Combining acellular nerve allografis with brain- derived neurotrophic factor transfected bone marrow mesenchymal stem cells restores sciatic nerve injury better than either intervention alone

In this study, we chemically extracted acellular nerve allografts from bilateral sciatic nerves, and repaired 10-mm sciatic nerve defects in rats using these grafts and brain-derived neurotrophic factor transfected bone marrow mesenchymal stem cells. Experiments were performed in three groups： the acellular nerve allograft bridging group, acellular nerve allograft ＋ bone marrow mesenchymal stem cells group, and the acellular nerve allograft ＋ brain-derived neurotrophic factor transfected bone marrow mesenchyrnal stem cells group. Results showed that at 8 weeks after bridging, sciatic functional index, triceps wet weight recovery rate, myelin thickness, and number of myelinated nerve fibers were significantly changed in the three groups. Variations were the largest in the acellular nerve allograft ＋ brain-derived neurotrophic factor transfected bone marrow mesenchymal stem cells group compared with the other two groups. Experimental findings suggest that chemically extracted acellular nerve allograft combined nerve factor and mesenchymal stem cells can promote the restoration of sciatic nerve defects. The repair effect seen is better than the single application of acellular nerve allograft or acellular nerve allograft combined mesenchymal stem cell transplantation.     

Combining acellular nerve allografts with brainderived neurotrophic factor transfected bone marrow mesenchymal stem cells restores sciatic nerve injury better than either intervention alone

In this study,we chemically extracted acellular nerve allografts from bilateral sciatic nerves,and repaired 10-mm sciatic nerve defects in rats using these grafts and brain-derived neurotrophic factor transfected bone marrow mesenchymal stem cells.Experiments were performed in three groups: the acellular nerve allograft bridging group,acellular nerve allograft + bone marrow mesenchymal stem cells group,and the acellular nerve allograft + brain-derived neurotrophic factor transfected bone marrow mesenchymal stem cells group.Results showed that at 8 weeks after bridging,sciatic functional index,triceps wet weight recovery rate,myelin thickness,and number of myelinated nerve fibers were significantly changed in the three groups.Variations were the largest in the acellular nerve allograft + brain-derived neurotrophic factor transfected bone marrow mesenchymal stem cells group compared with the other two groups.Experimental findings suggest that chemically extracted acellular nerve allograft combined nerve factor and mesenchymal stem cells can promote the restoration of sciatic nerve defects.The repair effect seen is better than the single application of acellular nerve allograft or acellular nerve allograft combined mesenchymal stem cell transplantation.     

Chemically extracted aceUular allogeneic nerve graft combined with ciliary neurotrophic factor promotes sciatic nerve repair

A chemically extracted acellular allogeneic nerve graft can reduce postoperative immune rejection, similar to an autologous nerve graft, and can guide neural regeneration. However, it remains poorly understood whether a chemically extracted acellular allogeneic nerve graft combined with neurotrophic factors provides a good local environment for neural regeneration. This study investigated the repair of injured rat sciatic nerve using a chemically extracted acellular allogeneic nerve graft combined with ciliary neurotrophic factor. An autologous nerve anastomosis group and a chemical acellular allogeneic nerve bridging group were prepared as controls. At 8 weeks after repair, sciatic functional index, evoked potential amplitude of the soleus muscle, triceps wet weight recovery rate, total number of myelinated nerve fibers and myelin sheath thickness were measured. For these indices, values in the three groups showed the autologous nerve anastomosis group 〉 chemically extracted acellular nerve graft ＋ ciliary neurotrophic factor group 〉 chemical acellular allogeneic nerve bridging group. These results suggest that chemically extracted acellular nerve grafts combined with ciliary neurotrophic factor can repair sciatic nerve defects, and that this repair is inferior to autologous nerve anastomosis, but superior to chemically extracted acellular allogeneic nerve bridging alone.     

