去细胞神经与自体神经移植桥接修复大鼠坐骨神经缺损的对比研究

目的观察同种异体去细胞神经与自体神经移植桥接修复大鼠坐骨神经缺损的神经再生情况。方法制备大鼠同种异体去细胞神经及大鼠坐骨神经缺损模型,修复12周后应用HE染色,Bielschowsky改良染色,Weil氏铁明矾苏木素染色,光镜下观察神经外膜上的微血管数和微血管面积百分比,计数单位面积的轴突数目,远端轴突密度/近端轴突密度为再生神经通过率,计数单位面积的有髓神经纤维数目和有髓神经纤维的直径。结果在坐骨神经纤维的再生神经纤维通过率、有髓神经纤维密度和直径、桥接体微血管的数目和微血管面积百分比等再生指标上,自体神经移植组略优于化学去细胞神经组。结论同种异体去细胞神经移植可促进神经再生,但仍然不如自体移植效果好。     

新鲜羊膜修复急性坐骨神经损伤北大核心

背景:改善局部微环境及减少局部瘢痕有利于周围神经再生促进神经功能恢复。目的:评价新鲜羊膜促进周围神经损伤后再生的效果。方法:选用成年SD大鼠60只,制备单侧坐骨神经急性损伤模型,随机分为人羊膜组、生物膜组、空白对照组,每组20只,均在显微镜下行神经吻接术,吻接处给予人新鲜羊膜、生物膜包裹,空白对照组修复神经后不做任何处理。术后2,4,8,12周行大体观察、光镜观察、免疫组织化学检测;术后4,8,12周行透射电镜观察、轴突成像分析、复合肌肉动作电位检测、坐骨神经功能指数测定。结果与结论:(1)大体观察:术后2周羊膜、生物膜局部稍有吸收,4周大部吸收,8周完全吸收。人羊膜组、生物膜组神经和周围组织稍有粘连且粘连较疏松,活动度可。空白对照组神经和周围组织广泛紧密粘连,钝性不易分离,活动度差;(2)光镜观察:术后2,4,8,12周,人羊膜组、生物膜组神经恢复情况明显优于空白对照组;(3)电镜观察:术后4周,3组神经纤维再生均不明显,板层结构均不清晰。术后8,12周,与空白对照组比较,人羊膜组、生物膜组神经纤维再生数量更多、髓鞘厚度厚、板层结构更清晰、轴突直径更大;(4)免疫组织化学检测:人羊膜组、生物膜组中S-100蛋白表达及分布均优于同时期空白对照组;(5)轴突图像分析:人羊膜组、生物膜组神经吻合口远端有髓神经纤维直径、髓鞘厚度及横截面有髓神经纤维数目均优于同时期空白对照组,差异有显著性意义(P<0.05);(6)神经电生理检测:与空白对照组比较,人羊膜组、生物膜组潜伏期短、波幅高及神经传导速度快,差异有显著性意义(P<0.05);(7)坐骨神经功能指数:人羊膜组、生物膜组坐骨神经功能指数均明显高于同时期空白对照组,差异有显著性意义(P<0.05);(8)结果表明,人羊膜作为一种生物材料修复周围神经损伤效果较好,可以减轻受损神经与周围组织的粘连和减少神经吻合处的瘢痕形成,可促进神经纤维再生、轴突直径增大、髓鞘增厚,可以减轻神经切口处炎性反应、免疫反应。     

