Human Adipose Stem Cells Improve Mechanical Allodynia and Enhance Functional Recovery in a Rat Model of Neuropathic Pain

Diabetic neuropathy: cutting-edge research and future directions

Diabetic neuropathy (DN) is a prevalent and debilitating complication of diabetes mellitus, significantly impacting patient quality of life and contributing to morbidity and mortality. Affecting approximately 50% of patients with diabetes, DN is predominantly characterized by distal symmetric polyneuropathy, leading to sensory loss, pain, and motor dysfunction, often resulting in diabetic foot ulcers and lower-limb amputations. The pathogenesis of DN is multifaceted, involving hyperglycemia, dyslipidemia, oxidative stress, mitochondrial dysfunction, and inflammation, which collectively damage peripheral nerves. Despite extensive research, disease-modifying treatments remain elusive, with current management primarily focusing on symptom control. This review explores the complex mechanisms underlying DN and highlights recent advances in diagnostic and therapeutic strategies. Emerging insights into the molecular and cellular pathways have unveiled potential targets for intervention, including neuroprotective agents, gene and stem cell therapies, and innovative pharmacological approaches. Additionally, novel diagnostic tools, such as corneal confocal microscopy and biomarker-based tests, have improved early detection and intervention. Lifestyle modifications and multidisciplinary care strategies can enhance patient outcomes. While significant progress has been made, further research is required to develop therapies that can effectively halt or reverse disease progression, ultimately improving the lives of individuals with DN. This review provides a comprehensive overview of current understanding and future directions in DN research and management.

Minimally invasive scar release by autologous adipose tissue transfer for post-traumatic neuropathic pain

Introduction

Addressing post traumatic lower limb neuropathic pain is challenging across medical specialties. To address this potentially devastating condition, several invasive and non-invasive approaches have been proposed with inconsistent results. Adipose fat transfer (AFT), also known as fat grafting, is a regenerative medicine technique in which a patient's own fat is harvested from one area of the body (usually through liposuction) and then injected into another area for various purposes, such as aesthetic contour enhancement or reconstruction and regeneration of scarred tissues.

Methods

We analyze the effects of fat grafting for neuropathic pain combined with neuroma excision (hybrid technique, hAFT) or alone (AFT). A retrospective review was conducted on 22 patients with neuropathic lower limb pain, after trauma or orthopedic surgery treated with hAFT (n = 9) or AFT (n = 13).

Results

Reduction in VAS scale more than 50 % was observed in 6 patients (66 %) treated with hybrid technique and in eleven patients (85 %) treated with AFT alone. Among these, complete pain reduction (>91 %) was achieved in 33.3 % of hAFT and 54 % of AFT technique. A 3.2 points reduction in VAS was found in the hAFT group versus 5.8 points in the AFT group (p = 0.035).

Conclusion

This pioneering use of AFT emerges as a minimally invasive breakthrough, promising significant improvement in reconstructing scarred subcutaneous tissue and managing neuropathic pain.

A multi-channel collagen conduit with aligned Schwann cells and endothelial cells for enhanced neuronal regeneration in spinal cord injury

Traumatic spinal cord injury (SCI) leads to Wallerian degeneration and the accompanying disruption of vasculature leads to ischemia, which damages motor and sensory function. Therefore, understanding the biological environment during regeneration is essential to promote neuronal regeneration and overcome this phenomenon. The band of Büngner is a structure of an aligned Schwann cell (SC) band that guides axon elongation providing a natural recovery environment. During axon elongation, SCs promote axon elongation while migrating along neovessels (endothelial cells [ECs]). To model this, we used extrusion 3D bioprinting to develop a multi-channel conduit (MCC) using collagen for the matrix region and sacrificial alginate to make the channel. The MCC was fabricated with a structure in which SCs and ECs were longitudinally aligned to mimic the sophisticated recovering SCI conditions. Also, we produced an MCC with different numbers of channels. The aligned SCs and ECs in the 9-channel conduit (9MCC-SE) were more biocompatible and led to more proliferation than the 5-channel conduit (5MCC-SE) in vitro. Also, the 9MCC-SE resulted in a greater healing effect than the 5MCC-SE with respect to neuronal regeneration, remyelination, inflammation, and angiogenesis in vivo. The above tissue recovery results led to motor function repair. Our results show that our 9MCC-SE model represents a new therapeutic strategy for SCI.

