-world impact. Here we have attempted to summarise the major components to consider during the development of emerging NGC technologies as a guide for those looking to develop new technology in this domain. We also examine a selection of the latest academic developments from the viewpoint of clinical translation, and discuss areas where we believe further work would be most likely to bring new NGC technologies to the clinic. STATEMENT OF SIGNIFICANCE: NGCs for peripheral nerve repairs represent an adaptable foundation with potential to incorporate modifications to improve nerve regeneration outcomes. In this review we outline the regulatory processes that functionally distinct NGCs may need to address and explore new modifications and the complications that may need to be addressed during the translation process from bench to clinic.

Mesenchymal Stem Cell Treatment Perspectives in Peripheral Nerve Regeneration: Systematic Review

Traumatic peripheral nerve lesions affect hundreds of thousands of patients every year; their consequences are life-altering and often devastating and cause alterations in movement and sensitivity. Spontaneous peripheral nerve recovery is often inadequate. In this context, nowadays, cell therapy represents one of the most innovative approaches in the field of nerve repair therapies. The purpose of this systematic review is to discuss the features of different types of mesenchymal stem cells (MSCs) relevant for peripheral nerve regeneration after nerve injury. The published literature was reviewed following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A combination of the keywords "nerve regeneration", "stem cells", "peripheral nerve injury", "rat", and "human" were used. Additionally, a "MeSH" research was performed in PubMed using the terms "stem cells" and "nerve regeneration". The characteristics of the most widely used MSCs, their paracrine potential, targeted stimulation, and differentiation potentials into Schwann-like and neuronal-like cells are described in this paper. Considering their ability to support and stimulate axonal growth, their remarkable paracrine activity, their presumed differentiation potential, their extremely low immunogenicity, and their high survival rate after transplantation, ADSCs appear to be the most suitable and promising MSCs for the recovery of peripheral nerve lesion. Clinical considerations are finally reported.

A comparison of the use of adipose-derived and bone marrow-derived stem cells for peripheral nerve regeneration in vitro and in vivo

Background

To date, it has repeatedly been demonstrated that infusing bone marrow-derived stem cells (BMSCs) into acellular nerve scaffolds can promote and support axon regeneration through a peripheral nerve defect. However, harvesting BMSCs is an invasive and painful process fraught with a low cellular yield.

Methods

In pursuit of alternative stem cell sources, we isolated stem cells from the inguinal subcutaneous adipose tissue of adult Sprague–Dawley rats (adipose-derived stem cells, ADSCs). We used a co-culture system that allows isolated adult mesenchymal stem cells (MSCs) and Schwann cells (SCs) to grow in the same culture medium but without direct cellular contact. We verified SC phenotype in vitro by cell marker analysis and used red fluorescent protein-tagged ADSCs to detect their fate after being injected into a chemically extracted acellular nerve allograft (CEANA). To compare the regenerative effects of CEANA containing either BMSCs or ADSCs with an autograft and CEANA only on the sciatic nerve defect in vivo, we performed histological and functional assessments up to 16 weeks after grafting.

Results

In vitro, we observed reciprocal beneficial effects of ADSCs and SCs in the ADSC–SC co-culture system. Moreover, ADSCs were able to survive in CEANA for 5 days after in vitro implantation. Sixteen weeks after grafting, all results consistently showed that CEANA infused with BMSCs or ADSCs enhanced injured sciatic nerve repair compared to the acellular CEANA-only treatment. Furthermore, their beneficial effects on sciatic injury regeneration were comparable as histological and functional parameters evaluated showed no statistically significant differences. However, the autograft group was roundly superior to both the BMSC- or ADSC-loaded CEANA groups.

Conclusion

The results of the present study show that ADSCs are a viable alternative stem cell source for treating sciatic nerve injury in lieu of BMSCs.

Stem-cell-based therapies to enhance peripheral nerve regeneration

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

Combined administration on You-Gui Yin and low-dose Raloxifene partially attenuates the bone loss in ovariectomized mice through the proliferation and osteogenic differentiation of bone marrow stromal cells

BACKGROUND

Osteoporosis is a systemic skeletal disease of fragility fractures due to the loss of mass and deterioration of the microarchitecture of bone.

PURPOSE

The aim of the study was to assess the osteogenic effects and the underlying mechanisms of the combined administration of You-Gui Yin (YGY) and Raloxifene hydrochloride (RLX) in ovariectomized (OVX) mice.

