组织工程周围神经修复坐骨神经缺损应用研究

目的应用组织工程方法构建周围神经以修复坐骨神经缺损.方法体外培养的雪旺细胞(SC)与牛去细胞基质(BAM)、胎牛血清和培养液按一定的比例混合注入聚乳酸聚羟基己酸共聚物(PLGA)导管中,构建成组织工程周围神经.30只SD大鼠随机分为3组,实验组:使用组织工程周围神经修复坐骨神经缺损;对照组:用不含雪旺细胞的导管修复;自体神经组:自体神经移植.16周后通过免疫组化、电生理、透射电镜、辣根过氧化物酶(HRP)逆行示踪及坐骨神经功能指数(SFI)等方法检测神经再生及坐骨神经功能恢复情况.结果 PLGA导管至16周已基本吸收,再生神经已通过缺损区长至远端,组织工程周围神经的修复效果接近自体神经组,优于空白组.结论体外构建的组织工程周围神经可以修复周围神经缺损.     

1101/带筋膜蒂的人工组织神经修复大鼠坐骨神经缺损的实验研究

目的 探索带筋膜蒂的人工组织神经修复周围神经缺损的可能性。 方法 选用健康SD大鼠40只,随机分为4组：实验组、自体神经组、硅胶管组及正常组,每组10只。实验组：切取一段坐骨神经造成10mm缺损,取缺损处周围组织筋膜瓣,一侧带蒂,以筋膜表面为管内壁缝合成管状,其内填充医用吸收性胶原海绵“体原素”,辅加神经营养因子,构成人工组织神经移植物,用它桥接坐骨神经缺损。自体神经组及硅胶管组：分别用自体神经移植及规格相匹配的医用硅胶管桥接大鼠坐骨神经10mm缺损。正常组：为无手术的正常对照组。术后各组大鼠常规饲养4个月后,对坐骨神经进行电生理学测定、形态学观察及计量学分析。结果 显示各项指标接近自体神经移植,明显优于硅胶管桥接移植。结论 带筋膜蒂的人工组织神经修复周围神经缺损是可行的     

以海洋生物单环刺缢及胶原海绵制成人工组织神经修复神经缺损

目的研究以去细胞的单环刺缢体壁和胶原海绵所构成的人工组织神经的组织相容性及修复神经缺损的效果。方法取大鼠40只随机分成实验组、自体神经组、硅胶管组及正常组。将去细胞的单环刺缢体壁缝合成神经导管,其内充填可吸收性胶原海绵,修复大鼠10mm坐骨神经缺损。术后4个月,通过组织形态学观察,了解该人工组织神经修复大鼠坐骨神经缺损的疗效。结果该人工组织神经组织相容性良好,神经功能恢复效果正常组>自体神经组>实验组>硅胶管组,实验组疗效与自体神经组接近,明显优于硅胶管组。结论将去细胞的单环刺缢体壁和胶原海绵制成人工组织神经修复周围神经缺损是可行的。     

自体微小颗粒骨复合几丁糖修复椎板缺损的有限元分析

背景：几丁糖具备良好的支架作用,不仅能够弥补自体微小颗粒骨结构松散的不足,防止其向植骨床外周扩散,减少骨流失,同时伴随颗粒骨的成骨过程几丁糖还可随之降解。 目的：探讨自体微小颗粒骨复合几丁糖修复椎板缺损的效果。 方法：健康成年杂种犬20只,均制备椎板缺损。随机分为 4组,复合组于椎板缺损区先充填一层几丁糖,再充填预制半干自体微小颗粒骨,后铺上一层几丁糖;自体微小颗粒骨组于椎板缺损区充填预制半干自体微小颗粒骨;几丁糖组于椎板缺损区充填几丁糖;空白组椎板缺损区不植入任何物质。术后8周,通过有限元方法对4 组模型的应力和位移变化进行比较。 结果与结论：关于位移值,几丁糖组>自体微小颗粒骨组>复合组,按照在一定载荷下位移越小刚度越大的理论,复合组模型刚度最大,自体微小颗粒骨组模型次之,几丁糖组模型刚度最小。提示几丁糖是微小颗粒骨的优良载体,自体微小颗粒骨复合几丁糖可有效修复椎板缺损,二者复合修复骨缺损的能力强于单纯微小颗粒骨。     

