Scaffoldless tissue-engineered nerve conduit promotes peripheral nerve regeneration and functional recovery after tibial nerve injury in rats

Damage to peripheral nerve tissue may cause loss of function in both the nerve and the targeted muscles it innervates. This study compared the repair capability of engineered nerve conduit （ENC）, engineered fibroblast conduit （EFC）, and autograft in a 10-mm tibial nerve gap. ENCs were fabricated utilizing primary fibroblasts and the nerve cells of rats on embryonic day 15 （E 15）. EFCs were fabricated utilizing primary fi- broblasts only. Following a 12-week recovery, nerve repair was assessed by measuring contractile properties in the medial gastrocnemius muscle, distal motor nerve conduction velocity in the lateral gastrocnemius, and histology of muscle and nerve. The autografts, ENCs and EFCs reestablished 96%, 87% and 84% of native distal motor nerve conduction velocity in the lateral gastrocnemius, 100%, 44% and 44% of native specific force of medical gastrocnemius, and 63%, 61% and 67% of native medial gastrocnemius mass, re- spectively. Histology of the repaired nerve revealed large axons in the autograft, larger but fewer axons in the ENC repair, and many smaller axons in the EFC repair. Muscle histology revealed similar muscle fiber cross-sectional areas among autograft, ENC and EFC repairs. In conclusion, both ENCs and EFCs promot- ed nerve regeneration in a 10-mm tibial nerve gap repair, suggesting that the El5 rat nerve cells may not be necessary for nerve regeneration, and EFC alone can suffice for peripheral nerve injury repair.

Biological conduit small gap sleeve bridging method for peripheral nerve injury: regeneration law of nerve fibers in the conduit

The clinical effects of 2-mm small gap sleeve bridging of the biological conduit to repair periph- eral nerve injury are better than in the traditional epineurium suture, so it is possible to replace the epineurium suture in the treatment of peripheral nerve injury. This study sought to identify the regeneration law of nerve fibers in the biological conduit. A nerve regeneration chamber was constructed in models of sciatic nerve injury using 2-mm small gap sleeve bridging of a biodegradable biological conduit. The results showed that the biological conduit had good his- tocompatibility. Tissue and cell apoptosis in the conduit apparently lessened, and regenerating nerve fibers were common. The degeneration regeneration law of Schwann cells and axons in the conduit was quite different from that in traditional epineurium suture. During the prime period for nerve fiber regeneration （2-8 weeks）, the number of Schwann cells and nerve fibers was higher in both proximal and distal ends, and the effects of the small gap sleeve bridging method were better than those of the traditional epineurium suture. The above results provide an objec- tive and reliable theoretical basis for the clinical application of the biological conduit small gap sleeve bridging method to repair peripheral nerve injury.

Bridging peripheral nerves using a deacetyl chitin conduit combined with short-term electrical stimulation

Previous studies have demonstrated that deacetyl chitin conduit nerve bridging or electrical stimulation can effectively promote the regeneration of the injured peripheral nerve. We hypoth-esized that the combination of these two approaches could result in enhanced regeneration. Rats with right sciatic nerve injury were subjected to deacetyl chitin conduit bridging combined with electrical stimulation （0.1 ms, 3 V, 20 Hz, for 1 hour）. At 6 and 12 weeks after treatment, nerve conduction velocity, myelinated axon number, ifber diameter, axon diameter and the thickness of the myelin sheath in the stimulation group were better than in the non-stimulation group. The results indicate that deacetyl chitin conduit bridging combined with temporary electrical stimu-lation can promote peripheral nerve repair.

