骨髓间充质细胞构建组织工程神经修复坐骨神经缺损

背景：许旺细胞是周围神经组织工程的种子细胞,但体外分离、培养、纯化许旺细胞较困难。脱细胞同种异体神经移植物具有较强的修复外周神经缺损的能力,且可诱导骨髓间充质细胞分化为类许旺细胞,理论上骨髓间充质细胞可替代许旺细胞作为种子细胞应用于周围神经组织工程。 目的：观察骨髓间充质细胞构建组织工程神经修复坐骨神经缺损的效果,评估骨髓间充质细胞作为种子细胞修复周围神经缺损的可行性。 设计、时间及地点：随机对照动物实验,于2008-07/12在大理学院基础医学院实验室完成。 材料：将30只SD大鼠按随机数字表法分为3组,每组10只。骨髓间充质细胞+异体移植组将骨髓间充质细胞复合脱细胞同种异体神经移植物培养的组织工程神经与两断端用10/0 无创线端端吻合;异体移植组将脱细胞同种异体神经移植物桥接;自体移植组将切断的坐骨神经旋转180°端端吻合。 方法：运用骨髓间充质细胞构建的组织工程神经修复大鼠10 mm坐骨神经缺损,移植后12周通过坐骨神经功能指数、腓肠肌湿质量恢复率、S-100免疫组织化学染色、电镜等方法观察移植物修复效果。 主要观察指标：复合物培养时观察细胞形态的变化;移植后观察坐骨神经功能指数及腓肠肌湿质量恢复率;通过甲苯胺蓝染色观察新生髓鞘形成和轴突生长及神经纤维的分布情况,结合透射电镜及S-100蛋白免疫组织化学染色,观察许旺细胞生长和神经纤维再生情况。 结果：坐骨神经功能指数及腓肠肌湿质量恢复率的检测结果显示骨髓间充质细胞+异体移植组优于异体移植组(P < 0.05)。骨髓间充质细胞+异体移植组复合物中S-100的表达明显高于异体移植组,有髓神经纤维数量、有髓纤维直径和髓鞘厚度均大于异体移植组(P < 0.05),修复效果接近自体移植组。 结论：骨髓间充质细胞构建的组织工程神经修复周围神经缺损的效果优于单纯的脱细胞同种异体神经移植物,骨髓间充质细胞作为种子细胞在周围神经组织工程中具有较强的应用价值。     

应用肌膜瓣包裹、羊膜管预置聚乳酸-羟基乙酸微丝模拟周围神经再生

背景：周围神经损伤部位的微环境状况是影响神经再生的重要因素之一。周围神经损伤后，良好的神经再生微环境有利于保护受损神经元、促进轴突的有效再生。 目的：应用肌膜瓣包裹、羊膜管预置聚乳酸-羟基乙酸微丝，充填大鼠自体周围神经组织浆模拟周围神经再生微环境，探讨其修复坐骨神经缺损的可行性。 设计、时间及地点：随机对照动物实验，于2006-06/2007-10在广东医学院实验动物中心完成。 材料：清洁级2月龄SD大鼠30只，随机分为实验组、对照组、标准组3组，每组10只，右侧为实验侧，左侧为正常对照侧。取健康、足月、顺产的新鲜胎儿羊膜(产妇知情同意) 制备羊膜基质膜。用医用Vicryl缝线和羊膜基质膜制备聚乳酸-羟基乙酸微丝桥接物。 方法：大鼠切除坐骨神经6.0 mm，自然回缩建立坐骨神经缺损模型。实验组采用带蒂肌膜瓣、人羊膜管预置Vicryl微丝并充填大鼠自体坐骨神经组织浆；对照组采用单纯人羊膜管充填大鼠自体坐骨神经组织浆；标准组采用自体神经移植，桥接大鼠坐骨神经缺损。 主要观察指标：术后8，12周行大体观察、组织学检查、胫前肌湿质量、有髓神经纤维通过率及神经电生理学检测。 结果：术后12周，实验组、标准组肌萎缩有所恢复，对照组则恢复不明显。实验、标准组患侧胫前肌色泽红润，饱满富有弹性；对照组色泽相对较暗，弹性度较差。术后8，12周3组胫前肌恢复率组间比较，术后12周3组有髓神经纤维总数、截面积，神经移植体血管数和血管截面积组间比较，以及小腿三头肌复合肌动作电位幅值组间比较，差异均有显著性意义(P < 0.05），其中标准组神经纤维再生质量最佳，实验组优于对照组。 结论：肌膜转位、羊膜管预置聚乳酸-羟基乙酸微丝，并填充大鼠自体周围神经组织浆导管能较好的模拟周围神经再生之微环境，促进神经纤维再生，但与自体神经移植尚有差距。     