Human umbilical cord mesenchymal stem cells promote peripheral nerve repair via paracrine mechanisms

Human umbilical cord-derived mesenchymal stem cells(h UCMSCs) represent a promising young-state stem cell source for cell-based therapy. h UCMSC transplantation into the transected sciatic nerve promotes axonal regeneration and functional recovery. To further clarify the paracrine effects of h UCMSCs on nerve regeneration, we performed human cytokine antibody array analysis, which revealed that h UCMSCs express 14 important neurotrophic factors. Enzyme-linked immunosorbent assay and immunohistochemistry showed that brain-derived neurotrophic factor, glial-derived neurotrophic factor, hepatocyte growth factor, neurotrophin-3, basic fibroblast growth factor, type I collagen, fibronectin and laminin were highly expressed. Treatment with h UCMSC-conditioned medium enhanced Schwann cell viability and proliferation, increased nerve growth factor and brain-derived neurotrophic factor expression in Schwann cells, and enhanced neurite growth from dorsal root ganglion explants. These findings suggest that paracrine action may be a key mechanism underlying the effects of h UCMSCs in peripheral nerve repair.     

Biological conduits combining bone marrow mesenchymal stem cells and extracellular matrix to treat long-segment sciatic nerve defects

The transplantation of polylactic glycolic acid conduits combining bone marrow mesenchymal stem cells and extracellular matrix gel for the repair of sciatic nerve injury is effective in some respects, but few data comparing the biomechanical factors related to the sciatic nerve are available. In the present study, rabbit models of 10-mm sciatic nerve defects were prepared. The rabbit models were repaired with autologous nerve, a polylactic glycolic acid conduit + bone marrow mesenchymal stem cells, or a polylactic glycolic acid conduit + bone marrow mesenchymal stem cells + extracellular matrix gel. After 24 weeks, mechanical testing was performed to determine the stress relaxation and creep parameters. Following sciatic nerve injury, the magnitudes of the stress decrease and strain increase at 7,200 seconds were largest in the polylactic glycolic acid conduit + bone marrow mesenchymal stem cells + extracellular matrix gel group, followed by the polylactic glycolic acid conduit + bone marrow mesenchymal stem cells group, and then the autologous nerve group. Hematoxylin-eosin staining demonstrated that compared with the polylactic glycolic acid conduit + bone marrow mesenchymal stem cells group and the autologous nerve group, a more complete sciatic nerve regeneration was found, including good myelination, regularly arranged nerve fibers, and a completely degraded and resorbed conduit, in the polylactic glycolic acid conduit + bone marrow mesenchymal stem cells + extracellular matrix gel group. These results indicate that bridging 10-mm sciatic nerve defects with a polylactic glycolic acid conduit + bone marrow mesenchymal stem cells + extracellular matrix gel construct increases the stress relaxation under a constant strain, reducing anastomotic tension. Large elongations under a constant physiological load can limit the anastomotic opening and shift, which is beneficial for the regeneration and functional reconstruction of sciatic nerve. Better regeneration was found with the polylactic glycolic acid conduit + bone marrow mesenchymal stem cells + extracellular matrix gel grafts than with the polylactic glycolic acid conduit + bone marrow mesenchymal stem cells grafts and the autologous nerve grafts.     

Polylactic-co-glycolic acid microspheres containing three neurotrophic factors promote sciatic nerve repair after injury

A variety of neurotrophic factors have been shown to repair the damaged peripheral nerve. However, in clinical practice, nerve growth factor, neurotrophin-3 and brain-derived neurotrophic factor are all peptides or proteins that may be rapidly deactivated at the focal injury site; their local effective concentration time following a single medication cannot meet the required time for spinal axons to regenerate and cross the glial scar. In this study, we produced polymer sustained-release microspheres based on the polylactic-co-glycolic acid copolymer; the microspheres at 300-μm diameter contained nerve growth factor, neurotrophin-3 and brain-derived neurotrophic factor. Six microspheres were longitudinally implanted into the sciatic nerve at the anastomosis site, serving as the experimental group; while the sciatic nerve in the control group was subjected to the end-to-end anastomosis using 10/0 suture thread. At 6 weeks after implantation, the lower limb activity, weight of triceps surae muscle, sciatic nerve conduction velocity and the maximum amplitude were obviously better in the experimental group than in the control group. Compared with the control group, more regenerating nerve fibers were observed and distributed in a dense and ordered manner with thicker myelin sheaths in the experimental group. More angiogenesis was also visible. Experimental findings indicate that polylactic-co-glycolic acid composite microspheres containing nerve growth factor, neurotrophin-3 and brain-derived neurotrophic factor can promote the restoration of sciatic nerve in rats after injury.     

