Fund Black scientists.

Our nationwide network of BME women faculty collectively argue that racial funding disparity by the National Institutes of Health (NIH) remains the most insidious barrier to success of Black faculty in our profession. We thus refocus attention on this critical barrier and suggest solutions on how it can be dismantled.

Derivation of Specific Neural Populations From Pluripotent Cells for Understanding and Treatment of Spinal Cord Injury.

Due to the nature of the biological response to traumatic spinal cord injury, there are very limited therapeutic options available to patients. Recent advances in cell transplantation have demonstrated the therapeutic potential of transplanting supportive cell types following spinal cord injury. In particular, pluripotent stem cell derived neural cells are of interest for future investigation. Use of pluripotent stem cells as the source allows many cell types to be produced from a population that can be expanded in vitro. In this review, we will discuss the signaling pathways that have been used to differentiate spinal neural phenotypes from pluripotent stem cells. Additionally, we will highlight methods that have been developed to direct the differentiation of pluripotent stem cells to specific neural fates. Further refinement and elaboration of these techniques might aid in elucidating the multitude of neuronal subtypes endogenous to the spinal cord, as well as produce further therapeutic options for spinal cord injury recovery. Developmental Dynamics 248:78-87, 2019. © 2018 Wiley Periodicals, Inc.

Stem cells for spinal cord injury: Strategies to inform differentiation and transplantation.

The complex pathology of spinal cord injury (SCI), involving a cascade of secondary events and the formation of inhibitory barriers, hampers regeneration across the lesion site and often results in irreversible loss of motor function. The limited regenerative capacity of endogenous cells after SCI has led to a focus on the development of cell therapies that can confer both neuroprotective and neuroregenerative benefits. Stem cells have emerged as a candidate cell source because of their ability to self-renew and differentiate into a multitude of specialized cell types. While ethical and safety concerns impeded the use of stem cells in the past, advances in isolation and differentiation methods have largely mitigated these issues. A confluence of work in stem cell biology, genetics, and developmental neurobiology has informed the directed differentiation of specific spinal cell types. After transplantation, these stem cell-derived populations can replace lost cells, provide trophic support, remyelinate surviving axons, and form relay circuits that contribute to functional recovery. Further refinement of stem cell differentiation and transplantation methods, including combinatorial strategies that involve biomaterial scaffolds and drug delivery, is critical as stem cell-based treatments enter clinical trials. Biotechnol. Bioeng. 2017;114: 245-259. © 2016 Wiley Periodicals, Inc.

Transgenic SCs expressing GDNF-IRES-DsRed impair nerve regeneration within acellular nerve allografts.

Providing temporally regulated glial cell line-derived neurotrophic factor (GDNF) to injured nerve can promote robust axon regeneration. However, it is poorly understood why providing highly elevated levels of GDNF to nerve can lead to axon entrapment in the zone containing elevated GDNF. This limited understanding represents an obstacle to the translation of GDNF therapies to treat nerve injuries clinically. Here, we investigated how transgenic Schwann cells (SCs) overexpressing GDNF-IRES-DsRed impact nerve regeneration. Cultured primary SCs were transduced with lentiviruses (GDNF-overexpressing transgenic SCs), one of which provides the capability to express high levels of GDNF and regulate temporal GDNF expression. These SC groups were transplanted into acellular nerve allografts (ANAs) bridging a 14 mm rat sciatic nerve defect. GDNF-overexpressing transgenic SCs expressing GDNF for as little as 1 week decreased axon regeneration across ANAs and caused extensive extracellular matrix (ECM) remodeling. To determine whether additional gene expression changes beyond GDNF transgene expression occurred in GDNF-overexpressing transgenic SCs, microarray analysis of GDNF-overexpressing transgenic SCs compared to untreated SCs was performed. Microarray analysis revealed a set of common genes regulated in transgenic SC groups expressing high levels of GDNF compared to untreated SCs. A co-culture model of GDNF-overexpressing transgenic SCs with fibroblasts (FBs) revealed differential FB ECM-related gene expression compared to untreated SCs. These data suggest a component of axon entrapment is independent of GDNF's impact on axons. Biotechnol. Bioeng. 2017;114: 2121-2130. © 2017 Wiley Periodicals, Inc.

