Tissue engineered regeneration of completely transected spinal cord using human mesenchymal stem cells

Evaluation of the Optimal Number of Implanted Mesenchymal Stem Cells for the Treatment of Post-Traumatic Syrinx and Recovery of Motor Activity after Chronic Spinal Cord Injury

The present work aims at determining the most effective dose (number) of mesenchymal stem cells (MSC) for its transplantation in order to treat chronic spinal cord injury (SCI) in mature Sprague-Dawley rats (n=24). MSC were obtained from bone marrow of 4-6-month-old Sprague-Dawley rats. Four weeks after SCI, MSC suspension (4 μl) was injected to experimental animals into the injured area in doses of 4×105, 8×105, or 106. Using MRI, diffusion tensor imaging (DTI), diffusion tensor tractography (DTT), immunohistochemistry, histological staining, and behavioral tests, we studied the effect of transplantation of MSC in different doses on the following parameters in rats with SCI: the size of lesion cavity and post-traumatic syrinx (PTS), glial scar formation, neuronal fibers remodeling, axonal regeneration and sprouting, vascularization, expression of neuronal factors, and motor functions. MSC administration improved motor function in rats after SCI due to stimulation of regeneration and sprouting of the axons, enhanced recovery of locomotor functions, reduction of PTS and the glial scar, and stimulation of vascularization and expression of the neurotrophic factors. The effects of MSC were dose-dependent; the most effective dose was 106 cells.

Anisotropic 3D scaffolds for spinal cord guided repair: Current concepts

A spinal cord injury (SCI) can be caused by unforeseen events such as a fall, a vehicle accident, a gunshot, or a malignant illness, which has a significant impact on the quality of life of the patient. Due to the limited regenerative potential of the central nervous system (CNS), SCI is one of the most daunting medical challenges of modern medicine. Great advances have been made in tissue engineering and regenerative medicine, which include the transition from two-dimensional (2D) to three-dimensional (3D) biomaterials. Combinatory treatments that use 3D scaffolds may significantly enhance the repair and regeneration of functional neural tissue. In an effort to mimic the chemical and physical properties of neural tissue, scientists are researching the development of the ideal scaffold made of synthetic and/or natural polymers. Moreover, in order to restore the architecture and function of neural networks, 3D scaffolds with anisotropic properties that replicate the native longitudinal orientation of spinal cord nerve fibres are being designed. In an effort to determine if scaffold anisotropy is a crucial property for neural tissue regeneration, this review focuses on the most current technological developments relevant to anisotropic scaffolds for SCI. Special consideration is given to the architectural characteristics of scaffolds containing axially oriented fibres, channels, and pores. By analysing neural cell behaviour in vitro and tissue integration and functional recovery in animal models of SCI, the therapeutic efficacy is evaluated for its successes and limitations.

Motor functional recovery efficacy of scaffolds with bone marrow stem cells in rat spinal cord injury: a Bayesian network meta-analysis

STUDY DESIGN

A Bayesian network meta-analysis.

OBJECTIVE

Spinal cord injury (SCI) can profoundly influence human health and has been linked to lifelong disability. More high-level evidence-based medical research is expected to evaluate the value of stem cells and biomaterial scaffold material therapy for SCI.

METHODS

We performed a comprehensive search of Web of Science, Cochrane databases, Embase, and PubMed databases. 18 randomized controlled trials including both scaffolds and BMSCs were included. We performed a Bayesian network meta-analysis to compare the motor functional recovery efficacy of different scaffolds with BMSCs in rat SCI.

RESULTS

In our Bayesian network meta-analysis, the motor functional recovery was found to benefit from scaffolds, BMSCs, and BMSCs combined with scaffolds, but the scaffold and BMSC groups had similar motor functional recovery efficacy, and the BMSCs combined with scaffolds group appeared to show better efficacy than BMSCs and scaffolds alone. Subgroup analysis showed that BMSCs+fibrin, BMSCs+ASC, BMSCs+gelatine, and BMSCs+collagen were the best four treatments for SCI in rat models.

CONCLUSIONS

These Bayesian network meta-analysis findings strongly indicated that BMSCs combined with scaffolds is more effective to improve motor functional recovery than BMSCs and scaffolds alone. The fibrin, gelatine, ASC, and collagen may be favourable scaffolds for the injured spinal cord and that scaffolds with BMSCs could be a promising option in regeneration therapy for patients with SCI.

