羧甲基壳聚糖-羧甲基纤维素防粘连膜的制备及其理化特性

背景：壳聚糖能有效预防粘连,可制成不同的剂型,如凝胶、溶液、海绵状以及薄膜等,但其缺点是溶液、凝胶易流动,不易在局部形成较高浓度,而单纯应用壳聚糖制成海绵状及薄膜机械强度及韧性不够。 目的：以羧甲基壳聚糖、羧甲基纤维素为主要成分,制备具有优良物理、生物性能,预防粘连的生物膜。 方法：将羧甲基壳聚糖和羧甲基纤维素按一定比例混合,加入戊二醛、硫酸铝铵进行双交联,甘油增塑。根据膜的色泽、拉伸强度、吸水率、溶胀比等指标通过正交试验筛选处方构成,优化膜的制备工艺,初步确定膜的制备工艺流程。通过扫描电镜、红外光谱等对制备样本的理化特性进行检测,并将膜植入SD大鼠体内观察膜的降解情况。 结果与结论：得到优化后膜的处方构成为：羧甲基壳聚糖/羧甲基纤维素为1∶1;硫酸铝铵浓度为0.15%;甘油含量为0.8%;戊二醛含量为0.003%。在以上工艺条件下制得的膜呈半透明状,微黄,上表面略粗躁,下表面光滑;膜的平均厚度为 0.09 mm;吸水率为964%;溶胀比为3.25;干态下膜的最大拉伸强度为20 MPa,湿态下膜的最大拉伸强度为5 MPa;接触角平均为35°。羧甲基壳聚糖和羧甲基纤维素间形成了较强的分子间作用力。膜表面结构呈相互交错的纤维状,表面有不规则的孔状结构。膜植入鼠体内后10 d左右水化成凝胶,1个月后体内完全降解吸收。提示羧甲基壳聚糖-羧甲基纤维素膜是一种生物相容性良好、可降解吸收、具有一定手术缝合强度的生物膜。     

三种羧甲基壳聚糖防粘连膜的降解及其生物相容性

背景：羧甲基壳聚糖膜降解快，降解率不容易测量，体外模拟与动物实验的相关性尚存在较大问题。 目的：找出适合体内降解的体外模型，并通过体内实验观察3种羧甲基壳聚糖膜的生物降解性与生物相容性。 设计、时间及地点：对比观察实验，于2007-09/2008-08在中国药品生物制品检定所医疗器械检测中心完成。 材料：1号样品：纯的羧甲基壳聚糖膜；2号样品：羧甲基壳聚糖︰纤维素︰聚乙烯醇=80︰10︰10︰3号样品：羧甲基壳聚糖︰纤维素︰聚乙烯醇=90︰5︰5，所有防粘连膜均采用水流延成型的方法制备。 方法：体外模拟：采用模拟体液和溶菌酶磷酸盐缓冲溶液作为降解介质；分别将3种膜样品定量后，浸泡于上述两种模拟介质中（质量︰体积< 1︰30）。定期取样，计算膜的降解百分率。体内试验：①取SD大鼠15只，背部皮下植入3种样品，样品间隔为1 cm以上，分别于7，15，33 d大体观察样品降解情况。②30只SD大鼠随机分为3组，每组10只。将样品放置进聚甲基丙烯酸甲酯管子中植入各组大鼠背部皮下，分别于7，15，22，33，77 d处死，每个时间点2只，从背部取出管子，计算降解率。③24只SD大鼠随机分为3组，每组8只。皮下埋植3种样品，分别于7，15，30，100 d处死，每个时间点2只，取埋植点组织，苏木精-伊红染色观察组织病理变化。 主要观察指标：①通过大体观察和质量损失率进行降解性能的研究。②观察植入后的组织病理情况。 结果：①两种体外降解模型都可以在一定程度上反映羧甲基壳聚糖膜的降解，酶解较模拟体液降解速度快，模型较为符合体内降解的真实情况。②添加少量纤维素和聚乙烯醇的羧甲基壳聚糖膜并不能很好地改善其降解性，但可以稍微改善降解后膜的完整性。③羧甲基壳聚糖由于降解快，会产生大量吞噬细胞和纤维细胞，导致出现一定的炎症；添加纤维素和聚乙烯醇的膜不仅不能够减小炎症，而且会延长愈合期，尤其是2号样品，炎症稍重。 结论：①利用溶菌酶模拟体内降解效果更好，有利于提高检测效率。②纯羧甲基壳聚糖防粘连膜炎性周期短，愈合快。     