Viral transduction of primary Schwann cells using a Cre-lox system to regulate GDNF expression.

Glial cell-line-derived neurotrophic factor (GDNF) is a potent neurotrophic factor known to enhance motor nerve regeneration following its delivery. However, recent studies have determined that extended GDNF delivery to regenerating axons can entrap motor axons at the site of GDNF delivery. This entrapment leads to reduced motor axons available to reinnervate muscle. To address this issue, we designed a cell-based GDNF expression system that can temporally regulate protein expression using an inducible gene excision mechanism to prevent entrapment at the site of expression. To design this system for regulation of GDNF expression, we transduced two lentiviral vectors, one containing a constitutively active GDNF transgene flanked by two loxP sites, and the other containing a tetracycline-inducible cre transgene along with its constitutively active transactivator, into Schwann cells (SCs). These SCs over-express GDNF, but expression can be suppressed through the administration of tetracycline family antibiotics, such as doxycycline. The engineered SCs produced significantly more GDNF as compared to untransduced controls, as measured by enzyme-linked immunosorbent assay (ELISA). Following doxycycline treatment, these SCs produced significantly lower levels of GDNF and induced less neurite extension as compared to untreated SCs. Engineered SCs treated with doxycycline showed a marked increase in Cre recombinase expression, as visualized by immunohistochemistry (IHC), providing evidence of a mechanism for the observed changes in GDNF expression levels and biological activity. This cell-based GDNF expression system could have potential for future in vivo studies to provide a temporally controlled GDNF source to promote axon growth.

A new method for generating high purity motoneurons from mouse embryonic stem cells.

A common problem with using embryonic stem (ES) cells as a source for analysis of gene expression, drug toxicity, or functional characterization studies is the heterogeneity that results from many differentiation protocols. The ability to generate large numbers of high purity differentiated cells from pluripotent stem cells could greatly enhance their utility for in vitro characterization studies and transplantation in pre-clinical injury models. Population heterogeneity is particularly troublesome for post-mitotic neurons, including motoneurons, because they do not proliferate and are quickly diluted in culture by proliferative phenotypes, such as glia. Studies of motoneuron biology and disease, in particular amyotrophic lateral sclerosis, can benefit from high purity motoneuron cultures. In this study, we engineered a transgenic-ES cell line where highly conserved enhancer elements for the motoneuron transcription factor Hb9 were used to drive puromycin N-acetyltransferase expression in ES cell-derived motoneurons. Antibiotic selection with puromycin was then used to obtain high purity motoneuron cultures following differentiation of mouse ES cells. Purity was maintained during maturation allowing the production of consistent, uniform populations of cholinergic ES cell-derived motoneurons. Appropriate functional properties of purified motoneurons were verified by acetylcholinesterase activity and electrophysiology. Antibiotic selection, therefore, can provide an inexpensive alternative to current methods for isolating ES cell-derived motoneurons at high purity that does not require specialized laboratory equipment and provides a unique platform for studies in motoneuron development and degeneration.

Schwann cells seeded in acellular nerve grafts improve functional recovery.

INTRODUCTION: This study evaluated whether Schwann cells (SCs) from different nerve sources transplanted into cold-preserved acellular nerve grafts (CP-ANGs) would improve functional regeneration compared with nerve isografts. METHODS: SCs isolated and expanded from motor and sensory branches of rat femoral and sciatic nerves were seeded into 14mm CP-ANGs. Growth factor expression, axonal regeneration, and functional recovery were evaluated in a 14-mm rat sciatic injury model and compared with isografts. RESULTS: At 14 days, motor or sensory-derived SCs increased expression of growth factors in CP-ANGs versus isografts. After 42 days, histomorphometric analysis found CP-ANGs with SCs and isografts had similar numbers of regenerating nerve fibers. At 84 days, muscle force generation was similar for CP-ANGs with SCs and isografts. SC source did not affect nerve fiber counts or muscle force generation. CONCLUSIONS: SCs transplanted into CP-ANGs increase functional regeneration to isograft levels; however SC nerve source did not have an effect.