周围神经损伤修复及功能恢复评价

摘要 目的：评价修复周围神经缺损的各种生物型人工材料的性能、应用以及功能恢复评定方法,寻找适宜的周围神经替代物。 方法：以“神经导管,周围神经损伤修复,生物材料,许旺细胞”为关键词,采用计算机检索2004-01/2010-11相关文章。纳入与生物材料以及组织工程神经相关的文章;排除重复研究或Meta分析类文章。以28篇文献为主,重点讨论周围神经修复生物型人工材料的种类、性能以及适宜的功能恢复评定方法。 结果：以脱细胞神经基质以及人工合成可降解材料为主体的复合型生物工程材料可作为较理想的支架材料应用于周围神经组织工程。脱细胞神经支架解决了自体神经来源受限、移植物排斥反应等问题,韧性与可塑性接近自体神经,微环境更利于周围神经再生。人工合成可降解材料具有生物降解、可塑性、一定的通透性等优势,且已有商品化成品出现。若将上述材料分别合理构建复合材料,有可能得到性能良好的组织工程神经移植物。周围神经修复后功能恢复评定方法主要以大体与形态学观察、组织学、神经肌肉机能学评定为主,辅以分子生物学技术。各类评定方法的应用有利于筛选出最适宜的周围神经损伤修复材料与构建方案。 结论：周围神经损伤修复生物型人工材料研究发展迅速,但仍没有超越自体神经移植的支架材料。脱细胞神经基质以及人工合成可降解材料复合构建支架可作为较好的周围神经支架,但仍需要与种子细胞、神经营养因子等联合构建,以取得良好的促进再生效果。当前,对周围神经损伤修复效果的评定更加注重于神经肌肉功能的恢复,迫切需要筛选出最佳的修复材料以及构建方案以满足组织工程神经移植以及功能康复的要求,达到对周围神经损伤后形态、结构修复与功能重建的目的。 关键词：神经组织工程;周围神经;功能恢复;生物型人工材料;神经移植物 doi:10.3969/j.issn.1673-8225.2011.08.030     

自体神经片段串联再生室修复神经缺损

背景：周围神经缺损在现代生产生活中极为常见,自体神经移植被公认为是修复神经缺损的“金标准”;但是自体神经来源受限,且会导致供区感觉功能障碍,感觉神经细小,无法满足较粗神经缺损的需要,限制了其在临床上的广泛应用。因此,人们一直在努力寻找一种自体神经替代物来桥接神经缺损,同种异体神经﹑自体非神经组织、高分子人工合成材料以及二十世纪80年代兴起的组织工程学人工神经研究,用于修复周围神经缺损,但效果都不理想,临床应用还有很大距离距。 目的：本研究即不是风靡世界的人工神经研究,也不是各种神经细胞的培养,而是从另外一个新角度,使神经缺损很简便易行的转化成多个再生室用自体神经片段串联起来,完成修复。探讨对长距离神经缺损修复的一种新方法。 设计、时间及地点：市场购买成品壳聚糖粉、胶原、CNTF、成年SD大耳白兔。随机分组。在辽宁医学院组织胚胎实验室,附属第一医院动物实验室于2009年6月至2010年1月实验完成。 材料：日本大耳白兔28只,辽宁医学院实验动物中心提供。成品壳聚糖粉、胶原、CNTF、Sigma公司产品。 方法：健康日本大耳白兔28只（4周龄）, 雌雄不限,随机分为A、B、C、D四组,每组7只。麻醉下解剖大耳白兔坐骨神经,分别在梨状肌下缘6mm以远,造成右侧坐骨神经12mm、16 mm、30mm的缺损。A组采用30mm自体神经切取后,翻转180度进行桥接;B、C、D组分别采用10mm自体神经片段串联两个等长(6mm、8mm、10mm)壳聚糖-胶原-CNTF复合再生室桥接坐骨神经缺损。 主要观察指标：四通道肌电图仪、BH-2型光学显微镜及摄像系统、日本日立H/7500电镜检测神经传导速度和再生神经有髓纤维数目。 结果：术后24周A、B、C、D四组坐骨神经传导速度（41.99±2.10）m/s （39.79±2.20 ）m/s（27.94±1.67）m/s（19.89±1.57）m/s;最远端所取标本神经纤维数目（612.8±7.63）.（604.5±7.18）.（341.8±7.19）.（276.2±7.52）。以上指标A、B组比较差异无统计学意义(P >0.05);A组与D、 C组比较差异有统计学意义（ P<0.05）。 结论：1、壳聚糖-胶原-CNTF再生室具有良好的组织相容性,对大白兔坐骨神经缺损具有良好的桥梁作用和促进神经生长作用。 2、串联两个6mm壳聚糖-胶原-CNTF复合再生室修复坐骨神经12mm缺损的效果,近似自体神经移植效果。 3、串联再生室自体神经片段的雪旺细胞是可以分泌多种神经活性物质,在有效趋化距离内,神经活性物质可充分发挥其作用。     