羧甲基壳聚糖/纳米胶原复合支架修复兔腓骨损伤******☆◆

背景：研究证实，壳聚糖及其衍生物可作为骨损伤的填充材料以及骨组织工程支架材料，但壳聚糖降解缓慢且不可控制的特性限制了其在骨组织工程中广泛应用。 目的：评估羧甲基壳聚糖/纳米胶原纤维复合支架对兔腓骨损伤的修复作用。 设计、时间及地点: 随机分组设计、对照动物实验，于2007-06/2008-03在清华大学生物科学与技术系生物膜与膜生物工程国家重点实验室完成。 材料: 以羧甲基壳聚糖和纳米胶原纤维为基础材料，模拟骨的结构设计制备了双层羧甲基壳聚糖/纳米胶原纤维复合支架。 方法：选择成年新西兰大白兔10只，按随机数字表法分为3组，阴性对照组2只，壳聚糖支架组4只，复合支架组4只。制备兔腓骨10 mm的损伤，分别以旷置缝合、植入壳聚糖支架、植入双层羧甲基壳聚糖/纳米胶原纤维复合支架处理各组。 主要观察指标：扫描电镜观察支架微观形貌。术后12周，检测损伤部位的再生情况，以四环素荧光和Von Kossa染色检测实验动物骨损伤部位新生骨钙化情况。 结果：10只兔均进入结果分析。①扫描电镜观察到外层致密光滑的壳聚糖膜和多孔的中心区域，多孔区域有大量纳米胶原纤维网络结构填充。其孔径分布的峰值为60~100 μm，孔隙率大于85％。②手术后12周，不脱钙切片的四环素染色，可发现阴性对照组两个断端间还没有连上，依旧以游离端存在。复合支架组移植物中形成多个大的钙化岛，其中心网状材料已经大部分降解，钙化岛分布在整个支架的内部区域；而壳聚糖支架组，材料基本没有降解，未见钙化区域。③Von Kossa银染色显示，复合支架组动物骨损伤的中心区域，出现染成黑色的钙化区，中间夹杂着中性红复染的骨组织细胞。壳聚糖支架组动物没有明显的钙化区，多为组织细胞充斥在材料的孔隙中，可见材料基本没有降解。 结论：双层羧甲基壳聚糖/纳米胶原纤维复合支架植入动物体内12周后，未见明显的炎症反应和坏死，降解明显，能够促进骨修复，是很有前景的骨组织工程用支架材料。     

羧甲基壳聚糖钙的制备及其性质结构分析

背景：羧甲基壳聚糖是壳聚糖改性得到的水溶性衍生物,具有多种生物活性,是金属离子的良好配体,可以与Ca2+进行络合配制一种新型生物材料。 目的：研究羧甲基壳聚糖钙盐的制备方法,并对其性质结构进行分析。 方法：羧甲基壳聚糖与氯化钙溶液反应生成羧甲基壳聚糖与钙的配合物,进行溶解度、羧甲基化度、旋转黏度、钙含量的测定,以及红外光谱、紫外光谱分析。 结果与结论：配合物钙含量在15%左右,与羧甲基壳聚糖相比其溶解度、红外光谱和紫外光谱都产生了改变。制备出的羧甲基壳聚糖与Ca2+的配合物,通过一系列性质结构分析,初步证明为一种新型含钙化合物。 关键词：羧甲基壳聚糖钙;红外光谱;紫外光谱;复合生物材料;钙 doi:10.3969/j.issn.1673-8225.2010.03.046     