重组腺病毒载体AxCA-BDNF基因转染修复坐骨神经损伤

背景：如何促进周围神经损伤修复与再生一直是基础与临床研究的热点。基因治疗有可能成为今后解决该问题的主要手段之一。 目的：观察携带小鼠脑源性神经营养因子(brain-derived neurotrophic factor,BDNF) cDNA表达片段的重组腺病毒载体AxCA-BDNF转染大鼠损伤坐骨神经后BDNF的表达,以及脊髓前角运动神经元的存活和神经生长情况。 方法：切除成年Wistar大鼠股中部10 mm长的坐骨神经,AxCA-BDNF转染组、BDNF组和对照组分别用硅胶管内置AxCA-BDNF原液,BDNF溶液或空白病毒稀释液桥接坐骨神经两断端。术后3,7,14 d,1,2,4个月应用原位杂交和免疫组织化学方法检测损伤坐骨神经及相应脊髓节段BDNF mRNA和蛋白的表达,并观察损伤坐骨神经的组织学及超微结构改变,再生的神经元及有髓神经纤维数目和髓鞘厚度。 结果与结论：术后3,7,14 d及1个月时,AxCA-BDNF转染组损伤坐骨神经近、远端神经干及脊髓(L_3~6)中BDNF mRNA和蛋白水平明显高于BDNF组和对照组(P < 0.01)。光、电镜病理组织学检查和图像分析证实,BDNF基因转染后,脊髓前角运动神经元存活数量、新生神经纤维数目及其髓鞘厚度、神经联接的再形成均明显优于对照组(P < 0.01)。说明经腺病毒介导转染的BDNF基因可在大鼠坐骨神经内有效表达,并通过轴突逆行转运到了相应的脊髓神经元,不仅能促进损伤神经纤维再生,也能保护损伤的脊髓神经元。     

自噬抑制剂3-甲基腺嘌呤可提高小鼠同种异体坐骨神经移植效率

文题释义： 细胞自噬：指细胞在受到创伤、饥饿、缺氧、感染等应激状态下的一种自我保护机制,这一过程可以无选择性地发生于所有真核细胞中,真核细胞通过自噬作用清除老化的细胞器和蛋白,以此来维持细胞生长发育的平衡。自噬过程主要的诱发因素是饥饿,即细胞营养物质的缺乏,此外也可通过一些感染、损伤、特定的蛋白如热休克蛋白、细胞因子等选择性地引发。 华勒氏变性：是指周围神经损伤后,残留的轴突及髓鞘结构迅速发生退化、崩解、吸收的过程。这一复杂过程有多种细胞因子及炎症细胞参与,是周围神经损伤后最重要的病理变化过程之一,影响损伤后续的修复再生。 背景：近年最新研究表明,华勒氏变性的发生与许旺细胞的自噬活动密切相关,对许旺细胞自噬活动进行调控,可以显著影响华勒氏变性的发生发展,从而改变后续的轴突再生及髓鞘化过程。 目的：在同种异体神经移植中对移植片段的细胞自噬过程进行抑制,观察是否影响移植后的修复效率。 方法：获取8只雌性C57BL/6J小鼠(购自北京维通利华)坐骨神经片段16条,分2组,分别于含自噬抑制剂3-甲基腺嘌呤的培养基及普通培养基中处理72 h。取16只雌性C57BL/6J小鼠,建立左侧坐骨神经缺损模型,实验组(n=8)植入含自噬抑制剂3-甲基腺嘌呤培养基处理过的坐骨神经片段,对照组(n=8)植入普通培养基处理的坐骨神经片段,术后2,4,6,8周,记录坐骨神经指数;术后8周取再生坐骨神经段,分别进行苏木精-伊红染色、免疫荧光染色、甲苯胺蓝染色、透射电镜观察等。动物实验通过北京协和医学院动物伦理委员会批准。 结果与结论：①实验组术后8周的坐骨神经指数高于对照组(P < 0.05),其余时间点两组间比较差异无显著性意义(P > 0.05);②苏木精-伊红染色显示,实验组神经组织完整,对照组神经组织可见大面积空洞;③免疫荧光染色显示,实验组可见较完整的神经束结构,对照组未见完整的神经束结构;④甲苯胺蓝染色显示,实验组可见有髓神经纤维和部分再生无髓神经纤维,对照组仅见少量有髓神经纤维与新生无髓轴突;⑤透射电镜显示,实验组髓鞘厚度及有髓纤维直径均大于对照组(P < 0.05);⑥结果表明应用3-甲基腺嘌呤处理移植前神经片段,可抑制许旺细胞自噬,有助于保留移植物髓鞘结构完整性,促进轴突再生及功能的恢复。 ORCID: 0000-0002-6259-2668(徐筑秋) 中国组织工程研究杂志出版内容重点：组织构建;骨细胞;软骨细胞;细胞培养;成纤维细胞;血管内皮细胞;骨质疏松;组织工程     