Current Concepts of Biomaterial Scaffolds and Regenerative Therapy for Spinal Cord Injury

Spinal cord injury (SCI) is a catastrophic condition associated with significant neurological deficit and social and financial burdens. It is currently being managed symptomatically, with no real therapeutic strategies available. In recent years, a number of innovative regenerative strategies have emerged and have been continuously investigated in preclinical research and clinical trials. In the near future, several more are expected to come down the translational pipeline. Among ongoing and completed trials are those reporting the use of biomaterial scaffolds. The advancements in biomaterial technology, combined with stem cell therapy or other regenerative therapy, can now accelerate the progress of promising novel therapeutic strategies from bench to bedside. Various types of approaches to regeneration therapy for SCI have been combined with the use of supportive biomaterial scaffolds as a drug and cell delivery system to facilitate favorable cell-material interactions and the supportive effect of neuroprotection. In this review, we summarize some of the most recent insights of preclinical and clinical studies using biomaterial scaffolds in regenerative therapy for SCI and summarized the biomaterial strategies for treatment with simplified results data. One hundred and sixty-eight articles were selected in the present review, in which we focused on biomaterial scaffolds. We conducted our search of articles using PubMed and Medline, a medical database. We used a combination of "Spinal cord injury" and ["Biomaterial", or "Scaffold"] as search terms and searched articles published up until 30 April 2022. Successful future therapies will require these biomaterial scaffolds and other synergistic approaches to address the persistent barriers to regeneration, including glial scarring, the loss of a structural framework, and biocompatibility. This database could serve as a benchmark to progress in future clinical trials for SCI using biomaterial scaffolds.

Stem Cell Strategies in Promoting Neuronal Regeneration after Spinal Cord Injury: A Systematic Review

Spinal cord injury (SCI) is a devastating condition with a significant medical and socioeconomic impact. To date, no effective treatment is available that can enable neuronal regeneration and recovery of function at the damaged level. This is thought to be due to scar formation, axonal degeneration and a strong inflammatory response inducing a loss of neurons followed by a cascade of events that leads to further spinal cord damage. Many experimental studies demonstrate the therapeutic effect of stem cells in SCI due to their ability to differentiate into neuronal cells and release neurotrophic factors. Therefore, it appears to be a valid strategy to use in the field of regenerative medicine. This review aims to provide an up-to-date summary of the current research status, challenges, and future directions for stem cell therapy in SCI models, providing an overview of this constantly evolving and promising field.

Bone marrow mesenchymal stem cells may attenuate lipopolysaccharide-induced liver injury via inhibiting the NLRP3 inflammasome and hepatocyte pyroptosis

BACKGROUND

The transplantation of bone marrow mesenchymal cells (BMSCs) has been shown to be an effective means of treating sepsis-related organ damage. Pytoptotic cell death, in turn, has recently been identified as a key driver of sepsis-related damage. At present, there are few studies on the effect of BMSC transplantation on pytoptotic cell death.

OBJECTIVE

We explored the ability of BMSCs to attenuate hepatic damage in a pyroptosis-related manner in a rat model of lipopolysaccharide (LPS)-induced liver injury.

METHODS

Following injury modeling and BMSC transplantation, we assessed the expression of the NLR family, pyrin domain containing 3 (NLRP3) inflammasome and key downstream pyroptosis-related signaling molecules.

RESULTS

It was found that BMSC transplantation was sufficient to significantly improve rat survival after LPS injection. Significantly reduced expression of the pyroptosis-related proteins NLRP3, caspase-1, IL-1β, and IL-18 in rats that had undergone BMSC transplantation compared to control animals. Notably, this activity was superior to single-agent administration of the NLRP3 inhibitor MCC950.

CONCLUSION

Our data suggest that BMSC transplantation may alleviate LPS-induced hepatic damage by suppressing the activation of the NLRP3 inflammasome and the induction of pyroptotic cell death.

Ambulation in Dogs With Absent Pain Perception After Acute Thoracolumbar Spinal Cord Injury

Acute thoracolumbar spinal cord injury (SCI) is common in dogs frequently secondary to intervertebral disc herniation. Following severe injury, some dogs never regain sensory function to the pelvic limbs or tail and are designated chronically "deep pain negative." Despite this, a subset of these dogs develop spontaneous motor recovery over time including some that recover sufficient function in their pelvic limbs to walk independently without assistance or weight support. This type of ambulation is commonly known as "spinal walking" and can take up to a year or more to develop. This review provides a comparative overview of locomotion and explores the physiology of locomotor recovery after severe SCI in dogs. We discuss the mechanisms by which post-injury plasticity and coordination between circuitry contained within the spinal cord, peripheral sensory feedback, and residual or recovered supraspinal connections might combine to underpin spinal walking. The clinical characteristics of spinal walking are outlined including what is known about the role of patient or injury features such as lesion location, timeframe post-injury, body size, and spasticity. The relationship between the emergence of spinal walking and electrodiagnostic and magnetic resonance imaging findings are also discussed. Finally, we review possible ways to predict or facilitate recovery of walking in chronically deep pain negative dogs. Improved understanding of the mechanisms of gait generation and plasticity of the surviving tissue after injury might pave the way for further treatment options and enhanced outcomes in severely injured dogs.

A combination of mesenchymal stem cells and scaffolds promotes motor functional recovery in spinal cord injury: a systematic review and meta-analysis

OBJECTIVE

There is controversy about the role of scaffolds as an adjunctive therapy to mesenchymal stem cell (MSC) transplantation in spinal cord injury (SCI). Thus, the authors aimed to design a meta-analysis on preclinical evidence to evaluate the effectiveness of combination therapy of scaffold + MSC transplantation in comparison with scaffolds alone and MSCs alone in improving motor dysfunction in SCI.

