Transplanted neural stem cells promote nerve regeneration in acute peripheral nerve traction injury: assessment using MRI. AJR Am J Roentgenol. 2011;196:1381-1387. [PMID: 21606303 DOI: 10.2214/ajr.10.5495]

Therapeutic role of neural stem cells in neurological diseases

The failure of endogenous repair is the main feature of neurological diseases that cannot recover the damaged tissue and the resulting dysfunction. Currently, the range of treatment options for neurological diseases is limited, and the approved drugs are used to treat neurological diseases, but the therapeutic effect is still not ideal. In recent years, different studies have revealed that neural stem cells (NSCs) have made exciting achievements in the treatment of neurological diseases. NSCs have the potential of self-renewal and differentiation, which shows great foreground as the replacement therapy of endogenous cells in neurological diseases, which broadens a new way of cell therapy. The biological functions of NSCs in the repair of nerve injury include neuroprotection, promoting axonal regeneration and remyelination, secretion of neurotrophic factors, immune regulation, and improve the inflammatory microenvironment of nerve injury. All these reveal that NSCs play an important role in improving the progression of neurological diseases. Therefore, it is of great significance to better understand the functional role of NSCs in the treatment of neurological diseases. In view of this, we comprehensively discussed the application and value of NSCs in neurological diseases as well as the existing problems and challenges.

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

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

Tracking Neural Stem Cells in vivo: Achievements and Limitations

Neural stem cell (NSC) therapies are developing rapidly and have been proposed as a treatment option for various neurological diseases, such as stroke, Parkinson's disease and multiple sclerosis. However, monitoring transplanted NSCs, exploring their location and migration, and evaluating their efficacy and safety have all become serious and important issues. Two main problems in tracking NSCs have been noted: labeling them for visibility and imaging them. Direct labeling and reporter gene labeling are the two main methods for labeling stem cells. Magnetic resonance imaging and nuclear imaging, including positron emission tomography, single-photon emission computed tomography, and optical imaging, are the most commonly used imaging techniques. Each has its strengths and weaknesses. Thus, multimodal imaging, which combines two or more imaging methods to complement the advantages and disadvantages of each, has garnered increased attention. Advances in image fusion and nanotechnology, as well as the exploration of new tracers and new imaging modalities have substantially facilitated the development of NSC tracking technology. However, the safety issues related to tracking and long-term tracking of cell viability are still challenges. In this review, we discuss the merits and defects of different labeling and imaging methods, as well as recent advances, challenges and prospects in NSC tracking.

Electrical stimulation of human neural stem cells via conductive polymer nerve guides enhances peripheral nerve recovery

Severe peripheral nerve injuries often result in permanent loss of function of the affected limb. Current treatments are limited by their efficacy in supporting nerve regeneration and behavioral recovery. Here we demonstrate that electrical stimulation through conductive nerve guides (CNGs) enhances the efficacy of human neural progenitor cells (hNPCs) in treating a sciatic nerve transection in rats. Electrical stimulation strengthened the therapeutic potential of NPCs by upregulating gene expression of neurotrophic factors which are critical in augmenting synaptic remodeling, nerve regeneration, and myelination. Electrically-stimulated hNPC-containing CNGs are significantly more effective in improving sensory and motor functions starting at 1-2 weeks after treatment than either treatment alone. Electrophysiology and muscle assessment demonstrated successful re-innervation of the affected target muscles in this group. Furthermore, histological analysis highlighted an increased number of regenerated nerve fibers with thicker myelination in electrically-stimulated hNPC-containing CNGs. The elevated expression of tyrosine kinase receptors (Trk) receptors, known to bind to neurotrophic factors, indicated the long-lasting effect from electrical stimulation on nerve regeneration and distal nerve re-innervation. These data suggest that electrically-enhanced stem cell-based therapy provides a regenerative rehabilitative approach to promote peripheral nerve regeneration and functional recovery.