Acellular allogeneic nerve grafting combined with bone marrow mesenchymal stem cell transplantation for the repair of long-segment sciatic nerve defects:biomechanics and validation of mathematical models

We hypothesized that a chemically extracted acellular allogeneic nerve graft used in combination with bone marrow mesenchymal stem cell transplantation would be an effective treatment for long-segment sciatic nerve defects. To test this, we established rabbit models of 30 mm sciatic nerve defects, and treated them using either an autograft or a chemically decellularized allogeneic nerve graft with or without simultaneous transplantation of bone marrow mesenchymal stem cells. We compared the tensile properties, electrophysiological function and morphology of the damaged nerve in each group. Sciatic nerves repaired by the allogeneic nerve graft combined with stem cell trans-plantation showed better recovery than those repaired by the acellular allogeneic nerve graft alone, and produced similar results to those observed with the autograft. These ifndings conifrm that a chemically extracted acellular allogeneic nerve graft combined with transplanta-tion of bone marrow mesenchymal stem cells is an effective method of repairing long-segment sciatic nerve defects.     

Chemically extracted acellular allogeneic nerve graft combined with ciliary neurotrophic factor promotes sciatic nerve repair

A chemically extracted acellular allogeneic nerve graft can reduce postoperative immune rejection, similar to an autologous nerve graft, and can guide neural regeneration. However, it remains poorly understood whether a chemically extracted acellular allogeneic nerve graft combined with neurotrophic factors provides a good local environment for neural regeneration. This study investigated the repair of injured rat sciatic nerve using a chemically extracted acellular allogeneic nerve graft combined with ciliary neurotrophic factor. An autologous nerve anastomosis group and a chemical acellular allogeneic nerve bridging group were prepared as controls. At 8 weeks after repair, sciatic functional index, evoked potential amplitude of the soleus muscle, triceps wet weight recovery rate, total number of myelinated nerve fibers and myelin sheath thickness were measured. For these indices, values in the three groups showed the autologous nerve anastomosis group chemically extracted acellular nerve graft + ciliary neurotrophic factor group chemical acellular allogeneic nerve bridging group. These results suggest that chemically extracted acellular nerve grafts combined with ciliary neurotrophic factor can repair sciatic nerve defects, and that this repair is inferior to autologous nerve anastomosis, but superior to chemically extracted acellular allogeneic nerve bridging alone.     

A simple model of radial nerve injury in the rhesus monkey to evaluate peripheral nerve repair

Current research on bone marrow stem cell transplantation and autologous or xenogenic nerve transplantation for peripheral nerve regeneration has mainly focused on the repair of peripher-al nerve defects in rodents. In this study, we established a standardized experimental model of radial nerve defects in primates and evaluated the effect of repair on peripheral nerve injury. We repaired 2.5-cm lesions in the radial nerve of rhesus monkeys by transplantation of autografts, acellular allografts, or acellular allografts seeded with autologous bone marrow stem cells. Five months after surgery, regenerated nerve tissue was assessed for function, electrophysiology, and histomorphometry. Postoperative functional recovery was evaluated by the wrist-extension test. Compared with the simple autografts, the acellular allografts and allografts seeded with bone marrow stem cells facilitated remarkable recovery of the wrist-extension functions in the rhesus monkeys. This functional improvement was coupled with radial nerve distal axon growth, a higher percentage of neuron survival, increased nerve fiber density and diameter, increased myelin sheath thickness, and increased nerve conduction velocities and peak amplitudes of compound motor action potentials. Furthermore, the quality of nerve regeneration in the bone marrow stem cells-laden allografts group was comparable to that achieved with autografts. The wrist-extension test is a simple behavioral method for objective quantification of peripheral nerve regeneration.     

富血小板血浆诱导骨髓间充质干细胞修复坐骨神经缺损：并与自体神经修复的效果相比较

目的：通过植入经PRP诱导的BMSCs结合化学萃取的去细胞神经修复坐骨神经缺损,观察其对周围神经的修复作用。 方法：32只新西兰大耳白兔,随机分成4组,即单纯的化学萃取的去细胞神经、BMSCs结合化学萃取的去细胞神经、经PRP诱导的BMSCs结合化学萃取的去细胞神和自体神经修复坐骨神经缺损,检测指标包括形态学观察、靶肌肉肌湿重恢复率、运动神经传导速度（MNCV）及轴突直径和髓鞘厚度等。 结果：结果显示,靶肌肉肌湿重恢复率、MNCV、轴突直径和髓鞘厚度和形态学观察在经PRP诱导的BMSCs结合化学萃取的去细胞神经组明显优于单纯的化学萃取的去细胞神经组和BMSCs结合化学萃取的去细胞神经组,而与自体神经修复组结果相似。 结论：经诱导后的BMSCs在体内具有SC的部分功能,可作为组织工程化外周神经的种子细胞,用于周围神经缺损的修复。     