Metabolic regulation of intrasynovial flexor tendon repair: The effects of dichloroacetate administration on early tendon healing in a canine model.

Enriched in glycolytic enzymes, paucicellular and hypovascular intrasynovial flexor tendons fail to mount an effective healing response after injury and repair. In contrast, well-vascularized extrasynovial flexor tendons possess high levels of oxidative phosphorylation (OXPHOS) enzymes and have a markedly improved healing capacity. This study was designed to compare the metabolic profiles of the two types of tendons and to evaluate the impact of metabolic reprogramming on early intrasynovial tendon healing in a clinically relevant canine model. Results showed that healthy intrasynovial tendons expressed higher levels of PDK1 and GAPDH and lower levels of SCX and IGF1 than did extrasynovial tendons. PDK1 encodes a subtype of pyruvate dehydrogenase kinase (PDK) that inhibits OXPHOS. Consistently, ATP production via glycolysis was favored in intrasynovial tendon cells whereas OXPHOS was the preferred pathway in extrasynovial tendon cells. Inhibition of glycolysis in vitro increased SCX expression in intrasynovial tendon cells. Therefore, dichloroacetate (DCA), a PDK1 inhibitor, was used in vivo to shift intrasynovial tendon ATP production from glycolysis to OXPHOS. Oral DCA administration reduced serum lactate concentration and increased acetyl-CoA content in repaired intrasynovial tendons and led to reduced TLR4 and IL1B and increased IGF1, SCX, and TGFB3 expressions in treated intrasynovial tendons compared to controls. Immunohistochemistry staining with anti-Ki67 and anti-CD31 antibodies revealed marked increases in cellularity and neovascularization in treated intrasynovial tendons. Clinical significance: The findings of this experiment indicate that improved gene expression and histological outcomes can be achieved by regulating glucose metabolism in the early stages following intrasynovial tendon repair.

The effects of NF-κB suppression on the early healing response following intrasynovial tendon repair in a canine model.

The highly variable clinical outcomes noted after intrasynovial tendon repair have been associated with an early inflammatory response leading to the development of fibrovascular adhesions. Prior efforts to broadly suppress this inflammatory response have been largely unsuccessful. Recent studies have shown that selective inhibition of IkappaB kinase beta (IKK-ß), an upstream activator of nuclear factor kappa-light chain enhancer of activated B cells (NF-κB) signaling, mitigates the early inflammatory response and leads to improved tendon healing outcomes. In the current study, we test the hypothesis that oral treatment with the IKK-ß inhibitor ACHP (2-amino-6-[2-(cyclopropylmethoxy)-6-hydroxyphenyl]-4-piperidin-4-yl nicotinenitrile an inhibitor) will modulate the postoperative inflammatory response and improve intrasynovial flexor tendon healing. To test this hypothesis, the flexor digitorum profundus tendon of 21 canines was transected and repaired within the intrasynovial region and assessed after 3 and 14 days. Histomorphometry, gene expression analyses, immunohistochemistry, and quantitative polarized light imaging were used to examine ACHP-mediated changes. ACHP led to reduction in phosphorylated p-65, indicating that NF-κB activity was suppressed. ACHP enhanced expression of inflammation-related genes at 3 days and suppressed expression of these genes at 14 days. Histomorphometry revealed enhanced cellular proliferation and neovascularization in ACHP-treated tendons compared with time-matched controls. These findings demonstrate that ACHP effectively suppressed NF-κB signaling and modulated early inflammation, leading to increased cellular proliferation and neovascularization without stimulating the formation of fibrovascular adhesions. Together, these data suggest that ACHP treatment accelerated the inflammatory and proliferative phases of tendon healing following intrasynovial flexor tendon repair. Clinical Significance: Using a clinically relevant large-animal model, this study revealed that targeted inhibition of nuclear factor kappa-light chain enhancer of activated B cells signaling with ACHP provides a new therapeutic strategy for enhancing the repair of sutured intrasynovial tendons.