METHODS

Electronic databases including Medline, Embase, Scopus, and Web of Science were searched from inception until the end of August 2018. Two independent reviewers screened related experimental studies. Animal studies that evaluated the effectiveness of scaffolds and/or MSCs on motor function recovery following experimental SCI were included. The findings were reported as standardized mean difference (SMD) and 95% confidence interval (CI).

RESULTS

A total of 34 articles were included in the meta-analysis. Analyses show that combination therapy in comparison with the scaffold group alone (SMD 2.00, 95% CI 1.53-2.46, p < 0.0001), the MSCs alone (SMD 1.58, 95% CI 0.84-2.31, p < 0.0001), and the nontreated group (SMD 3.52, 95% CI 2.84-4.20, p < 0.0001) significantly improved motor function recovery. Co-administration of MSCs + scaffolds only in the acute phase of injury (during the first 3 days after injury) leads to a significant recovery compared to scaffold alone (SMD 2.18, p < 0.0001). In addition, the cotransplantation of scaffolds with bone marrow-derived MSCs (SMD 1.99, p < 0.0001) and umbilical cord-derived MSCs (SMD 1.50, p = 0.001) also improved motor function following SCI.

CONCLUSIONS

The findings showed that scaffolds + MSCs is more effective than scaffolds and MSCs alone in improving motor function following SCI in animal models, when used in the acute phase of injury.

Regulation of autophagy in mesenchymal stem cells modulates therapeutic effects on spinal cord injury

Transplantation with mesenchymal stem cells (MSCs) has shown beneficial effects in treating spinal cord injury. Autophagy is an evolutionarily conserved process of degradation and recycling of cellular components that plays an important role in tissue homeostasis and cellular survival. Whether regulating autophagy in MSCs may affect their therapeutic potential in spinal cord injury repair has not yet been determined. In this study, autophagy was inhibited in MSCs with lentiviruses expressing short hairpin RNA (shRNA) to knock down Becn-1 expression, and autophagy was upregulated in MSCs under nutrient starvation. These MSCs were then labelled with Hoechst and applied to spinal cord-injured rats to evaluate their therapeutic effects. After transplanting MSCs into rats with spinal cord injuries, functional recovery, immunohistochemistry, and remyelination analyses were performed. After inducing autophagy, the MSCs exhibited an accumulation of LC3-positive autophagosomes in the cytoplasm. The expression levels of neurotrophic factors, including vascular endothelial growth factor and brain derived neurotrophic factor, were significantly higher in autophagic MSCs than normal MSCs. The in vivo study showed that more labelled MSCs migrated to the lesion site after induction of autophagy. Inducing autophagy in MSCs promoted functional recovery after spinal cord injury, whereas functional recovery was weak after inhibiting autophagy in MSCs. In contrast to the autophagy inhibition group, transplanting autophagic MSCs exhibited a greater positive impact on axon regeneration, growth of serotonergic fibers, blood vessel regeneration, and myelination, indicating a multifactorial contribution to spinal cord injury repair. These results suggest that autophagy plays important roles in MSCs during spinal cord injury repair. Regulation of autophagy in MSCs before in vivo transplantation may be a potential therapeutic interventional strategy for spinal cord injury.

Polymer scaffolds facilitate spinal cord injury repair

During the past decades, improving patient neurological recovery following spinal cord injury (SCI) has remained a challenge. An effective treatment for SCI would not only reduce fractured elements and isolate developing local glial scars to promote axonal regeneration but also ameliorate secondary effects, including inflammation, apoptosis, and necrosis. Three-dimensional (3D) scaffolds provide a platform in which these mechanisms can be addressed in a controlled manner. Polymer scaffolds with favorable biocompatibility and appropriate mechanical properties have been engineered to minimize cicatrization, customize drug release, and ensure an unobstructed space to promote cell growth and differentiation. These properties make polymer scaffolds an important potential therapeutic platform. This review highlights the recent developments in polymer scaffolds for SCI engineering. STATEMENT OF SIGNIFICANCE: How to improve the efficacy of neurological recovery after spinal cord injury (SCI) is always a challenge. Tissue engineering provides a promising strategy for SCI repair, and scaffolds are one of the most important elements in addition to cells and inducing factors. The review highlights recent development and future prospects in polymer scaffolds for SCI therapy. The review will guide future studies by outlining the requirements and characteristics of polymer scaffold technologies employed against SCI. Additionally, the peculiar properties of polymer materials used in the therapeutic process of SCI also have guiding significance to other tissue engineering approaches.

Establishing an Organotypic System for Investigating Multimodal Neural Repair Effects of Human Mesenchymal Stromal Stem Cells

Human mesenchymal stromal stem cells (hMSCs) hold regenerative medicine potential due to their availability, in vitro expansion readiness, and autologous feasibility. For neural repair, hMSCs show translational value in research on stroke, spinal cord injury (SCI), and traumatic brain injury. It is pivotal to establish multimodal in vitro systems to investigate molecular mechanisms underlying neural actions of hMSCs. Here, we describe a platform protocol on how to set up organotypic co-cultures of hMSCs (alone or polymer-scaffolded) with explanted adult rat dorsal root ganglia (DRGs) to determine neural injury and recovery events for designing implants to counteract neurotrauma sequelae. We emphasize in vitro hMSC propagation, polymer scaffolding, hMSC stemness maintenance, hMSC-DRG interaction profiling, and analytical formulas of neuroinflammation, trophic factor expression, DRG neurite outgrowth and tropic tracking, and in vivo verification of tailored implants in rodent models of SCI. © 2018 by John Wiley & Sons, Inc.