Adipose-derived stem cells modulate neuroinflammation and improve functional recovery in chronic constriction injury of the rat sciatic nerve

Introduction

Compressive neuropathy, a common chronic traumatic injury of peripheral nerves, leads to variable impairment in sensory and motor function. Clinical symptoms persist in a significant portion of patients despite decompression, with muscle atrophy and persistent neuropathic pain affecting 10%-25% of cases. Excessive inflammation and immune cell infiltration in the injured nerve hinder axon regeneration and functional recovery. Although adipose-derived stem cells (ASCs) have demonstrated neural regeneration and immunomodulatory potential, their specific effects on compressive neuropathy are still unclear.

Methods

We conducted modified CCI models on adult male Sprague-Dawley rats to induce irreversible neuropathic pain and muscle atrophy in the sciatic nerve. Intraneural ASC injection and nerve decompression were performed. Behavioral analysis, muscle examination, electrophysiological evaluation, and immunofluorescent examination of the injured nerve and associated DRG were conducted to explore axon regeneration, neuroinflammation, and the modulation of inflammatory gene expression. Transplanted ASCs were tracked to investigate potential beneficial mechanisms on the local nerve and DRG.

Results

Persistent neuropathic pain was induced by chronic constriction of the rat sciatic nerve. Local ASC treatment has demonstrated robust beneficial outcomes, including the alleviation of mechanical allodynia, improvement of gait, regeneration of muscle fibers, and electrophysiological recovery. In addition, locally transplanted ASCs facilitated axon remyelination, alleviated neuroinflammation, and reduced inflammatory cell infiltration of the injured nerve and associated dorsal root ganglion (DRG). Trafficking of the transplanted ASC preserved viability and phenotype less than 7 days but contributed to robust immunomodulatory regulation of inflammatory gene expression in both the injured nerve and DRG.

Discussion

Locally transplanted ASC on compressed nerve improve sensory and motor recoveries from irreversible chronic constriction injury of rat sciatic nerve via alleviation of both local and remote neuroinflammation, suggesting the promising role of adjuvant ASC therapies for clinical compressive neuropathy.

Heparin-Based Hydrogel Micropatches with Human Adipose-Derived Stem Cells: A Promising Therapeutic Approach for Neuropathic Pain Relief

This study explores the therapeutic efficacy of heparin-based hydrogel micropatches containing human adipose-derived stem cells (hASCs) in treating neuropathic pain caused by nerve damage. Our results showed that hASCs exhibited neuroregenerative and pain-relieving effects when used with heparin-based hydrogel micropatches in the neuropathic pain animal model. The use of this combination also produced enhanced cell viability and nerve regeneration. We conducted various neurological behavioral tests, dynamic plantar tests, histological examinations, and neuroelectrophysiological examinations to confirm the therapeutic effect. Our findings suggest that this approach could maximize therapeutic efficacy and improve the quality of life for patients suffering from neuropathic pain.

Autologous fat grafting to the paravertebral space seems to prevent the postherpetic neuralgia-A single-arm pilot study

INTRODUCTION

Postherpetic neuralgia (PHN) is one of the most common complications of Herpes zoster (HZ), yet the mechanism and the treatment for PHN remains elusive. We first performed this feasibility study to verify the safety and efficiency of autologous fat grafting into the paravertebral space in early HZ to prevent PHN.

METHODS

Patients suffering from HZ with a rash in chest, back, or abdomen were arranged for autologous fat grafting to the paravertebral space. The primary endpoint was the incidence of PHN, which was defined as persistence pain in the affected dermal area in 12 weeks after fat grafting. Secondary endpoints including patient-reported changes in pain intensity, assessed pain threshold and the quality of life during follow-ups.

RESULTS

Eight patients accept the intervention and completed all follow-ups. Most patients report immediate pain relief after injection, one patient has a mild to moderate dizzy symptom after injection. No other short- or long-term adverse events occurred. For primary outcome, all patients have a timely reduced pain intensity, with no PHN events occurred, as all patients report pain intensity ≤3 in the VAS scale in 3 months after treatment. For electrical pain threshold, we identify that fat grafting differentially increases sensation and pain threshold in HZ area and healthy skin of patients. Besides, our results indicate significant improvement in patients' life quality decrease in analgesic consumption.