周围神经组织工程进展

周围神经损伤以后的修复、再生和功能恢复一直是神经科学研究的热点，目前临床上主要采用自体神经移植的方法进行修复。但自体神经移植会造成供体功能丧失，且修复长度受限，大小难以匹配，可能形成神经瘤等．这些缺点限制了其临床应用。随着组织工程技术的兴起，目前提倡利用生物学和工程学原理开发能修复、维持和改善组织功能的替代品。周围神经组织工程旨在为神经缺损的修复提供供体，其核心是建立由生物材料和种子细胞构成的三维神经导管。     

脱细胞细胞外基质及其预构建桥接物修复坐骨神经缺损的实验研究

目的 比较脱细胞细胞外基质(acellular extracellular matris，AECM)同周围神经并行端侧吻合预构建桥接物修复坐骨神经缺损并与自体神经移植后神经再生的效果比较，探讨其修复长段周围神经缺损的可行性。方法 将组织工程化技术制备的AECM 10mm、15mm、20mm预构建，形成一种新的神经桥接物并对其进行了观察和动物移植试验。预构建即：将AECM与坐骨神经并行端侧吻合2周。结果 发现组织工程化技术制备的AECM虽然细胞被完全消蚀，但还具备原有三维结构及生物活性，经预构建后用其修复SD大鼠15mm坐骨神经缺损时，取得了接近自体神经移植的结果，并且没有缺血或炎性表现，无瘢痕形成。结论 这种新的AECM预构建桥接物有可能成为自体神经移植的替代材料。     

臂丛神经损伤后神经功能的重建：标准技术vs.新技术

臂丛神经受损可导致手臂、手失神经支配和难以忍受的神经性疼痛。最常用的臂丛神经损伤修复技术是自体感觉神经移植修复神经缺损,该技术对于神经功能的恢复的神经性疼痛的减轻作用并不可靠。我们评估了目前最好的臂丛神经修复技术和用填充了自体富血小板纤维蛋白的胶原管修复臂丛神经缺损,其能更好的促进神经功能恢复,减轻或使神经性疼痛消失;这些修复效果是传统神经移植无法达到的。     

