Peripheral nerve grafts and aFGF restore partial hindlimb function in adult paraplegic rats

Cell surface receptor-mediated signaling in CNS regeneration

Degenerative diseases and injuries of central nervous system (CNS) often cause nerve cell apoptosis and neural dysfunction. Protection of surviving cells or inducing the differentiation of stem cells into functional cells is considered to be an important way of neurorepair. In addition, transdifferentiation technology emerged recently is expected to provide new solutions for nerve regeneration. Cell surface receptors are transmembrane proteins embedded in cytoplasmic membrane, and play crucial roles in maintaining communication between extracellular signals and intracellular signaling processes. The extracellular microenvironment changed dramatically upon neural lesion, exploring the biological function of signals mediated by cell surface receptors will help to develop molecular strategies for nerve regeneration. An increasing number of studies have reported that cell surface receptor-mediated signaling affects the survival, differentiation, and functioning of neural cells, and even regulate their trans-lineage reprogramming. Here, we provide a review on the roles of cell surface receptors in CNS regeneration, thus providing new cues for better treatment of neurodegenerative diseases or nerve injury.

Suppression of Fibroblast Growth Factor Receptor-5 (FGFR5) has no Impact on Axon Regeneration after SCI

One of the most common forms of the mammalian central nervous system (CNS) injuries is spinal cord injury (SCI), and any lesion to the CNS can result in a lifelong functional impairment since CNS axons cannot regenerate. The relative axon regenerating genes following spinal SCI were examined using the regenerative SN, pSN + DC, and non-regenerating DC lesion models. By using qRT-PCR, we discovered that fibroblast growth factor receptor-5 (FGFR5) was 4.2-fold more highly expressed in non-regeneration lesions compared to intact control and regenerating animals. Furthermore, in cultured dorsal root ganglion neurons (DRGN), short interfering RNA (siRNA)-mediated knockdown of FGFR5 had no effect on DRGN neurite outgrowth, indicating that the gene's suppression has no effect on axon regeneration and may play other roles in the CNS besides axon regeneration.

Fibroblast Growth Factor Signalling in the Diseased Nervous System

Fibroblast growth factors (FGFs) act as key signalling molecules in brain development, maintenance, and repair. They influence the intricate relationship between myelinating cells and axons as well as the association of astrocytic and microglial processes with neuronal perikarya and synapses. Advances in molecular genetics and imaging techniques have allowed novel insights into FGF signalling in recent years. Conditional mouse mutants have revealed the functional significance of neuronal and glial FGF receptors, not only in tissue protection, axon regeneration, and glial proliferation but also in instant behavioural changes. This review provides a summary of recent findings regarding the role of FGFs and their receptors in the nervous system and in the pathogenesis of major neurological and psychiatric disorders.

Fibroblast Growth Factors as Tools in the Management of Neuropathic Pain Disorders

Neuropathic pain is caused by a damage to or dysfunction of the somatosensory nervous system. The main mechanisms underlying neuropathic pain include ectopic activity in nociceptive nerves, peripheral and central sensitization, impaired inhibitory modulation, and microglial activation. Fibroblast growth factors (FGFs) make up a large family of growth factors that mediate neural development, metabolism, and function through three main key signaling pathways, including RAS/MAP kinase pathway, PI3 kinase/Akt pathway, and PLCγ. An association between the members of the FGF system and the improvement of neuropathic pain has become evident, recently. These signaling molecules may be expected to provide new drug targets for the treatment of neuropathic pain. To the best of our knowledge, it is the first study that reviews the relationship between some members of the FGF system and neuropathic pain.

Growth factors-based therapeutic strategies and their underlying signaling mechanisms for peripheral nerve regeneration

Peripheral nerve injury (PNI), one of the most common concerns following trauma, can result in a significant loss of sensory or motor function. Restoration of the injured nerves requires a complex cellular and molecular response to rebuild the functional axons so that they can accurately connect with their original targets. However, there is no optimized therapy for complete recovery after PNI. Supplementation with exogenous growth factors (GFs) is an emerging and versatile therapeutic strategy for promoting nerve regeneration and functional recovery. GFs activate the downstream targets of various signaling cascades through binding with their corresponding receptors to exert their multiple effects on neurorestoration and tissue regeneration. However, the simple administration of GFs is insufficient for reconstructing PNI due to their short half‑life and rapid deactivation in body fluids. To overcome these shortcomings, several nerve conduits derived from biological tissue or synthetic materials have been developed. Their good biocompatibility and biofunctionality made them a suitable vehicle for the delivery of multiple GFs to support peripheral nerve regeneration. After repairing nerve defects, the controlled release of GFs from the conduit structures is able to continuously improve axonal regeneration and functional outcome. Thus, therapies with growth factor (GF) delivery systems have received increasing attention in recent years. Here, we mainly review the therapeutic capacity of GFs and their incorporation into nerve guides for repairing PNI. In addition, the possible receptors and signaling mechanisms of the GF family exerting their biological effects are also emphasized.

Emerging Therapeutic Strategies for Traumatic Spinal Cord Injury

Spinal cord injury (SCI) is a debilitating neurologic condition with tremendous socioeconomic impact on affected individuals and the health care system. The treatment of SCI principally includes surgical treatment and marginal pharmacologic and rehabilitation therapies targeting secondary events with minor clinical improvements. This unsuccessful result mainly reflects the complexity of SCI pathophysiology and the diverse biochemical and physiologic changes that occur in the injured spinal cord. Once the nervous system is injured, cascades of cellular and molecular events are triggered at varying times. Although the cascade of tissue reactions and cell injury develops over a period of days or weeks, the most extensive cell death in SCI occurs within hours of trauma. This situation suggests that early intervention is likely to be the most promising approach to rescue the cord from further and irreversible cell damage. Over the past decades, a wealth of research has been conducted in preclinical and clinical studies with the hope to find new therapeutic strategies. Researchers have identified several targets for the development of potential therapeutic interventions (e.g., neuroprotection, replacement of cells lost, removal of inhibitory molecules, regeneration, and rehabilitation strategies to induce neuroplasticity). Most of these treatments have passed preclinical and initial clinical evaluations but have failed to be strongly conclusive in the clinical setting. This narrative review provides an update of the many therapeutic interventions after SCI, with an emphasis on the underlying pathophysiologic mechanisms.

Single vs. Combined Therapeutic Approaches in Rats With Chronic Spinal Cord Injury

The regenerative capability of the central nervous system is limited after traumatic spinal cord injury (SCI) due to intrinsic and extrinsic factors that inhibit spinal cord regeneration, resulting in deficient functional recovery. It has been shown that strategies, such as pre-degenerated peripheral nerve (PPN) grafts or the use of bone marrow stromal cells (BMSCs) or exogenous molecules, such as chondroitinase ABC (ChABC) promote axonal growth and remyelination, resulting in an improvement in locomotor function. These treatments have been primarily assessed in acute injury models. The aim of the present study is to evaluate the ability of several single and combined treatments in order to modify the course of chronic complete SCI in rats. A complete cord transection was performed at the T9 level. One month later, animals were divided into five groups: original injury only (control group), and original injury plus spinal cord re-transection to create a gap to accommodate BMSCs, PPN, PPN + BMSCs, and PPN + BMSCs + ChABC. In comparison with control and single-treatment groups (PPN and BMSCs), combined treatment groups (PPN + BMSCs and PPN + BMSCs + ChABC) showed significative axonal regrowth, as revealed by an increase in GAP-43 and MAP-1B expression in axonal fibers, which correlated with an improvement in locomotor function. In conclusion, the combined therapies tested here improve locomotor function by enhancing axonal regeneration in rats with chronic SCI. Further studies are warranted to refine this promising line of research for clinical purposes.