DISCUSSION

Autologous fat transplantation to the paravertebral space is a safe and feasible technique in preventing PHN from HZ in a rash. Further randomized controlled trial to investigate the actual long-term benefice of autologous fat grafting to the paravertebral space in preventing PHN is needed.

TRIAL REGISTRATION

ChiCTR, (ChiCTR1900025416); registered August 26, 2019.

Application of adipose-derived mesenchymal stem cells in an in vivo model of peripheral nerve damage

Background

Neuropathic pain is one of the most difficult to treat chronic pain syndromes. It has significant effects on patients’ quality of life and substantially adds to the burden of direct and indirect medical costs. There is a critical need to improve therapies for peripheral nerve regeneration. The aim of this study is to address this issue by performing a detailed analysis of the therapeutic benefits of two treatment options: adipose tissue derived-mesenchymal stem cells (ASCs) and ASC-conditioned medium (CM).

Methods

To this end, we used an in vivo rat sciatic nerve damage model to investigate the molecular mechanisms involved in the myelinating capacity of ASCs and CM. Furthermore, effect of TNF and CM on Schwann cells (SCs) was evaluated. For our in vivo model, biomaterial surgical implants containing TNF were used to induce peripheral neuropathy in rats. Damaged nerves were also treated with either ASCs or CM and molecular methods were used to collect evidence of nerve regeneration. Post-operatively, rats were subjected to walking track analysis and their sciatic functional index was evaluated. Morphological data was gathered through transmission electron microscopy (TEM) of sciatic nerves harvested from the experimental rats. We also evaluated the effect of TNF on Schwann cells (SCs) in vitro. Genes and their correspondent proteins associated with nerve regeneration were analyzed by qPCR, western blot, and confocal microscopy.

Results

Our data suggests that both ASCs and CM are potentially beneficial treatments for promoting myelination and axonal regeneration. After TNF-induced nerve damage we observed an upregulation of c-Jun along with a downregulation of Krox-20 myelin-associated transcription factor. However, when CM was added to TNF-treated nerves the opposite effect occurred and also resulted in increased expression of myelin-related genes and their corresponding proteins.

Conclusion

Findings from our in vivo model showed that both ASCs and CM aided the regeneration of axonal myelin sheaths and the remodeling of peripheral nerve morphology.

Mesenchymal stem cells and extracellular vesicles for the treatment of pain: Current status and perspectives

Mesenchymal stem/stromal cells (MSCs) are multipotent progenitor cells of mesodermal origin. Due to their capacity for self-renewal and differentiation into several cell types, MSCs have been extensively studied in experimental biology and regenerative medicine in recent years. Moreover, MSCs release extracellular vesicles (EVs), which might be partly responsible for their regenerative properties. MSCs regulate several processes in target cells via paracrine signalling, such as immunomodulation, anti-apoptotic signalling, tissue remodelling, angiogenesis and anti-fibrotic signalling. The aim of this review is to provide a detailed description of the functional properties of MSCs and EVs and their potential clinical applications, with a special focus on pain treatment. The analgesic, anti-inflammatory and regenerative properties of MSCs and EVs will be discussed for several diseases, such as neuropathic pain, osteoarthritis and spinal cord injury.

A Review on Stem Cell Therapy for Neuropathic Pain

Neuropathic pain is a complex, chronic pain state that is heterogeneous in nature and caused by the consequence of a lesion or disease affecting the somatosensory system. Current medications give a long-lasting pain relief only in a limited percentage of patients also associated with numerous side effects. Stem cell transplantation is one of the attractive therapeutic platforms for the treatment of a variety of diseases, such as neuropathic pain. Here, the authors review the therapeutic effects of stem cell transplantation of different origin and species in different models of neuropathic pain disorders. Stem cell transplantation could alleviate the neuropathic pain; indeed, stem cells are the source of cells, which differentiate into a variety of cell types and lead trophic factors to migrate to the lesion site opposing the effects of damage. In conclusion, this review suggests that stem cell therapy can be a novel approach for the treatment of neuropathic pain.