他克莫司与肌源性干细胞联合应用对去细胞异体神经支架移植后神经再生和修复作用的影响

背景：肌源性干细胞作为种子细胞用于制备组织工程化人工神经已经被越来越多的学者所接受。他克莫司不仅具有抗免疫排斥的效果,还具有强大的促进神经再生和修复的作用。那么能否将两项因素与去细胞异体神经支架形成一个桥接体,既能抑制异体移植的免疫反应,又能有效促进损伤神经的再生与修复？ 目的：采用理化联合处理方法制备去细胞异体神经支架,探讨肌源性干细胞与免疫抑制剂他克莫司联合应用对去细胞异体神经支架移植后神经再生及功能恢复的影响。 方法：SD大鼠坐骨神经经脱细胞处理后形成异体神经桥接体。用100 μL微量注射器将含他克莫司与肌源性干细胞的凝胶注入异体神经支架,用以修复大鼠的坐骨神经缺损。32只成年SD大鼠,随机分为4组,每组8只。切断其左侧坐骨神经造成10 mm 的缺损。他克莫司+肌源性干细胞组、肌源性干细胞组、他克莫司组以注射植入后的异体神经进行桥接;对照组仅注入透明质酸凝胶。术后8,12周进行坐骨神经指数和神经电生理测定。术后12周进行大体观察,神经组织学和超微结构观察。 结果和结论：在同一时点他克莫司+肌源性干细胞组坐骨神经功能指数、坐骨神经运动传导速度恢复率、移植体及远段有髓纤维计数均优于其他3组(P < 0.05)。各组神经移植体粗细基本正常,表面大量血管分布,与周围组织轻度粘连;他克莫 司+肌源性干细胞组较其他3组再生神经纤维更加密集、排列规则整齐;移植体许旺细胞大量增殖,移植体中央及远段内的有髓神经纤维密度、直径高于肌源性干细胞组、他克莫司组,微束之间结缔组织少,接近于正常。说明肌源性干细胞和他克莫司联合应用促进去细胞异种神经移植的神经再生与功能恢复的效果优于单独应用。肌源性干细胞和他克莫司在周围神经损伤修复中是一对具有协同作用的因子。 关键词：周围神经损伤;异体神经移植;神经再生;肌源性干细胞;他克莫司 doi:10.3969/j.issn.1673-8225.2010.03.003     

1102/异种神经脱细胞移植物桥接大鼠坐骨神经缺损

目的　探讨异种神经脱细胞移植物桥接大鼠坐骨神经缺损后的神经再生及其再生过程中免疫排斥反应。 方法　用脱细胞兔周围神经作为移植物桥接大鼠坐骨神经1cm缺损;术后3、5、8、11、15天检测血液中淋巴细胞占白细胞百分比;3个月后取移植物及腓肠肌,用甲苯胺蓝、乙酰胆碱酯酶(AchE)、琥珀酸脱氢酶(SDH)组化染色,光、电镜观察神经再生及腓肠肌运动终板的恢复情况。　 结果　术后大鼠血液中淋巴细胞占白细胞的百分比与正常大鼠相比较无显著性差异,3个月后大鼠术侧下肢足趾能分开,行走时后蹬动作有力,针刺足底有逃避反应,桥接物内见有大量再生的坐骨神经纤维,腓肠肌肌纤维上见有呈AchE阳性的运动终板和神经纤维。　 结论　异种神经脱细胞移植物桥接大鼠坐骨神经缺损具有促进其再生的作用。     