牛膝活性提取物对大鼠坐骨神经横断的修复作用

目的:研究牛膝活性提取物(ABPPk)对大鼠坐骨神经横断的修复作用.方法:SD大鼠随机分为5组,ABPPk低、中、高剂量组(剂量分别为2.5、5.0、10.0 mg/kg),阳性对照组(弥可保,0.13mg/kg),生理盐水组(阴性对照).行大鼠左侧坐骨神经横断缝合术,术后每日腹腔注射给药.于术前1d和术后1、7、14、21、28 d行热痛阈实验,测定大鼠热痛阈值;术后7、14、21、28d行足迹实验,测定大鼠坐骨神经功能指数;术后28 d行电生理检测,测定大鼠复合肌动作电位;透射电镜观察大鼠再生有髓神经纤维的髓鞘厚度和髓鞘板层数目;行Masson三色染色观察大鼠腓肠肌肌纤维横截面.结果:与生理盐水组相比,ABPPk中、高剂量组大鼠热痛阈值、坐骨神经功能指数、复合肌动作电位幅度、再生有髓神经纤维髓鞘厚度、板层数目及腓肠肌肌纤维横截面积均增高,各剂量组之间呈量效关系.结论:ABPPk有利于轴突再生和髓鞘形成,能促进大鼠周围神经损伤后功能和形态的恢复.     

制备坐骨神经损伤大鼠模型:脊髓与局部神经电刺激的修复效果比较

背景:周围神经损伤后,损伤远端神经纤维出现Wallerian变性,近端相应节段脊髓出现神经元凋亡,导致轴突再生困难,影响神经损伤修复后的效果。目前针对周围神经损伤的研究大都局限在对损伤局部的修复与刺激,而对近端神经元胞体的研究相对较少。目的:比较脊髓电刺激与局部电刺激治疗周围神经损伤的疗效,探讨脊髓电刺激促进周围神经损伤修复的机制。方法:建立大鼠坐骨神经损伤模型,按随机数字表法分为3组,脊髓电刺激组、局部电刺激组和对照组各15只。测定造模后不同时期3组大鼠坐骨神经功能指数、小腿三头肌湿质量、脊髓神经元计数和超微结构、再生神经纤维髓鞘厚度及传导速度。结果与结论:造模后2周,大鼠坐骨神经功能指数比较脊髓电刺激组对照组,局部电刺激组对照组(P0.05);造模后4,6,8周,大鼠坐骨神经功能指数比较脊髓电刺激组局部电刺激组对照组(P0.05)。造模后2周,大鼠小腿三头肌湿重测定脊髓电刺激组对照组,局部电刺激组对照组(P0.05);造模后4,8周,大鼠小腿三头肌湿质量比较脊髓电刺激组局部电刺激组对照组(P0.05)。造模后2,4,8周,各组大鼠脊髓前角神经元计数脊髓电刺激组局部电刺激组对照组(P0.05)。造模后4,8周,各组大鼠再生神经纤维髓鞘厚度、坐骨神经传导速度比较,脊髓电刺激组局部电刺激组对照组(P均0.05)。提示周围神经损伤后给予相应节段脊髓电刺激,可以有效预防中枢神经元凋亡,促进轴突再生及神经功能恢复,且效果优于局部电刺激。     

