Repair Of Sciatic Nerve Defects Research Articles

Repair of Sciatic Nerve Defect in Rats With Acellular Nerve Allograft Carrying Vascular Endothelial Cells.

Acellular nerve allografts (ANAs) were developed to replace the autologous nerve grafts (ANGs) to fill the peripheral nerve defects. Poor vascularization relative to ANGs has been a limitation of application of ANAs. A total of 60 female Sprague-Dawley rats were assigned 3 groups. The rats in A group received ANGs, the rats in B group received ANAs, and the rats in C group were transplanted with ANA carrying endothelial cells (ANA + ECs). In the 1st, 2nd, 4th, and 12th postoperative weeks, 5 rats were selected from each group for evaluating sciatic function index (SFI), electrophysiology, maximum tetanic force recovery rate, tibialis anterior muscle weights recovery rate, and microvessel density. In the 12th postoperative week, the nerves were harvested and stained with toluidine blue and observed under an electron microscope to compare nerve fibers, myelin width, and G-ratio. All the rats survived. In the first and second postoperative weeks, more microvessels were found in the ANA + EC group. In the 12th postoperative week, the nerve fibers were more numerous, and G-ratio was smaller in the C group compared with the B group. The compound muscle action potential and maximum tetanic force recovery rate in the tibialis anterior muscle in the C group were better than those in the B group in the 12th postoperative week. The A group showed better performances in electrophysiology, maximum tetanic force, muscle wet weight, and nerve regeneration. ANA + ECs can promote early angiogenesis, promoting nerve regeneration and neurological function recovery.

The role of Gel-Ppy-modified nerve conduit on the repair of sciatic nerve defect in rat model.

The serious clinical challenge of peripheral nerve injury (PNI) is nerve regeneration. Nerve conduit represents a promising strategy to contribute to nerve regeneration by bridging injured nerve gaps. However, due to a unique microenvironment of nerve tissue, autologous nerves have not been substituted by nerve conduit. Nerve regeneration after nerve conduit implantation depends on many factors, such as conductivity and biocompatibility. Therefore, Gelatin (Gel) with biocompatibility and polypyrrole (Ppy) with conductivity is highly concerned. In this paper, Gel-Ppy modified nerve conduit was fabricated with great biocompatibility and conductivity to evaluate its properties of enhancing nerve regeneration in vivo and in vitro. The proliferation of Schwann cells on Gel-Ppy modified nerve conduit was remarkably increased. Consistent with in vitro results, the Gel-Ppy nerve conduit could contribute to the regeneration of Schwann cell in vivo. The axon diameters and myelin sheath thickness were also enhanced, resulting in the amelioration of muscle atrophy, nerve conduction, and motor function recovery. To explain this interesting phenomenon, western blot results indicated that the Gel-Ppy conduit facilitated nerve regeneration via upregulating the Rap1 pathway to induce neurite outgrowth. Therefore, the above results demonstrated that Gel-Ppy modified nerve conduit could provide an acceptable microenvironment for nerve regeneration and be popularized as a novel therapeutic strategy of PNI.

Combining chitin biological conduits with small autogenous nerves and platelet-rich plasma for the repair of sciatic nerve defects in rats.

AimsPeripheral nerve defects are often difficult to recover from, and there is no optimal repair method. Therefore, it is important to explore new methods of repairing peripheral nerve defects. This study explored the efficacy of nerve grafts constructed from chitin biological conduits combined with small autogenous nerves (SANs) and platelet‐rich plasma (PRP) for repairing 10‐mm sciatic nerve defects in rats.MethodsTo prepare 10‐mm sciatic nerve defects, SANs were first harvested and PRP was extracted. The nerve grafts consisted of chitin biological conduits combined with SAN and PRP, and were used to repair rat sciatic nerve defects. These examinations, including measurements of axon growth efficiency, a gait analysis, electrophysiological tests, counts of regenerated myelinated fibers and observations of their morphology, histological evaluation of the gastrocnemius muscle, retrograde tracing with Fluor‐Gold (FG), and motor endplates (MEPs) distribution analysis, were conducted to evaluate the repair status.ResultsTwo weeks after nerve transplantation, the rate and number of regenerated axons in the PRP‐SAN group improved compared with those in the PRP, SAN, and Hollow groups. The PRP‐SAN group exhibited better recovery in terms of the sciatic functional index value, composite action potential intensity, myelinated nerve fiber density, myelin sheath thickness, and gastrectomy tissue at 12 weeks after transplantation, compared with the PRP and SAN groups. The results of FG retrograde tracing and MEPs analyses showed that numbers of FG‐positive sensory neurons and motor neurons as well as MEPs distribution density were higher in the PRP‐SAN group than in the PRP or SAN group.ConclusionsNerve grafts comprising chitin biological conduits combined with SANs and PRP significantly improved the repair of 10‐mm sciatic nerve defects in rats and may have therapeutic potential for repairing peripheral nerve defects in future applications.