Modified acellular nerve-delivering PMSCs improve functional recovery in rats after complete spinal cord transection

Due to the poor regeneration capacity of neurons and the inhibitory microenvironment, spontaneous regeneration in spinal cord injury (SCI) remains challenging. Tissue engineering is considered a promising approach for enhancing the regeneration of SCI by reconstructing the inherent structure and improving the microenvironment. In this study, the possibility of engineering a nerve complex, which is constructed by acellular nerve delivering placenta mesenchymal stem cells (PMSCs), was assessed for the recovery of a transected spinal cord. Modified acellular nerve grafts were developed, and PMSCs labeled with green fluorescent protein (GFP) were seeded on the graft to construct the engineered nerve complex. Then, the engineered nerve complex was implanted into a 2 mm-length transected gap of the spinal cord. Four weeks after the transplantation, numerous surviving PMSCs were observed in the lesion cavity by immunofluorescence staining. Moreover, co-localization between GFP and neurofilament-200 (NF200) and Neuronal Class III β-Tubulin (Tuj1) was observed at the bridge interface. The PMSCs-graft group exhibited significant function improvement as evaluated by the Basso, Beattie and Bresnahan (BBB) locomotion score and footprint analysis. Eight weeks after surgery, the evoked response was restored in the PMSCs-graft group and numerous thick myelin sheathes were observed compared to that in the control groups. Collectively, our findings suggest that the nerve complex prepared by acellular nerve delivering PMSCs enhanced the structure and function regeneration of the spinal cord after SCI.

Fabrication and characterization of collagen-based injectable and self-crosslinkable hydrogels for cell encapsulation

Injectable and self-crosslinkable hydrogels have drawn much attention for their potential application as cell delivery carriers to deliver cells to the injury site of arbitrary shape. In this study, injectable and self-crosslinkable hydrogels were designed and fabricated based on collagen type I (Col I) and activated chondroitin sulfate (CS-sNHS) by physical and chemical crosslinking without the addition of any catalysts. The physical properties of hydrogels, including mechanical properties, swelling and degradation properties, were investigated. The results demonstrated that the physical properties of hydrogels, especially the stiffness of hydrogels, were readily tuned by varying the degree of substitution (DS) of CS-sNHS without changing the concentration of collagen-based precursor. Chondrocytes were encapsulated into hydrogels to investigate the effects of hydrogels on the survival, proliferation and extracellular matrix (ECM) secretion of cells by FDA/PI staining, CCK-8 test and histological staining. The results suggested that all of these hydrogels supported the survival and ECM secretion of chondrocytes, while there was more ECM secretion around chondrocytes encapsulated in hydrogel Col I/CS-sNHS56% in which the DS of CS-sNHS was 56%. When the neutral precursor solution for hydrogel of Col I or Col I/CS-sNHS56% was subcutaneously injected into SD rats, hydrogels both displayed acceptable biocompatibility in vivo. These results imply that these injectable and self-crosslinkable hydrogels are suitable candidates for applications in the fields of cell delivery and tissue engineering.

Multichannel polymer scaffold seeded with activated Schwann cells and bone mesenchymal stem cells improves axonal regeneration and functional recovery after rat spinal cord injury

The adult mammalian CNS has a limited capacity to regenerate after traumatic injury. In this study, a combinatorial strategy to promote axonal regeneration and functional recovery after spinal cord injury (SCI) was evaluated in adult rats. The rats were subjected to a complete transection in the thoracic spinal cord, and multichannel scaffolds seeded with activated Schwann cells (ASCs) and/or rat bone marrow-derived mesenchymal stem cells (MSCs) were acutely grafted into the 3-mm-wide transection gap. At 4 weeks post-transplantation and thereafter, the rats receiving scaffolds seeded with ASCs and MSCs exhibited significant recovery of nerve function as shown by the Basso, Beattie and Bresnahan (BBB) score and electrophysiological test results. Immunohistochemical analyses at 4 and 8 weeks after transplantation revealed that the implanted MSCs at the lesion/graft site survived and differentiated into neuron-like cells and co-localized with host neurons. Robust bundles of regenerated fibers were identified in the lesion/graft site in the ASC and MSC co-transplantation rats, and neurofilament 200 (NF) staining confirmed that these fibers were axons. Furthermore, myelin basic protein (MBP)-positive myelin sheaths were also identified at the lesion/graft site and confirmed via electron microscopy. In addition to expressing mature neuronal markers, sparse MSC-derived neuron-like cells expressed choline acetyltransferase (ChAT) at the injury site of the ASC and MSC co-transplantation rats. These findings suggest that co-transplantation of ASCs and MSCs in a multichannel polymer scaffold may represent a novel combinatorial strategy for the treatment of spinal cord injury.