Propofol promotes spinal cord injury repair by bone marrow mesenchymal stem cell transplantation

Propofol is a neuroprotective anesthetic. Whether propofol can promote spinal cord injury repair by bone marrow mesenchymal stem cells remains poorly understood. We used rats to investigate spinal cord injury repair using bone marrow mesenchymal stem cell transplantation combined with propofol administration via the tail vein. Rat spinal cord injury was clearly alleviated; a large number of newborn non-myelinated and myelinated nerve fibers appeared in the spinal cord, the numbers of CM-Dil-labeled bone marrow mesenchymal stem cells and fluorogold-labeled nerve fibers were increased and hindlimb motor function of spinal cord-injured rats was markedly improved. These improvements were more prominent in rats subjected to bone marrow mesenchymal cell transplantation combined with propofol administration than in rats receiving monotherapy. These results indicate that propofol can enhance the therapeutic effects of bone marrow mesenchymal stem cell transplantation on spinal cord injury in rats.     

Propofol injection combined with bone marrow mesenchymal stem cell transplantation better improves electrophysiological function in the hindlimb of rats with spinal cord injury than monotherapy

The repair effects of bone marrow mesenchymal stem cell transplantation on nervous system damage are not satisfactory. Propofol has been shown to protect against spinal cord injury. Therefore, this study sought to explore the therapeutic effects of their combination on spinal cord injury. Rat models of spinal cord injury were established using the weight drop method. Rats were subjected to bone marrow mesenchymal stem cell transplantation via tail vein injection and/or propofol injection via tail vein using an infusion pump. Four weeks after cell transplantation and/or propofol treatment, the cavity within the spinal cord was reduced. The numbers of PKH-26-positive cells and horseradish peroxidase-positive nerve fibers apparently increased in the spinal cord. Latencies of somatosensory evoked potentials and motor evoked potentials in the hindlimb were noticeably shortened, amplitude was increased and hindlimb motor function was obviously improved. Moreover, the combined effects were better than cell transplantation or propofol injection alone. The above data suggest that the combination of propofol injection and bone marrow mesenchymal stem cell transplantation can effectively improve hindlimb electrophysiological function, promote the recovery of motor funtion, and play a neuroprotective role in spinal cord injury in rats.     

Sciatic nerve repair by acellular nerve xenografts implanted with BMSCs in rats xenograft combined with BMSCs

Acellular nerves possess the structural and biochemical features similar to those of naive endoneurial tubes, and have been proved bioactive for allogeneil graft in nerve tissue engineering. However, the source of allogenic donators is restricted in clinical treatment. To explore sufficient substitutes for acellular nerve allografts (ANA), we investigated the effectiveness of acellular nerve xenografts (ANX) combined with bone marrow stromal cells (BMSCs) on repairing peripheral nerve injuries. The acellular nerves derived from Sprague-Dawley rats and New Zealand rabbits were prepared, respectively, and BMSCs were implanted into the nerve scaffolds and cultured in vitro. All the grafts were employed to bridge 1 cm rat sciatic nerve gaps. Fifty Wistar rats were randomly divided into five groups (n = 10 per group): ANA group, ANX group, BMSCs-laden ANA group, BMSCs-laden ANX group, and autologous nerve graft group. At 8 weeks post-transplantation, electrophysiological study was performed and the regenerated nerves were assayed morphologically. Besides, growth-promoting factors in the regenerated tissues following the BMSCs integration were detected. The results indicated that compared with the acellular nerve control groups, nerve regeneration and functional rehabilitation for the xenogenic nerve transplantation integrated with BMSCs were advanced significantly, and the rehabilitation efficacy was comparable with that of the autografting. The expression of neurotrophic factors in the regenerated nerves, together with that of brain-derived neurotrophic factor (BDNF) in the spinal cord and muscles were elevated largely. In conclusion, ANX implanted with BMSCs could replace allografts to promote nerve regeneration effectively, which offers a reliable approach for repairing peripheral nerve defects.     