靶肌肉注射促红细胞生成素对大鼠周围神经再生的作用

目的探讨靶肌肉注射人重组促红细胞生成素（recombinant human erythropoietin，rh-EP0）对大鼠坐骨神经损伤后神经再生的作用。方法选用健康雄性SD大鼠12只，制备大鼠右侧坐骨神经钳夹损伤模型。实验动物随机分为2组，每组6只，EPO组：靶肌肉注射rh-EPO2500U／kg；对照组：注射同体积的生理盐水。术后第7d、14d、21d观察坐骨神经功能指数（SFI），第21d组织学观察脊髓腰膨大（L4～L6）、夹伤远端坐骨神经、损伤侧腓肠肌组织并作图象分析测定脊髓前角运动神经元数、再生有髓神经纤维数、髓鞘厚度、轴突直径和腓肠肌肌细胞横截面积等指标。结果术后第7d两组SFI无显著性差异，术后第14d、21dEPO组SFI恢复程度明显大于对照组，差别有显著性意义（P〈0．05）；术后第21d损伤侧脊髓前角运动神经元数、再生有髓神经纤维数、髓鞘厚度、轴突直径和腓肠肌肌细胞横截面积等指标，EPO组均优于对照组（P〈0．01，P〈0．05）。结论靶肌肉注射rh-EPO能促进周围神经再生和功能恢复。     

神经生长因子不同给药方式对坐骨神经吻合后修复与再生的影响*

背景：神经生长因子对神经损伤后的修复有促进作用,但目前对不同用药方式的优劣性尚有争议。 目的：观察鞘膜内与局部应用神经生长因子对兔坐骨神经吻合后修复与再生的影响。 方法：将24只新西兰大白兔坐骨神经切断后再缝合,分别向兔鞘膜内或损伤局部注射30 μg神经生长因子或等量生理盐水。 结果与结论：坐骨神经损伤后12周,鞘膜内注射神经生长因子组损伤坐骨神经鞘膜增厚,神经纤维排列较整齐,与正常神经纤维差异不大;且其神经干传导速度、有髓神经纤维数目、髓鞘厚度也明显高于其他组(P < 0.05),损伤局部注射神经生长因子组次之。说明神经生长因子具有促进外周神经吻合后修复与再生的功能,鞘膜内应用优于局部注射。     

直流电场诱导神经干细胞桥接横断脊髓的实验研究

目的:探讨直流电场(direct current field,DC)诱导神经干细胞(neural stem cells,NSCs)桥接横断脊髓的作用。方法:将54只雌性成年SD大鼠随机分为脊髓损伤(spinal cord injury,SCI)组、NSCs移植组、NSCs移植联合直流电场诱导组(DC+NSCs组),各组分7,14,28d三个时间点取材,HE染色观察神经纤维再生情况,透射电镜下观察脊髓白质内髓鞘结构变化,免疫荧光染色检测髓磷脂碱性蛋白(myelin basic protein,MBP)表达变化。结果:在光镜下,DC+NSCs组神经纤维较其他两组都多,排布均匀且走行较规则,部分纤维穿越损伤脊髓断端两侧。在电镜下,DC+NSCs组髓鞘松散程度明显减轻,部分髓鞘结构规整,排列有序,线粒体肿胀减轻,微管空泡样变较轻,可发现大量突触,薄髓的再生髓鞘明显增多。DC+NSCs组大鼠脊髓组织中可见直径大小不等的MBP阳性的圆形结构,MBP阳性表达最多,较其他两组有显著性差异(P0.01)。结论:直流电场诱导NSCs治疗SCI可以促进损伤处脱髓的轴突再髓鞘化和MBP的表达,促进神经纤维再生,从而起到桥接横断脊髓的作用。     

脑源性神经营养因子对出生后大鼠周围神经髓鞘化的作用

目的:探讨脑源性神经营养因子(BDNF)对出生后大鼠周围神经髓鞘化的作用及其作用机制.方法:用光镜和电镜方法检测坐骨神经纤维的髓鞘化情况;用免疫印迹方法检测坐骨神经p75的表达;用免疫荧光方法检测坐骨神经雪旺细胞内核转录因子(NF-kB)的表达.结果:出生后3 d,与对照组相比,实验组坐骨神经髓鞘化的神经纤维数目减少,p75表达下调,雪旺细胞内NF-KB转移率下调;出生后14 d,与对照组相比,实验组坐骨神经出现较多的髓鞘化异常.结论:内源性BDNF影响出生后大鼠周围神经的髓鞘化,尤其在早期作用明显;内源性BDNF主要通过p75和NF-kB信号途径调节出生后大鼠周围神经的髓鞘化.     