Increased Understanding of Stem Cell Behavior in Neurodegenerative and Neuromuscular Disorders by Use of Noninvasive Cell Imaging

Numerous neurodegenerative and neuromuscular disorders are associated with cell-specific depletion in the human body. This imbalance in tissue homeostasis is in healthy individuals repaired by the presence of endogenous stem cells that can replace the lost cell type. However, in most disorders, a genetic origin or limited presence or exhaustion of stem cells impairs correct cell replacement. During the last 30 years, methods to readily isolate and expand stem cells have been developed and this resulted in a major change in the regenerative medicine field as it generates sufficient amount of cells for human transplantation applications. Furthermore, stem cells have been shown to release cytokines with beneficial effects for several diseases. At present however, clinical stem cell transplantations studies are struggling to demonstrate clinical efficacy despite promising preclinical results. Therefore, to allow stem cell therapy to achieve its full potential, more insight in their in vivo behavior has to be achieved. Different methods to noninvasively monitor these cells have been developed and are discussed. In some cases, stem cell monitoring even reached the clinical setting. We anticipate that by further exploring these imaging possibilities and unraveling their in vivo behavior further improvement in stem cell transplantations will be achieved.

A Proposal for a Rat Model of Spinal Cord Injury Featuring the Rubrospinal Tract and its Contributions to Locomotion and Skilled Hand Movement

Spinal cord injury and repair is a dynamic field of research. The development of reliable animal models of traumatic spinal cord injury has been invaluable in providing a wealth of information regarding the pathological consequences and recovery potential of this condition. A number of injury models have been instrumental in the elaboration and the validation of therapeutic interventions aimed at reversing this once thought permanent condition. In general, the study of spinal cord injury and repair is made difficult by both its anatomical complexity and the complexity of the behavior it mediates. In this perspective paper, we suggest a new model for spinal cord investigation that simplifies problems related to both the functional and anatomical complexity of the spinal cord. We begin by reviewing and contrasting some of the most common animal models used for investigating spinal cord dysfunction. We then consider two widely used models of spinal deficit-recovery, one involving the corticospinal tracts (CTS) and the other the rubrospinal tract (RST). We argue that the simplicity of the function of the RST makes it a useful model for studying the cord and its functional repair. We also reflect on two obstacles that have hindered progress in the pre-clinical field, delaying translation to the clinical setup. The first is recovery of function without reconnection of the transected descending fibers and the second is the use of behavioral paradigms that are not under the control of the descending fiber pathway under scrutiny.

Biomaterial bridges enable regeneration and re-entry of corticospinal tract axons into the caudal spinal cord after SCI: Association with recovery of forelimb function

Severed axon tracts fail to exhibit robust or spontaneous regeneration after spinal cord injury (SCI). Regeneration failure reflects a combination of factors, including the growth state of neuronal cell bodies and the regeneration-inhibitory environment of the central nervous system. However, while spared circuitry can be retrained, target reinnervation depends on longitudinally directed regeneration of transected axons. This study describes a biodegradable implant using poly(lactide-co-glycolide) (PLG) bridges as a carrier scaffold to support regeneration after injury. In order to detect regeneration of descending neuronal tracts into the bridge, and beyond into intact caudal parenchyma, we developed a mouse cervical implantation model and employed Crym:GFP transgenic mice. Characterization of Crym:GFP mice revealed that descending tracts, including the corticospinal tract, were labeled by green fluorescent protein (GFP), while ascending sensory neurons and fibers were not. Robust co-localization between GFP and neurofilament-200 (NF-200) as well as GFP and GAP-43 was observed at both the rostral and caudal bridge/tissue interface. No evidence of similar regeneration was observed in mice that received gelfoam at the lesion site as controls. Minimal co-localization between GFP reporter labeling and macrophage markers was observed. Taken together, these data suggest that axons originating from descending fiber tracts regenerated, entered into the PLG bridge at the rostral margin, continued through the bridge site, and exited to re-enter host tissue at the caudal edge of the intact bridge. Finally, regeneration through implanted bridges was associated with a reduction in ipsilateral forelimb errors on a horizontal ladder task.

Human mesenchymal stromal cells attenuate graft-versus-host disease and maintain graft-versus-leukemia activity following experimental allogeneic bone marrow transplantation

We sought to define the effects and underlying mechanisms of human, marrow-derived mesenchymal stromal cells (hMSCs) on graft-versus-host disease (GvHD) and graft-versus-leukemia (GvL) activity. Irradiated B6D2F1 mice given C57BL/6 BM and splenic T cells and treated with hMSCs had reduced systemic GvHD, donor T-cell expansion, and serum TNFα and IFNγ levels. Bioluminescence imaging demonstrated that hMSCs redistributed from lungs to abdominal organs within 72 hours, and target tissues harvested from hMSC-treated allogeneic BMT (alloBMT) mice had less GvHD than untreated controls. Cryoimaging more precisely revealed that hMSCs preferentially distributed to splenic marginal zones and regulated T-cell expansion in the white pulp. Importantly, hMSCs had no effect on in vitro cytotoxic T-cell activity and preserved potent GvL effects in vivo. Mixed leukocyte cultures containing hMSCs exhibited decreased T-cell proliferation, reduced TNFα, IFNγ, and IL-10 but increased PGE2 levels. Indomethacin and E-prostanoid 2 (EP2) receptor antagonisms both reversed while EP2 agonism restored hMSC-mediated in vitro T-cell suppression, confirming the role for PGE2 . Furthermore, cyclo-oxygenase inhibition following alloBMT abrogated the protective effects of hMSCs. Together, our data show that hMSCs preserve GvL activity and attenuate GvHD and reveal that hMSC biodistribute to secondary lymphoid organs wherein they attenuate alloreactive T-cell proliferation likely through PGE2 induction.

