Glial cell line-derived neurotrophic factor enhances axonal regeneration following sciatic nerve transection in adult rats

Schwann cell-encapsulated chitosan-collagen hydrogel nerve conduit promotes peripheral nerve regeneration in rodent sciatic nerve defect models

Chitosan has various tissue regeneration effects. This study was designed to investigate the nerve regeneration effect of Schwann cell (SC)-encapsulated chitosan-collagen hydrogel nerve conduit (CCN) transplanted into a rat model of sciatic nerve defect. We prepared a CCN consisting of an outer layer of chitosan hydrogel and an inner layer of collagen hydrogel to encapsulate the intended cells. Rats with a 10-mm sciatic nerve defect were treated with SCs encapsulated in CCN (CCN+), CCN without SCs (CCN-), SC-encapsulated silicone tube (silicone+), and autologous nerve transplanting (auto). Behavioral and histological analyses indicated that motor functional recovery, axonal regrowth, and myelination of the CCN+ group were superior to those of the CCN- and silicone+ groups. Meanwhile, the CCN- and silicone+ groups showed no significant differences in the recovery of motor function and nerve histological restoration. In conclusion, SC-encapsulated CCN has a synergistic effect on peripheral nerve regeneration, especially axonal regrowth and remyelination of host SCs. In the early phase after transplantation, SC-encapsulated CCNs have a positive effect on recovery. Therefore, using SC-encapsulated CCNs may be a promising approach for massive peripheral nerve defects.

Pro-inflammatory cytokines and leukocyte integrins associated with chronic neuropathic pain in traumatic and inflammatory neuropathies: Initial observations and hypotheses

Leukocyte infiltration and persistence within peripheral nerves have been implicated in chronic nociception pathogenesis in murine peripheral neuropathy models. Endoneurial cytokine and chemokine expression contribute to leukocyte infiltration and maintenance of a pro-inflammatory state that delays peripheral nerve recovery and promotes chronic pain behaviors in these mice. However, there has been a failure to translate murine model data into safe and effective treatments for chronic neuropathic pain in peripheral neuropathy patients, or develop reliable biomarkers that may help diagnose or determine treatment responses in affected patients. Initial work showed that persistent sciatic nerve CD11b+ CD45+ leukocyte infiltration was associated with disease severity in three mouse models of inflammatory and traumatic peripheral neuropathies, implying a direct contributing role in disease pathogenesis. In support of this, CD11b+ leukocytes were also seen in the sural nerve biopsies of chronic neuropathic pain patients with three different peripheral neuropathies. Systemic CD11b antagonism using a validated function-neutralizing monoclonal antibody effectively treated chronic nociception following unilateral sciatic nerve crush injury (a representative traumatic neuropathy model associated with axonal degeneration and increased blood-nerve barrier permeability) and does not cause drug addiction behaviors in adult mice. These data suggest that CD11b could be an effective molecular target for chronic neuropathic pain treatment in inflammatory and traumatic peripheral neuropathies. Despite known murine peripheral neuropathy model limitations, our initial work suggests that early expression of pro-inflammatory cytokines, such as tissue inhibitor of metalloproteinases-1 may predict subsequent chronic nociception development following unilateral sciatic nerve crush injury. Studies aligning animal model investigation with observational data from well-characterized human peripheral neuropathies, including transcriptomics and proteomics, as well as animal model studies using a human clinical trial design should foster the identification of clinically relevant biomarkers and effective targeted treatments with limited addiction potential for chronic neuropathic pain in peripheral neuropathy patients.

The Bridging Effect of Controlled-Release Glial Cell-Derived Neurotrophic Factor Microcapsules within Nerve Conduits on Rat Facial Nerve Regeneration

Objectives

The study is aimed at exploring the effect of the controlled release of the glial-derived neurotrophic factor (GDNF) on nerve regeneration.

Methods

The PLGA/chitosan composite nerve conduit was used to bridge the dissected trunk of the rat facial nerve. GDNF microcapsules were loaded into the nerve conduit. Nine weeks after surgery, the facial nerve zygomatic and buccal branches were labeled with fluorescent indicators. The incorrectly grown facial neurons were reversed and counted. The facial nerve functional recovery was assessed by measuring the maximum evoked potential.

Results

The nerve conduit was filled with different regenerating factors, such as the GDNF, GDNF microcapsules, or saline (control). The number of incorrectly regenerated neurons was lower with the nerve conduits filled with GDNF microcapsules than with those supplied with just the GDNF. However, neither the GDNF nor GDNF microcapsules affected the number of regenerated neurons. The functional recovery of the facial nerve was the best, with the nerve conduit filled with GDNF microcapsules closest to the healthy uncut facial nerve.

Conclusion

The stable slow-release GNDF microcapsule inside the biodegradable nerve conduit can reduce the extent of incorrect growth of the facial nerve neuron when bridging the dissected rat facial nerve trunk. The technique has a good effect on functional nerve recovery.

The Role of c-Jun and Autocrine Signaling Loops in the Control of Repair Schwann Cells and Regeneration

After nerve injury, both Schwann cells and neurons switch to pro-regenerative states. For Schwann cells, this involves reprogramming of myelin and Remak cells to repair Schwann cells that provide the signals and mechanisms needed for the survival of injured neurons, myelin clearance, axonal regeneration and target reinnervation. Because functional repair cells are essential for regeneration, it is unfortunate that their phenotype is not robust. Repair cell activation falters as animals get older and the repair phenotype fades during chronic denervation. These malfunctions are important reasons for the poor outcomes after nerve damage in humans. This review will discuss injury-induced Schwann cell reprogramming and the concept of the repair Schwann cell, and consider the molecular control of these cells with emphasis on c-Jun. This transcription factor is required for the generation of functional repair cells, and failure of c-Jun expression is implicated in repair cell failures in older animals and during chronic denervation. Elevating c-Jun expression in repair cells promotes regeneration, showing in principle that targeting repair cells is an effective way of improving nerve repair. In this context, we will outline the emerging evidence that repair cells are sustained by autocrine signaling loops, attractive targets for interventions aimed at promoting regeneration.

Tissue Engineered Neurovascularization Strategies for Craniofacial Tissue Regeneration

Craniofacial tissue injuries, diseases, and defects, including those within bone, dental, and periodontal tissues and salivary glands, impact an estimated 1 billion patients globally. Craniofacial tissue dysfunction significantly reduces quality of life, and successful repair of damaged tissues remains a significant challenge. Blood vessels and nerves are colocalized within craniofacial tissues and act synergistically during tissue regeneration. Therefore, the success of craniofacial regenerative approaches is predicated on successful recruitment, regeneration, or integration of both vascularization and innervation. Tissue engineering strategies have been widely used to encourage vascularization and, more recently, to improve innervation through host tissue recruitment or prevascularization/innervation of engineered tissues. However, current scaffold designs and cell or growth factor delivery approaches often fail to synergistically coordinate both vascularization and innervation to orchestrate successful tissue regeneration. Additionally, tissue engineering approaches are typically investigated separately for vascularization and innervation. Since both tissues act in concert to improve craniofacial tissue regeneration outcomes, a revised approach for development of engineered materials is required. This review aims to provide an overview of neurovascularization in craniofacial tissues and strategies to target either process thus far. Finally, key design principles are described for engineering approaches that will support both vascularization and innervation for successful craniofacial tissue regeneration.

The Clinical Effect of a Combination of Mouse Nerve Growth Factor and Methylcobalamin to Treat Lumbar Disc Herniation with Foot Drop: A Retrospective Cohort Study

Objective

To investigate the clinical effect of mouse nerve growth factor (mNGF) and methylcobalamin (MeCbl) for the treatment of lumbar disk herniation (LDH) with foot drop.

