视神经损伤与组织工程修复技术*★

视神经由视网膜神经节细胞轴索组成，因其周围无许旺细胞，属于中枢神经，故损伤后不能再生。1985年So和Aguayo进行周围神经视网膜移植成功,彻底改变了视神经损伤后不能再生的观念。目前神经损伤修复的方法有以下几种：①采用神经营养因子，如神经生长因子、睫状神经营养因子、脑源性神经营养因子等，这些因子具有促进视网膜神经节细胞再生和修复的作用。②基因矫正治疗与基因调控治疗通过改变宿主基因的表达，减少疾病所产生的效应，减缓疾病病程进展或提供对疾病的保护。③神经干细胞移植与组织工程化许旺细胞移植。但这些治疗方法尚处于动物实验阶段，如何及时有效地减少节细胞的凋亡和提高节细胞的存活率，在此基础上进一步促进神经的再生与修复，至今还没有一个完善的方法。     

睫状神经营养因子对坐骨神经切断吻合后大鼠脊髓前角胶质纤维酸性蛋白

背景：睫状神经营养因子具有多种生物活性,在神经系统发育、分化和损伤修复中具有重要意义。 目的：观察睫状神经营养因子对坐骨神经切断吻合后大鼠相应脊髓节段前角星形胶质细胞的特异标记物胶质纤维酸性蛋白表达的影响。 方法：将SD大鼠随机分为对照组、模型组、生理盐水组及药物组。除对照组外,对所有大鼠实施双侧坐骨神经切断吻合术,药物组手术区局部注射睫状神经营养因子100 ng/kg,1次/d,生理盐水组局部注射等量生理盐水。术后1,3,7,14,21,28 d取相应脊髓节段,免疫组织化学染色观察胶质纤维酸性蛋白的表达,苏木精-伊红染色、TUNEL染色对脊髓前角神经元进行计数。 结果与结论：大鼠坐骨神经切断吻合后相应脊髓节段星形胶质细胞胞体大,突起分枝多且粗大,神经元数目逐渐减少,凋亡神经元增多,胶质纤维酸性蛋白表达增高。与模型组和生理盐水组比较,药物组神经元存活数目增多,凋亡减少,胶质纤维酸性蛋白表达明显增加(P < 0.05或P < 0.01)。同时,药物组大鼠的运动功能障碍较轻,恢复较快。说明睫状神经营养因子可以通过促进大鼠脊髓前角胶质纤维酸性蛋白的表达起到神经保护作用。 关键词：胶质纤维酸性蛋白;睫状神经营养因子;星形胶质细胞;神经元凋亡;周围神经损伤     

胶质细胞源性神经营养因子研究进展

神经营养因子(neurotrophines, NTs)是一组多肽因子,可特异性地作用于某一种神经元或广谱地作用于多种神经元,促进神经元的存活和诱导突起生长.神经营养因子为一个大家族,参与神经系统的生长发育,功能维持和损伤修复.     

第三讲 神经营养因子的神经修复作用及其机制

神经营养因子是指机体产生的能够促进神经细胞存活、生长、分化的一类蛋白质因子.过去一直认为神经生长因子主要在发育过程中调节神经元存活,而对成年神经元不产生作用.近十五年来,这种传统观念才得以彻底改变,神经营养因子不仅在成年神经系统存在,而且能够阻止成年神经元损伤后神经元的死亡以及调节包括突触可塑性和神经递质传递等许多神经系统功能.这些发现,拓展了对神经修复策略的理解,使人们认识到,神经营养因子不仅可以减少神经变性阻止疾病进程,而且还具有刺激轴突生长、促进再生的功能.研究表明,对于阿尔茨海默病、帕金森病、亨廷顿病、肌萎缩性侧索硬化症、卒中、脊髓损伤和外周神经病变等,神经营养因子表现出能促进神经元的修复、轴突生长和功能性恢复的作用.神经营养因子极有可能成为将来治疗神经损伤和神经系统疾病的重要手段.     