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坐骨神经缺损

背景：作者前期已经成功将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,并证明可以促进周围神经再生。 目的：构建组织工程人工神经,观察和验证桥接大鼠坐骨神经缺损后的神经功能恢复情况。 方法：成年雄性SD大鼠60只构建大鼠坐骨神经15 mm缺损模型。随机分成3组,每组20只。桥接大鼠坐骨神经缺损,实验组采用组织工程人工神经,空白对照组采用无细胞组织工程神经支架,自体神经对照组采用自体神经移植。桥接后12周通过大体观察、胫骨前肌湿质量、组织学等方法分析坐骨神经组织学及功能恢复情况。 结果与结论：桥接术后12周：实验组大鼠肢体可以支撑着地,钳夹大鼠手术侧足底皮肤出现逃避反射,足底皮肤s-100蛋白染色呈阳性反应。实验组与自体神经移植组胫骨前肌湿质量比差异无显著性意义(P > 0.05)。实验组辣根过氧化物酶逆行示踪实验显示脊髓、后根神经节均可见数量不等的辣根过氧化物酶标记阳性细胞。实验组移植物与自体神经移植组有髓神经纤维数、髓鞘厚度、神经组织面积比较差异无显著性意义。实验结果验证了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,可以促进神经组织学的修复重建和功能的恢复。     

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。     

同种异体神经复合体桥接修复兔坐骨神经缺损与神经-肌结构重建及功能恢复

背景：课题组在前期研究中分别探讨了神经生长因子对胎兔许旺细胞培养的影响以及去细胞神经移植体的制备,并在体外成功制备出重新细胞化的神经移植复合体。 目的：探讨种植许旺细胞的去细胞同种异体神经移植对神经-肌结构重建和功能恢复的作用。 设计、时间及地点：随机对照动物实验,于2006-03/2007-06在河北医科大学第三医院中心实验室完成。 材料：健康成年新西兰白兔37只,1只用于制备去细胞神经桥接体,剩余36只随机分为实验组、对照组,18只/组。 方法：切取兔双侧坐骨神经,剥除周围组织,剪成约每段3 cm,放入TritonX-100水溶液中静置12 h,蒸馏水漂洗,以使溶于水的TritonX-100膜蛋白体复合物充分脱离神经干,如此反复,TritonX-100作用时间共为96 h,萃取好的去细胞神经桥接体在Hank s液中4 ℃保存。调整第2代许旺细胞浓度至1×1011 L-1,用100 μL微量注射器注入去细胞神经桥接体内,然后将神经段置于DMEM培养液中,即为同种异体神经复合体。实验组兔于膝关节上方造成20 mm长缺损,将种植许旺细胞的同种异体神经复合体缝接于坐骨神经两断端;对照组兔左侧坐骨神经造成20 mm长缺损后,用单纯的去细胞同种异体神经桥接物缝接神经两断端。 主要观察指标：分别于术后4,8,16周大体观察兔足部溃疡形成及愈合情况,通过肌电图、光镜、电镜等方法检测远端腓神经的轴突、髓鞘及胫骨前肌、运动终板的恢复情况。 结果：术后4,8,16周两组动物术区局部均未出现明显的排斥反应,实验组足部溃疡愈合情况、神经纤维数目、髓鞘及再生神经的超微结构、运动终板的形态及靶肌肉结构的恢复均优于对照组。术后4周两组均未见明显的神经传导,术后8,16周实验组胫骨前肌湿质量、神经传导速度均优于对照组(P < 0.05)。 结论：种植许旺细胞的去细胞同种异体神经复合体不仅能够为再生神经提供良好的支架作用,还能诱导和促进神经轴突和髓鞘的再生,对坐骨神经缺损后的神经-肌结构重建与功能恢复具有显著的促进作用。     