Methods

A total of 46 patients suffering from LDH with foot drop who underwent transforaminal lumbar interbody fusion (TLIF) surgery in our department from January 2015 to December 2017 were retrospectively analyzed. We divided these patients into two groups according to the different postoperative treatment which independently selected by patients after signing informed consent form: one group of 25 patients was treated with MeCbl alone (Group MeCbl), the other group of 21 patients was treated with a combination of mNGF and MeCbl (Group MeCbl+mNGF). Patient demographics, the visual analogue scale (VAS) scores, sensory and muscular strength improvement statistics at 1 week, 4 weeks, 12 weeks, and 12 months postoperatively were recorded. Motor/sensory deficits, sciatica and overall neurological outcome after treatment of MeCbl alone and combination of mNGF and MeCbl were retrospectively analyzed.

Results

The follow‐up ranged between 12 and 42 months (mean 20.8 months). There were no significant differences between these two groups of patients with respect to sex ratio, age, smoking, diabetes, disease course, section of protruding disc(s), muscular strength of foot dorsiflexion or preoperative visual analogue scale (VAS) score (P > 0.05). The VAS scores of Group MeCbl+mNGF were significantly lower than Group MeCbl at 1 week, 4 weeks, 12 weeks, and 12 months postoperatively (4.32 ± 0.75 vs 5.25 ± 0.79,2.65 ± 0.48 vs 3.42 ± 0.52, 1.72 ± 0.36 vs 2.45 ± 0.39, 1.12 ± 0.22 vs 1.52 ± 0.24, P < 0.05). The effective rates of sensory improvement were significantly higher in Group MeCbl+mNGF compared with Group MeCbl at 12‐week/12‐month follow‐up time point (90.48% vs 52.00%,95.24% vs 68.00%, P < 0.05). The effective rate of muscular strength improvement of the two groups did not differ significantly at 1 week after surgery but exhibited statistically significant differences at subsequent time points (61.90% vs 32.00%, 76.19% vs 44.00%, 80.95% vs 48.00%, P < 0.05).

Conclusions

Application of mNGF had clinical effects on promoting the recovery of neurological function in patients suffering from LDH with foot drop.

Graphene-based hybrid materials as promising scaffolds for peripheral nerve regeneration

Peripheral nerve injury (PNI) is a serious clinical health problem caused by the damage of peripheral nerves which results in neurological deficits and permanent disability. There are several factors that may cause PNI such as localized damage (car accident, trauma, electrical injury) and outbreak of the systemic diseases (autoimmune or diabetes). While various diagnostic procedures including X-ray, magnetic resonance imaging (MRI), as well as other type of examinations such as electromyography or nerve conduction studies have been efficiently developed, a full recovery in patients with PNI is in many cases deficient or incomplete. This is the reason why additional therapeutic strategies should be explored to favor a complete rehabilitation in order to get appropriate nerve injury regeneration. The use of biomaterials acting as scaffolds opens an interesting approach in regenerative medicine and tissue engineering applications due to their ability to guide the growth of new tissues, adhesion and proliferation of cells including the expression of bioactive signals. This review discusses the preparation and therapeutic strategies describing in vitro and in vivo experiments using graphene-based materials in the context of PNI and their ability to promote nerve tissue regeneration.

Effects of endogenous inflammation signals elicited by nerve growth factor, interferon-γ, and interleukin-4 on peripheral nerve regeneration

Background

Large gap healing is a difficult issue in the recovery of peripheral nerve injury. The present study provides in vivo trials of silicone rubber chambers filled with collagen containing IFN-γ or IL-4 to bridge a 15 mm sciatic nerve defect in rats. Fillings of NGF and normal saline were used as the positive and negative controls. Neuronal electrophysiology, neuronal connectivity, macrophage infiltration, location and expression levels of calcitonin gene-related peptide and histology of the regenerated nerves were evaluated.

Results

At the end of 6 weeks, animals from the groups of NGF and IL-4 had dramatic higher rates of successful regeneration (100 and 80%) across the wide gap as compared to the groups of IFN-γ and saline controls (30 and 40%). In addition, the NGF group had significantly higher NCV and shorter latency compared to IFN-γ group (P < 0.05). The IL-4 group recruited significantly more macrophages in the nerves as compared to the saline controls and the NGF-treated animals (P < 0.05).

Conclusions

The current study demonstrated that NGF and IL-4 show potential growth-promoting capability for peripheral nerve regeneration. These fillings in the bridging conduits may modulate local inflammatory conditions affecting recovery of the nerves.

Non-viral nucleic acid delivery to the central nervous system and brain tumors

Gene therapy is a rapidly emerging remedial route for many serious incurable diseases, such as central nervous system (CNS) diseases. Currently, nucleic acid medicines, including DNAs encoding therapeutic or destructive proteins, small interfering RNAs or microRNAs, have been successfully delivered to the CNS with gene delivery vectors using various routes of administration and have subsequently exhibited remarkable therapeutic efficiency. Among these vectors, non-viral vectors are favorable for delivering genes into the CNS as a result of their many special characteristics, such as low toxicity and pre-existing immunogenicity, high gene loading efficiency and easy surface modification. In this review, we highlight the main types of therapeutic genes that have been applied in the therapy of CNS diseases and then outline non-viral gene delivery vectors.

Relevance and Recent Developments of Chitosan in Peripheral Nerve Surgery

Developments in tissue engineering yield biomaterials with different supporting strategies to promote nerve regeneration. One promising material is the naturally occurring chitin derivate chitosan. Chitosan has become increasingly important in various tissue engineering approaches for peripheral nerve reconstruction, as it has demonstrated its potential to interact with regeneration associated cells and the neural microenvironment, leading to improved axonal regeneration and less neuroma formation. Moreover, the physiological properties of its polysaccharide structure provide safe biodegradation behavior in the absence of negative side effects or toxic metabolites. Beneficial interactions with Schwann cells (SC), inducing differentiation of mesenchymal stromal cells to SC-like cells or creating supportive conditions during axonal recovery are only a small part of the effects of chitosan. As a result, an extensive body of literature addresses a variety of experimental strategies for the different types of nerve lesions. The different concepts include chitosan nanofibers, hydrogels, hollow nerve tubes, nerve conduits with an inner chitosan layer as well as hybrid architectures containing collagen or polyglycolic acid nerve conduits. Furthermore, various cell seeding concepts have been introduced in the preclinical setting. First translational concepts with hollow tubes following nerve surgery already transferred the promising experimental approach into clinical practice. However, conclusive analyses of the available data and the proposed impact on the recovery process following nerve surgery are currently lacking. This review aims to give an overview on the physiologic properties of chitosan, to evaluate its effect on peripheral nerve regeneration and discuss the future translation into clinical practice.

Pretreatment of nerve grafts with resveratrol improves axonal regeneration following replantation surgery for nerve root avulsion injury in rats

BACKGROUND

Replantation of the avulsed nerve root has been proposed for the treatment of severe brachial plexus injury for several decades. However, due to the complexity of the technique and limited functional improvement, practical applications are yet to be implemented.

OBJECTIVE

In the present study, we investigated the effect of pretreatment with resveratrol on nerve autografts used for replantation surgery in a rat model of nerve root avulsion.

METHODS

Resveratrol pretreatment was performed using an explant culture technique. Two surgical procedures were performed. During the first surgery, Sprague-Dawley rats were subjected to left C6 nerve root avulsion, and nerves were harvested for autografting. The harvested grafts were explant-cultured for 1 week. A second procedure was performed to replant the C6 nerve root using the explant-cultured nerve graft 1 week after the first procedure. Histological and immunohistochemical analyses were performed 8 weeks after the second procedure. We first compared findings between explant-cultured nerve grafts and fresh nerve grafts, following which we compared findings between explant-cultured grafts pretreated with and without resveratrol. Changes induced within nerve grafts by 1 week of explant culture with or without resveratrol were investigated in vitro.

RESULTS

There was no significant difference in outcomes between 1 week-explant-cultured and fresh nerve grafts. Addition of resveratrol to the explant culture medium resulted in a significant increase in the number and myelin thickness of regenerated axons, and in the number of regenerating motor neurons in the C6 spinal cord segment. In vitro analyses revealed that nerve grafts pretreated with resveratrol exhibited significant increases in glial cell line-derived neurotrophic factor (GDNF) expression and the number of dedifferentiated Schwann cells.