腺病毒介导的神经营养素-3基因能够在大鼠脊髓前角运动神经元内过表达神经营养素-3

目的观察腺病毒介导的神经营养素-3(NT-3)基因在发出坐骨神经传出纤维的大鼠脊髓前角运动神经元的过表达。方法在坐骨神经内直接注射含有绿色荧光蛋白(GFP)基因(报告基因)的NT-3基因重组腺病毒(Ad-NT-3-GFP),7d后应用免疫荧光组织化学染色技术,在荧光显微镜下观察脊髓前角运动神经元的NT-3过表达。结果 GFP表达组(对照组)和NT-3加GFP表达组两组动物的L4和L5脊髓段横切片上,有绿色荧光蛋白阳性标记的细胞。在NT-3加GFP表达组,还可以观察到NT-3阳性标记的细胞,这种细胞能与绿色荧光蛋白阳性标记的细胞重合,是过表达NT-3的前角运动神经元。与GFP表达组的前角运动神经元形态比较,NT-3加GFP表达组的过表达NT-3的前角运动神经元呈现更富有分支的突起。结论腺病毒介导的NT-3基因能够在发出坐骨神经传出纤维的大鼠脊髓前角运动神经元内过表达NT-3,这为下一歩应用NT-3基因治疗策略修复实验性脊髓损伤提供初歩的实验资料。     

大鼠坐骨神经超微结构的老年性变化

为了研究老年大鼠坐骨神经超微结构特点,随机取3月龄(成年组)和24月(老年组)龄正常SD大鼠各10只,用电镜观察两组间坐骨神经超微结构的差异。结果显示:老年组大鼠坐骨神经内有髓纤维的百分比、轴突间胶原纤维密度以及Schwann细胞胞质中脂褐质沉积密度均多于成年组(P<0.05);但无髓纤维之百分比少于成年组(P<0.05)。上述结果提示坐骨神经内的有髓纤维与无髓纤维百分比、轴突间胶原纤维密度以及Schwann细胞胞质中脂褐质沉积密度是衡量大鼠坐骨神经老化的形态标志之一。     

A scanning electron microscopic study of peripheral nerve degeneration and regeneration

The left sciatic nerves of male Holtzman rats were exposed and crushed with a hemostat for 3 s at a point midway between the inferior gluteal nerve and the bifurcation into the tibial and common peroneal nerves. Normal myelinated axons appear in the scanning electron microscope as relatively smooth cylindrical structures with interweaving strands of collagen fibers coursing over their length. Nodes of Ranvier are seen as constrictions along the myelinated fibers. After crushing, the nerve fibers swell, and interruptions appear in the nodal and internodal regions causing a beaded morphology. The myelin sheaths fragment into numerous spherical bodies as the degenerative process progresses. Some remnants of myelin debris are found within the nerves 60 days following the lesion A few regenerating myelinated axons are observed within the connective tissue fibers and myelin debris distal to the crushed regions approx 15 days after placement of the lesion. By day 30 the nerves are relatively normal in appearance. The scanning electron micrographs provide a three-dimensional picture of the dynamic processes which occur during nerve degeneration and regeneration. These findings are correlated with previous studies and can serve as a basis for future scanning electron microscopic studies in this area of research.     