同种异体神经复合体修复兔周围神经缺损

背景：应用种植许旺细胞的去细胞同种异体神经复合体修复周围神经缺损,探索其对神经再生及功能恢复有更好的促进作用,并且免疫原性非常小。 目的：用种植胎兔许旺细胞的去细胞同种异体神经复合体修复兔缺损的坐骨神经,观察移植神经周围免疫细胞的变化及功能恢复。 　 方法：48只新西兰白兔随机分成实验组和对照组。两组动物均切除一段坐骨神经,造成2.0 cm长的缺损,实验组用种植胎兔许旺细胞的同种异体神经复合体修复坐骨神经;对照组仅用去细胞同种异体神经修复。移植后1,4,8周光镜观察移植段坐骨神经周围肌肉组织中免疫细胞的浸润情况,计数每个高倍视野免疫细胞的数量。移植后4,8,16周大体观察兔的足部溃疡形成及愈合情况,大体观察神经愈合情况;肌电图检查桥接段坐骨神经的传导速度。 结果与结论：手术区局部均未出现明显的排斥反应,实验组足部溃疡愈合情况优于对照组。移植后1周移植段坐骨神经周围肌肉组织中有大量淋巴细胞及巨噬细胞浸润,实验组明显多于对照组(P < 0.05);移植后4周,浸润的免疫细胞两组均较1周后明显减少,实验组减少更明显。移植后8周,浸润的免疫细胞更加减少,但两组间比较差异无显著性意义(P > 0.05)。移植后4周时,两组均未见明显的神经传导,8,16周神经传导速度实验组均优于对照组(P < 0.05)。提示,种植许旺细胞的去细胞同种异体神经复合体免疫原性非常小,对神经再生及功能恢复有更好的促进作用。     

无细胞神经移植物复合骨髓间充质干细胞修复大鼠坐骨神经缺损

背景：作者前期试验已成功制备了天然可生物降解的无细胞神经移植物并证明其可促进周围神经再生。 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并观察其修复大鼠坐骨神经缺损促进运动功能恢复的效果。 设计、时间及地点：随机对照动物实验，于2008-06/2009-02在辽宁医学院附属第一医院医学组织工程实验室完成。 材料：180~200 g成年健康雄性Wistar大鼠，用于制备无细胞神经移植物，100~120 g成年健康雄性Wistar大鼠，用于制备骨髓间充质干细胞，将骨髓间充质干细胞植入并与无细胞神经支架联合培养构建组织工程人工神经。 方法：180~200 g成年健康雄性SD大鼠60只构建坐骨神经15 mm缺损模型，随机分成3组，每组20只。①实验组采用组织工程人工神经桥接大鼠坐骨神经缺损。②空白对照组采用组织工程神经支架桥接大鼠坐骨神经缺损。③自体神经对照组采用自体神经移植桥接大鼠坐骨神经缺损。 主要观察指标：术后12周通过大体观察、电生理检测、组织学和小腿三头肌湿质量等方法分析评价运动功能恢复情况。 结果：①术后12周，实验组大鼠手术侧足趾可以分开，并且可以支撑着地；实验组大鼠再生神经传导速度与自体神经对照组相比，差异无显著性意义。②术后12周，实验组组织化学染色可见腓肠肌内有呈AchE阳性的运动终板整齐地排列于腓肠肌的中上部形成终板带，经结合镀银染色后可见再生的神经束及发出的分支与运动终板相连。③实验组与自体神经对照组胫骨前肌湿质量比差异无显著性意义。 结论：无细胞神经移植物复合骨髓间充质干细胞桥接大鼠坐骨神经缺损具有促进其运动功能恢复的作用。     