Monkey Recovery from Spinal Cord Hemisection: Nerve Repair Strategies for Rhesus Macaques

OBJECTIVE

Repair of spinal cord injury (SCI) using peripheral nerve graft (PNG) and acidic fibroblast growth factor (aFGF) has shown promising results in rats and a few human patients, but not in nonhuman primates. The aim of this study was to verify the effective use of PNG and aFGF for repairing incomplete SCI in nonhuman primates.

METHODS

Six adult rhesus macaques received spinal cord hemisection at T8 level and were grouped into repair and control groups (n = 3 in each). Animals in the repair group underwent nerve repair with autologous PNG plus aFGF immediately after lesioning. The control group received exactly the same operation for lesioning but no treatment. Postoperative behavioral evaluations, electrophysiologic tests (including motor and somatosensory evoked potentials), and magnetic resonance imaging were performed and compared between the 2 groups as well as histologic examination of the spinal cord cephalic to, at, and caudal to the lesion site after sacrifice.

RESULTS

Animals in the repair group had better motor function in the lower limbs at every observed time point and demonstrated more improvement on electrophysiologic examinations than the control group. The repair group had smaller areas of myelomalacia on magnetic resonance imaging around the lesion compared with the control group, suggesting diminished inflammatory responses with the repair strategy.

CONCLUSIONS

PNG plus aFGF for SCI in nonhuman primates yielded improvements in clinical behavior, electrophysiologic tests, and magnetic resonance imaging. This study suggests that the repair strategy is feasible and effective for nonhuman primate SCI. Further investigations are warranted to corroborate its effectiveness for clinical application.

Acidic Fibroblast Growth Factor in Spinal Cord Injury

Spinal cord injury (SCI), with an incidence rate of 246 per million person-years among adults in Taiwan, remains a devastating disease in the modern day. Elderly men with lower socioeconomic status have an even higher risk for SCI. Despite advances made in medicine and technology to date, there are few effective treatments for SCI due to limitations in the regenerative capacity of the adult central nervous system. Experiments and clinical trials have explored neuro-regeneration in human SCI, encompassing cell- and molecule-based therapies. Furthermore, strategies have aimed at restoring connections, including autologous peripheral nerve grafts and biomaterial scaffolds that theoretically promote axonal growth. Most molecule-based therapies target the modulation of inhibitory molecules to promote axonal growth, degrade glial scarring obstacles, and stimulate intrinsic regenerative capacity. Among them, acidic fibroblast growth factor (aFGF) has been investigated for nerve repair; it is mitogenic and pluripotent in nature and could enhance axonal growth and mitigate glial scarring. For more than 2 decades, the authors have conducted multiple trials, including human and animal experiments, using aFGF to repair nerve injuries, including central and peripheral nerves. In these trials, aFGF has shown promise for neural regeneration, and in the future, more trials and applications should investigate aFGF as a neurotrophic factor. Focusing on aFGF, the current review aimed to summarize the historical evolution of the utilization of aFGF in SCI and nerve injuries, to present applications and trials, to summarize briefly its possible mechanisms, and to provide future perspectives.

Time is spine: a review of translational advances in spinal cord injury

Acute traumatic spinal cord injury (SCI) is a devastating event with far-reaching physical, emotional, and economic consequences for patients, families, and society at large. Timely delivery of specialized care has reduced mortality; however, long-term neurological recovery continues to be limited. In recent years, a number of exciting neuroprotective and regenerative strategies have emerged and have come under active investigation in clinical trials, and several more are coming down the translational pipeline. Among ongoing trials are RISCIS (riluzole), INSPIRE (Neuro-Spinal Scaffold), MASC (minocycline), and SPRING (VX-210). Microstructural MRI techniques have improved our ability to image the injured spinal cord at high resolution. This innovation, combined with serum and cerebrospinal fluid (CSF) analysis, holds the promise of providing a quantitative biomarker readout of spinal cord neural tissue injury, which may improve prognostication and facilitate stratification of patients for enrollment into clinical trials. Given evidence of the effectiveness of early surgical decompression and growing recognition of the concept that "time is spine," infrastructural changes at a systems level are being implemented in many regions around the world to provide a streamlined process for transfer of patients with acute SCI to a specialized unit. With the continued aging of the population, central cord syndrome is soon expected to become the most common form of acute traumatic SCI; characterization of the pathophysiology, natural history, and optimal treatment of these injuries is hence a key public health priority. Collaborative international efforts have led to the development of clinical practice guidelines for traumatic SCI based on robust evaluation of current evidence. The current article provides an in-depth review of progress in SCI, covering the above areas.

Different Fgfs have distinct roles in regulating neurogenesis after spinal cord injury in zebrafish

Background

Despite conserved developmental processes and organization of the vertebrate central nervous system, only some vertebrates including zebrafish can efficiently regenerate neural damage including after spinal cord injury. The mammalian spinal cord shows very limited regeneration and neurogenesis, resulting in permanent life-long functional impairment. Therefore, there is an urgent need to identify the cellular and molecular mechanisms that can drive efficient vertebrate neurogenesis following injury. A key pathway implicated in zebrafish neurogenesis is fibroblast growth factor signaling.

Methods

In the present study we investigated the roles of distinct fibroblast growth factor members and their receptors in facilitating different aspects of neural development and regeneration at different timepoints following spinal cord injury. After spinal cord injury in adults and during larval development, loss and/or gain of Fgf signaling was combined with immunohistochemistry, in situ hybridization and transgenes marking motor neuron populations in in vivo zebrafish and in vitro mammalian PC12 cell culture models.

Results

Fgf3 drives neurogenesis of Islet1 expressing motor neuron subtypes and mediate axonogenesis in cMet expressing motor neuron subtypes. We also demonstrate that the role of Fgf members are not necessarily simple recapitulating development. During development Fgf2, Fgf3 and Fgf8 mediate neurogenesis of Islet1 expressing neurons and neuronal sprouting of both, Islet1 and cMet expressing motor neurons. Strikingly in mammalian PC12 cells, all three Fgfs increased cell proliferation, however, only Fgf2 and to some extent Fgf8, but not Fgf3 facilitated neurite outgrowth.

Conclusions

This study demonstrates differential Fgf member roles during neural development and adult regeneration, including in driving neural proliferation and neurite outgrowth of distinct spinal cord neuron populations, suggesting that factors including Fgf type, age of the organism, timing of expression, requirements for different neuronal populations could be tailored to best drive all of the required regenerative processes.

Functional improvement in chronic human spinal cord injury: Four years after acidic fibroblast growth factor

Few treatments have proven effective for patients with chronic spinal cord injury (SCI). This study aimed to evaluate the efficacy and safety of acidic fibroblast growth factor (aFGF) in human SCI. This was an open-label prospective clinical trial of aFGF with an extended follow-up to 48 months. All patients were treated with aFGF 3 times, including once directly applied to the injured spinal cord during neurolysis surgery, and twice via lumbar punctures at 3- and 6-months post-operation. Every patient was evaluated with standardized measurements of neurological functions. The trial initially enrolled 60 patients (30 cervical and 30 thoracolumbar SCI), but only 46 (21 cervical- and 25 thoracolumbar-SCI) completed the follow-up. The ASIA impairment scales, motor, pin prick, light touch, and FIM motor subtotal scores were all improved in both groups, except that the ASIA scores of light touch only demonstrated tendency of increase in the cervical-SCI group. All patients had a decrease in dependence, and there were no major adverse events or other oncological problems throughout the follow-up. At 48 months, the study demonstrated that aFGF was safe, feasible, and could yield modest functional improvement in chronic SCI patients. Further randomized control investigations are warranted for validation of its optimal dosage.