脑源性神经营养因子和睫状神经营养因子单独或联合体外诱导人脐带血来源的间充质干细胞向神经样细胞分化

背景：体外培养条件下脐血间充质干细胞可向神经样细胞诱导分化,一定浓度范围的脑源性神经营养因子和睫状神经营养因子联合体外诱导可获得较高的神经元分化比例。 目的：观察脑源性神经营养因子和睫状神经营养因子单独或联合体外诱导人脐带血来源的间充质干细胞分化成神经样细胞的可行性。 方法：取第5代的脐血间充质干细胞,分别用5,10,20 μg/L的脑源性神经营养因子和5,10,20 μg/L睫状神经营养因子单独或联合诱导脐血源间充质干细胞向神经样细胞分化,另设空白对照组无任何干预措施。倒置相差显微镜观察细胞形态变化,于实验第1,3,6天分别进行神经元特异性烯醇化酶和胶质纤维酸性蛋白免疫细胞化学染色,并计数分化为神经元样细胞及神经胶质细胞的比例。 结果与结论：①向神经细胞诱导后,人脐血源间充质干细胞形态明显改变,胞体收缩,胞核部分折光性增强,出现类似于树突及轴突样结构。②与空白对照组相比,脑源性神经营养因子和睫状神经营养因子能显著提高人脐血源间充质干细胞分化为神经元的比例。其中20 μg/L的脑源性神经营养因子联合20 μg/L睫状神经营养因子诱导人脐血源间充质干细胞分化为神经样细胞的比例最高。提示人脐血间充质干细胞经脑源性神经营养因子和睫状神经营养因子体外诱导,均能够分化为神经样细胞。     

短时低频电刺激体外培养许旺细胞髓鞘的形成

周围神经系统损伤后,短时低频电刺激已被证明可显著促进轴突再生和选择性功能修复,但目前对电刺激是否影响周围神经髓鞘的形成还知之甚少,而电刺激发挥作用究竟是通过神经元还是许旺细胞还有待证实。 目的：建立体外背根神经元与许旺细胞联合培养模型,观察短时低频电刺激对许旺细胞髓鞘形成的影响。 方法：体外培养背根神经元,纯化后预先施予电刺激(20 Hz,100 μs,3 V),持续作用1 h,24 h后再加入许旺细胞悬液制成背根神经元/许旺细胞联合培养模型。在此基础上,用L-ascorbic acid诱导髓鞘形成,分别于诱导后第7,14天观察培养体系中髓鞘的形成。 结果与结论：电刺激增强背根神经元分泌脑源性神经营养因子(P < 0.05),经电刺激作用的背根神经元再与许旺细胞联合培养,最终表现为髓鞘形成增多以及髓鞘蛋白表达上调(P < 0.05)。提示短时低频电刺激对体外许旺细胞髓鞘的形成具有促进作用,初步认为该作用至少通过刺激神经元分泌脑源性神经营养因子增多导致。     

白血病抑制因子在周围神经损伤修复中的应用

神经营养因子在周围神经损伤中的应用,是当前的一个研究热点。白血病抑制因子(LIF)是一种对感觉、运动和自主神经元都敏感的神经营养因子,周围神经损伤后其在损伤处的表达上调且逆行运输至神经元胞体的量增加,通过与相应受体结合后,起着维持损伤后神经元的存活;促进神经轴突的生长;参与神经损伤后的炎性反应;调节神经元基因和多种神经肽的表达;促进其它神经营养因子的分泌等生物效应,在周围神经修复再生过程的多个方面中起着重要的作用。     

睫状神经营养因子与神经再生

睫状神经营养因子 (Ciliary Neurotrophic Factor,CNTF)因最早发现于鸡胚眼组织中并对睫状神经元有营养作用而得名 [1 ] 。它不属于神经营养因子家族成员 ,与其无同源性 ,属非靶源性神经营养因子。 CNTF具有广泛的生物活性 ,可以促进运动神经元、感觉神经元、海马胆碱能神经元的存活 ,并具有损伤修复作用 [2 ] 。1　 CNTF的分子与基因结构CNTF是一种相对分子量为 2 0 0 0 0的含 2 0 0个氨基酸残基的酸性蛋白 ,等电点为 6.0 [3]。人类 CNTF分子量为 2 0～2 4k D)。在第 17位有一个 Cys,分子内无二硫键 ,无 N-糖基化位点、无信号肽…     

脑源性神经营养因子在阿尔茨海默病中的研究进展

脑源性神经营养因子足神经营养因子家族成员,对神经元损伤后再生修复和防止神经细胞退行性变等方面发挥重要作用的神经营养因子.阿尔茨海默病足一种常见的神经系统退行性疾病,其中Tau蛋白磷酸化促进了疾病的发生,而脑源性神经营养因子通过激活酪氨酸激酶受体可以阻止Tau蛋白磷酸化,从而影响疾病的发生发展.     