METHODS

First, a classic animal model was used to mimic postmenopausal osteoporosis through the removal of the ovary of mice. Second, the OVX mice were administered YGY, RLX, and YGY + RLX for 12 weeks. Next, the bone microtomographic histomorphometry and bone mineral density (BMD) were assessed by micro-CT, and the biochemical markers of procollagen type I N-terminal propeptide (P1NP) and beta-isomerized C-telopeptide (β-CTX) in serum were assessed. Finally, primary bone marrow stromal cells (BMSCs) were isolated from the tibia and cultured to evaluate cell proliferation and osteogenic differentiation.

RESULTS

The results showed that BMD on the YGY + RLX group was higher than that on the RLX group (p < 0.05) and did not have a significant difference when compared with the sham group. Notably, the YGY + RLX group had a dramatically increased trabecular number (Tb.N) compared with that of the YGY group (p < 0.05). Moreover, the BV/TV (bone volume/total volume) and Tb.N in the YGY + RLX group were higher than that in the RLX group (p < 0.05), and the Tb.Sp (trabecular separation) was lower than that in the RLX group (p < 0.05). Moreover, the serum level of P1NP from the YGY + RLX group dramatically increased when compared with that from the YGY and RLX groups (YGY group: p < 0.05; RLX groups: p < 0.01). Notably, there was no significant difference between the YGY and YGY + RLX groups. In addition, cell proliferation from the co-administration of YGY and RLX was clearly higher than a single use of YGY and RLX (p < 0.01, respectively). The ALP/BCA (alkaline phosphatase/bicinchoninic acid) in the YGY + RLX group was higher than that in the RLX group (p < 0.01).

CONCLUSION

Overall, co-administered YGY and RLX could partially attenuate bone loss and were more effective than individually using either one; this outcome might be associated with the proliferation and osteogenic differentiation of BMSCs.

Olfactory ensheathing cells promote nerve regeneration and functional recovery after facial nerve defects

Olfactory ensheathing cells from the olfactory bulb and olfactory mucosa have been found to increase axonal sprouting and pathfinding and promote the recovery of vibrissae motor performance in facial nerve transection injured rats. However, it is not yet clear whether olfactory ensheathing cells promote the reparation of facial nerve defects in rats. In this study, a collagen sponge and silicone tube neural conduit was implanted into the 6-mm defect of the buccal branch of the facial nerve in adult rats. Olfactory ensheathing cells isolated from the olfactory bulb of newborn Sprague-Dawley rats were injected into the neural conduits connecting the ends of the broken nerves, the morphology and function of the regenerated nerves were compared between the rats implanted with olfactory ensheathing cells with the rats injected with saline. Facial paralysis was assessed. Nerve electrography was used to measure facial nerve-induced action potentials. Visual inspection, anatomical microscopy and hematoxylin-eosin staining were used to assess the histomorphology around the transplanted neural conduit and the morphology of the regenerated nerve. Using fluorogold retrograde tracing, toluidine blue staining and lead uranyl acetate staining, we also measured the number of neurons in the anterior exterior lateral facial nerve motor nucleus, the number of myelinated nerve fibers, and nerve fiber diameter and myelin sheath thickness, respectively. After surgery, olfactory ensheathing cells decreased facial paralysis and the latency of the facial nerve-induced action potentials. There were no differences in the general morphology of the regenerating nerves between the rats implanted with olfactory ensheathing cells and the rats injected with saline. Between-group results showed that olfactory ensheathing cell treatment increased the number of regenerated neurons, improved nerve fiber morphology, and increased the number of myelinated nerve fibers, nerve fiber diameter, and myelin sheath thickness. In conclusion, implantation of olfactory ensheathing cells can promote regeneration and functional recovery after facial nerve damage in rats.