Guiding Device for Precision Grafting of Peripheral Nerves in Complete Thoracic Spinal Cord Injury: Design and Sizing for Clinical Trial

Background

In an effort to translate preclinical success in achieving spinal cord regeneration through peripheral nerve grafts, this study details the design and sizing of a guiding device for precision grafting of peripheral nerves for use in a clinical trial in complete (AIS-A) thoracic spinal cord injury (SCI). The device’s design and sizing are compared to a simulation of human spinal cord sizes based on the best available data.

Methods

Spinal cord segmental sizes were generated by computer simulation based on data from a meta-analysis recently published by our group. Thoracic segments T2–T12 were plotted, and seven elliptical shapes were positioned across the center of the distribution of sizes. Geometrical measures of error-of-fit were calculated. CAD modeling was used to create cranial and caudal interfaces for the human spinal cord, aiming to guide descending white matter tracts to gray matter at the caudal end of the device and ascending white matter tracts to gray matter at the cranial end of the device. The interfaces were compared qualitatively to the simulated spinal cord sizes and gray-to-white matter delineations.

Results

The mean error-of-fit comparing simulated spinal cord segments T2–T12 to the best elliptical shape was 0.41 and 0.36 mm, and the 95th percentile was found at 1.3 and 0.98 mm for transverse and anteroposterior diameter, respectively. A guiding device design was reached for capturing the majority of corticospinal axons at the cranial end of the device and guiding them obliquely to gray matter at the caudal end of the device. Based on qualitative comparison, the vast majority of spinal cord sizes generated indicate an excellent fit to the device’s interfaces.

Conclusion

A set of SCI guiding devices of seven sizes can cover the variability of human thoracic spinal cord segments T2–T12 with an acceptable error-of-fit for the elliptical shape as well as guiding channels. The computational framework developed can be used with other medical technologies involving the human spinal cord where exact sizes and positioning are of importance.

NT3-chitosan enables de novo regeneration and functional recovery in monkeys after spinal cord injury

Spinal cord injury (SCI) often leads to permanent loss of motor, sensory, and autonomic functions. We have previously shown that neurotrophin3 (NT3)-loaded chitosan biodegradable material allowed for prolonged slow release of NT3 for 14 weeks under physiological conditions. Here we report that NT3-loaded chitosan, when inserted into a 1-cm gap of hemisectioned and excised adult rhesus monkey thoracic spinal cord, elicited robust axonal regeneration. Labeling of cortical motor neurons indicated motor axons in the corticospinal tract not only entered the injury site within the biomaterial but also grew across the 1-cm-long lesion area and into the distal spinal cord. Through a combination of magnetic resonance diffusion tensor imaging, functional MRI, electrophysiology, and kinematics-based quantitative walking behavioral analyses, we demonstrated that NT3-chitosan enabled robust neural regeneration accompanied by motor and sensory functional recovery. Given that monkeys and humans share similar genetics and physiology, our method is likely translatable to human SCI repair.

hucMSC derived exosomes promote functional recovery in spinal cord injury mice via attenuating inflammation

The exploration of effective spinal cord injury (SCI) healing still remain a great challenge due to the high morbidity, complex pathology and unclear targets. Human umbilical cord mesenchymal stem cells (hucMSC) play an important role in tissue regeneration. However, transplanting stem cells has a potential risk of teratogenicity. Recent studies have suggested that exosomes secreted by stem cells may contribute to tissue injury repair. We hypothesized that the application of hucMSC derived exosomes may be a potential way for SCI treatment. Our studies showed the hucMSC derived exosomes with a mean particle size of 70 nm could effectively trigger the bone marrow derived macrophage (BMDM) polarization from M1 to a M2 phenotype. In vivo studies demonstrated that the hucMSC derived exosomes could improve the functional recovery after SCI through down-regulation of the inflammatory cytokines, such as TNF-α, MIP-1α, IL-6 and IFN-γ. Collectively, our findings indicated that hucMSC derived exosomes could facilitate spinal cord injury healing via attenuating the inflammation of the injury region. Our results provided a new perspective and therapeutic strategy for the use of hucMSC derived exosomes in soft tissue repair.

Current and Future Trends in Adipose Stem Cell Differentiation into Neuroglia

BACKGROUND

Neurological diseases and disorders pose a challenge for treatment and rehabilitation due to the limited capacity of the nervous system to repair itself. Adipose stem cells (ASCs) are more pliable than any adult stem cells and are capable of differentiating into non-mesodermal tissues, including neurons. Transdifferentiating ASCs to specific neuronal lineage cells enables us to deliver the right type of cells required for a replacement therapy into the nervous system.

METHODS

Several methodologies are being explored and tested to differentiate ASCs to functional neurons and glia with cellular factors and chemical compounds. However, none of these processes and prototypes has been wholly successful in changing the cellular structure and functional status of ASCs to become identical to neuroglial cells. In addition, successful integration and functional competence of these cells for use in clinical applications remain problematic. Photobiomodulation or low-level laser irradiation has been successfully applied to not only improve ASC viability and proliferation but has also shown promise as a possible enhancer of ASC differentiation.

CONCLUSIONS

Studies have shown that photobiomodulation improves the use of stem cell transplantation for neurological applications. This review investigates current neuro-differentiation inducers and suitable methodologies, including photobiomodulation, utilizing ASCs for induction of differentiation into neuronal lineages.

Local inhibition of matrix metalloproteinases reduced M2 macrophage activity and impeded recovery in spinal cord transected rats after treatment with fibroblast growth factor-1 and nerve grafts

Alternatively activated macrophages (M2 macrophages) promote central nervous system regeneration. Our previous study demonstrated that treatment with peripheral nerve grafts and fibroblast growth factor-1 recruited more M2 macrophages and improved partial functional recovery in spinal cord transected rats. The migration of macrophages is matrix metalloproteinase (MMP) dependent. We used a general inhibitor of MMPs to influence macrophage migration, and we examined the migration of macrophage populations and changes in spinal function. Rat spinal cords were completely transected at T₈, and 5 mm of spinal cord was removed (group T). In group R, spinal cord-transected rats received treatment with fibroblast growth factor-1 and peripheral nerve grafts. In group RG, rats received the same treatment as group R with the addition of 200 μM GM6001 (an MMP inhibitor) to the fibrin mix. We found that MMP-9, but not MMP-2, was upregulated in the graft area of rats in group R. Local application of the MMP inhibitor resulted in a reduction in the ratio of arginase-1 (M2 macrophage subset)/inducible nitric oxide synthase-postive cells. When the MMP inhibitor was applied at 8 weeks postoperation, the partial functional recovery observed in group R was lost. This effect was accompanied by a decrease in brain-derived neurotrophic factor levels in the nerve graft. These results suggested that the arginase-1 positive population in spinal cord transected rats is a migratory cell population rather than the phenotypic conversion of early iNOS⁺ cells and that the migration of the arginase-1⁺ population could be regulated locally. Simultaneous application of MMP inhibitors or promotion of MMP activity for spinal cord injury needs to be considered if the coadministered treatment involves M2 recruitment.