Autologous fat grafting for nerve regeneration and neuropathic pain: current state from bench-to-bedside

Despite recent advances in microsurgical techniques, functional recovery following peripheral nerve injury remains slow and inadequate. Poor peripheral nerve regeneration not only leaves patients with significant impairments, but also commonly leads to the development of debilitating neuropathic pain. Recent research has demonstrated the potential therapeutic benefits of adipose-derived stem cells, to enhance nerve regeneration. However, clinical translation remains limited due to the current regulatory burdens of the US FDA. A reliable and immediately translatable alternative is autologous fat grafting, where native adipose-derived stem cells present in the transferred tissue can potentially act upon regenerating axons. This review presents the scope of adipose tissue-based therapies to enhance outcomes following peripheral nerve injury, specifically focusing on their role in regeneration and ameliorating neuropathic pain.

Grafts of human adipose-derived stem cells into a biodegradable poly (acid lactic) conduit enhances sciatic nerve regeneration

Despite the regenerative potential of the Peripheral Nervous System (PNS), injuries with loss of a nerve segment make the functional recovery a challenge. This work aimed to investigate the effects of the association of biodegradable conduits of poly (lactic acid) (PLA) with human adipose-derived stem cells (hADSCs) on the regeneration of the sciatic nerve. C57BL / 6 male mice were submitted to sciatic nerve transection followed by tubulization with PLA conduit. Animals were allocated in two groups: the first received an injection of DMEM inside the conduit (DMEM) and the second received hADSCs inside it (hADSC). Sensory and motor functions were assessed by the pinprick test and electroneuromiography, respectively. To assess neuronal survival the retrograde tracer fluorogold was injected into the sciatic nerve distally to the lesion site. One week after that, animals were sacrificed, tissues harvested and processed for morphological evaluation. After eight weeks, all animals showed sensory recovery in the pinprick test and there was no significant difference between the two groups. The amplitude of the compound muscle action potential was higher in the hADSCs group. The number of myelinated nerve fibers, muscle cells and motor plates was higher in the hADSC group. There was also greater survival of sensory and motor neurons in the hADSC animals. These results suggest that the association of PLA conduit and cell therapy with hADSCs leads to a better functional and morphological recovery after sciatic nerve transection.

Diagnostic Efficacy of 18F-FDG PET/MRI in Peripheral Nerve Injury Models

The aim of this study was to evaluate the diagnostic efficacy of ¹⁸F-FDG PET/MRI in two different peripheral neuropathic pain models using the injured rat sciatic nerves. Twelve rats, with operation on left sciatic nerves, were evenly divided into three groups: sham surgery (control group), crushing injury and chronic constriction injury (CCI) (experimental groups). The nerve damage was assessed at 3 weeks postoperatively using following methods: paw withdrawal threshold values (RevWT), maximum standardized uptake values on PET/MRI images (SUVR), and counting the number of myelinated axons in proximal and distal sites of nerve injury (MAxR). The results were quantified and statistically analyzed. Compared to the control group, the crushing injury demonstrated significant differences in RevWT (p < 0.0001) and SUVR (p = 0.027) and the CCI group demonstrated significant differences in RevWT (p < 0.0001), SUVR (p = 0.001) and MAxR (p = 0.048). There were no significant differences between the two experimental groups for all assessments. Correlation analysis demonstrated that RevWT and SUVR assessments were highly correlated (r = -- 0.710, p = 0.010), and SUVR and MAxR were highly correlated (r = 0.611, p = 0.035). However, there was no significant correlation between RevWT and MAxR. The PET scan may be a valuable imaging modality to enable noninvasive, objective diagnosis of neuropathic pain caused by peripheral nerve injury. Also, MRI fused with PET may help clarify the anatomic location of soft tissue structures, including the peripheral nerves.

The Role of Fat Grafting in Alleviating Neuropathic Pain: A Critical Review of the Literature

Background

Neuropathic pain is one of the more severe types of chronic pain and presents a great challenge as response to medical therapy remains often unpredictable. With the opioid epidemic and the search for ways to avoid narcotics, physicians are seeking other modalities to treat neuropathic pain. In recent years, surgeons have explored various surgical avenues to improve outcomes. The aim of this review was to evaluate the current clinical evidence regarding the efficacy of fat grafting for the treatment of neuropathic pain.