Regeneration of nerve crush injury using adipose-derived stem cells: A multimodal comparison

Introduction: To restore full function following nerve crush injuries is critical but challenging. In an attempt to develop a viable therapy, we evaluated the effect of rat adipose‐derived stem cells (rASC) in 2 different settings of a sciatic crush injury model. Methods: In the first group, after 14 days of nerve crush injury, rASCs were injected distal to the lesion under ultrasound guidance. In the other group, alleviation of compression through clip removal (CR) was combined with epineural injection of rASCs. Gait analyses, MRI, gastrocnemius muscle weight ratio (MWR), and histomorphometry were performed for outcome analysis. Results: CR combined with rASC injection resulted in less muscle atrophy, as evidenced by MWR. These findings are further supported by better functional and anatomical outcomes. Discussion: Animals treated with CR and epineural stem cell injection showed enhanced anatomical and functional recovery. Muscle Nerve58: 566–572, 2018

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

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

Negative Pressure Therapy in the Regeneration of the Sciatic Nerve Using Vacuum - Assisted Closure in a Rabbit Model

Background

The aim of this study was to investigate the effects of negative pressure therapy in the regeneration of the rabbit sciatic nerve using vacuum assisted closure (VAC).

Material/Methods

Thirty male New Zealand white rabbits underwent surgical injury of the sciatic nerve, followed by negative pressure therapy using vacuum assisted closure (VAC), in three treatment groups: Group A: 0 kPa; Group B: −20 kPa; Group C: −40 kPa. At 12 weeks following surgery, the following factors were studied: motor nerve conduction velocity (MNCV); the number of myelinated nerve fibers; the wet weight of the gastrocnemius muscle. Gastrocnemius muscle and sciatic nerve tissue samples were studied for the expression of S100, and brain-derived neurotrophic factor (BDNF) using Western blot.

Results

At 12 weeks following VAC treatment, the MNCV, number of myelinated nerve fibers, and wet weight of the gastrocnemius muscle showed significant differences between the groups (p<0.05), in the following order: Group B >Group A >Group C. The sciatic nerve at 12 weeks following VAC in Group B and Group C showed a significant increase in expression of S100 and BDNF when compared with Group A; no significant differences were detected between Group B and Group C results from Western blot at 12 weeks.

Conclusions

The findings of this study, using negative pressure therapy in VAC in a rabbit model of sciatic nerve damage, have shown that moderate negative pressure was beneficial, but high values did not benefit sciatic nerve repair.

The interplay of peptide affinity and scaffold stiffness on neuronal differentiation of neural stem cells

Cells are sensitive to physical cues in their environment, such as the stiffness of the substrate, peptide density, and peptide affinity. Understanding how neural stem cells (NSCs) sense and respond to these matrix cues has the potential to improve disease outcome, particularly if a regenerative response can be exploited. While the material properties are known to influence other stem cells, little is known about how NSC differentiation is altered by this interplay of mechanical, or bulk properties, with peptide concentration and affinity, or microscale properties. We are interested in the combined effect of bulk and microscale features in an in vitro hydrogel model and therefore we investigated NSC differentiation by focusing on integrin interactions via RGD peptide affinity and concentration. Our studies demonstrated that the peptide concentration affected adhesion as there were more cells on scaffolds with 1 mM RGD than 2.5 mM RGD. The hydrogel stiffness affected neurite length in differentiating NSCs, as 0.1-0.8 kPa substrates promoted greater neurite extension than 4.2-7.9 kPa substrates. The NSCs differentiated towards β-ΙΙΙ tubulin positive cells on scaffolds with RGD after 7 days and those scaffolds containing 1 mM linear or cyclic RGD had longer neurite extensions than scaffolds containing 0.1 or 2.5 mM RGD. While peptide affinity had a lesser effect on the NSC response in our hydrogel system, blocking actin, myosin II, or integrin interactions resulted in changes to the cell morphology and focal adhesion assembly. Overall, these results demonstrated NSCs are more responsive to a change in tissue stiffness than peptide affinity in the range of gels tested, which may influence design of materials for neural tissue engineering.

Harnessing Nanotopography of Electrospun Nanofibrous Nerve Guide Conduits (NGCs) for Neural Tissue Engineering

The anatomical recovery of nerve defects with their neurological functions after an injury caused by diseases or accidents is an important clinical issue. The most efficient surgical technique so far to the nerve defects, which are unrepairable by direct end-to-end suture, can be autograft transplantation. The autograft transplantation, however, has disadvantages including multiple rounds of surgery, a shortage of nerve donor, and function loss at the donor site. Tissue-engineered nerve guide conduits (TENGCs) have emerged as a potential alternative to autologous nerve grafts for nerve regeneration and functional recovery. Various TENGCs researches are being carried out to improve characteristics and enhance functionality such as material selection, biomimetic, topography, and enhancement by the biomolecules additions. Among them, the customizable surface nanotopography of aligned fibrous TENGCs foster neural repair by providing a cell-friendly environment, permissiveness, guidance cues, and directional growth of the cells. Fibrous nerve guide conduits (NGCs) made of longitudinally ordered fibers is a promising candidate for nerve tissue engineering.