Fibroblast growth factors in the management of spinal cord injury

Spinal cord injury (SCI) possesses a significant health and economic burden worldwide. Traumatic SCI is a devastating condition that evolves through two successive stages. Throughout each of these stages, disturbances in ionic homeostasis, local oedema, ischaemia, focal haemorrhage, free radicals stress and inflammatory response were observed. Although there are no fully restorative cures available for SCI patients, various molecular, cellular and rehabilitative therapies, such as limiting local inflammation, preventing secondary cell death and enhancing the plasticity of local circuits in the spinal cord, were described. Current preclinical studies have showed that fibroblast growth factors (FGFs) alone or combination therapies utilizing cell transplantation and biomaterial scaffolds are proven effective for treating SCI in animal models. More importantly, some studies further demonstrated a paucity of clinical transfer usage to promote functional recovery of numerous patients with SCI. In this review, we focus on the therapeutic capacity and pitfalls of the FGF family and its clinical application for treating SCI, including the signalling component of the FGF pathway and the role in the central nervous system, the pathophysiology of SCI and the targets for FGF treatment. We also discuss the challenges and potential for the clinical translation of FGF-based approaches into treatments for 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.

Combinatory repair strategy to promote axon regeneration and functional recovery after chronic spinal cord injury

Eight weeks post contusive spinal cord injury, we built a peripheral nerve graft bridge (PNG) through the cystic cavity and treated the graft/host interface with acidic fibroblast growth factor (aFGF) and chondroitinase ABC (ChABC). This combinatorial strategy remarkably enhanced integration between host astrocytes and graft Schwann cells, allowing for robust growth, especially of catecholaminergic axons, through the graft and back into the distal spinal cord. In the absence of aFGF+ChABC fewer catecholaminergic axons entered the graft, no axons exited, and Schwann cells and astrocytes failed to integrate. In sharp contrast with the acutely bridge-repaired cord, in the chronically repaired cord only low levels of serotonergic axons regenerated into the graft, with no evidence of re-entry back into the spinal cord. The failure of axons to regenerate was strongly correlated with a dramatic increase of SOCS3 expression. While regeneration was more limited overall than at acute stages, our combinatorial strategy in the chronically injured animals prevented a decline in locomotor behavior and bladder physiology outcomes associated with an invasive repair strategy. These results indicate that PNG+aFGF+ChABC treatment of the chronically contused spinal cord can provide a permissive substrate for the regeneration of certain neuronal populations that retain a growth potential over time, and lead to functional improvements.

A Thermosensitive Heparin-Poloxamer Hydrogel Bridges aFGF to Treat Spinal Cord Injury

Acidic fibroblast growth factor (aFGF) exerts a protective effect on spinal cord injury (SCI) but is limited by the lack of physicochemical stability and the ability to cross the blood spinal cord barrier (BSCB). As promising biomaterials, hydrogels contain substantial amounts of water and a three-dimensional porous structure and are commonly used to load and deliver growth factors. Heparin can not only enhance growth factor loading onto hydrogels but also can stabilize the structure and control the release behavior. Herein, a novel aFGF-loaded thermosensitive heparin-poloxamer (aFGF-HP) hydrogel was developed and applied to provide protection and regeneration after SCI. To assess the effects of the aFGF-HP hydrogel, BSCB restoration, neuron and axonal rehabilitation, glial scar inhibition, inflammatory response suppression, and motor recovery were studied both in vivo and in vitro. The aFGF-HP hydrogels exhibited sustained release of aFGF and protected the bioactivity of aFGF in vitro. Compared to groups intravenously administered either drug-free HP hydrogel or aFGF alone, the aFGF-HP hydrogel group revealed prominent and attenuated disruption of the BSCB, reduced neuronal apoptosis, reactive astrogliosis, and increased neuron and axonal rehabilitation both in vivo and in vitro. This work provides an effective approach to enhance recovery after SCI and provide a successful strategy for SCI protection.

The Function of FGFR1 Signalling in the Spinal Cord: Therapeutic Approaches Using FGFR1 Ligands after Spinal Cord Injury

Extensive research is ongoing that concentrates on finding therapies to enhance CNS regeneration after spinal cord injury (SCI) and to cure paralysis. This review sheds light on the role of the FGFR pathway in the injured spinal cord and discusses various therapies that use FGFR activating ligands to promote regeneration after SCI. We discuss studies that use peripheral nerve grafts or Schwann cell grafts in combination with FGF1 or FGF2 supplementation. Most of these studies show evidence that these therapies successfully enhance axon regeneration into the graft. Further they provide evidence for partial recovery of sensory function shown by electrophysiology and motor activity evidenced by behavioural data. We also present one study that indicates that combination with additional, synergistic factors might further drive the system towards functional regeneration. In essence, this review summarises the potential of nerve and cell grafts combined with FGF1/2 supplementation to improve outcome even after severe spinal cord injury.

Cellular transplantation-based evolving treatment options in spinal cord injury

Spinal cord injury (SCI) often represents a condition of permanent neurologic deficit. It has been possible to understand and delineate the mechanisms contributing to loss of function following primary injury. The clinicians might hope to improve the outcome in SCI injury by designing treatment strategies that could target these secondary mechanisms of response to injury. However, the approaches like molecular targeting of the neurons or surgical interventions have yielded very limited success till date. In recent times, a great thrust is put on to the cellular transplantation mode of treatment strategies to combat SCI problems so as to gain maximum functional recovery. In this review, we discuss about the various cellular transplantation strategies that could be employed in the treatment of SCI. The success of such cellular approaches involving Schwann cells, olfactory ensheathing cells, peripheral nerve, embryonic CNS tissue and activated macrophage has been supported by a number of reports and has been detailed here. Many of these cell transplantation strategies have reached the clinical trial stages. Also, the evolving field of stem cell therapy has made it possible to contemplate the role of both embryonic stem cells and induced pluripotent stem cells to stimulate the differentiation of neurons when transplanted in SCI models. Moreover, the roles of tissue engineering techniques and synthetic biomaterials have also been explained with their beneficial and deleterious effects. Many of these cell-based therapeutic approaches have been able to cause only a little change in recovery and a combinatorial approach involving more than one strategy are now being tried out to successfully treat SCI and improve functional recovery.

Peripheral Nerve Transplantation Combined with Acidic Fibroblast Growth Factor and Chondroitinase Induces Regeneration and Improves Urinary Function in Complete Spinal Cord Transected Adult Mice

The loss of lower urinary tract (LUT) control is a ubiquitous consequence of a complete spinal cord injury, attributed to a lack of regeneration of supraspinal pathways controlling the bladder. Previous work in our lab has utilized a combinatorial therapy of peripheral nerve autografts (PNG), acidic fibroblast growth factor (aFGF), and chondroitinase ABC (ChABC) to treat a complete T8 spinal cord transection in the adult rat, resulting in supraspinal control of bladder function. In the present study we extended these findings by examining the use of the combinatorial PNG+aFGF+ChABC treatment in a T8 transected mouse model, which more closely models human urinary deficits following spinal cord injury. Cystometry analysis and external urethral sphincter electromyograms reveal that treatment with PNG+aFGF+ChABC reduced bladder weight, improved bladder and external urethral sphincter histology, and significantly enhanced LUT function, resulting in more efficient voiding. Treated mice's injured spinal cord also showed a reduction in collagen scaring, and regeneration of serotonergic and tyrosine hydroxylase-positive axons across the lesion and into the distal spinal cord. Regeneration of serotonin axons correlated with LUT recovery. These results suggest that our mouse model of LUT dysfunction recapitulates the results found in the rat model and may be used to further investigate genetic contributions to regeneration failure.