Grafting of detergent-denatured skeletal muscles provides effective conduits for extension of regenerating axons in the rat sciatic nerve

The basal laminae of muscle fibers, when treated by denaturing methods including freeze thawing, have been used as conduits for regenerating nerves. In this study, we developed a new method for denaturing skeletal muscle fibers through treatment with a biological detergent, sodium dodecyl sulfate. Laminin and type IV collagen proteins of muscle fiber basal laminae were preserved after the detergent treatment. A segment of detergent-denatured muscle was grafted to a 1-cm defect of the rat sciatic nerve. One week after grafting, regenerating axons immunostained for neurofilaments were seen extending within laminin-positive muscle fiber basal lamina tubes. Four weeks after grafting, numerous myelinated axons at a much higher level than the control unoperated sciatic nerve, were found in the middle of the graft. They were smaller in diameter than those in the control nerve. Distal host nerves were well reinnervated 4 weeks after grafting. These findings suggest that the basal laminae of detergent-denatured muscle fibers provide effective conduits for regenerating axons.     

Role of transthyretin in posttraumatic regeneration of the sciatic nerve in mouse

Although thyroid hormones are known to have a significant influence on the development of nervous system, the absence of changes in the brain of mice deficient in transthyretin--a protein providing thyroid hormone transport across the blood-brain and blood-nerve barrier--remains unexplained. Therefore, the aim of this study was to determine the effect of transthyretin on the formation of myelinated and unmyelinated nerve fibers in sciatic nerve of mice. The myelinated and unmyelinated nerve fibers were counted in sciatic nerve of 3-months-old normal and transthyretin-knockout (transthyretin(-/-)) mice 15 and 30 days after nerve crushing. No differences were detected in the number of myelinated and unmyelinated nerve fibers in intact control (wild-type) animals group vs. transthyretin(-/-) mice. By days 15 and 30 after nerve crushing the number of myelinated nerve fibers was diminished by 54.7 and 71.8%, respectively, in transthyretin(-/-) mice, as compared to that in control animals. The number of unmyelinated nerve fibers at day 15 after the injury was not different in transthyretin(-/-) and control mice, however, by day 30 the number of these fibers in control group was found to increase significantly, exceeding that one in transthyretin(-/-) mice by 27.9%. These results indicate the important contribution of transthyretin, as a thyroxin carrier protein, to the process of posttraumatic regeneration of sciatic nerve. The absence of changes in nerve fiber numbers in transthyretin-knockout mice in postembryonic period suggests the presence of transthyretin-independent mechanism of thyroxin transport into the peripheral nervous system.     

Neurotrophic modulation of myelinated cutaneous innervation and mechanical sensory loss in diabetic mice

Human diabetic patients often lose touch and vibratory sensations, but to date, most studies on diabetes-induced sensory nerve degeneration have focused on epidermal C-fibers. Here, we explored the effects of diabetes on cutaneous myelinated fibers in relation to the behavioral responses to tactile stimuli from diabetic mice. Weekly behavioral testing began prior to streptozotocin (STZ) administration and continued until 8 weeks, at which time myelinated fiber innervation was examined in the footpad by immunohistochemistry using antiserum to neurofilament heavy chain (NF-H) and myelin basic protein (MBP). Diabetic mice developed reduced behavioral responses to non-noxious (monofilaments) and noxious (pinprick) stimuli. In addition, diabetic mice displayed a 50% reduction in NF-H-positive myelinated innervation of the dermal footpad compared with non-diabetic mice. To test whether two neurotrophins nerve growth factor (NGF) and/or neurotrophin-3 (NT-3) known to support myelinated cutaneous fibers could influence myelinated innervation, diabetic mice were treated intrathecally for 2 weeks with NGF, NT-3, NGF and NT-3. Neurotrophin-treated mice were then compared with diabetic mice treated with insulin for 2 weeks. NGF and insulin treatment both increased paw withdrawal to mechanical stimulation in diabetic mice, whereas NT-3 or a combination of NGF and NT-3 failed to alter paw withdrawal responses. Surprisingly, all treatments significantly increased myelinated innervation compared with control-treated diabetic mice, demonstrating that myelinated cutaneous fibers damaged by hyperglycemia respond to intrathecal administration of neurotrophins. Moreover, NT-3 treatment increased epidermal Merkel cell numbers associated with nerve fibers, consistent with increased numbers of NT-3-responsive slowly adapting A-fibers. These studies suggest that myelinated fiber loss may contribute as significantly as unmyelinated epidermal loss in diabetic neuropathy, and the contradiction between neurotrophin-induced increases in dermal innervation and behavior emphasizes the need for multiple approaches to accurately assess sensory improvements in diabetic neuropathy.     