MiR-7 inhibited peripheral nerve injury repair by affecting neural stem cells migration and proliferation through cdc42

Objective Neural stem cells play an important role in the recovery and regeneration of peripheral nerve injury, and the microRNA-7 (miR-7) regulates differentiation of neural stem cells. This study aimed to explore the role of miR-7 in neural stem cells homing and proliferation and its influence on peripheral nerve injury repair. Methods The mice model of peripheral nerve injury was created by segmental sciatic nerve defect (sciatic nerve injury), and neural stem cells treatment was performed with a gelatin hydrogel conduit containing neural stem cells inserted into the sciatic nerve injury mice. The Sciatic Function Index was used to quantify sciatic nerve functional recovery in the mice. The messenger RNA and protein expression were detected by reverse transcription polymerase chain reaction and Western blot, respectively. Luciferase reporter assay was used to confirm the binding between miR-7 and the 3'UTR of cell division cycle protein 42 (cdc42). The neural stem cells migration and proliferation were analyzed by transwell assay and a Cell-LightTM EdU DNA Cell Proliferation kit, respectively. Results Neural stem cells treatment significantly promoted nerve repair in sciatic nerve injury mice. MiR-7 expression was decreased in sciatic nerve injury mice with neural stem cells treatment, and miR-7 mimic transfected into neural stem cells suppressed migration and proliferation, while miR-7 inhibitor promoted migration and proliferation. The expression level and effect of cdc42 on neural stem cells migration and proliferation were opposite to miR-7, and the luciferase reporter assay proved that cdc42 was a target of miR-7. Using co-transfection into neural stem cells, we found pcDNA3.1-cdc42 and si-cdc42 could reverse respectively the role of miR-7 mimic and miR-7 inhibitor on neural stem cells migration and proliferation. In addition, miR-7 mimic-transfected neural stem cells could abolish the protective role of neural stem cells on peripheral nerve injury. Conclusion MiR-7 inhibited peripheral nerve injury repair by affecting neural stem cells migration and proliferation through cdc42.

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.

Transplantation of Embryonic Spinal Cord Derived Cells Helps to Prevent Muscle Atrophy after Peripheral Nerve Injury

Injuries to peripheral nerves are frequent in serious traumas and spinal cord injuries. In addition to surgical approaches, other interventions, such as cell transplantation, should be considered to keep the muscles in good condition until the axons regenerate. In this study, E14.5 rat embryonic spinal cord fetal cells and cultured neural progenitor cells from different spinal cord segments were injected into transected musculocutaneous nerve of 200–300 g female Sprague Dawley (SD) rats, and atrophy in biceps brachii was assessed. Both kinds of cells were able to survive, extend their axons towards the muscle and form neuromuscular junctions that were functional in electromyographic studies. As a result, muscle endplates were preserved and atrophy was reduced. Furthermore, we observed that the fetal cells had a better effect in reducing the muscle atrophy compared to the pure neural progenitor cells, whereas lumbar cells were more beneficial compared to thoracic and cervical cells. In addition, fetal lumbar cells were used to supplement six weeks delayed surgical repair after the nerve transection. Cell transplantation helped to preserve the muscle endplates, which in turn lead to earlier functional recovery seen in behavioral test and electromyography. In conclusion, we were able to show that embryonic spinal cord derived cells, especially the lumbar fetal cells, are beneficial in the treatment of peripheral nerve injuries due to their ability to prevent the muscle atrophy.