Differential gene expression in motor and sensory Schwann cells in the rat femoral nerve.

Phenotypic differences in Schwann cells (SCs) may help to guide axonal regeneration down motor or sensory specific pathways following peripheral nerve injury. The goal of this study was to identify phenotypic markers for SCs harvested from the cutaneous (sensory) and quadriceps (motor) branches of the rat femoral nerve and to study the effects of expansion culture on the expression patterns of these motor or sensory phenotypic markers. RNA was extracted from SCs harvested from the motor and sensory branches of the rat femoral nerve and analyzed using Affymetrix Gene Chips (Rat Genome 230 v2.0 Array A). Genes that were upregulated in motor SCs compared with the sensory SCs or vice versa were identified, and the results were verified for a subset of genes using quantitative real-time polymerase chain reaction (qRT-PCR). The expression levels of the "phenotype-specific" genes were then evaluated in SC expansion cultures at various time points over 30 days by qRT-PCR to determine the effect of expansion on SC phenotype. Expression levels of the phenotype-specific genes were significantly altered after expansion culture for both the motor and the sensory markers compared with fresh nerve tissue. These results indicate that both motor and sensory SC gene expression patterns are disrupted during expansion in vitro and may affect the ability of SCs to express phenotype-specific genes after transplantation.

A transgenic mouse embryonic stem cell line for puromycin selection of V0V interneurons from heterogenous induced cultures.

BACKGROUND: Spinal interneurons (INs) relay sensory and motor control information between the brain and body. When this relay circuitry is disrupted from injury or disease, it is devastating to patients due to the lack of native recovery in central nervous system (CNS) tissues. Obtaining a purified population of INs is necessary to better understand their role in normal function and as potential therapies in CNS. The ventral V0 (V0V) INs are excitatory neurons involved in locomotor circuits and are thus of interest for understanding normal and pathological spinal cord function. To achieve scalable amounts of V0V INs, they can be derived from pluripotent sources, such as mouse embryonic stem cells (mESCs), but the resultant culture is heterogenous, obscuring the specific role of V0V INs. This study generated a transgenic mESC line to enrich V0V INs from induced cultures to allow for a scalable, enriched population for future in vitro and in vivo studies. METHODS: The transgenic Evx1-PAC mESC line was created by CRISPR-Cas9-mediated insertion of puromycin-N-acetyltransferase (PAC) into the locus of V0V IN marker Evx1. Evx1 and PAC mRNA expression were measured by qPCR. Viability staining helped establish the selection protocol for V0V INs derived from Evx1-PAC mESCs inductions. Immunostaining was used to examine composition of selected inductions. Cultures were maintained up to 30 days to examine maturation by expression of mature/synaptic markers, determined by immunostaining, and functional activity in co-cultures with selected motor neurons (MNs) and V2a INs on microelectrode arrays (MEAs). RESULTS: V0V IN inductions were best selected with 4 µg/mL puromycin on day 10 to 11 and showed reduction of other IN populations and elimination of proliferative cells. Long-term selected cultures were highly neuronal, expressing neuronal nuclear marker NeuN, dendritic marker MAP2, pre-synaptic marker Bassoon, and glutamatergic marker VGLUT2, with some cholinergic VAChT-expressing cells. Functional studies on MEAs showed that co-cultures with MNs or MNs plus V2a INs created neuronal networks with synchronized bursting. CONCLUSIONS: Evx1-PAC mESCs can be used to purify V0V IN cultures for largely glutamatergic neurons that can be used in network formation studies or for rodent models requiring transplanted V0V INs.