Stem cell regenerative therapy in alveolar cleft reconstruction

Achieving a successful and well-functioning reconstruction of craniofacial deformities still remains a challenge. As for now, autologous bone grafting remains the gold standard for alveolar cleft reconstruction. However, its aesthetic and functional results often remain unsatisfactory, which carries a long-term psychosocial and medical sequelae. Therefore, searching for novel therapeutic approaches is strongly indicated. With the recent advances in stem cell research, cell-based tissue engineering strategies move from the bench to the patients' bedside. Successful stem cell engineering employs a carefully selected stem cell source, a biodegradable scaffold with osteoconductive and osteoinductive properties, as well as an addition of growth factors or cytokines to enhance osteogenesis. This review highlights recent advances in mesenchymal stem cell tissue engineering, discusses animal models and case reports of stem cell enhanced bone regeneration, as well as ongoing clinical trials.

Cell Therapy Augments Functional Recovery Subsequent to Spinal Cord Injury under Experimental Conditions

The spinal cord injury leads to enervation of normal tissue homeostasis ultimately leading to paralysis. Until now there is no proper cure for the treatment of spinal cord injury. Recently, cell therapy in animal spinal cord injury models has shown some progress of recovery. At present, clinical trials are under progress to evaluate the efficacy of cell transplantation for the treatment of spinal cord injury. Different types of cells such as pluripotent stem cells derived neural cells, mesenchymal stromal cells, neural stem cells, glial cells are being tested in various spinal cord injury models. In this review we highlight both the advances and lacuna in the field of spinal cord injury by discussing epidemiology, pathophysiology, molecular mechanism, and various cell therapy strategies employed in preclinical and clinical injury models and finally we discuss the limitations and ethical issues involved in cell therapy approach for treating spinal cord injury.

Complete rat spinal cord transection as a faithful model of spinal cord injury for translational cell transplantation

Spinal cord injury (SCI) results in neural loss and consequently motor and sensory impairment below the injury. There are currently no effective therapies for the treatment of traumatic SCI in humans. Various animal models have been developed to mimic human SCI. Widely used animal models of SCI are complete or partial transection or experimental contusion and compression, with both bearing controversy as to which one more appropriately reproduces the human SCI functional consequences. Here we present in details the widely used procedure of complete spinal cord transection as a faithful animal model to investigate neural and functional repair of the damaged tissue by exogenous human transplanted cells. This injury model offers the advantage of complete damage to a spinal cord at a defined place and time, is relatively simple to standardize and is highly reproducible.

New trends in spinal cord tissue engineering

ABSTRACT 

Restoration of lost neuronal function after spinal cord injury still remains a considerable challenge for current medicine. Over the last decade, regenerative medicine has recorded rapid and promising advancements in stem cell research, genetic engineering and the progression of new sophisticated biomaterials as well as nanotechnology. This advancement has also been reflected in neural tissue engineering, where, along with the development of a new generation of well-designed biopolymer scaffolds, multifactorial therapeutic strategies are being validated in order to determine the greatest possible repair efficacy of the complex CNS pathophysiology. Much attention is currently focused on the designing of multifunctional polymer scaffolds as systems for targeted drug or gene delivery, electrical stimulation or as substrates creating a special micro-environment, promoting the growth and desired differentiation of various cell lines. In this review, the latest advances in biomaterial technology together with various combinatorial strategies designed to treat spinal cord injury treatment are summarized and discussed.

Evaluation of small intestine submucosa and poly(caprolactone-co-lactide) conduits for peripheral nerve regeneration

The present study employed nerve guidance conduits (NGCs) only, which were made of small intestine submucosa (SIS) and poly(caprolactone-co-lactide) (PCLA) to promote nerve regeneration in a peripheral nerve injury (PNI) model with nerve defects of 15 mm. The SIS- and PCLA-NGCs were easily prepared by rolling of a SIS sheet and a bioplotter using PCLA, respectively. The prepared SIS- and PCLA-NGCs fulfilled the general requirement for use as artificial peripheral NGCs such as easy fabrication, reproducibility for mass production, suturability, sterilizability, wettability, and proper mechanical properties to resist collapsing when applied to in vivo implantation. The SIS- and PCLA-NGCs appeared to be well integrated into the host sciatic nerve without causing dislocations and serious inflammation. All NGCs stably maintained their NGC shape for 8 weeks without collapsing, which matched well with the nerve regeneration rate. Staining of the NGCs in the longitudinal direction showed that the regenerated nerves grew successfully from the SIS- and PCLA-NGCs through the sciatic nerve-injured gap and connected from the proximal to distal direction along the NGC axis. SIS-NGCs exhibited a higher nerve regeneration rate than PCLA-NGCs. Collectively, our results indicate that SIS- and PCLA-NGCs induced nerve regeneration in a PNI model, a finding that has significant implications in the future with regard to the feasibility of clinical nerve regeneration with SIS- and PCLA-NGCs prepared through an easy fabrication method using promising biomaterials.

