神经生长因子与移植脾组织神经再生的关系

神经生长因子（nerve growth factor，NGF）是神经系统一种重要的生物活性因子。近年来研究发现了神经生长因子家族的其他成员，如脑源性神经生长因子（BDNF）、神经营养素．3（NT-3）、神经营养素4（NT-4）、神经营养素-6（NF-6）等,同时对神经生长因子的生物特性、分布和作用进行了广泛深入的研究。本文就神经生长因子的主要研究进展及其对再植脾神经再生的关系作一简述。     

全反式维甲酸诱导小鼠碱性磷酸酶基因启动子区染色体重构

背景：碱性磷酸酶基因是成骨细胞分化和骨形成的重要标志。在C3H10T1/2细胞中,全反式维甲酸可通过核受体上调小鼠碱性磷酸酶的表达,与MAPK通路无关。 目的：从染色体结构调控方面揭示全反式维甲酸上调碱性磷酸酶表达的分子机制。 方法：10^-6 mol/L全反式维甲酸处理C3H10T1/2细胞0,1,6,12 h,DNA酶Ⅰ超敏感实验确定全反式维甲酸调控区域的位置,染色质免疫共沉淀实验检验全反式维甲酸处理细胞后一系列转录相关因子与全反式维甲酸调控区域结合的量效关系以及时相分布。 结果与结论：DNA聚合酶Ⅰ超敏感实验表明,小鼠碱性磷酸酶启动子转录起始位点上游约520 bp附近为潜在的全反式维甲酸调控区域;染色质免疫共沉淀实验表明,全反式维甲酸对小鼠碱性磷酸酶的上调作用是通过一系列转录相关因子的时序性共同作用来实现。表明全反式维甲酸诱导小鼠碱性磷酸酶基因转录的过程中伴随着染色质重构和组蛋白的修饰作用。     

Insulin-like growth factor I promotes nerve regeneration: an experimental study on rat sciatic nerve

Insulin-like growth factor I (IGF-I; somatomedin C) has previously been demonstrated, with immunohistochemical methods, to accumulate locally at the site of trauma of an injured peripheral nerve. In the experiments reported here a Y-shaped silicone-chamber system was used to test if local infusion of IGF-I had supportive effects on nerve regeneration. The proximal end of a cut sciatic nerve was inserted into one channel of the Y-shaped chamber and the length and growth direction of the regenerating myelinated axons were evaluated after 1 month. When IGF-I (250 micrograms/ml 0.5 microliters/h) was infused into one channel by an osmotic pump, the length of the regenerating axons increased significantly compared to the control groups with no IGF-I added. In some instances the regenerating axons grew towards the osmotic pump. It is concluded that local infusion of IGF-I at appropriate concentration promotes regeneration of a peripheral nerve. It exerts a neuronotrophic but not a clear chemotactic effect.     

Beneficial effects of treadmill training in experimental diabetic nerve regeneration

OBJECTIVES:

We investigated the effects of treadmill training (10 weeks) on hindlimb motor function and nerve morphometric parameters in diabetic rats submitted to sciatic nerve crush.

MATERIALS AND METHOD:

Wistar rats (n = 64) were divided into the following groups: non-diabetic; trained non-diabetic; non-diabetic with sciatic nerve crush; trained non-diabetic with sciatic nerve crush; diabetic; trained diabetic; diabetic with sciatic nerve crush or trained diabetic with sciatic nerve crush. Diabetes was induced by streptozotocin injection (50 mg/kg, iv). Hindlimb motor function was evaluated weekly by assessing sciatic functional indices, and the proximal and distal portions of the sciatic nerve were used for morphometric analysis.