壳聚糖膜防治眼眶损伤后的软组织粘连

背景：可降解的壳聚糖膜高分子生物材料已在防止组织粘连中广泛应用,但由于眼眶空间较小,结构精细,目前尚未广泛应用。 目的：探讨壳聚糖膜在防治眼眶损伤后软组织粘连中的作用与机制。 方法：普通家兔10只随机数字表法分为壳聚糖膜组和对照组,建立成年家兔眼眶软组织粘连模型,壳聚糖膜组受损上直肌与结膜和相应骨膜之间置入15 mm×15 mm大小壳聚糖膜防粘连;对照组在损伤面间不用壳聚糖膜。 结果与结论：在采用防粘连措施前,两组粘连形成情况像似,4周后,壳聚糖膜组粘连情况较对照组减轻(P < 0.01)。壳聚糖膜组单位面积的成纤维细胞数量、胶原纤维吸光度值显著低于对照组(P < 0.01);胶原纤维的相对面积壳聚糖膜组低于对照组(P < 0.01)。两组家兔眼视网膜与视神经未发现明显变化。说明局部植入壳聚糖膜可以抑制成纤维细胞生长,减少胶原纤维的合成,防治眼眶损伤后软组织粘连,且对视网膜与视神经无毒副作用。     

骨形态发生蛋白2与壳聚糖神经支架复合体修复兔面神经损伤★

目的：应用生物可降解材料构成的导管通过载体与外源性骨形态发生蛋白（bone morphogenetic protein，BMP-2）相结合，构筑新型具有生物和人工合成材料优势的神经支架——组织工程复合体，探讨其对兔面神经损伤的修复。 方法：实验于2007-01/06在兰州大学动物实验中心完成。①自制BMP-2及壳聚糖神经支架和单纯壳聚糖神经支架。②暴露兔面神经上颊支，切除长2 mm神经，任其回缩，造成8 mm神经缺损的动物模型。③选择新西兰白兔24只，按随机数字表法分为2组，复合神经支架组和单纯壳聚糖神经支架组，每组12只。同时采用自身左右对照，设为对照组（自体神经离断后倒置，吻合于神经缺损处）。④一般观察：肉眼观察兔双侧颊肌萎缩程度及活动度。⑤形态学检查：术后16，30周，切取上颊支神经干，近侧吻合口纵切面行苏木精-伊红染色，观察神经再生情况；术后30周，透射电镜下观察再生神经超微结构；术后16，30周，用德国IBAS-I+Ⅱ型计算机图像处理系统作图像处理，计算神经纤维总数和纤维直径、轴突直径及髓鞘厚度。 结果：纳入动物24只，均进入结果分析。①大体形态：兔面神经上颊支损伤后2周面肌萎缩，复合神经支架组、单纯壳聚糖神经支架组、对照组分别于术后8，9，11周时开始逐渐恢复正常。②术后16周，单纯壳聚糖神经支架组与复合神经支架组光镜下可见神经外膜有新生血管，再生纤维呈束状分布，粗细不均匀，束间有新生血管。神经纤维排列整齐，无神经瘤形成。术后30周，光镜下可见复合神经支架组神经密集程度、血管化和髓鞘化程度优于单纯壳聚糖神经支架组。对照组形成的神经纤维束较为分散，不均匀，髓鞘处组织染色较差。③术后16,30周兔面神经再生神经图像分析结果：神经纤维的排列、血管化程度、直径和数目、髓鞘壁、轴突形状等各检测指标均优于单纯壳聚糖神经支架组。④术后30周，透射电镜下复合神经支架组神经再生超微形态学更接近对照组，优于单纯壳聚糖神经支架组。 结论：可吸收性BMP-2与壳聚糖神经支架复合体能有效地引导兔面神经再生并恢复其功能，优于单纯壳聚糖神经支架。     

羧甲基壳聚糖/羟乙基纤维素共混凝胶的制备及性能研究

摘要 背景：羟乙基纤维素通常可作为片剂和胶囊剂的崩解剂和黏合剂,羧甲基壳聚糖具有优良的增稠性、分散性、成膜性和凝胶性。利用羟乙基纤维素良好的生物黏附性能和溶胀性能,在酸性条件下具有良好的膨胀性能,可作为胃部膨大给药系统,适合于胃部滞留给药。 目的：本文拟制备以羟乙基纤维素作为辅料同时适合胃部滞留给药的凝胶。 方法：将羟乙基纤维素和羧甲基壳聚糖通过戊二醛交联制备羧甲基壳聚糖/羟乙基纤维素凝胶,考察不同质量比和在不同pH中的凝胶溶胀和释药性能特征。 主要观察指标：胃酸环境下凝胶的溶胀和释药特性。 结果：pH值为1.0时,凝胶的溶胀度比在pH值为3,5,7的溶胀度小。在CMCS与HEC比例为5：5时,其最大溶胀度可以达到4.2左右。pH=1.0时, CMCS：HEC=7：3,释放6小时后,药物释放百分比为50%。CMCS：HEC=5：5时,药物释放百分比约为80%。 结论：羧甲基壳聚糖/羟乙基纤维素共混凝胶适合于胃部滞留给药。 关键词：羧甲基壳聚糖,羟乙基纤维素,凝胶     