Flexor Tendon Injury and Repair. The Influence of Synovial Environment on the Early Healing Response in a Canine Model.

BACKGROUND: Environmental conditions strongly influence the healing capacity of connective tissues. Well-vascularized extrasynovial tendons typically undergo a robust wound-healing process following transection and repair. In contrast, avascular intrasynovial tendons do not mount an effective repair response. The current study tests the hypothesis that flexor tendons, as a function of their synovial environment, exhibit unique inflammatory, angiogenic, and metabolic responses to injury and repair. METHODS: Flexor tendons present a distinct opportunity to test the study hypothesis, as they have proximal regions that are extrasynovial and distal regions that are intrasynovial. In an internally controlled study design, the second and fifth forepaw flexor tendons were transected and repaired in either the extrasynovial or the intrasynovial anatomical region. Histological, gene expression, and proteomics analyses were performed at 3 and 7 days to define the early biological events that drive synovial environment-dependent healing responses. RESULTS: Uninjured intrasynovial tendons were avascular, contained high levels of proteoglycans, and expressed inflammatory factors, complement proteins, and glycolytic enzymes. In contrast, extrasynovial tendons were well vascularized, contained low levels of proteoglycans, and were enriched in inflammation inhibitors and oxidative phosphorylation enzymes. The response to injury and repair was markedly different between the 2 tendon regions. Extrasynovial tendons displayed a robust and rapid neovascularization response, increased expression levels of complement proteins, and an acute shift in metabolism to glycolysis, whereas intrasynovial tendons showed minimal vascularity and muted inflammatory and metabolic responses. CONCLUSIONS: The regional molecular profiles of intact and healing flexor tendons revealed extensive early differences in innate immune response, metabolism, vascularization, and expression of extracellular matrix as a function of the synovial environment. These differences reveal mechanisms through which extrasynovial tendons heal more effectively than do intrasynovial tendons. CLINICAL RELEVANCE: To improve outcomes after operative repair, future treatment strategies should promote features of extrasynovial healing, such as enhanced vascularization and modulation of the complement system and/or glucose metabolism.

Passive Clearing and 3D Lightsheet Imaging of the Intact and Injured Spinal Cord in Mice.

The spinal cord contains a diverse array of sensory and motor circuits that are essential for normal function. Spinal cord injury (SCI) permanently disrupts neural circuits through initial mechanical damage, as well as a cascade of secondary injury events that further expand the spinal cord lesion, resulting in permanent paralysis. Tissue clearing and 3D imaging have recently emerged as promising techniques to improve our understanding of the complex neural circuitry of the spinal cord and the changes that result from damage due to SCI. However, the application of this technology for studying the intact and injured spinal cord remains limited. Here, we optimized the passive CLARITY technique (PACT) to obtain gentle and efficient clearing of the murine spinal cord without the need for specialized equipment. We demonstrate that PACT clearing enables 3D imaging of multiple fluorescent labels in the spinal cord to assess molecularly defined neuronal populations, acute inflammation, long-term tissue damage, and cell transplantation. Collectively, these procedures provide a framework for expanding the utility of tissue clearing to enhance the study of spinal cord neural circuits, as well as cellular- and tissue-level changes that occur following SCI.

Fibrin matrices with affinity-based delivery systems and neurotrophic factors promote functional nerve regeneration.