CONCLUSIONS

Resveratrol may promote axonal regeneration following replantation surgery for the treatment of nerve root avulsion injury; however, further studies are required to verify these findings in humans.

Ivermectin Promotes Peripheral Nerve Regeneration during Wound Healing

Peripheral nerves have the capacity to regenerate due to the presence of neuroprotective glia of the peripheral nervous system, Schwann cells. Upon peripheral nerve injury, Schwann cells create a permissive microenvironment for neuronal regrowth by taking up cytotoxic glutamate and secreting neurotrophic signaling molecules. Impaired peripheral nerve repair is often caused by a defective Schwann cell response after injury, and there is a critical need to develop new strategies to enhance nerve regeneration, especially in organisms with restricted regenerative potential, such as humans. One approach is to explore mechanisms in lower organisms, in which nerve repair is much more efficient. A recent study demonstrated that the antiparasitic drug, ivermectin, caused hyperinnervation of primordial eye tissue in Xenopus laevis tadpoles. Our study aimed to examine the role of ivermectin in mammalian nerve repair. We performed in vitro assays utilizing human induced neural stem cells (hiNSCs) in co-culture with human dermal fibroblasts (hDFs) and found that ivermectin-treated hDFs promote hiNSC proliferation and migration. We also characterized the effects of ivermectin on hDFs and found that ivermectin causes hDFs to uptake extracellular glutamate, secrete glial cell-derived neurotrophic factor, develop an elongated bipolar morphology, and express glial fibrillary acidic protein. Finally, in a corresponding in vivo model, we found that localized ivermectin treatment in a dermal wound site induced the upregulation of both glial and neuronal markers upon healing. Taken together, we demonstrate that ivermectin promotes peripheral nerve regeneration by inducing fibroblasts to adopt a glia-like phenotype.

Glial-derived neurotrophic factor is essential for blood-nerve barrier functional recovery in an experimental murine model of traumatic peripheral neuropathy

There is emerging evidence that glial-derived neurotrophic factor (GDNF) is a potent inducer of restrictive barrier function in tight junction-forming microvascular endothelium and epithelium, including the human blood-nerve barrier (BNB) in vitro. We sought to determine the role of GDNF in restoring BNB function in vivo by evaluating sciatic nerve horseradish peroxidase (HRP) permeability in tamoxifen-inducible GDNF conditional knockout (CKO) adult mice following non-transecting crush injury via electron microscopy, with appropriate wildtype (WT) and heterozygous (HET) littermate controls. A total of 24 age-, genotype- and sex-matched mice >12 weeks of age were injected with 30 mg/kg HRP via tail vein injection 7 or 14 days following unilateral sciatic nerve crush, and both sciatic nerves were harvested 30 minutes later for morphometric assessment by light and electron microscopy. The number and percentage of HRP-permeable endoneurial microvessels were ascertained to determine the effect of GDNF in restoring barrier function in vivo. Following sciatic nerve crush, there was significant upregulation in GDNF protein expression in WT and HET mice that was abrogated in CKO mice. GDNF significantly restored sciatic nerve BNB HRP impermeability to near normal levels by day 7, with complete restoration seen by day 14 in WT and HET mice. A significant recovery lag was observed in CKO mice. This effect was independent on VE-Cadherin or claudin-5 expression on endoneurial microvessels. These results imply an important role of GDNF in restoring restrictive BNB function in vivo, suggesting a potential strategy to re-establish the restrictive endoneurial microenvironment following traumatic peripheral neuropathies.

Strategies to improve nerve regeneration after radical prostatectomy: a narrative review

Peripheral nerves are complex organs that spread throughout the entire human body. They are frequently affected by lesions not only as a result of trauma but also following radical tumor resection. In fact, despite the advancement in surgical techniques, such as nerve-sparing robot assisted radical prostatectomy, some degree of nerve injury may occur resulting in erectile dysfunction with significant impairment of the quality of life. The aim of this review was to provide an overview on the mechanisms of the regeneration of injured peripheral nerves and to describe the potential strategies to improve the regeneration process and the functional recovery. Yet, the recent advances in bio-engineering strategies to promote nerve regeneration in the urological field are outlined with a view on the possible future regenerative therapies which might ameliorate the functional outcome after radical prostatectomy.

Seeding nerve sutures with minced nerve-graft (MINE-G): a simple method to improve nerve regeneration in rats

BACKGROUND

The aim of this study was to assess the effect of seeding the distal nerve suture with nerve fragments in rats.

METHODS

On 20 rats, a 15 mm sciatic nerve defect was reconstructed with a nerve autograft. In the Study Group (10 rats), a minced 1 mm nerve segment was seeded around the nerve suture. In the Control Group (10 rats), a nerve graft alone was used. At 4 and 12 weeks, a walking track analysis with open field test (WTA), hystomorphometry (number of myelinated fibers (n), fiber density (FD) and fiber area (FA) and soleus and gastrocnemius muscle weight ratios (MWR) were evaluated. The Student t-test was used for statistical analysis.

RESULTS

At 4 and 12 weeks the Study Group had a significantly higher n and FD (p = .043 and .033). The SMWR was significantly higher in the Study Group at 12 weeks (p = .0207).

CONCLUSIONS

Seeding the distal nerve suture with nerve fragments increases the number of myelinated fibers, the FD and the SMWR. The technique seems promising and deserves further investigation to clarify the mechanisms involved and its functional effects.

Treatment with acetyl-L-carnitine exerts a neuroprotective effect in the sciatic nerve following loose ligation: a functional and microanatomical study

Peripheral neuropathies are chronic painful syndromes characterized by allodynia, hyperalgesia and altered nerve functionality. Nerve tissue degeneration represents the microanatomical correlate of peripheral neuropathies. Aimed to improve the therapeutic possibilities, this study investigated the hypersensitivity and the neuromorphological alterations related to the loose ligation of the sciatic nerve in rats. Effects elicited by treatment with acetyl-L-carnitine (ALCAR) in comparison to gabapentin were assessed. Axonal injury, reduction of myelin deposition and accumulation of inflammatory cells were detected in damaged nerve. A decrease of phosphorylated 200-kDa neurofilament (NFP) immunoreactivity and a redistribution in small clusters of myelin basic like-protein (MBP) were observed in ipsilateral nerves. Treatment with ALCAR (100 mg/kg intraperitoneally - i.p.) and gabapentin (70 mg/kg i.p.) administered bis in die for 14 days induced a significant pain relieving effect. ALCAR, but not gabapentin, significantly countered neuromorphological changes and increased axonal NFP immunoreactivity. These findings indicate that both ALCAR and gabapentin significantly decreased the hypersensitivity related to neuropathic lesions. The observation of the positive ALCAR effect on axonal and myelin sheath alterations in damaged nerve supports its use as neurorestorative agent against neuropathies through mechanism(s) consistent to those focused in this study.

GDNF From Human Periodontal Ligament Cells Treated With Pro-Inflammatory Cytokines Promotes Neurocytic Differentiation of PC12 Cells

Glial cell line-derived neurotrophic factor (GDNF) is known to mediate multiple biological activities such as promotion of cell motility and proliferation, and morphogenesis. However, little is known about its effects on periodontal ligament (PDL) cells. Recently, we reported that GDNF expression is increased in wounded rat PDL tissue and human PDL cells (HPDLCs) treated with pro-inflammatory cytokines. Here, we investigated the associated expression of GDNF and the pro-inflammatory cytokine interleukin-1 beta (IL-1β) in wounded PDL tissue, and whether HPDLCs secrete GDNF which affects neurocytic differentiation. Rat PDL cells near the wounded area showed intense immunoreactions against an anti-GDNF antibody, where immunoreactivity was also increased against an anti-IL-1β antibody. Compared with untreated cells, HPDLCs treated with IL-1β or tumor necrosis factor-alpha showed an increase in the secretion of GDNF protein. Conditioned medium of IL-1β-treated HPDLCs (IL-1β-CM) increased neurite outgrowth of PC12 rat adrenal pheochromocytoma cells. The expression levels of two neural regeneration-associated genes, growth-associated protein-43 (Gap-43), and small proline-rich repeat protein 1A (Sprr1A), were also upregulated in IL-1β-CM-treated PC12 cells. These stimulatory effects of IL-1β-CM were significantly inhibited by a neutralizing antibody against GDNF. In addition, U0126, a MEK inhibitor, inhibited GDNF-induced neurite outgrowth of PC12 cells. These findings suggest that an increase of GDNF in wounded PDL tissue might play an important role in neural regeneration probably via the MEK/ERK signaling pathway. J. Cell. Biochem. 118: 699-708, 2017. © 2016 Wiley Periodicals, Inc.