胶质细胞源性神经营养因子与脑缺血损伤

脑缺血损伤在世界范围内是人类致死的主要原因之一[1].临床和基础研究均表明,神经营养因子在脑缺血后神经元的损伤和修复过程中具有重要作用.胶质细胞源性神经营养因子(GDNF)是神经营养因子家庭中的一名新成员,在脑缺血损伤中对神经元具有保护作用,目前已经成为神经科学研究领域的一个"热点"[2].本文就GDNF对脑缺血损伤的保护作用有关内容作一综述.     

Peripheral nerve regeneration through optic nerve grafts

Summary Grafts of optic nerve were placed end-toend with the proximal stumps of severed common peroneal nerves in inbred mice. It was found that fraying the proximal end of adult optic nerve grafts to disrupt the glia limitans increased their chances of being penetrated by regenerating peripheral nerve fibres. Suturing grafts to the proximal stump also enhanced their penetration by axons. The maximum distance to which the axons grew through the CNS tissue remained about 1.5 mm from 2–12 weeks after grafting. Schwann cells were seldom identified in the grafts. Varicose and degenerating nerve fibres were often seen within the grafts. Some varicose profiles were shown to be the terminal parts of axons within the grafts. Axons containing clusters of organelles resembling synaptic vesicles became more abundant in the longerterm grafts. Immunohistochemical studies performed on sutured grafts using a polyclonal antiserum to neurofilaments confirmed the impressions given by the electron microscopical observations. Grafts of neonatal optic nerve lacked myelin debris but were not usually penetrated by regenerating peripheral axons within a 6-week period. Sixty minutes after the intravenous injection of horseradish peroxidase, reaction product could be detected in the extracellular spaces around blood vessels in all types of living optic nerve graft. This indicates that blood-borne macromolecules could penetrate the grafts. However the profiles of axons which were found within living optic nerve grafts had no obvious relationship to blood vessels and were usually surrounded by astrocytic processes. These results suggest that living astrocytes, rather than the absence of serum-derived trophic factors or the presence of CNS myelin, constitute the major barrier to the extension of axons and the migration of Schwann cells into CNS tissue.Supported by a grant from the Wellcome Trust     

Hemihypoglossal-facial nerve anastomosis for facial nerve palsy

BACKGROUND AND PURPOSE : Commonly used classic hypoglossal (CN XII) to facial nerve (CN VII) anastomosis has the disadvantage of tongue hemiatrophy. Thus, various attempts have been made to modify this method to reduce the tongue damage. The aim of this report was to present the results of hemihypoglossal-facial nerve anastomosis (HHFA) technique in relation to facial muscles reanimation and hemitongue atrophy. MATERIAL AND METHODS : The first 7 consecutive patients who underwent CN VII anastomosis with half of the CNXII, for which the follow-up period exceeded 12 months, were analysed. During the procedure, CN VII was transected as proximally as possible after drilling the mastoid process. CN XII was separated longitudinally into two parts at a short distance to allow suture of the stumps without any tension. One half of CN XII was transected and sutured to the distal stump of CN VII. Recovery from facial palsy was quantified with the House-Brackmann grading system (HB). Tongue function was assessed according to the scale proposed by Martins. RESULTS : Features of initial reinnervation of facial muscles were visible after 6 months in all 7 patients. All patients achieved satisfactory outcome of CN VII regeneration (HB grade III) until the last control examination (12-27 months after surgery, mean 16). No or minimal tongue atrophy without deviation (grades I-II according to the Martins scale) was found in 4 patients. Mild hemiatrophy with tongue deviation < 30 degrees (grade III) was visible in 3 patients. CONCLUSIONS : In our experience, HHFA is effective treatment of facial palsy and gives a chance to reduce damage of the tongue.     