RESULTS:

At 13 weeks post-injury, the distal nerve portion of all injured groups and the proximal nerve portion of the diabetic with sciatic nerve crush group presented altered morphometric parameters such as decreased myelinated fiber diameter (∼7.4±0.3µm vs ∼4.8±0.2µm), axonal diameter (∼5±0.2µm vs ∼3.5±0.1µm) and myelin sheath thickness (∼1.2±0.07µm vs ∼0.65±0.07µm) and an increase in the percentage of area occupied by endoneurium (∼28±3% vs ∼60±3%). In addition, in the non-diabetic with sciatic nerve crush group the proximal nerve portion showed a decreased myelinated fiber diameter (7.4±0.3µm vs 5.8±0.3µm) and myelin sheath thickness (1.29±0.08µm vs 0.92±0.08µm). The non-diabetic with sciatic nerve crush, trained non-diabetic with sciatic nerve crush, diabetic with sciatic nerve crush and trained diabetic with sciatic nerve crush groups showed normal sciatic functional index from the 4^th, 4^th, 9^th and 7^th week post-injury, respectively. Morphometric alterations in the proximal nerve portion of the diabetic with sciatic nerve crush and non-diabetic with sciatic nerve crush groups were either prevented or reverted to values similar to the non-diabetic group by treadmill training.

CONCLUSION:

Diabetic condition promoted delay in sciatic nerve regeneration. Treadmill training is able to accelerate hindlimb motor function recovery in diabetic injured rats and prevent or revert morphometric alterations in proximal nerve portions in non-diabetic and diabetic injured rats.     

神经生长因子及其受体在周围神经损伤再生中的作用机制

神经生长因子(nerve growth factor,NGF)作为最早发现的能够促进神经再生的神经营养因子(neurotrophin factors,NTFs),与其不同受体的相互作用对神经往往会产生促凋亡或抑制凋亡、维持生长、诱导再生、促进分化等两种相反的结局。对这些作用机制的研究有助于对周围神经损伤再生     

All-trans retinoic acid induces TLR-5 expression and cell differentiation and promotes flagellin-mediated cell functions in human THP-1 cells

Toll-like receptor 5 (TLR-5), which is expressed on macrophages and dendritic cells (DCs), is a crucial cell surface molecule that senses microbial-associated molecular patterns and initiates host innate immune responses upon infection with invaders that express flagellin. Little information is known about the induction factors and mechanisms of TLR-5 expression. In this study, we demonstrate that all-trans retinoic acid (ATRA) significantly up-regulated TLR-5 expression in human macrophage THP-1 cells by co-activating NF-κB and the RARα receptor and inducing the differentiation of CD11b(-)CD11c(-) THP-1 cells to CD11b(+)CD11c(low) cells. Furthermore, when stimulated with flagellin, ATRA-induced THP-1 cells expressed multiple cytokines, including TNF-α, IL-1beta, and IL-12p40, and several co-stimulatory molecules, such as CD40, CD80, CD86, and MHC class I and II. We also showed that when ATRA-induced THP-1 cells were stimulated with flagellin, the cells displayed an allostimulatory capacity rather than phagocytic activity. Taken together, our findings suggest that ATRA is a crucial immunostimulatory cofactor that induces the activation of macrophages and their subsequent differentiation into dendritic-like cells.     

全反式维甲酸诱导骨骼畸形大鼠血清及羊水内碱性成纤维细胞生长因子的表达简

目的探究应用全反式维甲酸诱导骨骼畸形大鼠血清及羊水内碱性成纤维细胞生长因子（FGF2）的表达。方法选择孕10d的Wistar大鼠50只,体质量250～300g。分实验组和对照组.每组各25只。实验组予溶有全反式维甲酸的大豆油（40mg／mL）,按照135mg/hg以灌胃方式给药制作骨骼畸形胎鼠模型;对照组给予等体积的大豆油。孕20d时处死母鼠,采集母鼠血液,实验组每窝选择骨骼畸形胎鼠4只,对照组每窝随机选取胎鼠4只,抽取胎鼠羊水标本,应用酶联免疫吸附分析测定血液及羊水内FGF2浓度：利用游标卡尺测量胎鼠头臀长,双前肢各段及双后肢的长度。结果实验组胎鼠出现四肢发育不良、脊柱裂、下颌裂等畸形。实验组胎鼠头臀长、双前肢各段及双后肢长度与对照组相比.差异具有统计学意义（P〈0.05）。实验组母鼠血液及胎鼠羊水内FGF2的浓度与对照组相比[（24.124±1.271）pg／mL vs（27.451±2.026）pg／mL,（23.918±0.369）pg／mL vs（27.305±2.125）pg／mL],差异具有统计学意义（P〈0.05）。结论全反式维甲酸诱导骨骼畸形大隐.FGF2表茯情况低干骨骼发育正常的大鼠。     