IL-1β-Activated Schwann Cells and Human Hair Keratin Compound Culture to Construct Artificial Nerve Bridging for Repair of Sciatic Nerve Defects in Sprague-Dawley Rats

Human hair keratin (HHK) and interleukin (IL)-1β-Activated Schwann Cells and Human Hair Keratin Compound Culture to Construct Artificial Nerve Bridging for Repair of Sciatic Nerve Defects in Sprague-Dawley Rats-activated Schwann cells were combined to construct artificial nerves. End-to-end anastomosis of nerve defects could repair the sciatic nerve defect in Sprague-Dawley (SD) rats. In this study, a neural injury animal model was used to simulate the repair process of artificial nerves to repair peripheral nerve injury. We found that HHK can act as a biodegradable scaffold to induce Schwann cells to dedifferentiate and then activate macrophages through proliferation and secretion of macrophage migration inhibitory factor and other active substances. A large number of macrophages appeared in the nerve terminal after peripheral nerve injury, such as phagocytic and scavenging degeneration of axons and the myelin sheath. Peripheral nerve damage was also caused by secreting related factors of neurons and other non-neuronal cells, which are involved in a complex relationship. Among them, IL-1β-Activated Schwann Cells and Human Hair Keratin Compound Culture to Construct Artificial Nerve Bridging for Repair of Sciatic Nerve Defects in Sprague-Dawley Rats and other active substances can induce Schwann cells to divide, proliferate, and differentiate, showing high expression of nerve growth factor (NGF) and other active substances, which can further activate macrophages and Schwann cells and promote nerve regeneration. This study describes HHK preparation and advantages, morphological changes of Schwann cells and macrophages in the process of nerve repair, expression of main active substances, and the effect of HHK artificial nerve implantation on animal nerve defect repair. We reveal a related mechanism of nerve repair. Funding Statement: The study was supported by the Medical Technique and Research of Guangdong Province, China (grant number A2017463); China Postdoctoral Science Foundation, China (grant number 2017M613432); Military medical science and technology youth training program (grant number 19QNP005) and Guangdong medical science and technology research foundation (grant number 2016102511210492). Declaration of Interests: The authors have declared that no competing interests exists. Ethical Approval Statement: The experimental protocols were reviewed and approved by the Institutional Animal Care and Use Committee of the Southern Medical University, Guangzhou, China.

Repair of sciatic nerve defects with VPA/PRGD conduits containing adipose-derived stem cells in a rat model

Objective To observe enhancing effect of nerve regeneration on peripheral nerve defect models bridged by VPA/PRGD conduit combined with adipose derived mesenchymal stem cells (ADSCs ). Methods From February, 2013 to August, 2014, the hollow nerve scaffolds were constructed by PRGD and VPA. The activity of AD-SCs proliferation was tested through the method of CCK-8. Moreover, the effect of VPA/PRGD conduit combined with ADSCs on peripheral nerve regeneration was evaluated, as well as recovery of motor function following sciatic nerve resection in rats. A 10 mm sciatic nerve deficit was created in a rat model and bridged by VPA/PRGD conduit combined with ADSCs (group A), VPA/PRGD conduit (group B) and autograft (group C) respectively. The results was analyzed by the method of group t-test of SPSS 19.0. Results At 3 d, 6 d, 9 d, CCK-8 test showed that the OD value of groups VPA/PRGD and control has no significance (P > 0.05 ). At 12 weeks after surgery, the numbers of regenerated nerve proximal to the tube of group A (268±7.48), group B (269±6.86) and group C (271±7.55), had no significant difference between two groups (P > 0.05). The numbers of regenerated nerve in the tube of group A (257±6.19) and group C (260±5.60) were significantly higher than those of group B (229±5.08) (P 0.05). The numbers of regenerated nerve distal to the tube of group A (246± 5.89) and group C (247±5.02) were significantly higher than those of group B (214±7.55) (P 0.05 ). Conclusion These promising results illustrate that this novel VPA/PRGD combined with ADSCs conduit can obviously facilitate the regeneration of injured nerve in rats. Key words: Nerve regeneration; Tissue engineering; Valproic acid; Adipose derived mesenehymal stem cell