Double labelling of human umbilical cord mesenchymal stem cells with Gd-DTPA and PKH26 and the influence on biological characteristics of hUCMSCs

The aim of this study was to determine whether double labelling of human umbilical cord mesenchymal stem cells (hUCMSCs) with gadolinium-diethylene triamine penta-acetic acid (Gd-DTPA) and PKH26 influences their biological characteristics. A tissue adherence technique was used to separate and purify the hUCMSCs and flow cytometry was performed to detect the surface markers expressed on them. Gd-DTPA and PKH26 were used to label the stem cells and MRI and fluorescence microscopy were used to detect the double-labelled hUCMSCs. A MTT assay was used to delineate the growth curve. Transmission electron microscopy (TEM) and atomic force microscopy were used to demonstrate the ultrastructural features of the hUCMSCs. Flow cytometry showed that hUCMSCs highly expressed CD29, CD90, CD44 and CD105. No expression of CD31, CD34 and CD45 was detected. Very low expression of HLA-DR and CD40 was detected. Atomic force microscopy showed these cells were long, spindle shaped, and the cytoplasm and nucleus had clear boundaries. After double labelling, TEM showed Gd particles aggregated in the cytoplasm in a cluster pattern. The proliferation activity, cell cycle, apoptosis and differentiation of the stem cells were not influenced by double labelling. Thus a tissue adherence technique is helpful to separate and purify hUCMSCs effectively; and Gd-DTPA and PKH26 are promising tracers in the investigation of migration and distribution of hUCMSCs in vivo.

Enhanced repair effect of toll-like receptor 4 activation on neurotmesis: assessment using MR neurography

BACKGROUND AND PURPOSE

Alternative use of molecular approaches is promising for improving nerve regeneration in surgical repair of neurotmesis. The purpose of this study was to determine the role of MR imaging in assessment of the enhanced nerve regeneration with toll-like receptor 4 signaling activation in surgical repair of neurotmesis.

MATERIALS AND METHODS

Forty-eight healthy rats in which the sciatic nerve was surgically transected followed by immediate surgical coaptation received intraperitoneal injection of toll-like receptor 4 agonist lipopolysaccharide (n = 24, study group) or phosphate buffered saline (n = 24, control group) until postoperative day 7. Sequential T2 measurements and gadofluorine M-enhanced MR imaging and sciatic functional index were obtained over an 8-week follow-up period, with histologic assessments performed at regular intervals. T2 relaxation times and gadofluorine enhancement of the distal nerve stumps were measured and compared between nerves treated with lipopolysaccharide and those treated with phosphate buffered saline.

RESULTS

Nerves treated with lipopolysaccharide injection achieved better functional recovery and showed more prominent gadofluorine enhancement and prolonged T2 values during the degenerative phase compared with nerves treated with phosphate buffered saline. T2 values in nerves treated with lipopolysaccharide showed a more rapid return to baseline level than did gadofluorine enhancement. Histology exhibited more macrophage recruitment, faster myelin debris clearance, and more pronounced nerve regeneration in nerves treated with toll-like receptor 4 activation.

CONCLUSIONS

The enhanced nerve repair with toll-like receptor 4 activation in surgical repair of neurotmesis can be monitored by using gadofluorine M-enhanced MR imaging and T2 relaxation time measurements. T2 relaxation time seems more sensitive than gadofluorine M-enhanced MR imaging for detecting such improved nerve regeneration.

Perspectives of employing mesenchymal stem cells from the Wharton's jelly of the umbilical cord for peripheral nerve repair

Mesenchymal stem cells (MSCs) from Wharton's jelly present high plasticity and low immunogenicity, turning them into a desirable form of cell therapy for the injured nervous system. Their isolation, expansion, and characterization have been performed from cryopreserved umbilical cord tissue. Great concern has been dedicated to the collection, preservation, and transport protocols of the umbilical cord after the parturition to the laboratory in order to obtain samples with higher number of viable MSCs without microbiological contamination. Different biomaterials like chitosan-silicate hybrid, collagen, PLGA90:10, poly(DL-lactide-ɛ-caprolactone), and poly(vinyl alcohol) loaded with electrical conductive materials, associated to MSCs have also been tested in the rat sciatic nerve in axonotmesis and neurotmesis lesions. The in vitro studies of the scaffolds included citocompatibility evaluation of the biomaterials used and cell characterization by imunocytochemistry, karyotype analysis, differentiation capacity into neuroglial-like cells, and flow cytometry. The regeneration process follow-up has been performed by functional analysis and the repaired nerves processed for stereological studies permitted the morphologic regeneration evaluation. The MSCs from Wharton's jelly delivered through tested biomaterials should be regarded a potentially valuable tool to improve clinical outcome especially after trauma to sensory nerves. In addition, these cells represent a noncontroversial source of primitive mesenchymal progenitor cells, which can be harvested after birth, cryogenically stored, thawed, and expanded for therapeutic uses. The importance of a longitudinal study concerning tissue engineering of the peripheral nerve, which includes a multidisciplinary team able to develop biomaterials associated to cell therapies, to perform preclinical trials concerning animal welfare and the appropriate animal model is here enhanced.