Role of nerve growth factor in experimental autoimmune encephalomyelitis

The expression of neural regulatory molecules by immune cells that infiltrate the nervous system upon injury may be a mechanism for cross-regulation between the nervous system and the immune system. Several lines of evidence implicate nerve growth factor (NGF) signaling through its receptors (TrkA and p75(NGFR)) as a potential source of communication between the two systems. We observed changes in NGF mRNA expression and protein secretion by T lymphocytes polarized toward the Th2 phenotype. The presence of NGF did not affect T cell proliferation or cytokine production in vitro. Mice treated with NGF by i. p. injection following induction of experimental autoimmune encephalomyelitis, an inflammatory, demyelinating disease of the central nervous system, showed a delayed onset of disease and lower clinical scores during the course of disease. These data suggest a role for NGF signaling in the regulation of the immune response, possibly by enhancing sympathetic innervation of lymphoid tissues.     

PDLLA/NGF复合膜用于自体神经移植促进神经再生实验研究

目的：探讨外消旋聚乳酸／神经生长因子(PDLLA／NGF)复合膜用于自体神经移植是否具有促进神经再生作用。方法：雌性Wistar大白鼠16只，随机分为2组：A组(自体神经移植)8只；B组(自体神经移植并包绕PDLLA／NGF复合膜)8只。显露每只动物的右侧坐骨神经，A组将坐骨神经切除10mm长一段，以外膜缝合法行原位移植；B组与A组同样行神经原位移植并在远近两个神经缝接部位各包绕1块PDLLA／NGF复合膜(含NGF总量为400u)。6个月后观察比较两组神经再生情况。结果：B组的小腿三头肌湿重恢复率、运动神经传导速度、再生的有髓神经纤维数量、直径、轴突直径、髓鞘厚度均优于A组：结论：PDLLA／NGF复合膜包绕自体神经移植的神经缝接部位具有促进神经再生作用.     

The role of basic fibroblast growth factor in peripheral nerve regeneration

In the peripheral nervous system regeneration and gradual functional restoration occur following peripheral nerve injury. Growth of regenerating axons depends on the presence of diffusible neurotrophic factors, in addition to the substratum. Neurotrophic factors that are involved in peripheral nerve regeneration include nerve growth factor, brain-derived neurotrophic factor, ciliary neurotrophic factor, glial cell line-derived neurotrophic factor, and interleukin-6. Recent functional and expression studies of basic fibroblast growth factor and its receptors have emphasized a physiological role of these molecules in the peripheral nervous system. Basic fibroblast growth factor and its receptors are constitutively expressed in dorsal root ganglia and the peripheral nerve. These molecules display an upregulation in dorsal root ganglia and in the proximal and distal nerve stumps following peripheral nerve injury. In the ganglia these molecules show a mainly neuronal expression, whereas at the lesion site of the nerve, Schwann cells and invading macrophages represent the main cellular sources of basic fibroblast growth factor and the receptors 1–3. Exogenously applied basic fibroblast growth factor mediates rescue effects on injured sensory neurons and supports neurite outgrowth of transectioned nerves. Regarding the expression pattern and the effects after exogenous administration of basic fibroblast growth factor, this molecule seems to play a physiological role during nerve regeneration. Thus, basic fibroblast growth factor could be a promising candidate to contribute to the development of new therapeutic strategies for the treatment of peripheral nerve injuries.     

维甲酸在轴突再生过程中的作用与机制

背景：维甲酸信号通路在神经系统形成、神经元的特化以及轴突生长过程中极为重要,近年的研究结果显示维甲酸在轴突再生过程中具有重要作用,但是却鲜有关于其确切作用分子机制的研究报道。 目的：对近年来维甲酸信号通路在轴突再生过程中的作用机制进行总结分析。 方法：以“维甲酸,中枢神经系统,神经损伤,轴突再生,作用机制”为中文捡索词,以“Retinoic acid, the central nervous system, nerve damage, axon regeneration, signaling pathway,mechanism”为英文检索词,检索维普和中国知网(CNKI)期刊全文数据库、PubMed网络数据库、BioMed Centeral 、Springer 、The Free Medical Journals、EBSCO和外文生物医学期刊全文数据库(Foreign Journals Integration System)2000年1月至2013年12月有关维甲酸在轴突再生中作用机制的研究报道,排除重复性研究和不典型报道。 结果与结论：急性中枢神经系统损伤后,机体轴突再生和功能恢复的能力极为有限。为了保持机体的某些特有功能,神经元轴突必须再生并再支配它的作用靶点,以实现机体结构和功能的恢复。中枢神经系统损伤后,维甲酸信号通路通过表达转录因子RAβ2 受体,可诱导轴突的再生;同时在背根神经节神经元中,经慢病毒转染表达RARβ2后可以引起胞内cAMP水平升高,从而促进神经轴突生长;在脊髓损伤后以及体外轴突生长抑制环境中,RA-RARβ途径可以直接抑制中枢神经再生抑制因子Nogo受体(NgR)复合体-Lingo-1的转录,从而促进轴突的再生。维甲酸信号通路正是通过以上一系列的分子机制在轴突再生过程中其重要的作用 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;组织工程全文链接：     