Acidic FGF promotes neurite outgrowth of cortical neurons and improves neuroprotective effect in a cerebral ischemic rat model

Acidic fibroblast growth factor (aFGF) is a neurotrophic factor which is a powerful neuroprotective and neuroregenerative factor of the nervous system. Prior study had shown that levels of FGFs significantly increase following ischemic injury, reflecting a physiological protection mechanism. However, few reports demonstrated the efficacy of applying aFGF in cerebral ischemia. A recent report showed that the intranasal aFGF treatment improved neurological functional recovery; however, it did not significantly reduce the lesion size in ischemic rats. The present study examines the neuroprotective effect of aFGF on cortical neuron-glial cultures under oxygen glucose deprivation (OGD)-induced cell damage and investigates whether epidural application of slow-released aFGF could improve benefit on ischemic stroke injury in conscious rats. We used a topical application of aFGF mixed in fibrin glue, a slow-release carrier, over the peri-ischemic cortex and examined such treatment on cerebral infarction and behavioral impairments of rats subjected to focal cerebral ischemia (FCI). Results demonstrate that aFGF effectively protected cortical neuron-glial cultures from OGD-induced neuronal damage. Neurite extension from cortical neurons was significantly enhanced by aFGF, mediated through activation of AKT and ERK. In addition, topical application of fibrin glue-mixed aFGF dose-dependently reduced ischemia-induced brain infarction and improved functional restoration in ischemic stroke rats. Slow-released aFGF not only protected hippocampal and cortical cell loss but reduced microglial infiltration in FCI rats. Our results suggest that aFGF mixed in fibrin glue could prolong the protective/regenerative efficacy of aFGF to the damaged brain tissue and thus improve the functional restorative effect of aFGF.

Expression of suppressor of cytokine signaling-3 (SOCS3) and its role in neuronal death after complete spinal cord injury

The present study investigates the endogenous expression of Suppressor of Cytokine Signaling-3 (SOCS3) after spinal cord injury (SCI) and its effect on SCI-induced cell death in vivo. In addition, we determined whether a reduction of SOCS3 expression induced by microinjection of short hairpin RNA (shSOCS3) carried by lentivirus into spinal cord provides cellular protection after SCI. We demonstrated that complete transection of rat T8 spinal cord induced SOCS3 expression at the mRNA and protein levels as early as 2days post-injury, which was maintained up to 14days. SOCS3 immunoreactivity was detected in neurons and activated microglia after SCI. We also demonstrated that SCI induces phosphorylation of proteins that are involved in signal transduction and transcription-3 (STAT3) in neurons, which induced SOCS3 expression. Western blot analyses and double-immunofluorescent staining showed significant up-regulation of the pro-apoptotic protein Bax, increases in the ratio of Bax to the anti-apoptotic protein Bcl-2, and up-regulation of cleaved caspase-3 in neurons. Treatment with shSOCS3 inhibited SCI-induced mRNA expression of SOCS3 2days post-injury and suppressed SCI-induced Bax expression 7days after SCI, both rostral and caudal to the lesion. Moreover, treatment with shSOCS3 inhibited SCI-induced neuronal death and protected neuronal morphology both rostral and caudal to the injury site 7days post-injury. Our results suggest that the STAT3/SOCS3 signaling pathway plays an important role in regulating neuronal death after SCI.

Bridging defects in chronic spinal cord injury using peripheral nerve grafts combined with a chitosan-laminin scaffold and enhancing regeneration through them by co-transplantation with bone-marrow-derived mesenchymal stem cells: case series of 14 patients

OBJECTIVE

To investigate the effect of bridging defects in chronic spinal cord injury using peripheral nerve grafts combined with a chitosan-laminin scaffold and enhancing regeneration through them by co-transplantation with bone-marrow-derived mesenchymal stem cells.

METHODS

In 14 patients with chronic paraplegia caused by spinal cord injury, cord defects were grafted and stem cells injected into the whole construct and contained using a chitosan-laminin paste. Patients were evaluated using the International Standards for Classification of Spinal Cord Injuries.

RESULTS

Chitosan disintegration leading to post-operative seroma formation was a complication. Motor level improved four levels in 2 cases and two levels in 12 cases. Sensory-level improved six levels in two cases, five levels in five cases, four levels in three cases, and three levels in four cases. A four-level neurological improvement was recorded in 2 cases and a two-level neurological improvement occurred in 12 cases. The American Spinal Impairment Association (ASIA) impairment scale improved from A to C in 12 cases and from A to B in 2 cases. Although motor power improvement was recorded in the abdominal muscles (2 grades), hip flexors (3 grades), hip adductors (3 grades), knee extensors (2-3 grades), ankle dorsiflexors (1-2 grades), long toe extensors (1-2 grades), and plantar flexors (0-2 grades), this improvement was too low to enable them to stand erect and hold their knees extended while walking unaided.

CONCLUSION

Mesenchymal stem cell-derived neural stem cell-like cell transplantation enhances recovery in chronic spinal cord injuries with defects bridged by sural nerve grafts combined with a chitosan-laminin scaffold.

Nerve regeneration restores supraspinal control of bladder function after complete spinal cord injury

A life-threatening disability after complete spinal cord injury is urinary dysfunction, which is attributable to lack of regeneration of supraspinal pathways that control the bladder. Although numerous strategies have been proposed that can promote the regrowth of severed axons in the adult CNS, at present, the approaches by which this can be accomplished after complete cord transection are quite limited. In the present study, we modified a classic peripheral nerve grafting technique with the use of chondroitinase to facilitate the regeneration of axons across and beyond an extensive thoracic spinal cord transection lesion in adult rats. The novel combination treatment allows for remarkably lengthy regeneration of certain subtypes of brainstem and propriospinal axons across the injury site and is followed by markedly improved urinary function. Our studies provide evidence that an enhanced nerve grafting strategy represents a potential regenerative treatment after severe spinal cord injury.

Axon regeneration and exercise-dependent plasticity after spinal cord injury

Current dogma states that meaningful recovery of function after spinal cord injury (SCI) will likely require a combination of therapeutic interventions comprised of regenerative/neuroprotective transplants, addition of neurotrophic factors, elimination of inhibitory molecules, functional sensorimotor training, and/or stimulation of paralyzed muscles or spinal circuits. We routinely use (1) peripheral nerve grafts to support and direct axonal regeneration across an incomplete cervical or complete thoracic transection injury, (2) matrix modulation with chondroitinase (ChABC) to facilitate axonal extension beyond the distal graft-spinal cord interface, and (3) exercise, such as forced wheel walking, bicycling, or step training on a treadmill. We and others have demonstrated an increase in spinal cord levels of endogenous neurotrophic factors with exercise, which may be useful in facilitating elongation and/or synaptic activity of regenerating axons and plasticity of spinal neurons below the level of injury.

Acute injury in the peripheral nervous system triggers an alternative macrophage response

BACKGROUND

The activation of the immune system in neurodegeneration has detrimental as well as beneficial effects. Which aspects of this immune response aggravate the neurodegenerative breakdown and which stimulate regeneration remains an open question. To unravel the neuroprotective aspects of the immune system we focused on a model of acute peripheral nerve injury, in which the immune system was shown to be protective.

METHODS

To determine the type of immune response triggered after axotomy of the sciatic nerve, a model for Wallerian degeneration in the peripheral nervous system, we evaluated markers representing the two extremes of a type I and type II immune response (classical vs. alternative) using real-time quantitative polymerase chain reaction (RT-qPCR), western blot, and immunohistochemistry.

RESULTS

Our results showed that acute peripheral nerve injury triggers an anti-inflammatory and immunosuppressive response, rather than a pro-inflammatory response. This was reflected by the complete absence of classical macrophage markers (iNOS, IFN γ, and IL12p40), and the strong up-regulation of tissue repair markers (arginase-1, Ym1, and Trem2). The signal favoring the alternative macrophage environment was induced immediately after nerve damage and appeared to be established within the nerve, well before the infiltration of macrophages. In addition, negative regulators of the innate immune response, as well as the anti-inflammatory cytokine IL-10 were induced. The strict regulation of the immune system dampens the potential tissue damaging effects of an over-activated response.