雷公藤多甙预处理对大鼠异体神经移植后神经再生的影响

目的 探讨中药雷公藤多甙（Tripterygium Glycoside,TG）预处理对大鼠异体坐骨神经移植后神经再生情况的影响。方法 成年健康雄性Wistar大鼠15只为供体,切取双侧15mm坐骨神经共30段。另选择40只成年健康雄性SD大鼠随机分为4组,均建立右侧坐骨神经缺损模型。设实验组A组：雷公藤预处理组,同时设3组对照组,B组：口服雷公藤组,C组：新鲜自体移植组,D组：新鲜异体移植组。术后于2、4、8、14周行坐骨神经功能指数(Sciatic functional Index,SFI)测定,对神经移植片段进行大体、光镜的组织学检查,并在术后14周行神经电生理检查,透射电镜观察,再生轴突图像分析。结果 术后A、B、C三组SFI均逐渐恢复,D组SFI一直无恢复,与A、B、C三组差异有统计学意义（P<0.05）。术后A、B组移植段早期急性排斥反应稍重于C组,但明显小于D组;而后A、B组移植段的炎性细胞浸润程度明显减轻,与C组相似。术后14周时A、B、C三组移植神经段神经传导速度、动作电位峰值差异无统计学意义（P>0.05）,且均大于D组,神经外膜构成完整,束膜、内膜厚度,分布及范围无明显差异,再生有髓神经神经纤维的面积,总数和髓鞘厚度差异无统计学意义（P>0.05）,而D组基本未见神经纤维再生。结论 异体神经段经雷公藤多甙预处理后可降低移植物与宿主间的免疫排斥反应,促进周围神经再生。     

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 effec-tively 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.     

Peripheral nerve regeneration through silicone chambers in streptozocin-induced diabetic rats

The silicone chamber model was used to evaluate peripheral nerve regeneration (PNR) in streptozocin (STZ)-induced diabetic rats. Diabetic and control animals underwent sciatic nerve transection and silicone chamber implantation establishing gaps of various lengths between the transected nerve ends. In animals with 5 and 10 mm gaps, diabetes was induced in experimental rats 1 week before surgery, and the animals were sacrificed 3 weeks after surgery. In animals with 8 mm gaps, diabetes induction occurred 3 days after surgery, and they were sacrificed after 7 weeks. Diabetic rats with 10 mm gaps demonstrated an impaired ability to form bridging cables, the initial step of regeneration through chambers. Morphometric studies of bridging cables between transected nerve ends demonstrated a significant reduction in the mean endoneurial area in diabetic animals with 5 and 8 mm gaps compared to controls. The number of regenerated myelinated axons in the chamber was significantly decreased in diabetic rats with 8 and 10 mm gaps. The mean myelinated fiber area in the regenerated cables of the diabetic group was significantly decreased with 5 mm gaps and significantly increased with 8 mm gaps compared to controls. Size-frequency histograms of regenerated myelinated fiber areas suggest a delay in the maturation of small caliber axons. Schwann cell migration across 5 mm gaps was examined with S-100 immunohistochemistry. The total distance of Schwann cell migration into cables from both proximal and distal ends was significantly reduced in diabetic animals. Characterization of PNR across gaps through silicone chambers in diabetic rats showed impairment in multiple aspects of the regenerative process, including cable formation, Schwann cell migration, and axonal regeneration.     

Human amnion tissue injected with human umbilical cord mesenchymal stem cells repairs damaged sciatic nerves in rats

Human umbilical cord mesenchymal stem cells,incorporated into an amnion carrier tubes,were assessed for nerve regeneration potential in a rat nerve defect model.Damaged nerves were exposed to human amnion carriers containing either human umbilical cord mesenchymal stem cell (cell transplantation group)or saline(control group).At 8,12,16 and 20 weeks after cell implantation,the sciatic functional index was higher in the cell transplantation group compared with the control group.Furthermore,electrophysiological examination showed that threshold stimulus and maximum stimulus intensity gradually decreased while compound action potential amplitude gradually increased.Hematoxylin-eosin staining showed that regenerating nerve fibers were arranged in nerve tracts in the cell transplantation group and connective tissue between nerve tracts and amnion tissue reduced over time.Gastrocnemius muscle cell diameter,wet weight and restoration ratio were increased.These data indicate that transplanted human umbilical cord mesenchymal stem cells,using the amnion tube connection method,promote restoration of damaged sciatic nerves in rats.     