Erythropoietin Attenuates the Apoptosis of Adult Neurons After Brachial Plexus Root Avulsion by Downregulating JNK Phosphorylation and c-Jun Expression and Inhibiting c-PARP Cleavage

In the present study, the effects of erythropoietin (EPO) on preventing adult neurons from apoptosis (introduced by brachial plexus avulsion) were examined, and the mechanism was analyzed. Fifty injury rat models were established in this study by using micro-hemostat forceps to pull out brachial plexus root from the intervertebral foramen in supine position. These models were divided into EPO group (avulsion + 1000 U/kg subcutaneously on alternate days) and control group (avulsion + normal saline). C5-T1 spinal cord was harvested at days 1, 2, 4, 7, and 14. Compared with the control group, the apoptosis of spinal motoneurons was significantly decreased on days 4 and 7 in the EPO group, which was also approved by TUNEL examination results. The detection of p-JNK and expression of c-Jun and cleavage of cleaved PARP (c-PARP) were also examined by immunohistochemistry and were increased immediately at day 1, and peaked at day 2, day 2, and day 4 in control group, respectively. However, the amounts were decreased and delayed by EPO treatment significantly at the same time points. In conclusion, the apoptosis of adult spinal motorneurons was associated with JNK phosphorylation, c-Jun expression, and caspase activity, and EPO-mediated neuronal protective effect is proved by downregulating the JNK phosphorylation and c-Jun expression and inhibiting of c-PARP cleavage.

Adjuvant neurotrophic factors in peripheral nerve repair with chondroitin sulfate proteoglycan-reduced acellular nerve allografts

BACKGROUND

Acellular nerve allografts are now standard tools in peripheral nerve repair because of decreased donor site morbidity and operative time savings. Preparation of nerve allografts involves several steps of decellularization and modification of extracellular matrix to remove chondroitin sulfate proteoglycans (CSPGs), which have been shown to inhibit neurite outgrowth through a poorly understood mechanism involving RhoA and extracellular matrix-integrin interactions. Chondroitinase ABC (ChABC) is an enzyme that degrades CSPG molecules and has been shown to promote neurite outgrowth after injury of the central and peripheral nervous systems. Variable results after ChABC treatment make it difficult to predict the effects of this drug in human nerve allografts, especially in the presence of native extracellular signaling molecules. Several studies have shown cross-talk between neurotrophic factor and CSPG signaling pathways, but their interaction remains poorly understood. In this study, we examined the adjuvant effects of nerve growth factor (NGF) and glial cell line-derived neurotrophic factor (GDNF) on neurite outgrowth postinjury in CSPG-reduced substrates and acellular nerve allografts.

MATERIALS AND METHODS

E12 chicken DRG explants were cultured in medium containing ChABC, ChABC + NGF, ChABC + GDNF, or control media. Explants were imaged at 3 d and neurite outgrowths measured. The rat sciatic nerve injury model involved a 1-cm sciatic nerve gap that was microsurgically repaired with ChABC-pretreated acellular nerve allografts. Before implantation, nerve allografts were incubated in NGF, GDNF, or sterile water. Nerve histology was evaluated at 5 d and 8 wk postinjury.

RESULTS

The addition of GDNF in vitro produced significant increase in sensory neurite length at 3 d compared with ChABC alone (P < 0.01), whereas NGF was not significantly different from control. In vivo adjuvant NGF produced increases in total myelinated axon count (P < 0.005) and motor axon count (P < 0.01), whereas significantly reducing IB4+ nociceptor axon count (P < 0.01). There were no significant differences produced by in vivo adjuvant GDNF.

CONCLUSIONS

This study provides initial evidence that CSPG-reduced nerve grafts may disinhibit the prosurvival effects of NGF in vivo, promoting motor axon outgrowth and reducing regeneration of specific nociceptive neurons. Our results support further investigation of adjuvant NGF therapy in CSPG-reduced acellular nerve grafts.

Valproic acid protection against the brachial plexus root avulsion-induced death of motoneurons in rats

In this study, the role of valproic acid (VPA) in protecting motoneuron after brachial plexus root avulsion was investigated in adult rats. Sixty rats were used in this study, and underwent the brachial plexus root avulsion injury, which was created by using a micro-hemostat forceps to pull out brachial plexus root from the intervertebral foramen. The animals were divided into two groups, VPA group administered with VPA dissolved in drinking water (300 mg/kg) daily, and control group had drinking water every day. The spinal cords (C5-T1) were harvested at day 1, 2, 3, 7, 14, and 28 for immunohistochemistry analysis, TUNEL staining, Nissl staining, and electron microscopy, respectively. The results showed that with VPA administration, the survival of motoneurons was promoted and the cell apoptosis was inhibited. The number of c-Jun and Bcl-2 positive motoneurons was increased immediately after avulsion both in control and VPA group, however, the percent of c-Jun positive motoneurons was decreased and the percent of Bcl-2 positive motoneurons was increased by VPA treatment significantly. Our results indicated that motoneurons were protected by VPA against cell death induced by brachial plexus root avulsion through c-Jun inhibition and Bcl-2 induction.

Nerve injury induces glial cell line-derived neurotrophic factor (GDNF) expression in Schwann cells through purinergic signaling and the PKC-PKD pathway

Upon peripheral nerve injury, specific molecular events, including increases in the expression of selected neurotrophic factors, are initiated to prepare the tissue for regeneration. However, the mechanisms underlying these events and the nature of the cells involved are poorly understood. We used the injury-induced upregulation of glial cell-derived neurotrophic factor (GDNF) expression as a tool to gain insights into these processes. We found that both myelinating and nonmyelinating Schwann cells are responsible for the dramatic increase in GDNF expression after injury. We also demonstrate that the GDNF upregulation is mediated by a signaling cascade involving activation of Schwann cell purinergic receptors, followed by protein kinase C signaling which activates protein kinase D (PKD), which leads to increased GDNF transcription. Given the potent effects of GDNF on survival and repair of injured peripheral neurons, we propose that targeting these pathways may yield therapeutic tools to treat peripheral nerve injury and neuropathies.

Dexamethasone and vitamin B(12) synergistically promote peripheral nerve regeneration in rats by upregulating the expression of brain-derived neurotrophic factor

INTRODUCTION

Dexamethasone and vitamin B(12) are currently used in the clinic to treat peripheral nerve damage but their mechanisms of action remain incompletely understood. In this study we hypothesized that dexamethasone and vitamin B(12) promote the production of endogenous neurotrophic factors, thereby enhancing peripheral nerve repair.

MATERIAL AND METHODS

Ninety-six adult male Wistar rats were employed to establish a sciatic nerve injury model. They were then randomly divided into 4 groups to be subjected to different treatment: saline (group A), dexamethasone (group B), vitamin B(12) (group C), and dexamethasone combined with vitamin B(12) (group D). The walking behavior of rats was evaluated by footprint analysis, and the nerve regeneration was assessed by electrophysiological analysis and ultrastructural examination. The expression of brain-derived neurotrophic factor (BDNF), glial cell-derived neurotrophic factor, NT-3 and IL-6 in the injured sciatic nerves was detected by immunohistochemical and RT-PCR analysis.

RESULTS

Dexamethasone and vitamin B(12) promoted the regeneration of myelinated nerve fibers and the proliferation of Schwann cells. Furthermore, dexamethasone and vitamin B(12) promoted the recovery of sciatic functional index and sensory nerve conduction velocity, and upregulated BDNF expression in the injured sciatic nerves.