Role of retinoic acid in lens regeneration.

Prompted by the actions of retinoids and their receptors in gene regulation, in the developing eye and especially in the lens, we have undertaken a detailed study to examine the effects of retinoids on urodele lens regeneration. First, we examined the effects of exogenous retinoids. It was found that exogenous retinoids had no significant effect on lens regeneration. However, when synthesis of retinoic acid was inhibited by disulfiram, or when the function of the retinoid receptors was impaired by using a RAR antagonist, the process of lens regeneration was dramatically affected. In the majority of the cases, lens regeneration was inhibited and lens morphogenesis was disrupted. In a few cases, we were also able to observe ectopic lens regeneration from places other than the normal site, which is from the dorsal iris. The most spectacular case was the regeneration of a lens from the cornea, an event possible only in premetamorphic frogs. These data show that inhibition of retinoid receptors is paramount for the normal course and distribution of lens regeneration. We have also examined expression of RAR-delta during lens regeneration. This receptor was expressed highly in the regenerating lens only. Therefore, it seems that this receptor is specific for the regeneration process and consequently such expression correlates well with the effects of RAR inhibition observed in our studies.     

Intracerebroventricular infusion of nerve growth factor induces pain-like response in rats

New strategies have recently been developed where infusion of neurotrophic factors into the brain can rescue different neuronal populations. However, negative side effects have been observed in clinical trials infusing nerve growth factor (NGF) into the lateral ventricle in man, namely pain. Little is known about pain behavior in animals after intracerebroventricular (i.c.v.) neurotrophic injections. Thus, we have examined the effects of i.c.v. infusion of NGF for 2 weeks on the behavioral response of rats to mechanical, cold and heat stimulation. Seven micrograms/day of NGF elicited a significant decrease in vocalization threshold to mechanical stimulation and a significantly increased response to cold and heat stimuli as compared with control. The concentration of NGF in cerebrospinal fluid (CSF) was significantly increased as compared with non-allodynic rats. The enhanced responses to mechanical and heat, but not to cold, stimulation were significantly reduced by CP-99994, a selective antagonist to tachykinin NK-1 receptors. When NGF was infused into the brain parenchyma (striatum, cortex and septum) no allodynic nor hyperalgesic responses could be detected. These results indicate that in rats i.c.v. but not intraparenchymal infusion of NGF induce mechanical and cold allodynia as well as heat hyperalgesia, which is mediated, at least in part, by activation of NK-1 receptors.     

All-trans retinoic acid modulates fas expression and enhances chemosensitivity of human medulloblastoma cells