One-stage human acellular nerve allograft reconstruction for digital nerve defects

Human acellular nerve allografts have a wide range of donor origin and can effectively avoid nerve injury in the donor area. Very little is known about one-stage reconstruction of digital nerve defects. The present study observed the feasibility and effectiveness of human acellular nerve allograft in the reconstruction of 5-cm digital nerve defects within 6 hours after injury. A total of 15 cases of nerve injury, combined with nerve defects in 18 digits from the Department of Emergency were enrolled in this study. After debridement, digital nerves were reconstructed using human acellular nerve allografts. The patients were followed up for 6–24 months after reconstruction. Mackinnon-Dellon static two-point discrimination results showed excellent and good rates of 89%. Semmes-Weinstein monofilament test demonstrated that light touch was normal, with an obvious improvement rate of 78%. These findings confirmed that human acellular nerve allograft for one-stage reconstruction of digital nerve defect after hand injury is feasible, which provides a novel trend for peripheral nerve reconstruction.     

富血小板血浆诱导骨髓间充质干细胞结合化学萃取去细胞神经修复坐骨神经缺损

背景：周围神经损伤早期许旺细胞尚未大量分裂增殖,此时由于解剖连续性的中断,通过轴浆逆向运输提供的营养因子骤减,缺乏神经营养因子支持的神经元有可能死亡,从而使周围神经不能再生或再生乏力。 目的：观察植入经富血小板血浆诱导的骨髓间充质干细胞结合去细胞神经修复坐骨神经缺损的效果。 方法：取新西兰大耳白兔制备坐骨神经缺损模型,随机抽签法分成4组：去细胞神经组,移植同种异体去细胞神经;骨髓间充质干细胞组,移植同种异体骨髓间充质干细胞结合化学萃取的同种异体去细胞神经：经诱导骨髓间充质干细胞组,移植经富血小板血浆诱导的同种异体骨髓间充质干细胞结合化学萃取的同种异体去细胞神经;自体神经组,移植自体神经。术后进行形态学观察与靶肌肉肌湿质量恢复率、运动神经传导速度、轴突直径和髓鞘厚度的检测。 结果与结论：经富血小板血浆诱导的骨髓间充质干细胞结合化学萃取的去细胞神经移植修复神经的靶肌肉肌湿质量恢复率、运动神经传导速度、轴突直径和髓鞘厚度及形态学观察明显优于移植单纯化学萃取的去细胞神经与骨髓间充质干细胞结合化学萃取的去细胞神经的效果,而与移植自体神经修复结果相似。说明经诱导后的骨髓间充质干细胞在体内具有许旺细胞的部分功能,可作为组织工程化外周神经的种子细胞,用于周围神经缺损的修复。     

Biodegradable chitin conduit tubulation combined with bone marrow mesenchymal stem cell transplantation for treatment of spinal cord injury by reducing glial scar and cavity formation

We examined the restorative effect of modified biodegradable chitin conduits in combination with bone marrow mesenchymal stem cell transplantation after right spinal cord hemisection injury. Immunohistochemical staining revealed that biological conduit sleeve bridging reduced glial scar formation and spinal muscular atrophy after spinal cord hemisection. Bone marrow mesenchymal stem cells survived and proliferated after transplantation in vivo, and differentiated into cells double-positive for S100(Schwann cell marker) and glial fibrillary acidic protein(glial cell marker) at 8 weeks. Retrograde tracing showed that more nerve fibers had grown through the injured spinal cord at 14 weeks after combination therapy than either treatment alone. Our findings indicate that a biological conduit combined with bone marrow mesenchymal stem cell transplantation effectively prevented scar formation and provided a favorable local microenvironment for the proliferation, migration and differentiation of bone marrow mesenchymal stem cells in the spinal cord, thus promoting restoration following spinal cord hemisection injury.     