Tissue-engineered nerve graft with tetramethylpyrazine for repair of sciatic nerve defects in rats

A tissue-engineered nerve with tetramethylpyrazine (TMP) was repaired for sciatic nerve defects in rats. A total of 55 adult Sprague Dawley (SD) rats were classified into 4 groups, with 15 rats in each of groups A, B, and C as well as 10 rats in group D. About 1.5cm of a sciatic nerve of the right hind limb located 0.5cm below the inferior margin of the piriformis was resected to form the defects. Four types of nerve grafts used for bridging nerve defects in the SD rats corresponded to the 4 groups: tissue-engineered nerves with TMP in group A, tissue-engineered nerves without TMP in group B, acellular nerve grafts (ANGs) in group C, and autologous nerves in group D. Twelve weeks post-surgery, the sciatic functional index, nerve conduction velocity, and gastrocnemius wet weight of groups A and D were higher than those of groups B and C (P<0.05). Results of fluorescence microscopy and histological staining indicated that group A performed better than groups B and C (P<0.05). Similarly, the number of horseradish peroxidase-labeled positive cells was significantly larger in group A than in groups B and C. Regenerative nerve fibers were abundant in group A and consisted mainly of myelinated nerve fibers, which were better than those in groups B and C (P<0.05). The study demonstrated that tissue-engineered nerves constructed by ANGs seeded with neural stem cells and combined with TMP can effectively repair sciatic nerve defects in rats.

Decellularized nerve xenograft combined with lycium barbarum polysaccharide for repair of sciatic nerve defect in rats

Objective To explore the effect of lycium barbarum polysaccharide (LBP) and decellularized nerve xenograft combination on nerve regeneration and recovery in repairing rat sciatic nerve defects. Methods Xenogeneic acellular nerve scaffolds were prepared by chemical extraction of tibial nerves from rabbits. A 10 mm left sciatic nerve defect model was created in 90 healthy adult Sprague-Dawley rats who were randomly divided into 5 groups: blank group (n=18), model group (n=18), LBP group (n=18), scaffold group (n=18), LBP and scaffold combination group (n=18). Two weeks after model creation. The sciatic nerve defect in LBP, scaffold and combination groups was repaired either by LBP, by scaffold, or by the LBP xenograft combination. After the second surgery, the rats survived for 4, 8 and 12 weeks, respectively. Gross observation of the scaffold, nerve conduction study to measure sciatic nerve motor nerve conduction velocity (MNCV), and neuromorphometry analysis of the graft were carried out at these three time points. Results Neuroma formation at the proximal nerve end was observed in the model group and LBP group. Adhesion of nerve ends to the surrounding tissue was more severe in the model group than in the LBP group. The sizes of the nerve grafts in the scaffold group and combination group were comparable. Proficient vascularization on the surface of these grafts was seen. There was only slight adhesion to the surrounding tissue. The regenerated nerve fibers in the combination group were denser and better oriented. Motor nerve conduction velocity recovery and the number of myelinated nerve fibers in the grafts were measured at 12 weeks postoperatively for blank, model, LBP, scaffold and combination groups, respectively. The differences among the groups were significant (P<0.05). Conclusion The combination of LBP and xenogeneic acellular nerve scaffold enhances peripheral nerve regeneration and recovery when used to repair nerve defects. Key words: Sciatic nerve; Nerve regeneration; Xenogeneic acellular nerve scaffold; Lycium barbarum polysaccharide

Allograft pretreatment for the repair of sciatic nerve defects: green tea polyphenols versus radiation.