Therapeutic strategies for peripheral nerve injury: decellularized nerve conduits and Schwann cell transplantation

In recent years, the use of Schwann cell transplantation to repair peripheral nerve injury has attracted much attention. Animal-based studies show that the transplantation of Schwann cells in combination with nerve scaffolds promotes the repair of injured peripheral nerves. Autologous Schwann cell transplantation in humans has been reported recently. This article reviews current methods for removing the extracellular matrix and analyzes its composition and function. The development and secretory products of Schwann cells are also reviewed. The methods for the repair of peripheral nerve injuries that use myelin and Schwann cell transplantation are assessed. This survey of the literature data shows that using a decellularized nerve conduit combined with Schwann cells represents an effective strategy for the treatment of peripheral nerve injury. This analysis provides a comprehensive basis on which to make clinical decisions for the repair of peripheral nerve injury.

Construction of a three-dimensional bionic nerve conduit containing two neurotrophic factors with separate delivery systems for the repair of sciatic nerve defects

Previous studies of nerve conduits have investigated numerous properties, such as conduit luminal structure and neurotrophic factor incorporation, for the regeneration of nerve defects. The present study used a poly（lactic-co-glycolic acid） （PLGA） copolymer to construct a three-dimensional （3D） bionic nerve conduit, with two channels and multiple microtubule lumens, and incorporating two neurotrophic factors, each with their own delivery system, as a novel environment for peripheral nerve regeneration. The efficacy of this conduit in repairing a 1.5 cm sciatic nerve defect was compared with PLGA-alone and PLGA-microfilament conduits, and autologous nerve transplantation. Results showed that compared with the other groups, the 3D bionic nerve conduit had the fastest nerve conduction velocity, largest electromyogram amplitude, and shortest electromyogram latency. In addition, the nerve fiber density, myelin sheath thickness and axon diameter were significantly increased, and the recovery rate of the triceps surae muscle wet weight was lowest. These findings suggest that 3D bionic nerve conduits can provide a suitable microenvironment for peripheral nerve regeneration to efficiently repair sciatic nerve defects. p

Efficacy of nanofibrous conduits in repair of longsegment sciatic nerve defects

Our previous studies have histomorphologically confirmed that nanofibrous poly（3-hydroxybutyrate- co-3-hydroxyvalerate） conduit can be used to repair 30-mm-long sciatic nerve defects. However, the repair effects on rat behaviors remain poorly understood. In this study, we used nanofibrous poly（3-hydroxybutyrate-co-3-hydroxyvalerate） conduit and autologous sciatic nerve to bridge 30-ram-long rat sciatic nerve gaps. Within 4 months after surgery, rat sciatic nerve functional re- covery was evaluated per month by behavioral analyses, including toe out angle, toe spread anal- ysis, walking track analysis, extensor postural thrust, swimming test, open-field analysis and no- ciceptive function. Results showed that rat sciatic nerve functional recovery was similar after nanofibrous poly（3-hydroxybutyrate-co-3-hydroxyvalerate） conduit and autologous nerve grafting. These findings suggest that nanofibrous poly（3-hydroxybutyrate-co-3-hydroxyvalerate） conduit is suitable in use for repair of long-segment sciatic nerve defects.

Nanofibrous nerve conduits for repair of 30-mm-long sciatic nerve defects

It has been confirmed that nanofibrous poly（3-hydroxybutyrate-co-3-hydroxyvalerate） nerve conduit can promote peripheral nerve regeneration in rats. However, its efficiency in repair of over 30-mm-long sciatic nerve defects needs to be assessed. In this study, we used a nanofibrous poly（3-hydroxybutyrate-co-3-hydroxyvalerate） nerve conduit to bridge a 30-mm-long gap in the rat sciatic nerve. At 4 months after nerve conduit implantation, regenerated nerves were macroscopi- cally observed and histologically assessed. In the nanofibrous graft, the rat sciatic nerve trunk had been reconstructed by restoration of nerve continuity and formation of myelinated nerve fiber. There were Schwann cells and glial cells in the regenerated nerves. Masson＇s trichrome staining showed that there were no pathological changes in the size and structure of gastrocnemius muscle cells on the operated side of rats. These findings suggest that nanofibrous poly（3-hydroxybutyrate-co-3- hydroxyvalerate） nerve conduit is suitable for repair of long-segment sciatic nerve defects.