Transplanted neuronal progenitor cells in a peripheral nerve gap promote nerve repair

A basic experiment of peripheral nerve regeneration using neuronal progenitor cells embedded in collagen gel was performed in a rat sciatic nerve defect. First, when neuronal progenitor cells derived from the fetal rat hippocampus were cultured in atelocollagen-containing medium, neurospheres positive for anti-nestin antibody were confirmed after 8 days. These cells differentiated into astrocytes positive for anti-glial fibrillary acidic protein (GFAP) antibody, oligodendrocytes positive for anti-galactocerebroside (GalC) antibody and neurons positive for anti-neurofilament 200 (NF200) antibody, and they were capable of extending axons. They also differentiated into Schwann-like supportive cells positive for anti-s100 and anti-p75 antibody. Next, a 15-mm defect was prepared in the sciatic nerve of mature rats, and the nerve was bridged with a silicone tube filled with neuronal progenitor cells (1 x 10(5)) embedded in collagen gel. The transplanted neuronal progenitor cells were labeled in advance with 5-bromo-2-deoxyuridine (BrdU). When the regenerated tissue was examined 6 weeks and 10 weeks after grafting, the number and diameter of myelinated fibers were significantly increased compared with a control tube without neuronal progenitor cells. Action potentials were detected in the regenerated nerve. Also, cells positive for both anti-BrdU antibody and anti-S100 or anti-p75 antibody were observed in the regenerated tissue, and part of the grafted neural stem cells were considered to have differentiated into Schwann cell-like supportive cells. From these results neuronal progenitor cells derived from the fetal rat hippocampus are considered to retain their proliferative and differentiating abilities in collagen gel, and when transplanted to a site of peripheral nerve defect, part of them differentiate into supportive cells and they contributed to promotion of axonal regeneration.     

Skeletal muscle-derived cells repair peripheral nerve defects in mice

Skeletal muscle-derived cells have strong secretory function,while skeletal muscle-derived stem cells,which are included in muscle-derived cells,can differentiate into Schwann cell-like cells and other cell types.However,the effect of muscle-derived cells on peripheral nerve defects has not been reported.In this study,5-mm-long nerve defects were created in the right sciatic nerves of mice to construct a peripheral nerve defect model.Adult female C57BL/6 mice were randomly divided into four groups.For the muscle-derived cell group,muscle-derived cells were injected into the catheter after the cut nerve ends were bridged with a polyurethane catheter.For external oblique muscle-fabricated nerve conduit and polyurethane groups,an external oblique muscle-fabricated nerve conduit or polyurethane catheter was used to bridge the cut nerve ends,respectively.For the sham group,the sciatic nerves on the right side were separated but not excised.At 8 and 12 weeks post-surgery,distributions of axons and myelin sheaths were observed,and the nerve diameter was calculated using immunofluorescence staining.The number,diameter,and thickness of myelinated nerve fibers were detected by toluidine blue staining and transmission electron microscopy.Muscle fiber area ratios were calculated by Masson’s trichrome staining of gastrocnemius muscle sections.Sciatic functional index was recorded using walking footprint analysis at 4,8,and 12 weeks after operation.The results showed that,at 8 and 12 weeks after surgery,myelin sheaths and axons of regenerating nerves were evenly distributed in the muscle-derived cell group.The number,diameter,and myelin sheath thickness of myelinated nerve fibers,as well as gastrocnemius muscle wet weight and muscle area ratio,were significantly higher in the muscle-derived cell group compared with the polyurethane group.At 4,8,and 12 weeks post-surgery,sciatic functional index was notably increased in the muscle-derived cell group compared with the polyurethane group.These criteria of the muscle-derived cell group were not significantly different from the external oblique muscle-fabricated nerve conduit group.Collectively,these data suggest that muscle-derived cells effectively accelerated peripheral nerve regeneration.This study was approved by the Animal Ethics Committee of Plastic Surgery Hospital,Chinese Academy of Medical Sciences(approval No.040)on September 28,2016.     