Pretreatment of nerve allografts by exposure to irradiation or green tea polyphenols can eliminate neuroimmunogenicity, inhibit early immunological rejection, encourage nerve regeneration and functional recovery, improve tissue preservation, and minimize postoperative infection. In the present study, we investigate which intervention achieves better results. We produced a 1.0 cm sciatic nerve defect in rats, and divided the rats into four treatment groups: autograft, fresh nerve allograft, green tea polyphenol-pretreated (1 mg/mL, 4°C) nerve allograft, and irradiation-pretreated nerve allograft (26.39 Gy/min for 12 hours; total 19 kGy). The animals were observed, and sciatic nerve electrophysiology, histology, and transmission electron microscopy were carried out at 6 and 12 weeks after grafting. The circumference and structure of the transplanted nerve in rats that received autografts or green tea polyphenol-pretreated nerve allografts were similar to those of the host sciatic nerve. Compared with the groups that received fresh or irradiation-pretreated nerve allografts, motor nerve conduction velocity in the autograft and fresh nerve allograft groups was greater, more neurites grew into the allografts, Schwann cell proliferation was evident, and a large number of new blood vessels was observed; in addition, massive myelinated nerve fibers formed, and abundant microfilaments and microtubules were present in the axoplasm. Our findings indicate that nerve allografts pretreated by green tea polyphenols are equivalent to transplanting autologous nerves in the repair of sciatic nerve defects, and promote nerve regeneration. Pretreatment using green tea polyphenols is better than pretreatment with irradiation.

Gait Cycle Analysis

Video-assisted gait kinetics analysis has been a sensitive method to assess rat sciatic nerve function after injury and repair. However, in conduit repair of sciatic nerve defects, previously reported kinematic measurements failed to be a sensitive indicator because of the inferior recovery and inevitable joint contracture. This study aimed to explore the role of physiotherapy in mitigating joint contracture and to seek motion analysis indices that can sensitively reflect motor function. Data were collected from 26 rats that underwent sciatic nerve transection and conduit repair. Regular postoperative physiotherapy was applied. Parameters regarding step length, phase duration, and ankle angle were acquired and analyzed from video recording of gait kinetics preoperatively and at regular postoperative intervals. Stride length ratio (step length of uninjured foot/step length of injured foot), percent swing of the normal paw (percentage of the total stride duration when the uninjured paw is in the air), propulsion angle (toe-off angle subtracted by midstance angle), and clearance angle (ankle angle change from toe off to midswing) decreased postoperatively comparing with baseline values. The gradual recovery of these measurements had a strong correlation with the post-nerve repair time course. Ankle joint contracture persisted despite rigorous physiotherapy. Parameters acquired from a 2-dimensional motion analysis system, that is, stride length ratio, percent swing of the normal paw, propulsion angle, and clearance angle, could sensitively reflect nerve function impairment and recovery in the rat sciatic nerve conduit repair model despite the existence of joint contractures.

Dorsal root ganglion-derived Schwann cells combined with poly(lactic-co-glycolic acid)/chitosan conduits for the repair of sciatic nerve defects in rats.

Schwann cells, nerve regeneration promoters in peripheral nerve tissue engineering, can be used to repair both the peripheral and central nervous systems. However, isolation and purification of Schwann cells are complicated by contamination with fibroblasts. Current reported measures are mainly limited by either high cost or complicated procedures with low cell yields or purity. In this study, we collected dorsal root ganglia from neonatal rats from which we obtained highly purified Schwann cells using serum-free melanocyte culture medium. The purity of Schwann cells (> 95%) using our method was higher than that using standard medium containing fetal bovine serum. The obtained Schwann cells were implanted into poly(lactic-co-glycolic acid)/chitosan conduits to repair 10-mm sciatic nerve defects in rats. Results showed that axonal diameter and area were significantly increased and motor functions were obviously improved in the rat sciatic nerve tissue. Experimental findings suggest that serum-free melanocyte culture medium is conducive to purify Schwann cells and poly(lactic-co-glycolic acid)/chitosan nerve conduits combined with Schwann cells contribute to restore sciatic nerve defects.