外源性神经生长因子诱导下自体静脉桥接修复神经缺损

背景：采用自体神经游离移植修复神经缺损效果比较理想,但有其弊端。为此寻求一种更佳修复神经缺损的治疗方法。 目的：验证及外源性神经生长因子诱导下自体静脉桥接神经缺损对神经再生的影响。 方法：采用Wistar大鼠建立周围神经缺损模型。随机将大鼠分为3组。实验组采用自体静脉桥接并注入神经生长因子;对照组采用自体静脉桥接并注入生理盐水;标准组采用自体神经桥接。分别于术后1,3个月,对实验动物进行活体观察,电生理检测及组织学检测。 结果与结论：3组实验动物均有神经再生及修复表现,但程度不同。实验组失神经表现恢复的较对照组早,电生理检测运动神经传导速度快,组织学检查再生神经纤维数量及质量明显高于对照组(P < 0.05);与“金标准”的自体神经桥接组比较无显著性意义(P > 0.05)。结果提示采用自体静脉桥接+神经生长因子诱导对周围神经缺损后的再生、修复具有有促进作用,可以使再生神经纤维的数量增加并显著提高再生神经纤维质量。     

Decellularized sciatic nerve matrix as a biodegradable conduit for peripheral nerve regeneration

The use of autologous nerve grafts remains the gold standard for treating nerve defects, but current nerve repair techniques are limited by donor tissue availability and morbidity associated with tissue loss. Recently, the use of conduits in nerve injury repair, made possible by tissue engineering, has shown therapeutic potential. We manufactured a biodegradable, collagen-based nerve conduit containing decellularized sciatic nerve matrix and compared this with a silicone conduit for peripheral nerve regeneration using a rat model. The collagen-based conduit contains nerve growth factor, brain-derived neurotrophic factor, and laminin, as demonstrated by enzyme-linked immunosorbent assay. Scanning electron microscopy images showed that the collagen-based conduit had an outer wall to prevent scar tissue infiltration and a porous inner structure to allow axonal growth. Rats that were implanted with the collagen-based conduit to bridge a sciatic nerve defect experienced significantly improved motor and sensory nerve functions and greatly enhanced nerve regeneration compared with rats in the sham control group and the silicone conduit group. Our results suggest that the biodegradable collagen-based nerve conduit is more effective for peripheral nerve regeneration than the silicone conduit.     

A collagen-based nerve guide conduit for peripheral nerve repair: an electrophysiological study of nerve regeneration in rodents and nonhuman primates

When a peripheral nerve is severed and left untreated, the most likely result is the formation of an endbulb neuroma; this tangled mass of disorganized nerve fibers blocks functional recovery following nerve injury. Although there are several different approaches for promoting nerve repair, which have been greatly refined over recent years, the clinical results of peripheral nerve repair remain very disappointing. In this paper we compare the results of a collagen nerve guide conduit to the more standard clinical procedure of nerve autografting to promote repair of transected peripheral nerves in rats and nonhuman primates. In rats, we tested recovery from sciatic nerve transection and repair by 1) direct microsurgical suture, 2) 4 mm autograft, or 3) entubulation repair with collagen-based nerve guide conduits. Evoked muscle action potentials (MAP) were recorded from the gastrocnemius muscle at 4 and 12 weeks following sciatic nerve transection. At 4 weeks the repair group of direct suture demonstrated a significantly greater MAP, compared to the other surgical repair groups. However, at 12 weeks all four surgical repair groups displayed similar levels of recovery of the motor response. In six adult male Macaca fascicularis monkeys the median nerve was transected 2 cm above the wrist and repaired by either a 4 mm nerve autograft or a collagen-based nerve guide conduit leaving a 4 mm gap between nerve ends. Serial studies of motor and sensory fibers were performed by recording the evoked MAP from the abductor pollicis brevis muscle (APB) and the sensory action potential (SAP) evoked by stimulation of digital nerves (digit II), respectively, up to 760 days following surgery. Evoked muscle responses returned to normal baseline levels in all cases. Statistical analysis of the motor responses, as judged by the slope of the recovery curves, indicated a significantly more rapid rate of recovery for the nerve guide repair group. The final level of recovery of the MAP amplitudes was not significantly different between the groups. In contrast, the SAP amplitude only recovered to the low normal range and there were no statistically significant differences between the two groups in terms of sensory recovery rates. The rodent and primate studies suggest that in terms of recovery of physiological responses from target muscle and sensory nerves, entubulation repair of peripheral nerves with a collagen-based nerve guide conduit over a short nerve gap (4 mm) is as effective as a standard nerve autograft.(ABSTRACT TRUNCATED AT 400 WORDS)     

Factors that influence peripheral nerve regeneration: an electrophysiological study of the monkey median nerve.