Evaluation of the long-term regenerative potential in an experimental nerve amputee model

In this study, we evaluated the long-term maintenance of regenerated axons in an experimental nerve amputee model. The sciatic nerve of adult rats was transected and repaired with a silicone tube leaving a short gap; the distal nerve segment was again transected 10 mm distally and the distal stump either introduced in a capped silicone chamber (amputee group) or connected to denervated targets (tibial branch into the gastrocnemius muscle and peroneal nerve apposed to skin) (reinnervation group). Morphological studies were performed at 2.5, 6, and 9 months after surgery. In all cases, axons regenerated across the silicone tube and grew in the distal nerve segment. In the amputee group, the morphological results show the expected features of a neuroma that is formed when regenerating axons are prevented from reaching the end organs, with a large number of axonal profiles indicative of regenerative sprouting. The number of myelinated axons counted at the distal nerve was sustained over 9 months follow-up, indicating that regenerated axons are maintained chronically. Immunohistochemical labeling showed maintained expression of choline acetyltransferase, calcitonin gene-related peptide, and growth-related peptides 43 in the distal neuroma at 6 and 9 months. Reconnection of the distal nerve to foreign targets mildly improved the pattern of nerve regeneration, decreasing the number of excessive sprouts. These results indicate that axons regenerated may be eventually interfaced with external input-output systems over long time, even if ending in the absence of distal targets as will occur in amputee limbs.     

Simultaneous gradual lengthening of both proximal and distal nerve stumps for repair of peripheral nerve defect in rats

We investigated nerve regeneration following the repair of a segmental nerve defect induced by direct end-to-end neurorrhaphy after simultaneous gradual lengthening of both proximal and distal nerve stumps in rats. A 15-mm-long nerve segment was resected from the sciatic nerve of each rat. The proximal and distal nerve stumps, respectively, were directly lengthened at a rate of 1 mm/day using a custom-made external nerve-lengthening device. After being lengthened for 14 days, both nerve stumps were refreshed, and direct end-to-end neurorrhaphy was performed. For a control, 15-mm nerve grafting was performed immediately after nerve resection. Nerve regeneration was evaluated by motor nerve conduction velocity, muscle contraction force, and histological studies at 6, 8, and 14 weeks after initial nerve resection in both groups. As a result, at 8 and 14 weeks, the motor nerve conduction velocity was significantly higher in the nerve-lengthening group than in the autografting group. In addition, at 14 weeks, the tetanic force and wet weight of the gastrocnemius muscle were significantly higher in the nerve-lengthening group than in the autografting group. Histologically, the mean axonal diameter of myelinated nerve fibers and the total number of myelinated nerve fibers were also significantly higher in the nerve-lengthening group than in the autografting group for each evaluation period. It appears that the simultaneous gradual lengthening of both proximal and distal nerve stumps might have potential application in the repair of peripheral nerve defects.     

Numbers of regenerating axons in parent and tributary peripheral nerves in the rat

This study is concerned with numerical parameters of axonal regeneration in peripheral nerves. Our first finding is that the number of axons that regenerate into the distal stump of a somatic nerve at a particular time after transection is partially dependent on the type of lesion used to interrupt the axons. The second question concerns the proportion of axons that regenerate into the distal stump of a parent nerve compared to the proportions that regenerate into tributary nerves that arise from the parent. The proportions of regenerated myelinated axons in the nerve to the medial gastrocnemius muscle and myelinated and unmyelinated axons in the sural nerve are the same as the proportions of myelinated and unmyelinated axons that regenerate into the distal stump of the sciatic nerve for the crush, 0 and 4 mm gap transections. Proportionally fewer axons regenerate into the tributary nerves following the 8 mm gap transection, however. This implies that the length of the gap has an influence on whether or not axons in tributary nerves regenerate in concert with axons in the distal stump of the parent nerve. The unmyelinated fibers in the nerve to the medial gastrocnemius muscle are different because they do not regenerate in proportion to those in the distal stump of the sciatic nerve. We also provide evidence to indicate that myelinated axons branch whereas unmyelinated fibers end blindly when they enter the distal stump after crossing a sciatic nerve transection. Finally the normal arrangement of perineurial cells seems to be disrupted after the sciatic nerve regenerates across a gap.