MR imaging and T2 measurements in peripheral nerve repair with activation of Toll-like receptor 4 of neurotmesis

OBJECTIVE

To investigate the role of MR imaging in neurotmesis combined with surgical repair and Toll-like receptor 4 (TLR4) activation.

METHODS

Forty-eight rats received subepineurial microinjection of the TLR4 agonist lipopolysaccharide (LPS, n = 24) or phosphate buffered saline (PBS, n = 24) immediately after surgical repair of the transected sciatic nerve. Sequential fat-suppressed T2-weighted imaging and quantitative T2 measurements were obtained at 3, 7, 14 and 21 days after surgery, with histologic assessments performed at regular intervals. T2 relaxation times and histological quantification of the distal stumps were measured and compared.

RESULTS

The distal stumps of transected nerves treated with LPS or PBS both showed persistent enlargement and hyperintense signal. T2 values of the distal stumps showed a rapid rise to peak level followed by a rapid decline pattern in nerves treated with LPS, while exhibiting a slow rise to peak value followed by a slow decline in nerves treated with PBS. Nerves treated with LPS exhibited more prominent macrophage recruitment, faster myelin debris clearance and more pronounced nerve regeneration.

CONCLUSION

Nerves treated with TLR4 activation had a characteristic pattern of T2 value change over time. Longitudinal T2 measurements can be used to detect the enhanced repair effect associated with TLR4 activation in the surgical repair of neurotmesis.

KEY POINTS

• TLR4 activation had additional beneficial effects on neurotmesis beyond surgical repair. • TLR4 activation had a characteristic time course of T2 values. • T2 measurements can help detect beneficial effects with TLR4 activation.

The regeneration potential after human and autologous stem cell transplantation in a rat sciatic nerve injury model can be monitored by MRI

Traumatic nerve injuries are a major clinical challenge. Tissue engineering using a combination of nerve conduits and cell-based therapies represents a promising approach to nerve repair. The aim of this study was to examine the regeneration potential of human adipose-derived stem cells (hASCs) after transplantation in a nonautogenous setting and to compare them with autogenous rat ASCs (rASCs) for early peripheral nerve regeneration. Furthermore, the use of MRI to assess the continuous process of nerve regeneration was elaborated. The sciatic nerve injury model in female Sprague-Dawley rats was applied, and a 10-mm gap created by using a fibrin conduit seeded with the following cell types: rASCs, Schwann cell (SC)-like cells from rASC, rat SCs (rSCs), hASCs from the superficial and deep abdominal layer, as well as human stromal vascular fraction (1 × 10(6) cells). As a negative control group, culture medium only was used. After 2 weeks, nerve regeneration was assessed by immunocytochemistry. Furthermore, MRI was performed after 2 and 4 weeks to monitor nerve regeneration. Autogenous ASCs and SC-like cells led to accelerated peripheral nerve regeneration, whereas the human stem cell groups displayed inferior results. Nevertheless, positive trends could be observed for hASCs from the deep abdominal layer. By using a clinical 3T MRI scanner, we were able to visualize the graft as a small black outline and small hyperintensity indicating the regenerating axon front. Furthermore, a strong correlation was found between the length of the regenerating axon front measured by MRI and the length measured by immunocytochemistry (r = 0.74, p = 0.09). We successfully transplanted and compared human and autologous stem cells for peripheral nerve regeneration in a rat sciatic nerve injury model. Furthermore, we were able to implement the clinical 3T MRI scanner to monitor the efficacy of cellular therapy over time.