Stem cell treatment of degenerative eye disease

Stem cell therapies are being explored extensively as treatments for degenerative eye disease, either for replacing lost neurons, restoring neural circuits or, based on more recent evidence, as paracrine-mediated therapies in which stem cell-derived trophic factors protect compromised endogenous retinal neurons from death and induce the growth of new connections. Retinal progenitor phenotypes induced from embryonic stem cells/induced pluripotent stem cells (ESCs/iPSCs) and endogenous retinal stem cells may replace lost photoreceptors and retinal pigment epithelial (RPE) cells and restore vision in the diseased eye, whereas treatment of injured retinal ganglion cells (RGCs) has so far been reliant on mesenchymal stem cells (MSC). Here, we review the properties of non-retinal-derived adult stem cells, in particular neural stem cells (NSCs), MSC derived from bone marrow (BMSC), adipose tissues (ADSC) and dental pulp (DPSC), together with ESC/iPSC and discuss and compare their potential advantages as therapies designed to provide trophic support, repair and replacement of retinal neurons, RPE and glia in degenerative retinal diseases. We conclude that ESCs/iPSCs have the potential to replace lost retinal cells, whereas MSC may be a useful source of paracrine factors that protect RGC and stimulate regeneration of their axons in the optic nerve in degenerate eye disease. NSC may have potential as both a source of replacement cells and also as mediators of paracrine treatment.

Stem cell therapy in spinal trauma: Does it have scientific validity?

Stem cell-based interventions aim to use special regenerative cells (stem cells) to facilitate neuronal function beyond the site of the injury. Many studies involving animal models of spinal cord injury (SCI) suggest that certain stem cell-based therapies may restore function after SCI. Currently, in case of spinal cord injuries, new discoveries with clinical implications have been continuously made in basic stem cell research, and stem cell-based approaches are advancing rapidly toward application in patients. There is a huge base of preclinical evidence in vitro and in animal models which suggests the safety and clinical efficacy of cellular therapies after SCI. Despite this, data from clinical studies is not very encouraging and at times confounding. Here, we have attempted to cover preclinical and clinical evidence base dealing with safety, feasibility and efficacy of cell based interventions after SCI. The limitations of preclinical data and the reasons underlying its failure to translate in a clinical setting are also discussed. Based on the evidence base, it is suggested that a multifactorial approach is required to address this situation. Need for standardized, stringently designed multi-centric clinical trials for obtaining validated proof of evidence is also highlighted.

Gene therapy strategies for the treatment of spinal cord injury

Spinal cord injury is a complex pathology often resulting in functional impairment and paralysis. Gene therapy has emerged as a possible solution to the problems of limited neural tissue regeneration through the administration of factors promoting axonal growth, while also offering long-term local delivery of therapeutic molecules at the injury site. Of note, gene therapy is our response to the requirements of neural and glial cells following spinal cord injury, providing, in a time-dependent manner, growth substances for axonal regeneration and eliminating axonal growth inhibitors. Herein, we explore different gene therapy strategies, including targeting gene expression to modulate the presence of neurotrophic growth or survival factors and increase neural tissue plasticity. Special attention is given to describing advances in viral and non-viral gene delivery systems, as well as the available routes of gene delivery. Finally, we discuss the future of combinatorial gene therapies and give consideration to the implementation of gene therapy in humans.

Perspectives on tissue-engineered nerve regeneration for the treatment of spinal cord injury

Over the past few decades, substantial progress has been made to safely improve nerve function in spinal cord injury (SCI) patients through the regeneration of injured nerve tissue. This perspective focuses on an extensive overview of SCI research as well as tissue-engineered nerve regeneration for the treatment of SCI.

Neurotrauma and mesenchymal stem cells treatment: From experimental studies to clinical trials

Mesenchymal stem cell (MSC) therapy has attracted the attention of scientists and clinicians around the world. Basic and pre-clinical experimental studies have highlighted the positive effects of MSC treatment after spinal cord and peripheral nerve injury. These effects are believed to be due to their ability to differentiate into other cell lineages, modulate inflammatory and immunomodulatory responses, reduce cell apoptosis, secrete several neurotrophic factors and respond to tissue injury, among others. There are many pre-clinical studies on MSC treatment for spinal cord injury (SCI) and peripheral nerve injuries. However, the same is not true for clinical trials, particularly those concerned with nerve trauma, indicating the necessity of more well-constructed studies showing the benefits that cell therapy can provide for individuals suffering the consequences of nerve lesions. As for clinical trials for SCI treatment the results obtained so far are not as beneficial as those described in experimental studies. For these reasons basic and pre-clinical studies dealing with MSC therapy should emphasize the standardization of protocols that could be translated to the clinical set with consistent and positive outcomes. This review is based on pre-clinical studies and clinical trials available in the literature from 2010 until now. At the time of writing this article there were 43 and 36 pre-clinical and 19 and 1 clinical trials on injured spinal cord and peripheral nerves, respectively.