Retinoic acid (RA) can promote human medulloblastoma cells Med-3 toward differentiation but is not sufficient to induce cell death, suggesting its limited effect on medulloblastomas. On the other hand, the differentiated tumour cells have been supposed to be more sensitive to chemotherapeutic drugs. To elucidate this possibility for medulloblastoma cells, 10 microM/l RA, 1.0 microg/ml cisplatin (CP) and their half-dosage combinations were utilized in this study to treat Med-3 cells and their influences in cell proliferation, morphology and death patterns were evaluated. In parallel, the expressions of Fas and its ligand (FasL) were analyzed by immunocytochemical staining and Western blot hybridization. Anti-Fas antibody was used to incubate the Med-3 cells pretreated by 10 microM/l RA or 1.0 microg/ml CP. It was revealed that RA and CP could inhibit cell growth but rarely induce apoptosis. Combination of half doses each of RA and CP effectively caused most of tumour cells to die of apoptosis within 6 days. FasL molecules in 29 kDa and 37 kDa were detected in Med-3 cells with and without the treatments. The Fas molecule around 30 kDa and located in the cytoplasm was found in the normally cultured cells and the cells treated by CP. An additional 45 kDa Fas band with the appearance of its cell surface labeling was detected in the cells treated by 10 microM/l RA and by 5 microM/l RA + 0.5 microg/ml CP. The anti-Fas antibody could efficiently induce apoptosis only in the cell populations pretreated by RA. Our data thus suggest that RA can enhance the chemosensitivity of human medulloblastoma Med-3 cells presumably via modulating the Fas expression pattern. The RA/CP combined regimen would be a potential therapeutic approach for medulloblastomas.     

All-trans retinoic acid syndrome. Case report and a review of the literature

We described a patient with acute promyelocytic leukemia (APL) who developed all-trans retinoic acid syndrome (ATRAS) and reviewed the literature. ATRAS presents in patients with APL treated with all-trans retinoic acid (ATRA). It has an incidence from 5%-27% with mortality of 29%. It is secondary to ATRA effect on promyelocyte differentiation, which causes systemic inflammatory response syndrome, endothelium damage with increase in capillary permeability, microcirculation obstruction, and tissue infiltration. ATRAS clinical manifestations are fever, hypotension, respiratory, renal and hepatic insufficiency, lung infiltrates, pleural and pericardic effusion, and generalized edema. Treatment is based on ATRA suspension, support measures, and steroids.     

神经再生素促进神经干细胞的生长和分化

目的:研究神经再生素对体外培养神经干细胞分化的促进作用及对其生长相关蛋白(GAP43)、神经丝蛋白(NF-H)表达的影响.方法:取出生3～5d的新生SD大鼠大脑皮层进行神经干细胞的体外培养、鉴定,神经干细胞与0、 1、 2mg/L的神经再生素(NRF)共培养8d,相差显微镜观察分析,应用Real-time PCR对与不同浓度的NRF(0、 1、 2、 4、 8mg/L)共培养8d的神经干细胞进行GAP43、 NF-H的表达量检测.结果:成功培养出具有多向分化潜能的神经干细胞;神经再生素可明显促进神经干细胞的分化,并能在一定范围内随浓度递增而有效促进GAP43、 NF-H的表达,且最佳作用浓度为4mg/L.结论:神经再生素可以促进神经干细胞的生长和分化.     

Wide range of lineages of cells expressing nerve growth factor mRNA in the nerve lesions of patients with vasculitic neuropathy: an implication of endoneurial macrophage for nerve regeneration

In situ localization of nerve growth factor (NGF) mRNA was examined in the nerve lesions of patients with vasculitic neuropathy. Double labeling of in situ hybridization for NGF mRNA and immunohistochemistry for cell markers showed that NGF mRNA was expressed in a wide range of lineages of cells: Schwann cells, infiltrating macrophages, T cells and perivascular cells. Round-shaped macrophages with early-phase features expressed high levels of NGF mRNA, in contrast to late-phase polymorphic macrophages, which expressed low levels of NGF mRNA. NGF mRNA was also expressed universally in T cells with various cell surface markers. Epineurial macrophages surrounding vasculitic lesions and endoneurial T cells expressed high levels of NGF mRNA in the damaged nerves. Moreover, the extent of endoneurial NGF expression level in macrophages was closely related to the degree of axonal regeneration. These results suggest that NGF is expressed in a wide range of lineages of cells but is differentially expressed spatially in vasculitic nerve lesions, and that the expressed NGF, particularly in macrophages, may play an important role in the nerve regeneration process.     

Fimbria-fornix lesion increases nerve growth factor content in adult rat septum and hippocampus

Bilateral complete transection of the fimbria-fornix causes a significant increase in nerve growth factor (NGF) content both in the septum and hippocampus of the adult rat as measured by a sensitive immunoassay 7 days after lesioning. The finding, that elevation of NGF in septum (250%) was much more pronounced than that in the hippocampus (30-50%), cannot be explained by retrograde axonal transport. Degeneration of central cholinergic neurons might be a potential trigger for NGF production in the CNS.