改性壳聚糖防粘连膜修复坐骨神经损伤

背景：研究表明壳聚糖与动物及人体具有较好的生物相容性、可降解性,可支持许旺细胞在壳聚糖膜上生长,而且能够明显抑制成纤维细胞生长。 目的：观察改性壳聚糖防粘连膜对大鼠坐骨神经再生修复的影响。 方法：切断60只SD大鼠双侧坐骨神经,缝合外膜,随机在一侧坐骨神经缝合处包裹改性壳聚糖防粘连膜,以另一侧为对照。术后20,30,40 d 进行电生理及组织学检测,观察改性壳聚糖防粘连膜对大鼠坐骨神经损伤修复的影响。 结果与结论：早期改性壳聚糖防粘连膜治疗侧神经断端的炎性反应较对照侧明显,随着膜的自行降解,炎症反应逐渐减轻,神经缝合口纤维组织增生减少。与对照侧相比,大鼠坐骨神经损伤30 d后,改性壳聚糖防粘连膜治疗侧神经传导速度恢复快,比目鱼肌记录到的神经-肌肉电潜伏期缩短(P < 0.05)。30 d后各时点与对照侧比较,改性壳聚糖防粘连膜治疗侧坐骨神经再生轴索密度大于对照侧(P < 0.05)。说明改性壳聚糖防粘连膜虽早期会加重周围神经损伤的炎性反应,但随着膜的降解,炎症反应逐渐减轻,可减轻神经缝合口纤维组织增生,防止粘连,因而有利于神经传导速度恢复及轴索生长。     

羧甲基壳聚糖钙体外细胞毒性实验研究

目的 评价羧甲基壳聚糖钙体外成骨细胞毒性。方法 体外合成羧甲基壳聚糖钙并通过MTT法检测羧甲基壳聚糖钙浸提液对原代培养SD大鼠成骨细胞的毒性作用,以第1、2、3、5、7天为检测时间点,计算细胞相对增值率,对材料毒性进行分级。正常培养基作为对照组。结果 羧甲基壳聚糖钙与羧甲基壳聚糖的红外光谱比较特征性波峰发生了改变,提示羧甲基壳聚糖与钙离子发生了络合;羧甲基壳聚糖钙浸提掖对成骨细胞各时间点的毒性分级为0或1级,无细胞毒性。结论 羧甲基壳聚糖钙具有良好的细胞相容性,无细胞毒性,是一种有应用潜力的新型生物材料。     

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。     

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.     

Interleukin-10 reduces scarring and enhances regeneration at a site of sciatic nerve repair

Abstract   Axonal regeneration at a site of peripheral nerve repair can be impeded by the formation of scar tissue, which creates a mechanical barrier and initiates the development of multiple branched axonal sprouts that form a neuroma. We have investigated the hypothesis that the application of a scar-reducing agent to the nerve repair site would permit better axonal regeneration. In anaesthetised C57 Black-6 mice, the left sciatic nerve was sectioned and immediately re-approximated using four epineurial sutures. In five groups of eight mice, we injected transforming growth factor-β3 (50 or 500 ng), interleukin-10 (IL-10) (125 or 500 ng), or saline into and around the repair site, both before and after the nerve section. Another group of eight animals acted as sham-operated controls. After 6 weeks, the outcome was assessed by recording compound action potentials (CAPs), measuring collagen levels using picrosirius red staining, and counting the number of myelinated axons proximal and distal to the repair. CAPs evoked by electrical stimulation distal to the repair were significantly smaller in all repair groups except for the low-dose IL-10 group, where they were not significantly different from that in controls. The area of staining for collagen had significantly increased in all repair groups except for the low-dose IL-10 group, which was not significantly different from that in controls. The myelinated fibre counts were always higher distal to the repair site, but there were no significant differences between groups. We conclude that administration of a low-dose of IL-10 to a site of sciatic nerve repair reduces scar formation and permits better regeneration of the damaged axons.     