Electrical stimulation promotes regeneration and re-myelination of axons of injured facial nerve in rats

Objective To investigate the effects of electrical stimulation (ES) on the nerve regeneration and functional recovery of facial expression muscles in facial nerve defect rats. Methods Sixty rats were surgically introduced with a 1-cm defect on the right facial nerves and evenly divided into the Surgery group (Group A, the main trunk of the right facial nerve was surgically cut-off with a 1.0 cm at the foramina stylomastoideum) and the Surgery + ES group (Group B). Twenty normal rats were as normal control group (without receiving surgery or ES). For rats in group B, the orbicularis oris muscle of the right paralyzed face was stimulated with an electrical pulse of 3 V, 20 Hz and 0.3 mA for 1 h each day. The effects of ES on the facial muscle movement, compound muscle action potentials (CMAPs), histological structure, and the expression levels of S100B and NF200 proteins were comparatively studied. Results In group A, facial paralysis scores were slightly improved from day 1 to 28; the facial nerve trunks had swelled and malformed till day 14; and CMAPs could be induced in fewer animals and were abnormal, resulting in a slow recovery of the facial muscle movement. In group B, facial paralysis scores were improved from 4 to 2.6 during the 4 weeks; more rats showed a higher amplitude and shorter latency of CMAPs from day 14 to 28 after surgery; and increased axons and the expression of S100B and NF200 proteins and gradually decreased swelling in the injured facial nerve. Conclusion ES promotes outgrowth and myelination of axons and a partial functional recovery of facial muscles in injured facial nerve rats.

An update-tissue engineered nerve grafts for the repair of peripheral nerve injuries

Peripheral nerve injuries (PNI) are caused by a range of etiologies and result in a broad spectrum of disability. While nerve autografts are the current gold standard for the reconstruction of extensive nerve damage, the limited supply of autologous nerve and complications associated with harvesting nerve from a second surgical site has driven groups from multiple disciplines, including biomedical engineering, neurosurgery, plastic surgery, and orthopedic surgery, to develop a suitable or superior alternative to autografting. Over the last couple of decades, various types of scaffolds, such as acellular nerve grafts (ANGs), nerve guidance conduits, and non-nervous tissues, have been filled with Schwann cells, stem cells, and/or neurotrophic factors to develop tissue engineered nerve grafts (TENGs). Although these have shown promising effects on peripheral nerve regeneration in experimental models, the autograft has remained the gold standard for large nerve gaps. This review provides a discussion of recent advances in the development of TENGs and their efficacy in experimental models. Specifically, TENGs have been enhanced via incorporation of genetically engineered cells, methods to improve stem cell survival and differentiation, optimized delivery of neurotrophic factors via drug delivery systems (DDS), co-administration of platelet-rich plasma (PRP), and pretreatment with chondroitinase ABC (Ch-ABC). Other notable advancements include conduits that have been bioengineered to mimic native nerve structure via cell-derived extracellular matrix (ECM) deposition, and the development of transplantable living nervous tissue constructs from rat and human dorsal root ganglia (DRG) neurons. Grafts composed of non-nervous tissues, such as vein, artery, and muscle, will be briefly discussed.

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

Objective

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

Materials and Methods

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

Results

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

Conclusion

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

Orientated Guidance of Peripheral Nerve Regeneration Using Conduits with a Microtube Array Sheet (MTAS)

Material surface topography has been shown to affect the biological behavior of cells in vitro; however, the in vivo effect on peripheral nerve regeneration has not been explored. Here, we studied the potential of a microtube array sheet (MTAS) with a unique longitudinal surface topography to promote peripheral nerve regeneration efficiency, both in vivo and in vitro. Schwann cells, spinal cord motor neurons, and dorsal root ganglion neurons were seeded on the MTAS to study the effect of the construct on the biological properties and behaviors of neural cells. The MTAS guided the oriented migration of Schwann cells without affecting other critical biological properties, such as proliferation and neurotrophin expression. In addition, the MTAS guided the directed extension of neurites from both types of neurons. Next, we tested the capability of the MTAS to facilitate peripheral nerve regeneration by bridging a 10 mm sciatic nerve defect in rats with a nerve conduit equipped with an MTAS lining. The MTAS significantly promoted peripheral nerve regeneration, as suggested by the greater fiber caliber in the midconduit and the greater abundance of fibers in nerve segment distal to the conduit. Moreover, scanning electron microscopy (SEM) analysis suggested the orientated guidance of nerve regeneration by the MTAS, as indicated by the smaller eccentricity of the nerve fibers and the concordant arrangement of the collagen fiber in both the fibers and the matrix in the MTAS group. Our results collectively suggest that the conduits with the MTAS developed in this study have significant potential for facilitating peripheral nerve regeneration by modifying critical biological behaviors and guiding orientated nerve growth.