Regeneration in the peripheral nervous system is often incomplete though it is uncertain which factors, such as the type and extent of the injury or the method or timing of repair, determine the degree of functional recovery. Serial electrophysiological techniques were used to follow recovery from median nerve lesions (n = 46) in nonhuman primates over 3 to 4 years, a time span comparable with such lesions in humans. Nerve gap distances of 5, 20, or 50mm were repaired with nerve grafts or collagen-based nerve guide tubes, and three electrophysiological outcome measures were followed: (1) compound muscle action potentials in the abductor pollicis brevis muscle, (2) the number and size of motor units in reinnervated muscle, and (3) compound sensory action potentials from digital nerve. A statistical model was used to assess the influence of three variables (repair type, nerve gap distance, and time to earliest muscle reinnervation) on the final recovery of the outcome measures. Nerve gap distance and the repair type, individually and concertedly, strongly influenced the time to earliest muscle reinnervation, and only time to reinnervation was significant when all three variables were included as outcome predictors. Thus, nerve gap distance and repair type exert their influence through time to muscle reinnervation. These findings emphasize that factors that control early axonal outgrowth influence the final level of recovery attained years later. They also highlight that a time window exists within which axons must grow through the distal nerve stump in order for recovery after nerve lesions to be optimal. Future work should focus on interventions that may accelerate the growth of axons from the lesion site into the distal nerve stump.     

Preparation and biological evaluation of chitosan–collagen–icariin composite scaffolds for neuronal regeneration

In this study the chitosan/collagen/icariin composite scaffolds for nerve regeneration were produced by blending and crosslinking chitosan with collagen and icariin. The microstructure of the composite scaffolds was observed by scanning electron microscopy. 3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide and attachment assays were conducted, respectively, to investigate the biocompatibility of the scaffolds. Cell cultural tests showed that the channel-structured porous scaffolds acted as a positive factor to support connective nerve cell growth. After culture, cells showed a clear flow trend to move close to the composite scaffolds in culture solution, arranging in spiral-like, and aligned parallel to the orientation of the channel structure on the surface of scaffolds. When compared to pure chitosan and chitosan/collagen scaffolds, Schwann cells and PC12 cells on the chitosan/collagen/icariin composite scaffolds exhibited the greatest proliferation and longest average neurite length. These results suggested that the chitosan/collagen/icariin composite scaffolds are potential cell carriers in nerve tissue engineering.     

Chitosan tubes enriched with fresh skeletal muscle fibers for delayed repair of peripheral nerve defects

Nerve regeneration after delayed nerve repair is often unsuccessful. Indeed, the expression of genes associated with regeneration, including neurotrophic and gliotrophic factors, is drastically reduced in the distal stump of chronically transected nerves; moreover, Schwann cells undergo atrophy, losing their ability to sustain regeneration. In the present study, to provide a three-dimensional environment and trophic factors supporting Schwann cell activity and axon re-growth, we combined the use of an effective conduit(a chitosan tube) with a promising intraluminal structure(fresh longitudinal skeletal muscle fibers). This enriched conduit was used to repair a 10-mm rat median nerve gap after 3-month delay and functional and morphometrical analyses were performed 4 months after nerve reconstruction. Our data show that the enriched chitosan conduit is as effective as the hollow chitosan conduit in promoting nerve regeneration,and its efficacy is not statistically different from the autograft, considered the "gold standard" technique for nerve reconstruction. Since hollow tubes not always lead to good results after long defects( 20 mm), we believe that the conduit enriched with fresh muscle fibers could be a promising strategy to repair longer gaps, as muscle fibers create a favorable three-dimensional environment and release trophic factors. All procedures were approved by the Bioethical Committee of the University of Torino and by the Italian Ministry of Health(approval number: 864/2016/PR) on September 14, 2016.     