Mesenchymal stem cell treatment for peripheral nerve injury:a narrative review

Peripheral nerve injuries occur as the result of sudden trauma and lead to reduced quality of life.The peripheral nervous system has an inherent capability to regenerate axons.However,peripheral nerve regeneration following injury is generally slow and incomplete that results in poor functional outcomes such as muscle atrophy.Although conventional surgical procedures for peripheral nerve injuries present many benefits,there are still several limitations including scarring,difficult accessibility to donor nerve,neuroma formation and a need to sacrifice the autologous nerve.For many years,other therapeutic approaches for peripheral nerve injuries have been explored,the most notable being the replacement of Schwann cells,the glial cells responsible for clearing out debris from the site of injury.Introducing cultured Schwann cells to the injured sites showed great benefits in promoting axonal regeneration and functional recovery.However,there are limited sources of Schwann cells for extraction and difficulties in culturing Schwann cells in vitro.Therefore,novel therapeutic avenues that offer maximum benefits for the treatment of peripheral nerve injuries should be investigated.This review focused on strategies using mesenchymal stem cells to promote peripheral nerve regeneration including exosomes of mesenchymal stem cells,nerve engineering using the nerve guidance conduits containing mesenchymal stem cells,and genetically engineered mesenchymal stem cells.We present the current progress of mesenchymal stem cell treatment of peripheral nerve injuries.

壳聚糖改性的聚乳酸-羟基乙酸共聚物神经导管的制备、表征及其生物学性能

目的:制备用于神经修复及再生的壳聚糖改性聚乳酸-羟基乙酸共聚物(PLGA)神经导管支架。方法:利用静电纺丝技术制备不同比例的PLGA纤维膜,并按聚乳酸比例依次增长的顺序层层卷绕制备梯度降解的PLGA神经导管支架,用壳聚糖通过截留法对导管进行改性,电镜观察其微观形貌,红外光谱分析壳聚糖的截留情况,利用接触角测量仪检测导管亲水性,通过测量导管体积和干重计算孔隙率,通过拉伸实验检测导管力学性能。利用CCK-8实验检测大鼠神经施万细胞RSC96在壳聚糖改性的PLGA神经导管预处理培养基中的增殖情况,荧光显微镜下观察RSC96细胞在壳聚糖改性的PLGA纤维膜上的生长情况。结果:静电纺丝得到的PLGA纤维直径均匀,呈现取向分布。经壳聚糖改性,PLGA神经导管的亲水性有所提高,孔隙率有所下降,力学强度显著提高。RSC96细胞在壳聚糖改性的PLGA神经导管预处理培养基中增殖良好,在壳聚糖改性的PLGA纤维膜上的生长方向与纤维膜的取向一致。结论:壳聚糖改性的PLGA神经导管具有良好的亲水性和力学性能以及细胞相容性,可作为神经修复再生支架。

带长引水道抽水蓄能机组调节系统非线性建模与仿真平台开发

针对带长引水道抽水蓄能机组调节系统非线性建模过程中存在的问题,采用分段建模原理建立长引水系统模型,引入RBF神经网络模型对水泵水轮机全特性曲线的发电工况区进行非线性逼近,在其S特性区充分取点,设定合理的目标精度进行训练,得到能反映S特性的水泵水轮机模型,并进行了空载频率扰动和增减负荷试验。仿真结果表明,所建模型在一定程度上反映了实际机组特性,由此基于LabWindows/CVI虚拟仪器开发软件,应用ActiveX交互技术实现仿真平台与MATLAB的通信,开发了所建模型相应的仿真平台,为研究人员和现场运行维护人员进行仿真测试提供了一种友好的人机交互仿真环境,可为同类仿真平台的开发提供参考。

基于BP的燃气管道评估专家系统设计与实现

BP神经网络具有并行处理、自适应学习、容错能力好等优点,根据地下燃气管道安全评估的应用要求,对其算法进行改进,结合专家系统的设计思路,构造了一个基于BP神经网络的地下燃气管道安全评估专家系统,包括知识表示、知识获取和推理解释等模块。然后利用已有的样本编制软件进行实验,结果表明,该系统评估正确率达91%,推理效率高、扩展性好,从而很好地满足了实际应用的要求。神经网络为专家系统的发展提供了一条新的途径。