Cell therapy for spinal cord injuries: what is really going on?

During the last two decades, many experiments have examined the ability of cell transplants to ameliorate the loss of function after spinal cord injuries, with the hope of developing interventions to benefit patients. Although many reports suggest positive effects, there is growing concern over the quality of the available preclinical data. It is therefore important to ask whether this worldwide investigative process is close to defining a cell transplant protocol that could be translated into human patients with a realistic chance of success. This review systematically examines the strength of the preclinical evidence and outlines mechanisms by which transplanted cells may mediate their effects in spinal cord injuries. First, we examined changes in voluntary movements in the forelimb associated with cell transplants after partial cervical lesions. Second, we examined the efficacy of transplanted cells to restore electrophysiological conduction across a complete thoracic lesion. We postulated that cell therapies found to be successful in both models could reasonably have potential to treat human patients. We conclude that although there are data to support a beneficial effect of cell transplantation, most reports provide only weak evidence because of deficits in experimental design. The mechanisms by which transplanted cells mediate their functional effects remain unclear.

Management strategies for acute spinal cord injury: current options and future perspectives

PURPOSE OF REVIEW

Spinal cord injury is a devastating acute neurological condition with loss of function and poor long-term prognosis. This review summarizes current management strategies and innovative concepts on the horizon.

RECENT FINDINGS

The routine use of steroids in patients with spinal cord injuries has been largely abandoned and considered a 'harmful standard of care'. Prospective trials have shown that early spine stabilization within 24  h results in decreased secondary complication rates. Neuronal plasticity and axonal regeneration in the adult spinal cord are limited due to myelin-associated inhibitory molecules, such as Nogo-A. The experimental inhibition of Nogo-A ameliorates axonal sprouting and functional recovery in animal models.

SUMMARY

General management strategies for acute spinal cord injury consist of protection of airway, breathing, oxygenation and control of blood loss with maintenance of blood pressure. Unstable spine fractures should be stabilized early to allow unrestricted mobilization of patients with spinal cord injuries and to decrease preventable complications. Steroids are largely considered obsolete and have been abandoned in clinical guidelines. Nogo-A represents a promising new pharmacological target to promote sprouting of injured axons and restore function. Prospective clinical trials of Nogo-A inhibition in patients with spinal cord injuries are currently under way.

Using extracellular matrix for regenerative medicine in the spinal cord

Regeneration within the mammalian central nervous system (CNS) is limited, and traumatic injury often leads to permanent functional motor and sensory loss. The lack of regeneration following spinal cord injury (SCI) is mainly caused by the presence of glial scarring, cystic cavitation and a hostile environment to axonal growth at the lesion site. The more prominent experimental treatment strategies focus mainly on drug and cell therapies, however recent interest in biomaterial-based strategies are increasing in number and breadth. Outside the spinal cord, approaches that utilize the extracellular matrix (ECM) to promote tissue repair show tremendous potential for various application including vascular, skin, bone, cartilage, liver, lung, heart and peripheral nerve tissue engineering (TE). Experimentally, it is unknown if these approaches can be successfully translated to the CNS, either alone or in combination with synthetic biomaterial scaffolds. In this review we outline the first attempts to apply the potential of ECM-based biomaterials and combining cell-derived ECM with synthetic scaffolds.

How Can Nanotechnology Help to Repair the Body? Advances in Cardiac, Skin, Bone, Cartilage and Nerve Tissue Regeneration

Nanotechnologists have become involved in regenerative medicine via creation of biomaterials and nanostructures with potential clinical implications. Their aim is to develop systems that can mimic, reinforce or even create in vivo tissue repair strategies. In fact, in the last decade, important advances in the field of tissue engineering, cell therapy and cell delivery have already been achieved. In this review, we will delve into the latest research advances and discuss whether cell and/or tissue repair devices are a possibility. Focusing on the application of nanotechnology in tissue engineering research, this review highlights recent advances in the application of nano-engineered scaffolds designed to replace or restore the followed tissues: (i) skin; (ii) cartilage; (iii) bone; (iv) nerve; and (v) cardiac.

Cell transplantation for spinal cord injury: a systematic review

Cell transplantation, as a therapeutic intervention for spinal cord injury (SCI), has been extensively studied by researchers in recent years. A number of different kinds of stem cells, neural progenitors, and glial cells have been tested in basic research, and most have been excluded from clinical studies because of a variety of reasons, including safety and efficacy. The signaling pathways, protein interactions, cellular behavior, and the differentiated fates of experimental cells have been studied in vitro in detail. Furthermore, the survival, proliferation, differentiation, and effects on promoting functional recovery of transplanted cells have also been examined in different animal SCI models. However, despite significant progress, a "bench to bedside" gap still exists. In this paper, we comprehensively cover publications in the field from the last years. The most commonly utilized cell lineages were covered in this paper and specific areas covered include survival of grafted cells, axonal regeneration and remyelination, sensory and motor functional recovery, and electrophysiological improvements. Finally we also review the literature on the in vivo tracking techniques for transplanted cells.