Superparamagnetic iron oxide nanoparticles as MRI contrast agents for non-invasive stem cell labeling and tracking

Stem cells hold great promise for the treatment of multiple human diseases and disorders. Tracking and monitoring of stem cells in vivo after transplantation can supply important information for determining the efficacy of stem cell therapy. Magnetic resonance imaging (MRI) combined with contrast agents is believed to be the most effective and safest non-invasive technique for stem cell tracking in living bodies. Commercial superparamagnetic iron oxide nanoparticles (SPIONs) in the aid of transfection agents (TAs) have been applied to labeling stem cells. However, owing to the potential toxicity of TAs, more attentions have been paid to develop novel SPIONs with specific surface coating or functional moieties which facilitate effective cell internalization in the absence of TAs. This review aims to summarize the recent progress in the design and preparation of SPIONs as cellular MRI probes, to discuss their applications and current problems facing in stem cell labeling and tracking, and to offer perspectives and solutions for the future development of SPIONs in this field.

Pericytes derived from adipose-derived stem cells protect against retinal vasculopathy

Background

Retinal vasculopathies, including diabetic retinopathy (DR), threaten the vision of over 100 million people. Retinal pericytes are critical for microvascular control, supporting retinal endothelial cells via direct contact and paracrine mechanisms. With pericyte death or loss, endothelial dysfunction ensues, resulting in hypoxic insult, pathologic angiogenesis, and ultimately blindness. Adipose-derived stem cells (ASCs) differentiate into pericytes, suggesting they may be useful as a protective and regenerative cellular therapy for retinal vascular disease. In this study, we examine the ability of ASCs to differentiate into pericytes that can stabilize retinal vessels in multiple pre-clinical models of retinal vasculopathy.

Methodology/Principal Findings

We found that ASCs express pericyte-specific markers in vitro. When injected intravitreally into the murine eye subjected to oxygen-induced retinopathy (OIR), ASCs were capable of migrating to and integrating with the retinal vasculature. Integrated ASCs maintained marker expression and pericyte-like morphology in vivo for at least 2 months. ASCs injected after OIR vessel destabilization and ablation enhanced vessel regrowth (16% reduction in avascular area). ASCs injected intravitreally before OIR vessel destabilization prevented retinal capillary dropout (53% reduction). Treatment of ASCs with transforming growth factor beta (TGF-β1) enhanced hASC pericyte function, in a manner similar to native retinal pericytes, with increased marker expression of smooth muscle actin, cellular contractility, endothelial stabilization, and microvascular protection in OIR. Finally, injected ASCs prevented capillary loss in the diabetic retinopathic Akimba mouse (79% reduction 2 months after injection).

Conclusions/Significance

ASC-derived pericytes can integrate with retinal vasculature, adopting both pericyte morphology and marker expression, and provide functional vascular protection in multiple murine models of retinal vasculopathy. The pericyte phenotype demonstrated by ASCs is enhanced with TGF-β1 treatment, as seen with native retinal pericytes. ASCs may represent an innovative cellular therapy for protection against and repair of DR and other retinal vascular diseases.

Nonclinical safety strategies for stem cell therapies

Recent breakthroughs in stem cell biology, especially the development of the induced pluripotent stem cell techniques, have generated tremendous enthusiasm and efforts to explore the therapeutic potential of stem cells in regenerative medicine. Stem cell therapies are being considered for the treatment of degenerative diseases, inflammatory conditions, cancer and repair of damaged tissue. The safety of a stem cell therapy depends on many factors including the type of cell therapy, the differentiation status and proliferation capacity of the cells, the route of administration, the intended clinical location, long term survival of the product and/or engraftment, the need for repeated administration, the disease to be treated and the age of the population. Understanding the product profile of the intended therapy is crucial to the development of the nonclinical safety study design.

In vivo healing of meniscal lacerations using bone marrow-derived mesenchymal stem cells and fibrin glue

Fibrin glue created from a patient's own blood can be used as a carrier to deliver cells to the specific site of an injury. An experimental model for optimizing various permutations of this delivery system in vivo was tested in this study. Harvested equine meniscal sections were reapposed with fibrin glue or fibrin glue and equine bone marrow-derived mesenchymal stem cells (BMSCs). These constructs were then implanted subcutaneously in nude mice. After harvesting of the constructs, BMSC containing constructs showed significantly increased vascularization, and histology showed subjectively decreased thickness of repair tissue and increased total bonding compared to fibrin alone constructs. This model allowed direct comparison of different meniscal treatment groups while using a small number of animals. This in vivo model could be valuable in the future to optimize fibrin and cellular treatments for meniscal lesions in the horse and potentially humans as well.