CONCLUSIONS

Dexamethasone and vitamin B(12) promote peripheral nerve repair in a rat model of sciatic nerve injury through the upregulation of BDNF expression. These findings provide new insight into the neurotrophic effects of dexamethasone and vitamin B(12) and support the application of these agents in clinical treatment of peripheral nerve injury.

Effects of Hedysari Polysaccharides on Regeneration and Function Recovery Following Peripheral Nerve Injury in Rats

It has been demonstrated that aqueous extract of Radix Hedysari Prescription and modified Radix Hedysari Prescription could improve the regeneration of injured peripheral nerve. Radix Hedysari is a main component in these two formulas. We hypothesized that Hedysari polysaccharides (HPS), a main active ingredient, could also enhance peripheral nerve regeneration after nerve injury in adult animals. In the present study, we examined the effects of HPS on sciatic nerve regeneration for 6 weeks following clamping in rats (administrated orally of 2 ml HPS liquid daily, 0.25 g/ml). The results showed that HPS was able to enhance sciatic function index (SFI) value, tibial function index (TFI) value, peroneal nerve function index (PFI) value, conduction velocity, and the number of regenerated myelinated nerve fibers, suggesting the potential clinical application of HPS for the treatment of peripheral nerve injury in humans.

Recruitment by SDF-1α of CD34-positive cells involved in sciatic nerve regeneration

Object

Increased integration of CD34+ cells in injured nerve significantly promotes nerve regeneration, but this effect can be counteracted by limited migration and short survival of CD34+ cells. SDF-1α and its receptor mediate the recruitment of CD34+ cells involved in the repair mechanism of several neurological diseases. In this study, the authors investigate the potentiation of CD34+ cell recruitment triggered by SDF-1α and the involvement of CD34+ cells in peripheral nerve regeneration.

Methods

Peripheral nerve injury was induced in 147 Sprague-Dawley rats by crushing the left sciatic nerve with a vessel clamp. The animals were allocated to 3 groups: Group 1, crush injury (controls); Group 2, crush injury and local application of SDF-1α recombinant proteins; and Group 3, crush injury and local application of SDF-1α antibody. Electrophysiological studies and assessment of regeneration markers were conducted at 4 weeks after injury; neurobehavioral studies were conducted at 1, 2, 3, and 4 weeks after injury. The expression of SDF-1α, accumulation of CD34+ cells, immune cells, and angiogenesis factors in injured nerves were evaluated at 1, 3, 7, 10, 14, 21, and 28 days after injury.

Results

Application of SDF-1α increased the migration of CD34+ cells in vitro, and this effect was dose dependent. Crush injury induced the expression of SDF-1α, with a peak of 10–14 days postinjury, and this increased expression of SDF-1α paralleled the deposition of CD34+ cells, expression of VEGF, and expression of neurofilament. These effects were further enhanced by the administration of SDF-1α recombinant protein and abolished by administration of SDF-1α antibody. Furthermore, these effects were consistent with improvement in measures of neurological function such as sciatic function index, electrophysiological parameters, muscle weight, and myelination of regenerative nerve.

Conclusions

Expression of SDF-1α facilitates recruitment of CD34+ cells in peripheral nerve injury. The increased deposition of CD34+ cells paralleled significant expression of angiogenesis factors and was consistent with improvement of neurological function. Utilization of SDF-1α for enhancing the recruitment of CD34+ cells involved in peripheral nerve regeneration may be considered as an alternative treatment strategy in peripheral nerve disorders.

Peripheral Nerve Regeneration Following Crush Injury to Rat Peroneal Nerve by Aqueous Extract of Medicinal Mushroom Hericium erinaceus (Bull.: Fr) Pers. (Aphyllophoromycetideae)

Nerve crush injury is a well-established axonotmetic model in experimental regeneration studies to investigate the impact of various pharmacological treatments. Hericium erinaceus is a temperate mushroom but is now being cultivated in tropical Malaysia. In this study, we investigated the activity of aqueous extract of H. erinaceus fresh fruiting bodies in promoting functional recovery following an axonotmetic peroneal nerve injury in adult female Sprague-Dawley rats by daily oral administration. The aim was to investigate the possible use of this mushroom in the treatment of injured nerve. Functional recovery was assessed in behavioral experiment by walking track analysis. Peroneal functional index (PFI) was determined before surgery and after surgery as rats showed signs of recovery. Histological examinations were performed on peroneal nerve by immunofluorescence staining and neuromuscular junction by combined silver-cholinesterase stain. Analysis of PFI indicated that return of hind limb function occurred earlier in rats of aqueous extract or mecobalamin (positive control) group compared to negative control group. Regeneration of axons and reinnervation of motor endplates in extensor digitorum longus muscle in rats of aqueous extract or mecobalamin group developed better than in negative control group. These data suggest that daily oral administration of aqueous extract of H. erinaceus fresh fruiting bodies could promote the regeneration of injured rat peroneal nerve in the early stage of recovery.

Analgesic and antineuropathic drugs acting through central cholinergic mechanisms

The role of muscarinic and nicotinic cholinergic receptors in analgesia and neuropathic pain relief is relatively unknown. This review describes how such drugs induce analgesia or alleviate neuropathic pain by acting on the central cholinergic system. Several pharmacological strategies are discussed which increase synthesis and release of acetylcholine (ACh) from cholinergic neurons. The effects of their acute and chronic administration are described. The pharmacological strategies which facilitate the physiological functions of the cholinergic system without altering the normal modulation of cholinergic signals are highlighted. It is proposed that full agonists of muscarinic or nicotinic receptors should be avoided. Their activation is too intense and un-physiological because neuronal signals are distorted when these receptors are constantly activated. Good results can be achieved by using agents that are able to a) increase ACh synthesis, b) partially inhibit cholinesterase activity c) selectively block the autoreceptor or heteroreceptor feedback mechanisms. Activation of M(1) subtype muscarinic receptors induces analgesia. Chronic stimulation of nicotinic (N(1)) receptors has neuronal protective effects. Recent experimental results indicate a relationship between repeated cholinergic stimulation and neurotrophic activation of the glial derived neurotrophic factor (GDNF) family. At least 9 patents covering novel chemicals for cholinergic system modulation and pain control are discussed.

Sciatic nerve regeneration by microporous nerve conduits seeded with glial cell line-derived neurotrophic factor or brain-derived neurotrophic factor gene transfected neural stem cells

Neurotrophic factors such as the glial cell line-derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor (BDNF) promote nerve cell survival and regeneration, but their efficacy in repairing a longer gap defect of rat sciatic nerve (15 mm) has not been established. In this study, two recombinant mammalian vectors containing either rat GDNF gene or BDNF gene were constructed and each was transfected into neural stem cells (NSCs). It was found that the transfection of GDNF or BDNF gene into NSCs led to significantly enhanced expression of GDNF or BDNF mRNA. The amount of GDNF or BDNF protein secreted from the transfected NSCs showed a 3.3-fold or 2.5-fold increase than that from nontransfected NSCs, respectively. The regeneration capacity of rat sciatic nerve in a poly(D,L-lactide) conduit seeded with GDNF or BDNF-transfected NSCs was evaluated by the histology, functional gait, and electrophysiology after 8 weeks of implantation. It was observed that the degree of myelination and the size of regenerated tissue in the conduits seeded with GDNF- and BDNF-transfected NSCs were higher than those seeded with the nontransfected NSCs. Conduits seeded with GDNF-transfected NSCs had the greatest number of blood vessels. The functional recovery assessed by the functional gait and electrophysiology was significantly improved for conduits seeded with GDNF or BDNF-transfected NSCs. It was concluded that the genetically modified NSCs may have potential applications in promoting nerve regeneration and functional recovery.