Methods

A critical review was conducted to examine the current clinical evidence of fat grafting as a therapy for neuropathic pain caused by neuromas, peripheral neuralgia, migraine and headaches, neuropathic scar pain, and postmastectomy pain syndrome.

Results

The precise mechanism role of fat grafting in modulating neuropathic pain remains unclear, but it appears to reduce pain levels through the anti-inflammatory effects of adipose-derived stem cells and mechanical cushioning by fat.

Conclusions

Fat grafting is an emerging therapy for chronic neuropathic pain of various etiologies. Although promising results have been reported, sample size and level of evidence of current studies are low. The encouraging results, however, are worthy of further clinical and scientific study. The minimally invasive nature of fat grafting and favorable risk profile make this an attractive therapy for neuropathic pain.

The role of undifferentiated adipose-derived stem cells in peripheral nerve repair

Peripheral nerve injuries impose significant health and economic consequences, yet no surgical repair can deliver a complete recovery of sensory or motor function. Traditional methods of repair are less than ideal: direct coaptation can only be performed when tension-free repair is possible, and transplantation of nerve autograft can cause donor-site morbidity and neuroma formation. Cell-based therapy delivered via nerve conduits has thus been explored as an alternative method of nerve repair in recent years. Stem cells are promising sources of the regenerative core material in a nerve conduit because stem cells are multipotent in function, abundant in supply, and more accessible than the myelinating Schwann cells. Among different types of stem cells, undifferentiated adipose-derived stem cell (uASC), which can be processed from adipose tissue in less than two hours, is a promising yet underexplored cell type. Studies of uASC have emerged in the past decade and have shown that autologous uASCs are non-immunogenic, easy to access, abundant in supply, and efficacious at promoting nerve regeneration. Two theories have been proposed as the primary regenerative mechanisms of uASC: in situ trans-differentiation towards Schwann cells, and secretion of trophic and anti-inflammatory factors. Future studies need to fully elucidate the mechanisms, side effects, and efficacy of uASC-based nerve regeneration so that uASCs can be utilized in clinical settings.

'Surface Transplantation' for Nerve Injury and Repair: The Quest for Minimally Invasive Cell Delivery

Cell transplantation is an ambitious, but arguably realistic, therapy for repair of the nervous system. Cell delivery is a major challenge for clinical translation, especially given the apparently inhibitory astrogliotic environment in degenerated tissue. However, astrogliotic tissue also contains endogenous structural and biochemical cues that can be harnessed for functional repair. Minimizing damage to these cues during cell delivery could enhance cell integration. This theory is supported by studies with an auditory astrocyte scar model, in which cells delivered onto the surface of the damaged nerve were more successfully integrated in the host than those injected into the tissue. We consider the application of this less invasive approach for nerve injury and its potential application to some neurodegenerative disorders.

Autologous Adipose-Derived Stem Cells Reduce Burn-Induced Neuropathic Pain in a Rat Model

Background: Burn scar pain is considered as neuropathic pain. The anti-inflammation and anti-neuroinflammation effects of adipose-derived stem cells (ASCs) were observed in several studies. We designed a study using a murine model involving the transplantation of autologous ASCs in rats subjected to burn injuries. The aim was to detect the anti-neuroinflammation effect of ASC transplantation and clarify the relationships between ASCs, scar pain, apoptosis and autophagy. Methods: We randomized 24 rats into 4 groups as followings: Group A and B, received saline injections and autologous transplantation of ASCs 4 weeks after sham burn, respectively; Group C and D, received saline injections and autologous transplantation 4 weeks after burn injuries. A designed behavior test was applied for pain evaluation. Skin tissues and dorsal horn of lumbar spinal cords were removed for biochemical analysis. Results: ASC transplantation significantly restored the mechanical threshold reduced by burn injury. It also attenuated local inflammation and central neuroinflammation and ameliorated apoptosis and autophagy in the spinal cord after the burn injury. Conclusion: In a rat model, autologous ASC subcutaneous transplantation in post-burn scars elicited anti-neuroinflammation effects locally and in the spinal cord that might be related to the relief of post-burn neuropathic pain and attenuated cell apoptosis. Thus, ASC transplantation post-burn scars shows the potential promising clinical benefits.