Glial-derived neurotrophic factor (GDNF) and nerve growth factor (NGF) have both been shown to enhance peripheral nerve regeneration following injury and target different neuronal populations. The delivery of either growth factor at the site of injury may, therefore, result in quantitative differences in motor nerve regeneration and functional recovery. In this study we evaluated the effect of affinity-based delivery of GDNF or NGF from fibrin-filled nerve guidance conduits (NGCs) on motor nerve regeneration and functional recovery in a 13 mm rat sciatic nerve defect. Seven experimental groups were evaluated consisting of GDNF or NGF and the affinity-based delivery system (DS) within NGCs, control groups excluding the DS and/or growth factor, and nerve isografts. Groups with growth factor in the conduit demonstrated equivalent or superior performance in behavioral tests and relative muscle mass measurements compared to isografts at 12 weeks. Additionally, groups with GDNF demonstrated greater specific twitch and tetanic force production in extensor digitorum longus (EDL) muscle than the isograft control, while groups with NGF produced demonstrated similar force production compared to the isograft control. Assessment of motor axon regeneration by retrograde labeling further revealed that the number of ventral horn neurons regenerating across NGCs containing GDNF and NGF DS was similar to the isograft group and these counts were greater than the groups without growth factor. Overall, the GDNF DS group demonstrated superior functional recovery and equivalent motor nerve regeneration compared to the isograft control, suggesting it has potential as a treatment for motor nerve injury.

Tissue-engineered fibrin scaffolds containing neural progenitors enhance functional recovery in a subacute model of SCI.

Two recurring problems with stem/neural progenitor cell (NPC) transplantation therapies for spinal cord injury (SCI) are poor cell survival and uncontrolled cell differentiation. The current study evaluated the viability and differentiation of embryonic stem cell-derived neural progenitor cells (ESNPCs) transplanted within fibrin scaffolds containing growth factors (GFs) and a heparin-binding delivery system (HBDS) to enhance cell survival and direct differentiation into neurons. Mouse ESNPCs were generated from mouse embryonic stem cells (ESCs) using a 4-/4+ retinoic acid (RA) induction protocol that resulted in a population of cells that was 70% nestin positive NPCs. The ESNPCs were transplanted directly into a rat subacute dorsal hemisection lesion SCI model. ESNPCs were either encapsulated in a fibrin scaffold; encapsulated in fibrin containing the HBDS, neurotrophin-3 (NT-3) and platelet derived growth factor (PDGF-AA); or encapsulated in fibrin scaffolds with NT-3 and PDGF-AA without the HBDS. We report that the combination of GFs and fibrin scaffold (without HBDS) enhanced the total number of ESNPCs present in the treated spinal cords and increased the number of ESNPC-derived NeuN positive neurons 8 weeks after transplantation. All experimental groups treated with ESNPCs exhibited an increase in behavioral function 4 weeks after transplantation. In a subset of animals, the ESNPCs over-proliferated as evidenced by SSEA-1 positive/Ki67 positive ESCs found at 4 and 8 weeks. These results demonstrate the potential of tissue-engineered fibrin scaffolds to enhance the survival of NPCs and highlight the need to purify cell populations used in therapies for SCI.

Controlled delivery of glial cell line-derived neurotrophic factor enhances motor nerve regeneration.

PURPOSE: To determine the effect of a motor-specific neurotrophic factor, glial-derived neurotrophic factor (GDNF) on motor nerve regeneration. METHODS: We used a nerve conduit filled with a fibrin-based delivery system that provided controlled release of GDNF during nerve regeneration. The motor branch of the rat femoral nerve was used to assess motor nerve regeneration across a 5-mm gap. Four experimental groups (n = 4 to n = 8) were evaluated. These included GDNF with the fibrin-based delivery system (GDNF-DS), fibrin alone, empty conduit (negative control), and nerve isograft (positive control). Nerves were harvested at 5 weeks for analysis by histomorphometry and electron microscopy. RESULTS: At 5 mm distal to the conduit or isografts, the GDNF-DS group was not significantly different from the nerve isograft group in the following histomorphometric measures: total nerve fibers, percentage of neural tissue, and nerve density. Both the GDNF-DS and isograft groups had significantly more fibers and a higher percentage of neural tissue than fibrin alone and empty conduit groups. There were no differences in fiber width among all groups. By electron microscopy, the GDNF-DS and isograft groups also demonstrated more organized nerve architecture than the fibrin alone and empty conduit groups. CONCLUSIONS: The delivery of GDNF from the fibrin-based delivery system promotes motor nerve regeneration at a level similar to an isograft in the femoral motor nerve model. This study gives insight into the potential beneficial role of GDNF in the treatment of motor nerve injuries.