CONCLUSIONS

We here demonstrate that acute peripheral nerve injury triggers an inherent protective environment by inducing the M2 phenotype of macrophages and the expression of arginase-1. We believe that the M2 phenotype, associated with a sterile inflammatory response and tissue repair, might explain their neuroprotective capacity. As such, shifting the neurodegeneration-induced immune responses towards an M2/Th2 response could be an important therapeutic strategy.

Regulation of chondroitin sulphate proteoglycan and reactive gliosis after spinal cord transection: effects of peripheral nerve graft and fibroblast growth factor 1

AIMS

The combined treatment of peripheral nerve (PN) graft and fibroblast growth factor (FGF)-1 for spinal cord injury produces functional recovery, but how it affects injury events is still unknown. This project studied the effect of PN graft and FGF-1 on white matter degeneration following spinal cord injury.

METHODS

Rats were divided into four groups: (i) complete spinal cord transection and T8 segment removed; the remaining three groups underwent transection followed by (ii) PN grafting; (iii) supply of exogenous FGF-1; and (iv) PN grafting plus FGF-1 treatment. Chondroitin sulphate proteoglycan (CSPG) deposition, astrocytes and macrophage activation, cavity size, and calcitonin gene-related peptide and synaptophysin immunoreactivity were compared.

RESULTS

Peripheral nerve grafting increased CSPG levels compared to transection surgery alone. This CSPG was associated with the proximity to the PN graft. FGF-1 reduced CSPG deposition in grafted animals regardless of the proximity to the graft. The CSPG reduction was accompanied by reduced GFAP expression and macrophage activation. The amount of CSPG with dissociated glycosaminoglycan did not differ between groups. FGF-1 in Schwann cell-astrocyte coculture did not reduce CSPG deposition. Furthermore, the PN graft increased the calcitonin gene-related peptide immunoreactivity and altered the distribution of synaptophysin-positive axons.

CONCLUSION

Peripheral nerve graft supported sensory re-innervation and partial protection of the grey matter, but up-regulated CSPG in the graft-stump junction compared to non-grafted rats. The reduction of CSPG was caused by FGF-1-PN synergy, and did not involve dissociation of CSPG or the suppression of a general immune response.

Adeno-associated virus-mediated human acidic fibroblast growth factor expression promotes functional recovery of spinal cord-contused rats

BACKGROUND

Following spinal cord injury, the delivery of neurotrophic factors to the injured spinal cord has been shown to promote axonal regeneration and functional recovery. In previous studies, we showed that acidic fibroblast growth factor (aFGF) is a potent neurotrophic factor that promotes the regeneration of axotomized spinal cord or dorsal root ganglion neurones.

METHODS

We constructed a recombinant adeno-associated virus (AAV) vector to express human aFGF and evaluated aFGF expression and function in AAV-aFGF-infected PC12 cells. We analyzed AAV-green fluorescent protein (GFP) tropism and AAV-mediated aFGF expression in contused spinal cords. Animals received behavioural testing to evaluate the functional recovery.

RESULTS

Overexpression of aFGF was shown in AAV-aFGF-infected PC12 cells in a dose-dependent manner. Concurrently, neurite extension and cell number were significantly increased in AAV-aFGF infected cells. AAV-mediated GFP expression persisted for at least 5 weeks in contused spinal cords, and the most prominently transduced cells were neurones. Contusive injury reduced endogenous aFGF expression in spinal cords. Overexpression of aFGF was demonstrated in AAV-aFGF transduced spinal cords compared to AAV-GFP transduced spinal cords at 3 and 14 days post-injury. Evaluation of motor function revealed that the improvement of AAV-aFGF-treated rats was prominent. Both AAV-aFGF- and recombinant human aFGF-treated rats revealed significantly better recovery at 5 weeks post-injury, compared to vehicle- and AAV-GFP-treated rats.

CONCLUSIONS

These data suggest that supplement of aFGF improve the functional recovery of spinal cord-contused rats and that AAV-aFGF-mediated gene transfer could be a clinically feasible therapeutic approach for patients after nervous system injuries.

Acid fibroblast growth factor and peripheral nerve grafts regulate Th2 cytokine expression, macrophage activation, polyamine synthesis, and neurotrophin expression in transected rat spinal cords

Spinal cord injury elicits an inflammatory response that recruits macrophages to the injured spinal cord. Quantitative real-time PCR results have shown that a repair strategy combining peripheral nerve grafts with acidic fibroblast growth factor (aFGF) induced higher interleukin-4 (IL-4), IL-10, and IL-13 levels in the graft areas of rat spinal cords compared with transected spinal cords at 10 and 14 d. This led to higher arginase I-positive alternatively activated macrophage (M2 macrophage) responses. The gene expression of several enzymes involved in polyamine biosynthesis pathways was also upregulated in the graft areas of repaired spinal cords. The treatment induced a twofold upregulation of polyamine levels at 14 d, as confirmed by HPLC. Polyamines are important for the repair process, as demonstrated by the observation that treatment with inhibitors of arginase I and ornithine decarboxylase attenuates the functional recoveries of repaired rats. After 14 d, the treatment also induced the expression of neurotrophin nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF), as well as M2 macrophages within grafted nerves expressing BDNF. IL-4 was upregulated in the injury sites of transected rats that received aFGF alone compared with those that received nerve grafts alone at 10 d. Conversely, nerve graft treatment induced NGF and BDNF expression at 14 d. Macrophages expressing polyamines and BDNF may benefit axonal regeneration at 14 d. These results indicate that aFGF and nerve grafts regulate different macrophage responses, and M2 macrophages may play an important role in axonal regeneration after spinal cord injury in rats.

Acidic fibroblast growth factor for repair of human spinal cord injury: a clinical trial

OBJECT

The study aimed to verify the safety and feasibility of applying acidic fibroblast growth factor (aFGF) with fibrin glue in combination with surgical neurolysis for nonacute spinal cord injury.

METHODS

This open-label, prospective, uncontrolled human clinical trial recruited 60 patients with spinal cord injuries (30 cervical and 30 thoracolumbar). The mean patient age was 36.5 ± 15.33 (mean ± SD) years, and the male/female ratio was 3:1. The mean time from injury to treatment was 25.7 ± 26.58 months, and the cause of injury included motor vehicle accident (26 patients [43.3%]), fall from a height (17 patients [28.3%]), sports (4 patients [6.7%]), and other (13 patients [21.7%]). Application of aFGF with fibrin glue and duraplasty was performed via laminectomy, and an adjuvant booster of combined aFGF and fibrin glue (2 ml) was given at 3 and 6 months postsurgery via lumbar puncture. Outcome measurements included the American Spinal Injury Association (ASIA) motor scores, sensory scores, impairment scales, and neurological levels. Examination of functional independence measures, visual analog scale, MR imaging, electrophysiological and urodynamic studies, hematology and biochemistry tests, tumor markers, and serum inflammatory cytokines were all conducted. All adverse events were monitored and reported. Exclusions were based on refusal, unrelated adverse events, or failure to participate in the planned rehabilitation.