Neural Stem Cell Affinity of Chitosan and Feasibility of Chitosan-Based Porous Conduits as Scaffolds for Nerve Tissue Engineering

Neural stem cells （NSCs） are currently considered as powerful candidate seeding cells for regeneration of both spinal cords and peripheral nerves. In this study, NSCs derived from fetal rat cortices were co-cultured with chitosan to evaluate the cell affinity of this material. The results showed that NSCs grew and proliferated well on chitosan films and most of them differentiated into neuron-like cells after 4 days of culture. Then, molded and braided chitosan conduits were fabricated and characterized for their cytotoxicity, swelling, and mechanical properties. Both types of conduits had no cytotoxic effects on fibroblasts （L929 cells） or neuroblastoma （Neuro-2a） cells. The molded conduits are much softer and more flexible while the braided conduits possess much better mechanical properties, which suggests different potential applications.

Angiogenesis in tissue-engineered nerves evaluated objectively using MICROFIL perfusion and micro-CT scanning

Angiogenesis is a key process in regenerative medicine generally, as well as in the specific field of nerve regeneration. However, no convenient and objective method for evaluating the angiogenesis of tissue-engineered nerves has been reported. In this study, tissue-engineered nerves were constructed in vitro using Schwann cells differentiated from rat skin-derived precursors as supporting cells and chitosan nerve conduits combined with silk fibroin fibers as scaffolds to bridge 10-mm sciatic nerve defects in rats. Four weeks after surgery, three-dimensional blood vessel reconstructions were made through MICROFIL perfusion and micro-CT scanning, and parameter analysis of the tissue-engineered nerves was performed. New blood vessels grew into the tissue-engineered nerves from three main directions： the proximal end, the distal end, and the middle. The parameter analysis of the three-dimensional blood vessel images yielded several parameters, including the number, diameter, connection, and spatial distribution of blood vessels. The new blood vessels were mainly capillaries and microvessels, with diameters ranging from 9 to 301 μm. The blood vessels with diameters from 27 to 155 μm accounted for 82.84% of the new vessels. The microvessels in the tissue-engineered nerves implanted in vivo were relatively well-identified using the MICROFIL perfusion and micro-CT scanning method, which allows the evaluation and comparison of differences and changes of angiogenesis in tissue-engineered nerves implanted in vivo.

Repair of peripheral nerve defects by nerve transposition using small gap bio-sleeve suture with different inner diameters at both ends

During peripheral nerve transposition repair, if the diameter difference between transposed nerves is large or multiple distal nerves must be repaired at the same time, traditional epineurial neurorrhaphy has the problem of high tension at the suture site, which may even lead to the failure of nerve suture. We investigated whether a small gap bio-sleeve suture with different inner diameters at both ends can be used to repair a 2-mm tibial nerve defect by proximal transposition of the common peroneal nerve in rats and compared the results with the repair seen after epineurial neurorrhaphy. Three months after surgery, neurological function, nerve regeneration, and recovery of nerve innervation muscle were assessed using the tibial nerve function index, neuroelectrophysiological testing, muscle biomechanics and wet weight measurement, osmic acid staining, and hematoxylin-eosin staining. There was no obvious inflammatory reaction and neuroma formation in the tibial nerve after repair by the small gap bio-sleeve suture with different inner diameters at both ends. The conduction velocity, muscle strength, wet muscle weight, cross-sectional area of muscle fibers, and the number of new myelinated nerve fibers in the biosleeve suture group were similar to those in the epineurial neurorrhaphy group. Our findings indicate that small gap bio-sleeve suture with different inner diameters at both ends can achieve surgical suture between nerves of different diameters and promote regeneration and functional recovery of injured peripheral nerves.

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 dehridement, 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.