Conductive Core-Sheath Nanofibers and Their Potential Application in Neural Tissue Engineering.

We have prepared conductive core-sheath nanofibers via a combination of electrospinning and aqueous polymerization. Specifically, nanofibers electrospun from poly(ε-caprolactone) (PCL) and poly((L)-lactide) (PLA) were employed as templates to generate uniform sheaths of polypyrrole (PPy) via in situ polymerization. These conductive core-sheath nanofibers offer a unique system for studying the synergistic effect of different cues on neurite outgrowth in vitro. We found that explanted dorsal root ganglia (DRG) adhered well to the conductive core-sheath nanofibers and generated neurites across the surface when there was a nerve growth factor in the medium. Furthermore, the neurites could be oriented along one direction and enhanced by 82% in terms of maximum length when uniaxially aligned conductive core-sheath nanofibers are compared with their random counterparts. Electrical stimulation, when applied through the mats of conductive core-sheath nanofibers, was found to further increase the maximum length of neurite for random and aligned samples by 83% and 47%, respectively, relative to the controls without electrical stimulation. Combined together, these results suggest the potential use of the conductive core-sheath nanofibers as scaffolds in applications such as neural tissue engineering.

Controlled release of neurotrophin-3 from fibrin-based tissue engineering scaffolds enhances neural fiber sprouting following subacute spinal cord injury.

This study investigated whether delayed treatment of spinal cord injury with controlled release of neurotrophin-3 (NT-3) from fibrin scaffolds can stimulate enhanced neural fiber sprouting. Long Evans rats received a T9 dorsal hemisection spinal cord injury. Two weeks later, the injury site was re-exposed, and either a fibrin scaffold alone, a fibrin scaffold containing a heparin-based delivery system with different concentrations of NT-3 (500 and 1,000 ng/mL), or a fibrin scaffold containing 1,000 ng/mL of NT-3 (no delivery system) was implanted into the injury site. The injured spinal cords were evaluated for morphological differences using markers for neurons, astrocytes, and chondroitin sulfate proteoglycans 2 weeks after treatment. The addition of 500 ng/mL of NT-3 with the delivery system resulted in an increase in neural fiber density compared to fibrin alone. These results demonstrate that the controlled release of NT-3 from fibrin scaffolds can enhance neural fiber sprouting even when treatment is delayed 2 weeks following injury.

Matrices, scaffolds & carriers for cell delivery in nerve regeneration.

Nerve injuries can be life-long debilitating traumas that severely impact patients' quality of life. While many acellular neural scaffolds have been developed to aid the process of nerve regeneration, complete functional recovery is still very difficult to achieve, especially for long-gap peripheral nerve injury and most cases of spinal cord injury. Cell-based therapies have shown many promising results for improving nerve regeneration. With recent advances in neural tissue engineering, the integration of biomaterial scaffolds and cell transplantation are emerging as a more promising approach to enhance nerve regeneration. This review provides an overview of important considerations for designing cell-carrier biomaterial scaffolds. It also discusses current biomaterials used for scaffolds that provide permissive and instructive microenvironments for improved cell transplantation.

Cell therapy for spinal cord regeneration.

This review presents a summary of the various types of cellular therapy used to treat spinal cord injury. The inhibitory environment and loss of axonal connections after spinal cord injury pose many obstacles to regenerating the lost tissue. Cellular therapy provides a means of restoring the cells lost to the injury and could potentially promote functional recovery after such injuries. A wide range of cell types have been investigated for such uses and the advantages and disadvantages of each cell type are discussed along with the research studying each cell type. Additionally, methods of delivering cells to the injury site are evaluated. Based on the current research, suggestions are given for future investigation of cellular therapies for spinal cord regeneration.