Transplantation of collagen-chitosan nerve conduits filled with glial cell line-derived neurotrophic factor gene-modified schwann cells for the repair of sciatic nerve defect

To explore the effects of the transplantation of collagen-chitosan nerve scaffold containing glial cell line-derived neurotrophic factor(GDNF)gene modified schwann cells on the recovery of long-distance sciatic nerve defect. The rat models of 8 mm long-distance sciatic nerve defect were established and divided into three groups, with 6 rats in each group. In GDNF-Sch group, the defect was repaired by GDNF modified Schwann cells combined with collagen-chitosan nerve scaffold. In Sch group, the defect was repaired by Schwann cells combined with collagen-chitosan nerve scaffold. In the control group, the defect was repaired by autologous nerve graft. Sciatic function index(SFI)was detected 3, 6, and 12 weeks after surgery. After 12 weeks, the tibialis anterior muscle wet weight, electrophysiology, and regenerated nerve morphology were detected. The SFI in the operated side significantly differed among these three groups after 6 and 12 weeks(P<0.05). Along with prolonged treatment, the GDNF-Sch group had similar SFI recovery with the control group but significantly better SFI recovery than Sch group. After 12 weeks, the sensory nerve conduction velocity in the GDNF-Sch and Sch group was not significantly different(P>0.05)but was significantly lower than that in the control group(P<0.05). Both the GDNF-Sch group and Sch group had significantly lower sensory nerve amplitude comparing with the control group(P<0.05), whereas that in the GDNF-Sch group was significantly higher than that in the Sch group(P<0.05). GDNF-Sch group and the control group had significantly higher motor nerve conduction velocity and amplitude than Sch group(P<0.05), while no such statistically significant difference was seen between the two groups(P >0.05). After 12 weeks, the wet weight of the bridging side of the tibial muscle in the control group, Sch group, and GDNF-Sch group was(0.360±0.020), (0.250±0.018), and(0.310±0.025)g, which were significantly lower than the control side [(0.440±0.031), (0.420±0.024), and(0.430±0.027)g, respectively(P<0.05)]. Muscle wet weight in bridge side of GDNF-Sch group and the control group were significantly higher than in Sch group(P<0.05), but it was not significantly different between the GDNF-Sch group and the control group(P>0.05). Transplantation of collagen-chitosan nerve scaffold containing GDNF gene modified Schwann cells can remarkably facilitate sciatic nerve defect recovery, with a milimar effectiveness as autologous nerve grafting.

Repair of sciatic nerve defects using tissue engineered nerves.

In this study, we constructed tissue-engineered nerves with acellular nerve allografts in Sprague-Dawley rats, which were prepared using chemical detergents-enzymatic digestion and mechanical methods, in combination with bone marrow mesenchymal stem cells of Wistar rats cultured in vitro, to repair 15 mm sciatic bone defects in Wistar rats. At postoperative 12 weeks, electrophysiological detection results showed that the conduction velocity of regenerated nerve after repair with tissue-engineered nerves was similar to that after autologous nerve grafting, and was higher than that after repair with acellular nerve allografts. Immunohistochemical staining revealed that motor endplates with acetylcholinesterase-positive nerve fibers were orderly arranged in the middle and superior parts of the gastrocnemius muscle; regenerated nerve tracts and sprouted branches were connected with motor endplates, as shown by acetylcholinesterase histochemistry combined with silver staining. The wet weight ratio of the tibialis anterior muscle at the affected contralateral hind limb was similar to the sciatic nerve after repair with autologous nerve grafts, and higher than that after repair with acellular nerve allografts. The hind limb motor function at the affected side was significantly improved, indicating that acellular nerve allografts combined with bone marrow mesenchymal stem cell bridging could promote functional recovery of rats with sciatic nerve defects.

Nanoparticles carrying neurotrophin-3-modified Schwann cells promote repair of sciatic nerve defects.

Schwann cells and neurotrophin-3 play an important role in neural regeneration, but the secretion of neurotrophin-3 from Schwann cells is limited, and exogenous neurotrophin-3 is inactived easily in vivo. In this study, we have transfected neurotrophin-3 into Schwann cells cultured in vitro using nanoparticle liposomes. Results showed that neurotrophin-3 was successfully transfected into Schwann cells, where it was expressed effectively and steadily. A composite of Schwann cells transfected with neurotrophin-3 and poly(lactic-co-glycolic acid) biodegradable conduits was transplanted into rats to repair 10-mm sciatic nerve defects. Transplantation of the composite scaffold could restore the myoelectricity and wave amplitude of the sciatic nerve by electrophysiological examination, promote nerve axonal and myelin regeneration, and delay apoptosis of spinal motor neurons. Experimental findings indicate that neurotrophin-3 transfected Schwann cells combined with bridge grafting can promote neural regeneration and functional recovery after nerve injury.