RESULTS

Forty-nine patients (26 with cervical and 23 with thoracolumbar injuries) completed the 24-month trial. Compared with preoperative conditions, the 24-month postoperative ASIA motor scores improved significantly in the cervical group (from 27.6 ± 15.55 to 37.0 ± 19.93, p < 0.001) and thoracolumbar group (from 56.8 ± 9.21 to 60.7 ± 10.10, p < 0.001). The ASIA sensory scores also demonstrated significant improvement in light touch and pinprick in both groups: from 55.8 ± 24.89 to 59.8 ± 26.47 (p = 0.049) and 56.3 ± 23.36 to 62.3 ± 24.87 (p = 0.003), respectively, in the cervical group and from 75.7 ± 15.65 to 79.2 ± 15.81 (p < 0.001) and 78.2 ± 14.72 to 82.7 ± 16.60 (p < 0.001), respectively, in the thoracolumbar group. At 24-month follow-up, the ASIA impairment scale improved significantly in both groups (30% cervical [p = 0.011] and 30% thoracolumbar [p = 0.003]). There was also significant improvement in neurological level in the cervical (from 5.17 ± 1.60 to 6.27 ± 3.27, p = 0.022) and thoracolumbar (from 18.03 ± 4.19 to 18.67 ± 3.96, p = 0.001) groups. The average sum of motor items in functional independence measure also had significant improvement in both groups (p < 0.05). The walking/wheelchair locomotion subscale showed increased percentages of patients who were ambulatory (from 3.4% to 13.8% and from 17.9% to 35.7% in the cervical and thoracolumbar groups, respectively). There were no related adverse events.

CONCLUSIONS

The use of aFGF for spinal cord injury was safe and feasible in the present trial. There were significant improvements in ASIA motor and sensory scale scores, ASIA impairment scales, neurological levels, and functional independence measure at 24 months after treatment. Further large-scale, randomized, and controlled investigations are warranted to evaluate the efficacy and long-term results.

Peripheral nerve grafts support regeneration after spinal cord injury

Traumatic insults to the spinal cord induce both immediate mechanical damage and subsequent tissue degeneration leading to a substantial physiological, biochemical, and functional reorganization of the spinal cord. Various spinal cord injury (SCI) models have shown the adaptive potential of the spinal cord and its limitations in the case of total or partial absence of supraspinal influence. Meaningful recovery of function after SCI will most likely result from a combination of therapeutic strategies, including neural tissue transplants, exogenous neurotrophic factors, elimination of inhibitory molecules, functional sensorimotor training, and/or electrical stimulation of paralyzed muscles or spinal circuits. Peripheral nerve grafts provide a growth-permissive substratum and local neurotrophic factors to enhance the regenerative effort of axotomized neurons when grafted into the site of injury. Regenerating axons can be directed via the peripheral nerve graft toward an appropriate target, but they fail to extend beyond the distal graft-host interface because of the deposition of growth inhibitors at the site of SCI. One method to facilitate the emergence of axons from a graft into the spinal cord is to digest the chondroitin sulfate proteoglycans that are associated with a glial scar. Importantly, regenerating axons that do exit the graft are capable of forming functional synaptic contacts. These results have been demonstrated in acute injury models in rats and cats and after a chronic injury in rats and have important implications for our continuing efforts to promote structural and functional repair after SCI.

Improvement of gait patterns in step-trained, complete spinal cord-transected rats treated with a peripheral nerve graft and acidic fibroblast growth factor

The effects of peripheral nerve grafts (PNG) and acidic fibroblast growth factor (alpha FGF) combined with step training on the locomotor performance of complete spinal cord-transected (ST, T8) adult rats were studied. Rats were assigned randomly to five groups (N=10 per group): sham control (laminectomy only), ST only, ST-step-trained, repaired (ST with PNG and alpha FGF treatment), or repaired-step-trained. Step-trained rats were stepped bipedally on a treadmill 20 min/day, 5 days/week for 6 months. Bipolar intramuscular EMG electrodes were implanted in the soleus and tibialis anterior (TA) muscles of ST-step-trained (n=3) and repaired-step-trained (n=2) rats. Gait analysis was conducted at 3 and 6 months after surgery. Stepping analysis was completed on the best continuous 10-s period of stepping performed in a 2-min trial. Significantly better stepping (number of steps, stance duration, swing duration, maximum step length, and maximum step height) was observed in the repaired and repaired-step-trained than in the ST and ST-step-trained rats. Mean EMG amplitudes in both the soleus and TA were significantly higher and the patterns of activation of flexors and extensors more reciprocal in the repaired-step-trained than ST-step-trained rats. 5-HT fibers were present in the lumbar area of repaired but not ST rats. Thus, PNG plus alpha FGF treatment resulted in a clear improvement in locomotor performance with or without step training. Furthermore, the number of 5-HT fibers observed below the lesion was related directly to stepping performance. These observations indicate that the improved stepping performance in Repaired rats may be due to newly formed supraspinal control via regeneration.

Biomaterials for neural-tissue engineering — Chitosan supports the survival, migration, and differentiation of adult-derived neural stem and progenitor cells

Neural precursor cells (NPCs or stem and progenitor cells) are promising in transplantation strategies to treat an injury to the central nervous system, such as a spinal cord injury (SCI), because of their ability to differentiate into neurons and glia. Transplantation studies to date have met with limited success for a number of reasons, including poor cell survival. One way to encourage cell survival in injured tissue is to provide the cells with a scaffold to enhance their survival, their integration, and potentially their differentiation into appropriate cell types. Towards this end, four amine-functionalized hydrogels were screened in vitro for adult murine NPC viability, migration, and differentiation: chitosan, poly(oligoethylene oxide dimethacrylate-co-2-amino ethyl methacrylate), blends of poly(oligoethylene oxide dimethacrylate-co-2-amino ethyl methacrylate), and poly(vinyl alcohol), and poly(glycerol dimethacrylate-co-2-amino ethyl methacrylate). The greatest cell viability was found on chitosan at all times examined, Chitosan had the greatest surface amine content and the lowest equilibrium water content, which likely contributed to the greater NPC viability observed over three weeks in culture. Only chitosan supported survival of multipotent stem cells and the differentiation of the progenitors into neurons, astrocytes, and oligodendrocytes. Plating intact NPC colonies revealed greater cell migration on chitosan relative to the other hydrogels. Importantly, long term cultures on chitosan showed no significant difference in total cell counts over time, suggesting no net cell growth. Together, these findings reveal chitosan as a promising material for the delivery of adult NPC cell-based therapies.

A neural repair treatment with gait training improves motor function recovery after spinal cord injury

Aimed to develop an effective approach for treating spinal cord injury (SCI), we investigated the effectiveness of a treatment strategy that combined peripheral nerve grafting, nerve growth factors and functional task based physical therapy on non-human primate models. SCI was by unilateral surgical hemi-section at the T8 spine level (approximately 4 mm gap). Two of the 4 subjects as treatment received the transplants of sural nerve segments as well as infused acidic fibroblast growth factor (aFGF) to the injured spinal cord. All four subjects received physical therapy and bipedal walking training on a treadmill to promote motor function recovery. A comprehensive evaluation system including general observation in the home cage, behavioral test and clinic score system was used to assess the effect of the treatment. The recovery of functional mobility in treated group is much faster than the control group. The treated group started to move around in their cages within a week and continued to improve in walking performance as measured by gait symmetry, while the control group developed spasticity and rigidity with a much slower and less functional recovery of mobility. All these results suggest that the treatment strategy of peripheral nerve grafting with aFGF combined with physical therapy is effective to treat SCI.