Peripheral nerve regeneration across an 80-mm gap bridged by a polyglycolic acid (PGA)–collagen tube filled with laminin-coated collagen fibers: a histological and electrophysiological evaluation of regenerated nerves

We evaluated peripheral nerve regeneration across an 80-mm gap using a novel artificial nerve conduit. The conduit was made of a polyglycolic acid (PGA)–collagen tube filled with laminin-coated collagen fibers. Twelve beagle dogs underwent implantation of the nerve conduit across an 80-mm gap in the left peroneal nerve. In four other dogs used as negative controls, the nerve was resected and left unconnected. Histological observation showed that numerous unmyelinated and myelinated nerve fibers, all smaller in diameter and with a thinner myelin sheath than normal nerve fibers, regrew through and beyond the gap 12 months after implantation. The distribution of the regenerated axonal diameters was different from that of the normal axonal diameters. Compound muscle action potentials, motor evoked potentials, and somatosensory evoked potentials were recorded in most animals 3 months after implantation. Peak amplitudes and latencies recovered gradually, which indicating the functional establishment of the nerve connection with the target organs. In addition to the ordinary electrophysiological recoveries, potentials with distinct latencies originating from Aα, Aδ and C fibers became distinguishable at the 6th lumbar vertebra following stimulation of the peroneal nerve distal to the gap 12 months after implantation. The pattern of walking without load was restored to almost normal 10–12 months after implantation. Neither electrophysiological nor histological restoration was obtained in the controls. Our nerve conduit can guide peripheral nerve elongation and lead to favorable functional recovery across a wider nerve gap than previously reported artificial nerve conduits.     

Electrical stimulation does not enhance nerve regeneration if delayed after sciatic nerve injury: the role of fibrosis

Electrical stimulation has been shown to accelerate and enhance nerve regeneration in sensory and motor neurons after injury, but there is little evidence that focuses on the varying degrees of fibrosis in the delayed repair of peripheral nerve tissue. In this study, a rat model of sciatic nerve transection injury was repaired with a biodegradable conduit at 1 day, 1 week, 1 month and 2 months after injury, when the rats were divided into two subgroups. In the experimental group, rats were treated with electrical stimuli of frequency of 20 Hz, pulse width 100 ms and direct current voltage of 3 V; while rats in the control group received no electrical stimulation after the conduit operation. Histological results showed that stained collagen fibers comprised less than 20% of the total operated area in the two groups after delayed repair at both 1 day and 1 week but after longer delays, the collagen fiber area increased with the time after injury. Immunohistochemical staining revealed that the expression level of transforming growth factor β(an indicator of tissue fibrosis) decreased at both 1 day and 1 week after delayed repair but increased at both 1 and 2 months after delayed repair. These findings indicate that if the biodegradable conduit repair combined with electrical stimulation is delayed, it results in a poor outcome following sciatic nerve injury. One month after injury, tissue degeneration and distal fibrosis are apparent and are probably the main reason why electrical stimulation fails to promote nerve regeneration after delayed repair.     

神经桥接与导管套接修复猫动眼神经形态学观察

目的探求导管修复颅内段动眼神经的可行性.方法 20只健康家猫随机分为2组.将右侧动眼神经于脑池段切断后,分组采用自体神经桥接和导管套接的方法修复.术后14周末光镜、电镜观察神经纤维的连续性、再生纤维数目和直径.结果神经修复14周后,神经桥接组67%、导管套接组75%的动物其动眼神经功能均有一定程度的恢复.形态学显示两组均取得较好的神经再生效果,两组间再生纤维直径差异无显著性(P>0.05),但导管套接组再生神经纤维数目较多,差异有显著性(P<0.05).结论导管套接法可作为颅内段动眼神经损伤后的一种修复方法,其疗效近似或稍优于神经桥接法.     