Construction of tissue engineered nerve grafts and their application in peripheral nerve regeneration

Surgical repair of severe peripheral nerve injuries represents not only a pressing medical need, but also a great clinical challenge. Autologous nerve grafting remains a golden standard for bridging an extended gap in transected nerves. The formidable limitations related to this approach, however, have evoked the development of tissue engineered nerve grafts as a promising alternative to autologous nerve grafts. A tissue engineered nerve graft is typically constructed through a combination of a neural scaffold and a variety of cellular and molecular components. The initial and basic structure of the neural scaffold that serves to provide mechanical guidance and optimal environment for nerve regeneration was a single hollow nerve guidance conduit. Later there have been several improvements to the basic structure, especially introduction of physical fillers into the lumen of a hollow nerve guidance conduit. Up to now, a diverse array of biomaterials, either of natural or of synthetic origin, together with well-defined fabrication techniques, has been employed to prepare neural scaffolds with different structures and properties. Meanwhile different types of support cells and/or growth factors have been incorporated into the neural scaffold, producing unique biochemical effects on nerve regeneration and function restoration. This review attempts to summarize different nerve grafts used for peripheral nerve repair, to highlight various basic components of tissue engineered nerve grafts in terms of their structures, features, and nerve regeneration-promoting actions, and finally to discuss current clinical applications and future perspectives of tissue engineered nerve grafts.

Distribution of glial cell line-derived neurotrophic factor receptor alpha-1 in the brain of adult zebrafish

Glial cell line-derived neurotrophic factor (GDNF) is a potent trophic factor for several types of neurons in the central and peripheral nervous systems. The biological activity of GDNF is mediated by a multicomponent receptor complex that includes a common transmembrane signaling component (the rearranged during transfection (RET) proto-oncogene product, a tyrosine kinase receptor) as well as a GDNF family receptor alpha (GFRalpha) subunit, a high-affinity glycosyl phosphatidylinositol (GPI)-linked binding element. Among the four known GFRalpha subunits, GFRalpha1 preferentially binds to GDNF. In zebrafish (Danio rerio) embryos, the expression of the GFRalpha1a and GFRalpha1b genes has been shown in primary motor neurons, the kidney, and the enteric nervous system. To examine the activity of GFRalpha in the adult brain of a lower vertebrate, we have investigated the localization of GFRalpha1a and GFRalpha1b mRNA and the GFRalpha1 protein in zebrafish. GFRalpha1a and GFRalpha1b transcripts were observed in brain extracts by reverse transcription-polymerase chain reaction. Whole-mount in-situ hybridization experiments revealed a wide distribution of GFRalpha1a and GFRalpha1b mRNAs in various regions of the adult zebrafish brain. These included the olfactory bulbs, dorsal and ventral telencephalic area (telencephalon), preoptic area, dorsal and ventral thalamus, posterior tuberculum and hypothalamus (diencephalon), optic tectum (mesencephalon), cerebellum, and medulla oblongata (rhombencephalon). Finally, expression patterns of the GFRalpha1 protein, detected immunohistochemically, correlated well with the mRNA expression and provided further insights into translational activity at the neuroanatomical level. In conclusion, the current study demonstrated that the presence of GFRalpha1 persists beyond the embryonic development of the zebrafish brain and, together with the GDNF ligand, is probably implicated in the brain physiology of an adult teleost fish.

Enhancement of regeneration with glia cell line-derived neurotrophic factor-transduced human amniotic fluid mesenchymal stem cells after sciatic nerve crush injury

OBJECT

Human amniotic fluid-derived mesenchymal stem cells (AFMSCs) have been shown to promote peripheral nerve regeneration, and the local delivery of neurotrophic factors may additionally enhance nerve regeneration capacity. The present study evaluates whether the transplantation of glia cell line-derived neurotrophic factor (GDNF)-modified human AFMSCs may enhance regeneration of sciatic nerve after a crush injury.

METHODS

Peripheral nerve injury was produced in Sprague-Dawley rats by crushing the left sciatic nerve using a vessel clamp. Either GDNF-modified human AFMSCs or human AFMSCs were embedded in Matrigel and delivered to the injured nerve. Motor function and electrophysiological studies were conducted after 1 and 4 weeks. Early or later nerve regeneration markers were used to evaluate nerve regeneration. The expression of GDNF in the transplanted human AFMSCs and GDNF-modified human AFMSCs was monitored at 7-day intervals.

RESULTS

Human AFMSCs were successfully transfected with adenovirus, and a significant amount of GDNF was detected in human AFMSCs or the culture medium supernatant. Increases in the sciatic nerve function index, the compound muscle action potential ratio, conduction latency, and muscle weight were found in the groups treated with human AFMSCs or GDNF-modified human AFMSCs. Importantly, the GDNF-modified human AFMSCs induced the greatest improvement. Expression of markers of early nerve regeneration, such as increased expression of neurofilament and BrdU and reduced Schwann cell apoptosis, as well as late regeneration markers, consisting of reduced vacuole counts, increased expression of Luxol fast blue and S100 protein, paralleled the results of motor function. The expression of GDNF in GDNF-modified human AFMSCs was demonstrated up to 4 weeks; however, the expression decreased over time.

CONCLUSIONS

The GDNF-modified human AFMSCs appeared to promote nerve regeneration. The consecutive expression of GDNF was demonstrated in GDNF-modified human AFMSCs up to 4 weeks. These findings support a nerve regeneration scenario involving cell transplantation with additional neurotrophic factor secretion.

A high-fat diet induces lower expression of retinoid receptors and their target genes GAP-43/neuromodulin and RC3/neurogranin in the rat brain

Numerous studies have reported an association between cognitive impairment in old age and nutritional factors, including dietary fat. Retinoic acid (RA) plays a central role in the maintenance of cognitive processes via its nuclear receptors (NR), retinoic acid receptor (RAR) and retinoid X receptor (RXR), and the control of target genes, e.g. the synaptic plasticity markers GAP-43/neuromodulin and RC3/neurogranin. Given the relationship between RA and the fatty acid signalling pathways mediated by their respective NR (RAR/RXR and PPAR), we investigated the effect of a high-fat diet (HFD) on (1) PUFA status in the plasma and brain, and (2) the expression of RA and fatty acid NR (RARbeta, RXRbetagamma and PPARdelta), and synaptic plasticity genes (GAP-43 and RC3), in young male Wistar rats. In the striatum of rats given a HFD for 8 weeks, real-time PCR (RT-PCR) revealed a decrease in mRNA levels of RARbeta ( - 14 %) and PPARdelta ( - 13 %) along with an increase in RXRbetagamma (+52 %). Concomitantly, RT-PCR and Western blot analysis revealed (1) a clear reduction in striatal mRNA and protein levels of RC3 ( - 24 and - 26 %, respectively) and GAP-43 ( - 10 and - 42 %, respectively), which was confirmed by in situ hybridisation, and (2) decreased hippocampal RC3 and GAP-43 protein levels (approximately 25 %). Additionally, HFD rats exhibited a significant decrease in plasma ( - 59 %) and brain ( - 6 %) n-3 PUFA content, mainly due to the loss of DHA. These results suggest that dietary fat induces neurobiological alterations by modulating the brain RA signalling pathway and n-3 PUFA content, which have been previously correlated with cognitive impairment.

Synergistic effects of NGF, CNTF and GDNF on functional recovery following sciatic nerve injury in rats

PURPOSE

To investigate the synergistic effects of nerve growth factor (NGF), ciliary neurotrophic factor (CNTF) and glia cell line-derived neurotrophic factor (GDNF) on survival and growth of sensory neurons and motoneurons, as well as on the functional recovery following sciatic nerve injury in rats.

METHODS

Experimental rats and neurons were randomized into 8 groups: NGF group, CNTF group, GDNF group, NGF+CNTF group, CNTF+GDNF group, NGF+GDNF group, NGF+CNTF+GDNF group and control group. Each group received local intramuscular injection of indicated NTFs according to the treatment protocol. The sciatic nerve function index (SFI), nerve conduction velocity and wet weight recovery rate of gastrocnemius muscle were tested to evaluate the functional recovery in vivo. A 2 (presence or absence of NGF) x 2 (presence or absence of CNTF) x 2 (presence or absence of GDNF) analysis of variance (ANOVA) was used to examine the main effects and interactions among NGF, CNTF and GDNF, and one-way ANOVA was calculated for multiple comparison.