The Use of Fiber-Reinforced Scaffolds Cocultured with Schwann Cells and Vascular Endothelial Cells to Repair Rabbit Sciatic Nerve Defect with Vascularization

To explore the feasibility of biodegradable fiber-reinforced 3D scaffolds with satisfactory mechanical properties for the repair of long-distance sciatic nerve defect in rabbits and effects of vascularized graft in early stage on the recovery of neurological function, Schwann cells and vascular endothelial cells were cocultured in the fiber-reinforced 3D scaffolds. Experiment group which used prevascularized nerve complex for the repair of sciatic nerve defect and control group which only cultured with Schwann cells were set. The animals in both groups underwent electromyography to show the status of the neurological function recovery at 4, 8, and 16 weeks after the surgery. Sciatic nerve regeneration and myelination were observed under the light microscope and electron microscope. Myelin sheath thickness, axonal diameter, and number of myelinated nerve fiber were quantitatively analyzed using image analysis system. The recovery of foot ulcer, the velocity of nerve conduction, the number of regenerating nerve fiber, and the recovery of ultrastructure were increased in the experimental group than those in the control group. Prevascularized tissue engineered fiber-reinforced 3D scaffolds for the repair of sciatic nerve defects in rabbits can effectively promote the recovery of neurological function.

Nanoparticles carrying neurotrophin-3-modified Schwann cells promote repair of sciatic nerve defects

Nanoparticles carrying neurotrophin-3-modified Schwann cells promote repair of sciatic nerve defects

Chemoattractive capacity of different lengths of nerve fragments bridging regeneration chambers for the repair of sciatic nerve defects.

A preliminary study by our research group showed that 6-mm-long regeneration chamber bridging is equivalent to autologous nerve transplantation for the repair of 12-mm nerve defects. In this study, we compared the efficacy of different lengths (6, 8, 10 mm) of nerve fragments bridging 6-mm regeneration chambers for the repair of 12-mm-long nerve defects. At 16 weeks after the regeneration chamber was implanted, the number, diameter and myelin sheath thickness of the regenerated nerve fibers, as well as the conduction velocity of the sciatic nerve and gastrocnemius muscle wet weight ratio, were similar to that observed with autologous nerve transplantation. Our results demonstrate that 6-, 8- and 10-mm-long nerve fragments bridging 6-mm regeneration chambers effectively repair 12-mm-long nerve defects. Because the chemoattractive capacity is not affected by the length of the nerve fragment, we suggest adopting 6-mm-long nerve fragments for the repair of peripheral nerve defects.

Study on molecular mechanism for improving neural regeneration after repair of sciatic nerve defect in rat by acellular nerve allograft

Discuss the molecular mechanism for improving neural regeneration after repair of sciatic nerve defect in rat by acellular nerve allograft (ANA). Randomly divide 36 Wistar rats into six groups as normal control group, autografting group, and bridging groups of 2, 4, 8, 12 weeks, six rats for each group. Observe the expression of brain-derived neurotrophic factor (BDNF) in L(4) spinal cord and anterior tibial muscle at the injury site, calcitonin gene-related peptide (CGRP) protein as well as mRNA, respectively. 12w after operation, histopathological observation was performed. 2w after ANA bridging the sciatic nerve defect in rats, it was observed that the expression level of BDNF in spinal cord at the injury site and CGRP protein increased, reaching the peak level at 4w, lasting till 8w, then decreased but still significantly higher than that in normal control group at 12w, and was not significantly different compared with that in autografting group. However, the expression level of BDNF in anterior tibial muscle decreased gradually within the initial 4w, then increased progressively, reaching normal level at 12w, and was not significantly different compared with that in autografting group. The expression of BDNF mRNA and CGRPmRNA was essentially the same. 12w after operation, there was nerve regeneration in bridging group of 12w and autografting group. ANA possessed fine histocompatibility, and might substitute autograft to repair long-segment defect of sciatic nerve in rats. This action might be related to upregulation of protein and mRNA expression for BDNF and CGRP in spinal cord.