A cellular spinal cord scaffold seeded with rat adipose‑derived stem cells facilitates functional recovery via enhancing axon regeneration in spinal cord injured rats

Spinal cord injury (SCI), usually resulting in severe sensory and motor deficits, is a major public health concern. Adipose-derived stem cells (ADSCs), one type of adult stem cell, are free from ethical restriction, easily isolated and enriched. Therefore, ADSCs may provide a feasible cell source for cell-based therapies in treatment of SCI. The present study successfully isolated rat ADSCs (rADSCs) from Sprague-Dawley male rats and co-cultured them with acellular spinal cord scaffolds (ASCs). Then, a rat spinal cord hemisection model was built and rats were randomly divided into 3 groups: SCI only, ASC only, and ASC + ADSCs. Furthermore, behavioral tests were conducted to evaluate functional recovery. Hematoxylin & Eosin staining and immunofluorence were carried out to assess histopathological remodeling. In addition, biotinylated dextran amines anterograde tracing was employed to visualize axon regeneration. The data demonstrated that harvested cells, which were positive for cell surface antigen cluster of differentiation (CD) 29, CD44 and CD90 and negative for CD4, detected by flow cytometry analysis, held the potential to differentiate into osteocytes and adipocytes. Rats that received transplantation of ASCs seeded with rADSCs benefited greatly in functional recovery through facilitation of histopathological rehabilitation, axon regeneration and reduction of reactive gliosis. rADSCs co-cultured with ASCs may survive and integrate into the host spinal cord on day 14 post-SCI.

New approach for the treatment of neuropathic pain: Fibroblast growth factor 1 gene-transfected adipose-derived mesenchymal stem cells

BACKGROUND

Neuropathic pain triggered by peripheral nerve lesion is extremely difficult to manage with current approaches, hence the importance of exploring therapeutic alternatives.

METHODS

We have analysed adipose-derived mesenchymal stem cells (AD-MSCs) and fibroblast growth factor 1 gene-transfected adipose-derived mesenchymal stem cells (AD-MSCs ^FGF1 ) on chronic constriction injury (CCI). The mechanical and thermal hypersensitivity were assessed using the von Frey filament, radiant heat and acetone drop tests. Histopathological and apoptotic changes and the level of FGF1, GFAP and TNFα proteins were assessed in the lumbar portion (L4-L6). Moreover, AD-MSCs ^FGF1 were labelled with ^99m Tc -HMPAO and isolated organ counting were performed upon AD-MSCs ^FGF1 administration.

RESULTS

Administration of AD-MSCs ^FGF1 attenuated the CCI-induced mechanical and thermal hypersensitivity. Spinal structural alterations and apoptosis were decreased in the AD-MSCs ^FGF1 group. The injection of either phosphate-buffered saline or normal NIH3T3 fibroblasts could not attenuate the behavioural symptoms of neuropathic pain. Increased genetically engineered cells were counted in the injured sciatic nerve and the elevated levels of FGF1 were detected in the spinal tissue. Stem cell therapy lead to decrement the level of the CCI-induced TNF-α and GFAP expression.

CONCLUSION

The intravenous administration of AD-MSCs ^FGF1 could be considered as a potential remedy for the management of neuropathic pain.

SIGNIFICANCE

AD-MSCs ^FGF1 attenuated the CCI-induced mechanical and thermal hypersensitivity. Spinal structural alterations and apoptosis were significantly decreased in the AD-MSCs ^FGF1 group. Elevated levels of FGF1 were detected in the spinal tissue.

Nanofiber Scaffolds as Drug Delivery Systems to Bridge Spinal Cord Injury

The complex pathophysiology of spinal cord injury (SCI) may explain the current lack of an effective therapeutic approach for the regeneration of damaged neuronal cells and the recovery of motor functions. A primary mechanical injury in the spinal cord triggers a cascade of secondary events, which are involved in SCI instauration and progression. The aim of the present review is to provide an overview of the therapeutic neuro-protective and neuro-regenerative approaches, which involve the use of nanofibers as local drug delivery systems. Drugs released by nanofibers aim at preventing the cascade of secondary damage (neuro-protection), whereas nanofibrous structures are intended to re-establish neuronal connectivity through axonal sprouting (neuro-regeneration) promotion, in order to achieve a rapid functional recovery of spinal cord.