Transplantation-mediated strategies to promote axonal regeneration following spinal cord injury

Devastating central nervous system injuries and diseases continue to occur in spite of the tremendous efforts of various prevention programs. The enormity and annual escalation of healthcare costs due to them require that therapeutic strategies be responsibly developed. The dysfunctions that occur after injury and disease are primarily due to neurotransmission damage. The last two decades of both experimental and clinical research have demonstrated that neural and non-neural tissue and cell transplantation is a viable option for ameliorating dysfunctions to markedly improve quality of life. Moreover, significant progress has been made with tissue and cell transplantation in studies of pathophysiology, plasticity, sprouting, regeneration, and functional recovery. This article will review information about the ability and potential, particularly for traumatic spinal cord injury, that neural and non-neural tissue and cell transplantation has to replace lost neurons and glia, to reconstruct damaged neural circuitry, and to restore neurotransmitters, hormones, neurotrophic factors, and neurotransmission. Donor tissues and cells to be discussed include peripheral nerve, fetal spinal cord and brain, central and peripheral nervous systems' glia, stem cells, those that have been genetically engineered, and non-neural ones. Combinatorial approaches and clinical research are also reviewed.

Outcomes of common peroneal nerve lesions after surgical repair with acidic fibroblast growth factor

BACKGROUND

There have been no clinical trials concerning the effect of acidic fibroblast growth factor (aFGF) on human peripheral nerve lesions. Our interest was focused on the question of whether a repair strategy incorporating growth factors could be applied to repair of common peroneal nerve lesions.

METHODS

This study involved three groups of patients with common peroneal nerve lesions: group 1 (n = 21) received surgical repair with fibrin glue added with aFGF; group 2 (n = 8) received surgical repair only; group 3 (n = 16) did not receive any surgical intervention. All patients received electrophysiologic examinations and physical examination at baseline, 6 months, and 12 months postsurgically.

RESULTS

Group 1 demonstrated significantly increased average muscle strength score by 0.4299 and 0.5045 at 6 and 12 months after the operation (p = 0.0197 and 0.0297, respectively). In groups 2 and 3 patients, however, significant increase of average muscle strength scores was not achieved either at 6 or 12 months postoperatively. During the first follow-up evaluation the average muscle strength score in group 1 (3.06 +/- 1.60) was significantly higher than those in group 2 (1.04 +/- 0.86) and group 3 (1.65 +/- 1.43) (p = 0.005). However, significant difference was not achieved during the second follow-up evaluation.

CONCLUSION

This study demonstrated the potential of this innovative repair strategy with aFGF treatment to facilitate nerve regeneration and motor function recovery following peripheral nerve lesions.

Current status of acute spinal cord injury pathophysiology and emerging therapies: promise on the horizon

This review summarizes the current understanding of spinal cord injury pathophysiology and discusses important emerging regenerative approaches that have been translated into clinical trials or have a strong potential to do so. The pathophysiology of spinal cord injury involves a primary mechanical injury that directly disrupts axons, blood vessels, and cell membranes. This primary mechanical injury is followed by a secondary injury phase involving vascular dysfunction, edema, ischemia, excitotoxicity, electrolyte shifts, free radical production, inflammation, and delayed apoptotic cell death. Following injury, the mammalian central nervous system fails to adequately regenerate due to intrinsic inhibitory factors expressed on central myelin and the extracellular matrix of the posttraumatic gliotic scar. Regenerative approaches to block inhibitory signals including Nogo and the Rho-Rho-associated kinase pathways have shown promise and are in early stages of clinical evaluation. Cell-based strategies including using neural stem cells to remyelinate spared axons are an attractive emerging approach.

Involvement of acidic fibroblast growth factor in spinal cord injury repair processes revealed by a proteomics approach

Acidic fibroblast growth factor (aFGF; also known as FGF-1) is a potent neurotrophic factor that affects neuronal survival in the injured spinal cord. However, the pathological changes that occur with spinal cord injury (SCI) and the attribution to aFGF of a neuroprotective effect during SCI are still elusive. In this study, we demonstrated that rat SCI, when treated with aFGF, showed significant functional recovery as indicated by the Basso, Beattie, and Bresnahan locomotor rating scale and the combined behavior score (p < 0.01-0.001). Furthermore proteomics and bioinformatics approaches were adapted to investigate changes in the global protein profile of the damaged spinal cord tissue when experimental rats were treated either with or without aFGF at 24 h after injury. We found that 51 protein spots, resolvable by two-dimensional PAGE, had significant differential expression. Using hierarchical clustering analysis, these proteins were categorized into five major expression patterns. Noticeably proteins involved in the process of secondary injury, such as astrocyte activation (glial fibrillary acidic protein), inflammation (S100B), and scar formation (keratan sulfate proteoglycan lumican), which lead to the blocking of injured spinal cord regeneration, were down-regulated in the contusive spinal cord after treatment with aFGF. We propose that aFGF might initiate a series of biological processes to prevent or attenuate secondary injury and that this, in turn, leads to an improvement in functional recovery. Moreover the quantitative expression level of these proteins was verified by quantitative real time PCR. Furthermore we identified various potential neuroprotective protein factors that are induced by aFGF and may be involved in the spinal cord repair processes of SCI rats. Thus, our results could have a remarkable impact on clinical developments in the area of spinal cord injury therapy.

Clinical studies in spinal cord injury: moving towards successful trials

Spinal cord injury is a devastating condition for which there is still no cure. Many new therapies have emerged in the past few decades that have attempted to improve the outcome after injury, with varying levels of supporting experimental and clinical data. Most studies have been preliminary and have lacked control groups, but positive results can often be embraced by clinicians and patients who are faced without an alternative, despite the poor design and bias of many studies. This article is a review of clinical studies in spinal cord injury and discusses guidelines for future clinical trial design.

Are rodents an appropriate pre-clinical model for treating spinal cord injury? Examples from the respiratory system

Because most studies of the effects of spinal cord injury (SCI) and resulting repair and treatments use rodent models, it is important to determine if these models are relevant to humans. In this review, we focus on alterations in respiratory function as a result of SCI. Several injury paradigms have been used in the rat to examine restoration of post-lesion respiratory function and potential benefits from repair strategies designed for humans. Unlike the corticospinal locomotor system, respiratory neural organization is well preserved between rodents and humans, and resembles the general organization of motor pathways in primates. These similarities justify the use of the rodent respiratory system as a model to analyze SCI and putative repair strategies.

Nerve repair using acidic fibroblast growth factor in human cervical spinal cord injury: a preliminary Phase I clinical study

Object

The aim of this study was to assess functional outcomes of nerve repair using acidic fibroblast growth factor (FGF) in patients with cervical spinal cord injury (SCI).

Methods

Nine patients who had cervical SCI for longer than 5 months were included in pre- and postoperative assessments of their neurological function. The assessments included evaluating activities of daily living, associated functional ability, and degree of spasticity, motor power, sensation, and pain perception. After the first set of assessments, the authors repaired the injured segment of the spinal cord using a total laminectomy followed by the application of fibrin glue containing acidic FGF. Clinical evaluations were conducted 1, 2, 3, 4, 5, and 6 months after the surgery. Preoperative versus postoperative differences in injury severity and grading of key muscle power and sensory points were calculated using the Wilcoxon signed-rank test.

Results

The preoperative degree of injury severity, as measured using the American Spinal Injury Association (ASIA) scoring system, showed that preoperative motor (52.4 ± 25.9 vs 68.6 ± 21.5), pinprick (61.0 ± 34.9 vs 71.6 ± 31.0), and light touch scores (57.3 ± 33.9 vs 71.9 ± 30.2) were significantly lower than the respective postoperative scores measured 6 months after surgery (p = 0.005, 0.012, and 0.008, respectively).

Conclusions

Based on the significant difference in ASIA motor and sensory scale scores between the preoperative status and the 6-month postoperative follow-up, this novel nerve repair strategy of using acidic FGF may have a role in the repair of human cervical SCI. Modest nerve regeneration occurred in all 9 patients after this procedure without any observed adverse effects. This repair strategy thus deserves further investigation, clinical consideration, and refinement.