RESULTS

NGF and GDNF acted significantly on the survival of sensory neuron and motoneuron, respectively. CNTF was a dominant factor promoting cell body development, and GDNF had the most powerful effect on neurite outgrowth and elongation of sensory neurons and motoneurons. Combined administration of the three factors resulted in optimal functional recovery following sciatic nerve injury in rats.

CONCLUSIONS

It is demonstrated that differential and complementary biological effects of various neurotrophic factors contribute to synergistic promotion of nervous function recovery.

Neurotrophic actions of bone marrow stromal cells on primary culture of dorsal root ganglion tissues and neurons

Application of adult bone marrow stromal cells (BMSCs) provides therapeutic benefits to the treatment of neurological insults. The aim of this study was to explore the potential of nonhematopoietic BMSCs to produce soluble factors and stimulate signaling pathways in neurons that mediate trophic effects. A combination of enzyme-linked immunosorbent assay and two-dimensional gel electrophoresis coupled with mass spectrometry showed that the BMSCs released into the culture medium an array of soluble factors such as nerve growth factor, brain-derived neurotrophic factor, basic fibroblast growth factor, and ciliary neurotrophic factor, which have been shown to exhibit potent neurotrophic effects on neural cells. Immunochemistry, cell viability assay, and quantitative real-time RT-PCR collectively showed that neurite outgrowth and neurogenesis in cultured rat dorsal root ganglion (DRG) explants and neurons were enhanced after they were cocultured with rat BMSCs. Western blot analysis revealed that BMSC-conditioned medium activated phosphorylation of mitogen-activated protein kinase/extracellular signal-regulated protein kinase and/or phosphoinositide 3-kinase/serine/threonine kinase (PI3K/Akt) in primary culture of rat DRG neurons, which suggested that BMSCs trigger endogenous survival signaling pathways in neurons through their secreted soluble factors. Our data help to elucidate the mechanisms by which BMSCs function as a cell therapy agent in peripheral nerve regeneration.

GDNF-enhanced axonal regeneration and myelination following spinal cord injury is mediated by primary effects on neurons

We previously demonstrated that coadministration of glial cell line-derived neurotrophic factor (GDNF) with grafts of Schwann cells (SCs) enhanced axonal regeneration and remyelination following spinal cord injury (SCI). However, the cellular target through which GDNF mediates such actions was unclear. Here, we report that GDNF enhanced both the number and caliber of regenerated axons in vivo and increased neurite outgrowth of dorsal root ganglion neurons (DRGN) in vitro, suggesting that GDNF has a direct effect on neurons. In SC-DRGN coculture, GDNF significantly increased the number of myelin sheaths produced by SCs. GDNF treatment had no effect on the proliferation of isolated SCs but enhanced the proliferation of SCs already in contact with axons. GDNF increased the expression of the 140 kDa neural cell adhesion molecule (NCAM) in isolated SCs but not their expression of the adhesion molecule L1 or the secretion of the neurotrophins NGF, NT3, or BDNF. Overall, these results support the hypothesis that GDNF-enhanced axonal regeneration and SC myelination is mediated mainly through a direct effect of GDNF on neurons. They also suggest that the combination of GDNF administration and SC transplantation may represent an effective strategy to promote axonal regeneration and myelin formation after injury in the spinal cord.

Delivery of adipose-derived precursor cells for peripheral nerve repair

To test the hypothesis that the transplantation of adipose precursor cells (APCs) improves nerve regeneration and functional recovery, human APCs were transplanted into the lumen of a nerve guide in a 6-mm unilateral sciatic nerve defect in athymic rats. The three control groups for the study were biodegradable, polycaprolactone-based nerve conduit without APCs, autograft, and empty defect. Behavioral tests were performed every 3 weeks, and the sciatic functional index (SFI) was calculated based on measurements from the hindlimb prints. After 12 weeks, the nerve as well as right and left gastrocnemius muscles were removed and preserved for histological evaluation. Full regeneration of the sciatic nerve occurred on the rats that received the autograft, the guide, and the guide with APCs; no regeneration was observed on any of the rats in which the defect was left untreated (empty defect). APCs survived transplantation for up to 12 weeks in the injured peripheral nerve. No significant colocalization was observed between the immunostaining for glial fibrillary protein and anti-human lamin A/C, implying that the APCs did not differentiate into Schwann cells at the site of injury. In comparison with the rats with untreated defects, a decrease in muscle atrophy was observed on those rats that received the autograft and the guide with cells as indicated by the gastrocnemius muscle weight ratio and the muscle fiber ratio. Significant differences in SFI were observed 3 weeks postinjury between the rats in which the guide was left empty and those that received the guide with APCs; however, these differences were not observed at 12 weeks. The transplantation of APCs promoted the formation of a more robust nerve as evidenced by the results from the cross-sectional area of regenerated nerve, and the transplantation of APCs produced a decrease in muscle atrophy.

Novel cell-based therapeutic strategy for ischemic colitis with use of bone marrow-derived mononuclear cells in rats

PURPOSE

Ischemic colitis is a common disorder of the large bowel. In the clinical setting, some patients suffer refractory ischemic colitis regardless of conventional treatment. Meanwhile, bone marrow-derived mononuclear cells are known to accelerate neovascularization. The purpose of this study was to verify the effects of bone marrow-derived mononuclear cells on ischemic colitis in rats.

METHODS

An ischemic colitis model was established by partial obstruction of the rectum and interruption of the marginal vessel in the immunodeficient rat. Bone marrow-derived mononuclear cells from a Wistar rat were injected into the ischemic area one day later than the ischemia (Group MNC). As a control, phosphate-buffered saline was injected in the same manner (Group PBS). Seven days after cell transplantation, each rat was evaluated for histology and colic motility.

RESULTS

Compared with Group PBS scores, the Group MNC macroscopic and microscopic colitis severity scores were significantly reduced. Moreover, the density of the capillary and myenteric plexus was significantly higher in Group MNC than in Group PBS (9.55 +/- 0.74 vs. 4.61 +/- 0.22, respectively, P < 0.01; and 8.57 +/- 0.41 vs. 5.93 +/- 0.31, respectively, P < 0.02). The whole-gut transit time was significantly shorter in Group MNC compared with Group PBS (472.7 +/- 17.6 vs. 584.8 +/- 24.0 minutes, respectively, P < 0.01). Transplanted cells were detected in all layers of the intestinal wall; however, these cells did not differentiate into vascular or neural cells.

CONCLUSIONS

These results suggest that transplantation of bone marrow-derived mononuclear cells might enhance not only tissue regeneration and angiogenesis but also neurogenesis. Transplantation of bone marrow-derived mononuclear cells may be a useful therapeutic strategy for ischemic colitis.

Lumbricus extract promotes the regeneration of injured peripheral nerve in rats

BACKGROUND

Earthworms regenerate amputated parts of their body if the nervous system is intact. Lumbricus is one traditional Chinese medicine (TCM), which has been used in China to promote nerve function for hundreds of years.

AIM OF THE STUDY

To investigate the beneficial effect of lumbricus extract on peripheral nerve regeneration in rats.

MATERIALS AND METHODS

Nerve function was surgically impaired in Sprague-Dawley (SD) rats by clamping of the left sciatic nerve. The sham-operated group (surgery but no sciatic nerve clamping), control group, and treatment group were treated with 2 ml 0.9% NaCl, 0.9% NaCl, and lumbricus extract (1g/ml), respectively. Treatments were administered once daily after the operation for 6 weeks. During this period, motor function was monitored by walking track analysis, conduction function of injured sciatic nerve was monitored by electrophysiology, and regeneration of myelinated nerve was assessed by immunohistochemistry.

RESULTS

(1) For nerve function index value, treatment group is higher than control group. (2) For conduction velocity of injured sciatic nerve, treatment group is higher than control group at week 3 and 6. (3) For the number of regenerated myelinated nerve fibers, treatment group is higher than control group at week 2 and 6.