End-to-side neurorrhaphy repairs peripheral nerve injury: sensory nerve induces motor nerve regeneration

End-to-side neurorrhaphy is an option in the treatment of the long segment defects of a nerve.It involves suturing the distal stump of the disconnected nerve(recipient nerve) to the side of the intimate adjacent nerve(donor nerve).However,the motor-sensory specificity after end-to-side neurorrhaphy remains unclear.This study sought to evaluate whether cutaneous sensory nerve regeneration induces motor nerves after end-to-side neurorrhaphy.Thirty rats were randomized into three groups:(1) end-to-side neurorrhaphy using the ulnar nerve(mixed sensory and motor) as the donor nerve and the cutaneous antebrachii medialis nerve as the recipient nerve;(2) the sham group:ulnar nerve and cutaneous antebrachii medialis nerve were just exposed;and(3) the transected nerve group:cutaneous antebrachii medialis nerve was transected and the stumps were turned over and tied.At 5 months,acetylcholinesterase staining results showed that 34% ± 16% of the myelinated axons were stained in the end-to-side group,and none of the myelinated axons were stained in either the sham or transected nerve groups.Retrograde fluorescent tracing of spinal motor neurons and dorsal root ganglion showed the proportion of motor neurons from the cutaneous antebrachii medialis nerve of the end-to-side group was 21% ± 5%.In contrast,no motor neurons from the cutaneous antebrachii medialis nerve of the sham group and transected nerve group were found in the spinal cord segment.These results confirmed that motor neuron regeneration occurred after cutaneous nerve end-to-side neurorrhaphy.     

Changes in nerve microcirculation following peripheral nerve compression

Following peripheral nerve compression, peripheral nerve microcirculation plays important roles in regulating the nerve microenvironment and neurotrophic substances, supplying blood and oxygen and maintaining neural conduction and axonal transport. This paper has retrospectively analyzed the articles published in the past 10 years that addressed the relationship between peripheral nerve compression and changes in intraneural microcirculation. In addition, we describe changes in different peripheral nerves, with the aim of providing help for further studies in peripheral nerve microcirculation and understanding its protective mechanism, and exploring new clinical methods for treating peripheral nerve compression from the perspective of neural microcirculation.     

Sural nerve biopsy may predict future nerve dysfunction

Objective – Sural nerve pathology in peripheral neuropathy shows correlation with clinical findings and neurophysiological tests. The aim was to investigate progression of nerve dysfunction over time in relation to a baseline nerve biopsy. Methods – Baseline myelinated nerve fiber density (MNFD) was assessed in sural nerve biopsies from 10 men with type 2 diabetes, 10 with impaired and 10 with normal glucose tolerance. Nerve conduction and quantitative perception thresholds were estimated at baseline and follow‐up (7–10 years later). Results – Subjects with low MNFD (≤ 4700 fibers/mm²) showed decline of peroneal amplitude (P < 0.02) and conduction velocity (P < 0.04), as well as median nerve sensory amplitude (P < 0.05) and motor conduction velocity (P < 0.04) from baseline to follow‐up. In linear regression analyses, diabetes influenced decline of nerve conduction. MNFD correlated negatively with body mass index (r = ?0.469; P < 0.02). Conclusion – Low MNFD may predict progression of neurophysiological dysfunction and links obesity to myelinated nerve fiber loss.     

颅内腓神经移植面神经重建术--附2例报告

目的 探讨腓神经移植面神经重建的手术方法和临床疗效。方法 根据House-Brackman面瘫分级方法,2例面瘫分级为Ⅳ级的无法保留面神经的听神经瘤患者,先行肿瘤全切除,随后立即行面神经重建术。取腓神经作为神经供体,暴露内听道内面神经残端及颅内最粗的副神经,将腓神经置于面-副神经之间行神经端-端吻合。结果 施行颅内面神经重建的2例患者,手术后面瘫程度改善,预后良好,术后1年随访,面瘫分级分别达到Ⅲ级和Ⅳ级。结论 面神经重建可与听神经瘤切除术同期完成,为恢复面神经运动功能较为有效的手术方法之一。     

Tissue-engineered nerve for repair of sciatic nerve injury

Three articles regarding the use of nerve fragments bridging regeneration chambers, three-dimensional bionic nerve conduits and multiwalled carbon nanotubes for repair of sciatic nerve injury were reported in Neural Regeneration Research. We hope that our readers find these papers useful to their research.     

Sensory nerve conduction study of the mental nerve

We describe a technique for sensory nerve conduction study of the mental nerve. A monopolar recording needle is placed near the mandibular foramen using the same approach as that for routine inferior alveolar nerve block in dentistry, and a surface reference electrode is positioned over the ipsilateral mastoid process. Sensory nerve action potentials to stimulation of the mental nerve at the chin can be reliably recorded orthodromically in normal healthy subjects. The method is simple and well tolerated and provides a useful means to evaluate mental nerve function electrophysiologically.