合成材料神经导管与自体神经移植修复周围神经缺损的比较

背景:生物可降解材料制成的神经导管可在体内降解,避免出现的神经卡压等问题,因而受到越来越多的关注。目的:比较自体神经移植与3种合成可生物降解材料神经导管在修复周围神经损伤的效果差异。方法:通过电生理学检测,形态学观察等神经恢复效果评价方法,对比分析近年来常用的胶原神经导管、DL-乳酸-ε-己内酯神经导管、聚乙醇酸神经导管与自体神经移植修复周围神经缺损的效果。结果与结论:虽然神经导管与自体神经移植相比在理论上有其优势的一面,但不同合成材料的神经导管之间在神经功能恢复中存在明显差异性,DL-乳酸-ε-己内酯神经导管修复效果与自体神经移植无明显差异,是较为理想的神经导管材料,聚乙醇酸神经导管因自身的因素影响其降解性能,在3种神经导管中的修复周围神经损伤效果最差,胶原神经导管需要交联剂改善其机械性能,其修复周围神经损伤效果居于前两者之间,因此,这3种神经导管在神经功能再生方面还有潜在的缺陷,不能完全替代自体神经移植,而且3者之间的性价比,还缺少足够的大样本长期随机对照实验结果来验证,还需要进一步的实验观察。

胶原/丝素导管介导雪旺细胞联合神经干细胞修复坐骨神经缺损

目的 观察胶原/丝素导管介导雪旺细胞联合神经干细胞所构建的组织工程化神经修复大鼠10 mm坐骨神经缺损的效果.方法 体外分离培养乳鼠坐骨神经雪旺细胞（SCs）,并做S-100蛋白免疫荧光鉴定;从孕14 - 15 d的SD大鼠体内取出子鼠,分离纯化获得原代神经干细胞（NSCs）进行体外培养.实验分为4组,每组10只：自体神经移植组（A组）、胶原/丝素导管介导雪旺细胞联合神经干细胞移植组（B组）、胶原/丝素导管移植组（C组）、单纯损伤组（D组）.SCs-NSCs与胶原/丝素导管联合培养14 d后,行扫描电镜观察.分别将3种不同移植物桥接于大鼠坐骨神经10 cm缺损处,并在12周后进行大体观察、电生理学检测、形态学观察及计量学分析.结果 术后12周,桥接组都不同程度地实现了坐骨神经缺损再通,且实验动物未出现明显排斥及炎性反应.神经电生理学检测坐骨神经复合肌动作电位（CMAPs）波幅分别为：未手术正常侧（21.00±1.83） mV,A组（15.00±1.12） mV,B组（13.00±1.06） mV,C组（6.00±0.58） mV,透射电子显微镜再生神经纤维髓鞘厚度分别为：A组（0.80±0.15） μm,B组（0.70±0.11） μm,C组（0.30±0.07） μm,D组（0.25±0.06） μm.统计结果表明：A组与B组之间差异无统计学意义（P＞0.05）,但两者相对C组及D组差异有统计学意义（P＜0.05）.结论 SCs和NSCs能够在胶原/丝素导管上共同生长分化,生物相容性良好.胶原/丝素导管介导雪旺细胞联合神经干细胞所构建的组织工程化神经对坐骨神经缺损的修复具有良好的桥接和促神经生长作用.

神经干细胞与雪旺细胞联合应用于神经损伤修复的研究进展

雪旺细胞是周围神经系统特有的神经胶质细胞,也是髓鞘形成细胞,能提供多种细胞因子和营养因子支持受损轴突再生并通过增殖分化形成髓鞘包绕新生轴突。神经干细胞是神经系统发育过程中保留下来的具有多向分化潜能的原始细胞,具有免疫原性低、组织融合性好、可自我更新等特点。雪旺细胞与神经干细胞对于外周神经损伤的修复与再生有着重要作用。近来随着显微外科技术的发展,利用神经导管联合神经干细胞与雪旺细胞桥接神经断端以实现周围神经损伤的修复吸引了越来越多研究者的兴趣。