CONCLUSIONS

Lumbricus extract appears to enhance sciatic nerve regeneration and function recovery following injury, suggesting the clinical potential of lumbricus extract on the treatment of peripheral nerve injury in humans.

Expression of the regeneration-associated protein SPRR1A in primary sensory neurons and spinal cord of the adult mouse following peripheral and central injury

Small proline-rich repeat protein 1A (SPRR1A) is expressed in dorsal root ganglion (DRG) neurons following peripheral nerve injury but it is not known whether SPRR1A is differentially expressed following injury to peripheral versus central DRG projections and a detailed characterization of expression in sensory neuron subpopulations and spinal cord has not been performed. Here we use immunocytochemical techniques to characterize SPRR1A expression following sciatic nerve, dorsal root, and dorsal column injury in adult mice. SPRR1A was not detected in naïve spinal cord, DRG, or peripheral nerves and there was minimal expression following injury to the centrally projecting branches of DRG neurons. However, following peripheral (sciatic) nerve injury, intense SPRR1A immunoreactivity was observed in the dorsal horn and motoneurons of the spinal cord, in L4/5 DRG neurons, and in the injured nerve. A time-course study comparing expression following sciatic nerve crush and transection revealed maximum SPRR1A levels at day 7 in both models. However, while SPRR1A was downregulated to baseline by 30 days postlesion following crush injury, it remained elevated 30 days after transection. Cell-size and double-labeling studies revealed that SPRR1A was expressed by DRG cells of all sizes and colocalized with classical markers of DRG subpopulations and their primary afferent terminals. High coexpression of SPRR1A with activating transcription factor-3 and growth-associated protein-43 was observed, indicating that it is expressed by injured and regenerating neurons. This study supports the hypothesis that SPRR1A is a regeneration-associated gene and that SPRR1A provides a valuable marker to assess the regenerative potential of injured neurons.

Histopathological analysis of gangliosides use in peripheral nerve regeneration after axonotmesis in rats

PURPOSE: To analyze the action of gangliosides in peripheral nerve regeneration in the sciatic nerve of the rat. METHODS: The sample was composed of 96 male Wistar rats. The animals were anaesthetized and, after identification of the anaesthesic plane, an incision was made in the posterior region of the thigh, followed by skin and muscle divulsion. The right sciatic nerve was isolated and compressed for 2 minutes. Continuous suture of the skin was performed. The animals were randomly divided into two groups: the experimental group (EG), which received subcutaneous injection of gangliosides, and the control group (CG), which received saline solution (0.9%) to mimic the effects of drug administration. RESULTS: No differences were observed between the experimental and control groups evaluated on the eighth day of observation. At 15 and 30 days the EG showed an decrease in Schwann cell activity and an apparent improvement in fibre organization; at 60 days, there was a slight presence of Schwann cells in the endoneural space and the fibres were organized, indicating nerve regeneration. At 15 and 30 days, the level of cell reaction in the CG had diminished, but there were many cells with cytoplasm in activity and in mitosis; at 60 days, hyperplastic Schwann cells and mitotic activity were again observed, as well as nerve regeneration, but to a lesser extent than in the EG. CONCLUSION: The administration of exogenous gangliosides seems to improve nerve regeneration.

Chronic nerve compression injury induces a phenotypic switch of neurons within the dorsal root ganglia

Chronic nerve compression (CNC) injury initiates a series of pathological changes within the peripheral nerve at the site of injury. However, to date, little work has been performed to explore neuronal cell body responses to CNC injury. Here we show a preferential upregulation of growth-associated protein-43 (GAP-43) and enhanced Fluoro Ruby uptake by the small-diameter calcitonin gene-related protein (CGRP) and isolectin B4 (IB4)-positive neurons in the L4 and L5 ipsilateral dorsal root ganglion (DRG) 2 weeks and 1 month post injury. Furthermore, L4 and L5 DRGs ipsilateral to CNC injury also demonstrated a marked reduction in neurofilament 200 (NF-200) neurons and an increase in CGRP and IB4 neurons at early time points. All numbers normalized to values comparable to those of control when the DRG was evaluated 6 months post injury. Quantification of glial-derived neurotrophic factor (GDNF) protein revealed an upregulation in L4 and L5 DRG followed by a return to baseline values at later stages following injury. Upregulation of GDNF expression by Schwann cells was also readily apparent with both immunohistochemistry and Western blot analysis of 1 month compressed sciatic nerve specimens. Thus, CNC induces a phenotypic change in the DRG that appears to be temporally associated with increases in GDNF protein expression at and near the site of the compression injury in the nerve.

Post-injury regeneration in rat sciatic nerve facilitated by neurotrophic factors secreted by amniotic fluid mesenchymal stem cells

Amniotic fluid mesenchymal stem cells have the ability to secrete neurotrophic factors that are able to promote neuron survival in vitro. The purpose of this study was to evaluate the effects of neurotrophic factors secreted by rat amniotic fluid mesenchymal stem cells on regeneration of sciatic nerve after crush injury. Fifty Sprague-Dawley rats weighing 250-300 g were used. The left sciatic nerve was crushed with a vessel clamp. Rat amniotic fluid mesenchymal stem cells embedded in fibrin glue were delivered to the injured nerve. Enzyme-linked immunosorbent assay (ELISA) and immunocytochemistry were used to detect neurotrophic factors secreted by the amniotic fluid mesenchymal stem cells. Nerve regeneration was assessed by motor function, electrophysiology, histology, and immunocytochemistry studies. Positive CD29/44, and negative CD11b/45, as well as high levels of expression of brain-derived neurotrophic factor, glia cell line-derived neurotrophic factor, ciliary neurotrophic factor (CNTF), nerve growth factor, and neurotrophin-3 (NT-3) were demonstrated in amniotic fluid mesenchymal stem cells. Motor function recovery, the compound muscle action potential, and nerve conduction latency showed significant improvement in rats treated with amniotic fluid mesenchymal stem cells. ELISA measurement in retrieved nerves displayed statistically significant elevation of CNTF and NT-3. The immunocytochemical studies demonstrated positive staining for NT-3 and CNTF in transplanted cells. The histology and immunocytochemistry studies revealed less fibrosis and a high level of expression of S-100 and glial fibrillary acid protein at the crush site. Rat amniotic fluid mesenchymal stem cells may facilitate regeneration in the sciatic nerve after crush injury. The increased nerve regeneration found in this study may be due to the neurotrophic factors secreted by amniotic fluid mesenchymal stem cells.

Variations in glial cell line-derived neurotrophic factor release from biodegradable nerve conduits modify the rate of functional motor recovery after rat primary nerve repairs

Accelerating axonal regeneration to shorten the delay of reinnervation and improve functional recovery after a peripheral nerve lesion is a clinical demand and an experimental challenge. We developed a resorbable nerve conduit (NC) for controlled release of glial cell line-derived neurotrophic factor (GDNF) with the aim of assessing motor functional recovery according to the release kinetics of this factor in a short gap model. Different types of resorbable NCs were manufactured from a collagen tube and multiple coating layers of poly(lactide-coglycolide), varying in poly(lactide-coglycolide) type and coating thickness to afford three distinct release kinetics of the neurotrophic factor. GDNF release was quantified in vitro. End-to-end suture and GDNF-free NC served as controls. Thirty-five Wistar rats underwent surgery. Motor recovery was followed from 1 to 12 weeks after surgery by video gait analysis. Morphometrical data were obtained at mid-tube level and distal to the NC. NCs were completely resorbed within 3 months with minimal inflammation. GDNF induced a threefold overgrowth of fibers at mid-tube level. However, the number of fibers was similar in the distal segment of all groups. The speed of recovery was inversely proportional to the number of fibers at the NC level but the level of recovery was similar for all groups at 3 months. The resorbable conduits proved their ability to modulate axonal regrowth through controlled release of GDNF. In relation to the dose delivered, GDNF strikingly multiplied the number of myelinated fibers within the NC but this increase was not positively correlated with the return of motor function in this model.