Taking a bite out of spinal cord injury: do dental stem cells have the teeth for it?

Dental stem cells are an emerging star on a stage that is already quite populated. Recently, there has been a lot of hype concerning these cells in dental therapies, especially in regenerative endodontics. It is fitting that most research is concentrated on dental regeneration, although other uses for these cells need to be explored in more detail. Being a true mesenchymal stem cell, their capacities could also prove beneficial in areas outside their natural environment. One such field is the central nervous system, and in particular, repairing the injured spinal cord. One of the most formidable challenges in regenerative medicine is to restore function to the injured spinal cord, and as yet, a cure for paralysis remains to be discovered. A variety of approaches have already been tested, with graft-based strategies utilising cells harbouring appropriate properties for neural regeneration showing encouraging results. Here we present a review focusing on properties of dental stem cells that endorse their use in regenerative medicine, with particular emphasis on repairing the damaged spinal cord.

Hypoxia-specific, VEGF-expressing neural stem cell therapy for safe and effective treatment of neuropathic pain

Vascular endothelial growth factor (VEGF) is an angiogenic cytokine that stimulates the differentiation and function of vascular endothelial cells. VEGF has been implicated in improving nervous system function after injury. However, uncontrolled overexpression of VEGF increases the risk of tumor formation at the site of gene delivery. For this reason, VEGF expression needs to be strictly controlled. The goal of the present study was to understand the effects of hypoxia-induced gene expression system to control VEGF gene expression in neural stem cells (NSCs) on the regeneration of neural tissue after sciatic nerve injury. In this study, we used the erythropoietin (Epo) enhancer-SV40 promoter system (EpoSV-VEGF-NSCs) for hypoxia-specific VEGF expression. We used three types of NSCs: DsRed-NSCs as controls, SV-VEGF-NSCs as uncontrolled VEGF overexpressing NSCs, and EpoSV-VEGF-NSCs. For comparison of VEGF expression at normoxia and hypoxia, we measured the amount of VEGF secreted. VEGF expression decreased at normoxia and increased at hypoxia for EpoSV-VEGF-NSCs; thus, EpoSV-VEGF-NSCs controlled VEGF expression, dependent upon oxygenation condition. To demonstrate the therapeutic effect of EpoSV-VEGF-NSCs, we transplanted each cell line in a neuropathic pain sciatic nerve injury rat model. The transplanted EpoSV-VEGF-NSCs improved sciatic nerve functional index (SFI), mechanical allodynia, and re-myelination similar to the SV-VEGF-NSCs. Additionally, the number of blood vessels increased to a level similar to that of the SV-VEGF-NSCs. However, we did not observe tumor generation in the EpoSV-VEGF-NSC animals that were unlikely to have tumor formation in the SV-VEGF-NSCs. From our results, we determined that EpoSV-VEGF-NSCs safely regulate VEGF gene expression which is dependent upon oxygenation status. In addition, we found that they are therapeutically appropriate for treating sciatic nerve injury.

Drug delivery, cell-based therapies, and tissue engineering approaches for spinal cord injury

Spinal cord injury (SCI) results in devastating neurological and pathological consequences, causing major dysfunction to the motor, sensory, and autonomic systems. The primary traumatic injury to the spinal cord triggers a cascade of acute and chronic degenerative events, leading to further secondary injury. Many therapeutic strategies have been developed to potentially intervene in these progressive neurodegenerative events and minimize secondary damage to the spinal cord. Additionally, significant efforts have been directed toward regenerative therapies that may facilitate neuronal repair and establish connectivity across the injury site. Despite the promise that these approaches have shown in preclinical animal models of SCI, challenges with respect to successful clinical translation still remain. The factors that could have contributed to failure include important biologic and physiologic differences between the preclinical models and the human condition, study designs that do not mirror clinical reality, discrepancies in dosing and the timing of therapeutic interventions, and dose-limiting toxicity. With a better understanding of the pathobiology of events following acute SCI, developing integrated approaches aimed at preventing secondary damage and also facilitating neuroregenerative recovery is possible and hopefully will lead to effective treatments for this devastating injury. The focus of this review is to highlight the progress that has been made in drug therapies and delivery systems, and also cell-based and tissue engineering approaches for SCI.