The effect of antibodies to TGF-beta1 and TGF-beta2 at a site of sciatic nerve repair

Scar formation at a site of nerve injury can cause a mechanical barrier to axonal regeneration and lead to the development of multiple axonal sprouts to form a neuroma. We have investigated the hypothesis that the application of a scar-preventing agent to a nerve repair site would enhance regeneration of the nerve and reduce neuroma formation. The left sciatic nerve was exposed under general anaesthesia in 18 adult Sprague-Dawley rats. In 12 animals, the nerve was sectioned and immediately re-approximated using four epineurial sutures, and in 6 of these animals neutralising antibodies to transforming growth factor (TGF)-beta1 and TGF-beta2 were injected into and around the repair site. The six other animals acted as controls. After 7 weeks, the outcome was assessed by recording compound action potential (CAP) ratios, measuring collagen levels using picrosirius red staining, and counting the number of myelinated axons proximal and distal to the repair. After repair alone, the mean percentage of area of staining (PAS) for collagen within the nerve had significantly increased. However, after repair with the administration of antibodies, the PAS was not significantly different from that in the sham controls. After administration of antibodies, the CAP ratios were significantly smaller than in controls but not after repair alone. In both nerve injury groups, the myelinated fibre counts were significantly increased distal to the injury site, but there was no difference between these two groups. We conclude that administration of antibodies to TGF-beta1 and TGF-beta2 reduced scar formation at the repair site but did not enhance regeneration of the nerve or reduce the development of multiple axonal sprouts.     

Ganglioside promotes the bridging of sciatic nerve defects in cryopreserved peripheral nerve allografts

Previous studies have shown that exogenous gangliosides promote nervous system regeneration and synapse formation.In this study,10 mm sciatic nerve segments from New Zealand rabbits were thawed from cryopreservation and were used for the repair of left sciatic nerve defects through allograft bridging.Three days later,1 m L ganglioside solution(1 g/L) was subcutaneously injected into the right hind leg of rabbits.Compared with non-injected rats,muscle wet weight ratio was increased at 2–12 weeks after modeling.The quantity of myelinated fibers in regenerated sciatic nerve,myelin thickness and fiber diameter were elevated at 4–12 weeks after modeling.Sciatic nerve potential amplitude and conduction velocity were raised at 8 and 12 weeks,while conduction latencies were decreased at 12 weeks.Experimental findings indicate that ganglioside can promote the regeneration of sciatic nerve defects after repair with cryopreserved peripheral nerve allografts.     

An electrophysiological and histological study of myelinated axon regeneration after peripheral nerve injury and repair in the cat

Electrophysiological and histological methods have been combined to obtain quantitative measures of the success of regeneration of myelinated axons in a cutaneous nerve after injury and repair by a variety of procedures. Following a simple transection injury more axons regenerated successfully when the nerve was repaired by epineurial suturing or stump suturing than when it was left unrepaired; both types of repair gave similar results. After loss of a 10-mm piece of the nerve trunk, repair with an autograft produced more regeneration than when the nerve was left untouched, but repair by stump mobilization with epineurial suturing made matters worse. On the whole, the regenerated afferents had receptive field properties similar to those found in control animals but there was a higher incidence of units that could not be typed using conventional criteria. A small proportion of them had split receptive fields. Fibre diameters and conduction velocities were reduced compared with controls; this was particularly so through the neuroma and in the distal stump. There was also evidence of abnormal interactions, possibly ephaptic, between some regenerated axons.     

Effects of 660‐nm gallium–aluminum–arsenide low‐energy laser on nerve regeneration after acellular nerve allograft in rats