Peripheral nerve regeneration across an 80-mm gap bridged by a polyglycolic acid (PGA)-collagen tube filled with laminin-coated collagen fibers: a histological and electrophysiological evaluation of regenerated nerves

We evaluated peripheral nerve regeneration across an 80-mm gap using a novel artificial nerve conduit. The conduit was made of a polyglycolic acid (PGA)-collagen tube filled with laminin-coated collagen fibers. Twelve beagle dogs underwent implantation of the nerve conduit across an 80-mm gap in the left peroneal nerve. In four other dogs used as negative controls, the nerve was resected and left unconnected. Histological observation showed that numerous unmyelinated and myelinated nerve fibers, all smaller in diameter and with a thinner myelin sheath than normal nerve fibers, regrew through and beyond the gap 12 months after implantation. The distribution of the regenerated axonal diameters was different from that of the normal axonal diameters. Compound muscle action potentials, motor evoked potentials, and somatosensory evoked potentials were recorded in most animals 3 months after implantation. Peak amplitudes and latencies recovered gradually, which indicating the functional establishment of the nerve connection with the target organs. In addition to the ordinary electrophysiological recoveries, potentials with distinct latencies originating from Aalpha, Adelta and C fibers became distinguishable at the 6th lumbar vertebra following stimulation of the peroneal nerve distal to the gap 12 months after implantation. The pattern of walking without load was restored to almost normal 10-12 months after implantation. Neither electrophysiological nor histological restoration was obtained in the controls. Our nerve conduit can guide peripheral nerve elongation and lead to favorable functional recovery across a wider nerve gap than previously reported artificial nerve conduits.     

Chitosan tube bridging autologous nerve segments for the repair of long-segmental sciatic nerve defects

BACKGROUND:Previous tissue-engineered nerve studies have focused on artificial nerve and nerve cell cultures.The effects of regeneration chambers with autologous nerve bridging for the repair of nerve defects remain unclear.OBJECTIVE:To explore the feasibility and advantages of chitosan tube bridging autologous nerve segments for repairing 12-mm sciatic nerve defects in rats.DESIGN,TIME AND SETTING:A randomized,controlled,animal study using nerve tissue engineering was performed at the Animal Laboratory and Laboratory of Histology and Embryology,Liaoning Medical University from June 2008 to March 2009.MATERIALS:Chitosan powder was purchased from Jinan Haidebei Marine Bioengineering,China.METHODS:A sciatic nerve segment of approximately 8 mm was excised from the posterior margin of the piriformis muscle of Sprague Dawley rats.The two nerve ends shrank to form a 12-mm defect,and the nerve defect was repaired using a chitosan tube bridging autologous nerve segment (bridge group),a chitosan tube-encapsulated autologous nerve segment (encapsulation group),and a chitosan tube alone (chitosan tube alone group),respectively.MAIN OUTCOME MEASURES:Histological and ultrastructural changes of the injured sciatic nerve;number of regenerated myelinated nerve fibers; nerve conduction velocity; leg muscle atrophy; and sciatic nerve functional index.RESULTS:At 4 months after implantation,the chitosan tube was absorbed.The tube was thin,but maintained the original shape,and vascular proliferation was observed around the tube.In the bridge group,regenerative myelinated nerve fibers were thick and orderly,with a thick myelin sheath and intact axonal structure.The number of myelinated nerve fibers and nerve conduction velocity were significantly greater compared with the other groups (P< 0.01).Moreover,nerve and muscle function was significantly improved following chitosan tube bridging autologous nerve segment treatment compared with the other groups (P< 0.05 or P < 0.01).CONCLUSION:Chitosan tube bridging autologous nerve segments exhibited better repair effects on nerve defects compared with chitosan tubeencapsulated autologous nerve segments and a chitosan tube alone.This method provided a simple and effective treatment for long-segmental nerve defects.