骨髓间充质干细胞尾静脉移植脊髓损伤大鼠脑源性神经营养因子及神经生长因子的表达

背景：骨髓间充质干细胞移植对脊髓损伤有治疗作用,但其机制尚不完全清楚。 目的：应用免疫组织化学方法观察骨髓间充质干细胞静脉移植损伤脊髓局部脑源性神经营养因子及神经生长因子的表达,分析骨髓间充质干细胞移植治疗大鼠脊髓损伤的作用途径。 方法：运用改良Allen法制备T10脊髓外伤性截瘫大鼠模型,假手术组6只,脊髓损伤组24只随机分为对照组和骨髓间充质干细胞移植组。骨髓间充质干细胞移植组、假手术组接受骨髓间充质干细胞单细胞悬液1 mL(1×106 cells)自大鼠尾静脉缓慢注射移植,对照组静脉注射PBS 1 mL。 结果与结论：脊髓损伤后损伤局部的脑源性神经营养因子、神经生长因子表达增加,骨髓间充质干细胞静脉注射移植后能促进脊髓损伤局部脑源性神经营养因子、神经生长因子更进一步的表达,这可能是促进神经结构及神经功能恢复的因素之一。     

无细胞神经支架复合骨髓间充质干细胞构建组织工程人工神经修复坐骨神经缺损*☆

背景：作者已经成功制备了无细胞神经移植物,并且复合骨髓间充质干细胞构建组织工程人工神经桥接大鼠坐骨神经缺损。 目的：无细胞神经移植物复合骨髓间充质干细胞构建组织工程人工神经修复大鼠坐骨神经缺损后运动功能的恢复。 方法：成年雄性SD大鼠构建大鼠坐骨神经15 mm缺损模型,分别应用组织工程人工神经、组织工程神经支架或自行神经桥接坐骨神经缺损。桥接后20周再生神经电生理学测定,手术侧胫骨前肌湿质量、腓肠肌组织学及透视电镜分析。 结果与结论：桥接20周后,组织工程人工神经与自体神经移植组胫骨前肌湿质量比较,差异无显著性意义(P > 0.05),神经干传导速度为(30.56±2.15)m/s。结果提示,无细胞神经移植物复合骨髓间充质干细胞构建的组织工程人工神经桥接大鼠坐骨神经缺损后,可以促进再生神经运动功能的恢复。     

Repair of extended peripheral nerve lesions in rhesus monkeys using acellular allogenic nerve grafts implanted with autologous mesenchymal stem cells

Despite intensive efforts in the field of peripheral nerve injury and regeneration, it remains difficult in humans to achieve full functional recovery following extended peripheral nerve lesions. Optimizing repair of peripheral nerve injuries has been hindered by the lack of viable and reliable biologic or artificial nerve conduits for bridging extended gaps. In this study, we utilized chemically extracted acellular allogenic nerve segments implanted with autologous non-hematopoietic mesenchymal stem cells (MSCs) to repair a 40 mm defect in the rhesus monkey ulnar nerve. We found that severely damaged ulnar nerves were structurally and functionally repaired within 6 months following placement of the MSC seeded allografts in all animals studied (6 of 6, 100%). Furthermore, recovery with the MSC seeded allografts was similar to that observed with Schwann cell seeded allografts and autologous nerve grafts. The findings presented here are the first demonstration of the successful use of autologous MSCs, expanded in culture and implanted in a biological conduit, to repair a peripheral nerve gap in primates. Given the difficulty in isolating and purifying sufficient quantities of Schwann cells for peripheral nerve regeneration, the use of MSCs to seed acellular allogenic nerve grafts may prove to be a novel and promising therapeutic approach for repairing severe peripheral nerve injuries in humans.     

Does glioblastoma cyst fluid promote sciatic nerve regeneration?

Glioblastoma cyst fluid contains growth factors and extracellular matrix proteins which are known as neurotrophic and neurite-promoting agents. Therefore, we hypothesized that glioblastoma cyst fluid can promote the regeneration of injured peripheral nerves. To validate this hypothesis, we transected rat sciatic nerve, performed epineural anastomosis, and wrapped the injured sciatic nerve with glioblastoma cyst fluid- or saline-soaked gelatin sponges. Neurological function and histomorphological examinations showed that compared with the rats receiving local saline treatment, those receiving local glioblastoma cyst fluid treatment had better sciatic nerve function, fewer scars, greater axon area, counts and diameter as well as fiber diameter. These findings suggest that glioblastoma cyst fluid can promote the regeneration of injured sciatic nerve and has the potential for future clinical application in patients with peripheral nerve injury.