Purpose : The purpose of this study was to explore and discuss the effects of 660‐nm gallium–aluminum–arsenide low‐energy laser (GaAlAs LEL) irradiation on neural regeneration after acellular nerve allograft repair of the sciatic nerve gap in rats. Methods : Eight male and female Sprague–Dawley rats were used as nerve donors, and 32 healthy Wistar rats were randomly divided into four groups: normal control group, acellular rat sciatic nerve (ARSN) group, laser group, and autograft group. Twelve weeks after surgery, nerve conduction velocity, restoration rate of tibialis anterior wet muscle weight, myelinated nerve number, and calcitonin gene‐related peptide (CGRP) protein and mRNA expression of the spinal cord and muscle at the injury site were quantified and statistically analyzed. Results : Compared with the ARSN group, laser therapy significantly increased nerve conduction velocity, restoration rate of tibialis anterior wet muscle weight, myelinated nerve number, and CGRP protein and mRNA expression of the L₄ spinal cord at the injury site. Conclusions : These findings demonstrate that 660‐nm GaAlAs LEL therapy upregulates CGRP protein and mRNA expression of the L₄ spinal cord at the injury site and increases the rate of regeneration and target reinnervation after acellular nerve allograft repair of the sciatic nerve gap in rats. Low‐energy laser irradiation may be a useful, noninvasive adjunct for promoting nerve regeneration in surgically induced defects repaired with ARSN. Synapse 64:152–160, 2010. © 2009 Wiley‐Liss, Inc.     

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.     

The role of trkB receptor in the formation of post-traumatic neuroma

The outcome of peripheral nerve injury is often impaired by post-traumatic neuroma developing at the injury site. Neuroma is usually accompanied by neuropathic pain, which is usually resistant to most analgesics and presents a serious clinical problem. The mechanisms underlying post-traumatic neuroma remain unclear, but they are likely associated with regeneration processes. Brain-derived neurotrophic factor (BDNF) and its receptor, trkB, are strongly implicated in axonal regeneration after injury. The aim of this work was to examine the role of trkB in post-traumatic neuroma formation. The sciatic nerve was transected in wild-type and heterozygous trkB-deficient mice. The nerve was either left cut or immediately sewn up or the gap injury model was performed. The gap was provided with an autologous or cross (obtained from another genetic group) graft. Sixteen weeks after surgery, the animals were sacrificed and histologic evaluations were performed. We found very limited or no neuroma formation in wild-type animals, regardless of the surgical procedure. In the majority of trkB-deficient mice, the post-traumatic neuroma was found at the end of the proximal stump of the transected nerve. In the gap injury model, in trkB-deficient animals receiving wild-type graft, there was no neuroma at the join site between the graft and distal stump of the nerve. In contrast, if the graft was autologous, neuroma formed at both joints. We also noticed many more mast cells accumulated at the surgery site in trkB-deficient than in wild-type animals. These results indicate the important role of BDNF receptor in post-traumatic neuroma formation.     

Changes in myelinated and unmyelinated axon numbers in the proximal parts of rat sural nerves after two types of injury

Counts of myelinated and unmyelinated axon profiles have been made from normal, uninjured rat sural nerves and from nerves injured 6 months earlier in one of two ways. In one group of rats the nerve was simply cut and left to regenerate, leading to the development of a neuroma in continuity, while in the second group the nerve was cut but then ligated as well to prevent regeneration; this led to stump neuroma formation. After nerve transection and regeneration, with subsequent formation of a neuroma in continuity, there was no change in the number of myelinated axon profiles found 25 mm proximal to the old injury site when compared with control, but there was an 18% reduction (P < 0.05) in the number of unmyelinated axon profiles. Immediately proximal to the injury site the picture was similar, with there still being the same number of myelinated axon profiles as in control material but here the reduction in unmyelinated axon numbers was slightly greater at 24% (P < 0.05). In the proximal part of nerves that had been cut and stump neuroma formation induced there was a large increase (33%) in myelinated axon profiles over and above control values (P < 0.001) but the number of unmyelinated profiles was the same as in controls. Closer to the stump neuroma the number of myelinated axon profiles had increased yet further to be 88% (P < 0.001) above control while the number of unmyelinated ones remained no different from control. Our interpretation of these results is that after nerve transection and regeneration there is no loss of peripheral neurons supporting myelinated axons but some loss of those supporting unmyelinated ones. If a cut nerve is prevented from regenerating and a stump neuroma forms, however, a vigorous sprouting response is triggered in neurons with myelinated axons while those supporting unmyelinated axons are possibly prevented from dying. The reaction of peripheral neurons to injury is such that the number of axons they support varies along the nerve as one goes disto-proximally away from the injury site. Thus discrepancies in results from different laboratories have come about because material for axon counting has been taken from different points along the nerve relative to the injury site and also because the material has been taken from nerves injured in different ways.