P(LLA-CL) nerve conduits of electrospun nanofibers for repair of sciatic nerve defect in rats

Objective To investigate the effects of P(LLA-CL) nerve conduits of electrospun nanofibers in repairing sciatic nerve defect in rats. Methods Fifty-four rats were randomly divided into three groups,with eighteen rats in each group. A 15 mm defect in the left sciatic nerve was created in the rats and was repaired with P (LLA-CL) conduits ( group A), with silicon conduits ( group B), and with autografts ( group C),respectively. Nerve regeneration was evaluated with gross observation, SFI (Sciatic Functional Index),neuroelectrophysiological examination, muscle weight, neuromorphometry and electron microscopy at 4 weeks,8weeks and 12 weeks after the operation. Results Regenerating axons reached mid-tube level in group A 4 weeks after the surgery. At 8 weeks the regenerating fibers had traversed the entire length of the conduit although the nerve fibers were thin. At 12 weeks the regenerated nerve fibers were much thicker and less adhesive. SFI,electrophysiological evaluation, wet weight of gastrocnemius and soleus muscles, and neuromorphometry in group A were slightly inferior to those of group C but significantly better than those of group B. Conclusion PLLACL nerve conduits of eleetrospun nanofibers can effectively promote nerve regeneration of rat sciatic nerve. They can potentially be used as a substitute for autogafts to repair nerve defects. Key words: Peripheral nerves; Nerve regeneration; Animal experimentation; Poly(L-lactide-coepsilon-caprolactone)

Repair of sciatic nerve defect with implantation of glial cell line-derived neurotrophic factor locally secreting mesenchymal stem cells in rabbits

Objective To investigate the repairative effect of local high expression of glial cell line-derived neurotrophic factor （GDNF） in the repair of sciatic nerve defects. Green fluorescent protein （GFP） gene was used as reporter gene. Two groups including gel matrix control group and gel matrix plus MSCs group were set （ 10 rabbits per group）. Methods GDNF secreting mesenchymal stem cells （MSCs） mediated by lentiviral vectors were suspended in Matrigel to produce the artificial graft, and then it was locally implanted to a 20 mm-long sciatic nerve defect in rabbits. Results In the GDNF group,the nerve continuity was restored in seven rabbits and the functional amelioration of the wounded limb was apparent. While there found no restoration of the nerve continuity in the control groups. The migration distance of GDNF secreting MSCs was 20 mm, suggesting a good integration of the transplanted cells with host cells. The glial fibrillary acidic protein （GFAP） ＋ green fluorescent protein （GFP） and -100 protein GFP accounted for 60% and 70% respectively in the experimental group, while it was only 40% and 30% in gel matrix plus MSCs group. Conclusions Local implantation of GDNF secreting MSCs can promote the regeneration and functional recovery of the sciatic nerves. GDNF seems to play an important role in inducing transdifferentiation of MSCs to Schwann cell lineage. Key words: Sciatic nerve; Mesenchymal stem cells; Glial cell line-derived neurotrophic factor

The Delayed Repair of Sciatic Nerve Defects with Tissue-engineered Nerve Grafts in Rats

The purpose of this study was to evaluate the feasibility of using tissue-engineered nerve grafts for delayed repair of peripheral nerve defects. A 1-month delayed, 10-mm long sciatic nerve defect was created for rats, which were divided into three grafted groups and a non-grafted group. For bridging the nerve defects, the rats in three grafted groups were subjected to surgical repair with tissue-engineered nerve grafts made of a chitosan/polyglycolic acid (PGA) conduit filled with neural stem cells (NSCs), chitosan/PGA conduits, and autologous nerve grafts, respectively. At 3 months after nerve grafting, the data from electrophysiology, retrograde tracing and histological investigation revealed that the better outcomes in sciatic nerve regeneration and target muscle re-innervation were achieved in three grafted groups as compared to those in non-grafted group without major differences between three grafted groups. Our results suggest that grafting of chitosan/PGA conduits might be a promising technique for repairing peripheral nerve injuries after a 1-month delay, while introduction of NSCs seem to show no significant additional benefits to regenerative outcomes.