抑制AChE后对神经再生的影响——AChE可能有神经营养因子样作用

乙酰胆硷酯酶(ACHE)在神经系统的分布模式多年来一直令人困惑。近年对AChE的非胆硷能递质传递功能的研究已引起了相当的重视。本文研究了大鼠坐骨神经压榨后,肌肉注射不可逆的胆硷酯酶抑制剂DFP,通过Bodian染色和透射电镜观察神经损伤后溃变和再生的过程。结果显示DFP注射动物损伤神经的再生能力明显减弱,表现为(1)再生纤维生长速度较对照组减慢(p<0.01),(2)新生纤维数量减少(3)溃变物质清除缓慢,(4)雪旺氏细胞增生欠活跃。上述结果表明AChE在其参与胆硷能递质传递之外还和神经组织的维持和再生有一定的关系。结合AChE在神经发育和生长中的一些间接证据,本文讨论了AChE很可能有神经营养因子样作用的问题。     

Expression of R-cadherin in the regenerating chick sciatic nerve

The ultrastructural localization of R-cadherin in normal and regenerating chick sciatic nerves was investigated immunocytochemically, and was compared with that of N-cadherin. R-cadherin was found on the plasmalemmae of axons and Schwann cells where cell-cell contacts were made in the normal unmyelinated fibers. It was also noted that R-cadherin was expressed on the axolemmae where regenerating axons contacted with each other, and formed fasciculations. The normal myelinated fibers displayed no immunoreactivity except at the mesaxon. These findings of R-cadherin were almost the same as those of N-cadherin of our previous study. N- and R-cadherin seemed to be co-expressed at the cell-cell contact points as mentioned above in the double labeling study. It is probable that cadherins contribute to the pathfinding of regenerating axons by causing them to form fasciculation. However, it seemed that there was no selective sorting of axons by N- and R-cadherin during regeneration as far as the present study was concerned.     

Extracellular matrix of human amnion manufactured into tubes as conduits for peripheral nerve regeneration

The human amnion consists of the epithelial cell layer and underlying connective tissue. After removing the epithelial cells, the resulting acellular connective tissue matrix was manufactured into thin dry sheets called amnion matrix sheets. The sheets were further processed into tubes, amnion matrix tubes (AMTs), of varying diameters, with the walls of varying numbers of amnion matrix sheets with or without a gelatin coating. The AMTs were implanted into rat sciatic nerves. Regenerating nerves extended in bundles through tubes of 1-2 mm in diameter and further elongated into host distal nerves 1-3 weeks after implantation. Morphometrical analysis of the regenerated nerve cable at the middle of each amnion matrix tube 3 weeks after implantation was performed. The average numbers of myelinated axons were almost the same (ca. 80-112/10(4) microm(2)) in AMTs of 1-2 mm in diameter, as in the normal sciatic nerve (ca. 95/10(4) microm(2)). No myelinated fibers were found in AMTs composed of multiple thin tubes of 0.2 mm in diameter. The myelinated axons were thinner in implanted tubes than those in the normal sciatic nerve. The rate of occurrences of myelinated axons less than 4 microm in diameter was significantly higher in the AMTs, whereas axons in the normal sciatic nerve were diverse in distribution, with the highest population at 8-12 microm in diameter. Reinnervation to the gastrocnemius muscle was demonstrated electrophysiologically 9 months after implantation. It was concluded that the extracellular matrix sheet from the human amnion is an effective conduit material for peripheral nerve regeneration.