组织外植块对培养的鸡胚背根节神经突起生长的影响

为了解神经元的发育和周围组织的关系,本文分别用了:(1)10天鸡胚背根节与10天鸡胚心脏、皮肤、角膜、骨骼肌、肠、大脑、脊髓外植块联合培养;(2)不同时期的鸡角膜与不同胚龄的鸡胚背根节联合培养;(3)10天鸡胚背根节与雏鸡角膜内、外层联合培养。实验结果表明鸡胚心脏、皮肤和角膜外植块对背根节神经突起生长具较强的促进作用且对生长方向有明显诱导作用;骨骼肌、肠和大脑对神经突起生长也有不同程度促进作用,但脊髓却无明显作用。14、16、18天鸡胚角膜对8、10、12、14天鸡胚背根节神经突起生长有明显促进作用;12、14天鸡胚背根节在各时期角膜作用下神经突起生长都较丰富。含上皮层的雏鸡角膜外植块促进背根节神经突起生长的作用比含内皮层的角膜外植块强。     

激活素A与NGF协同刺激鸡胚背根神经节神经突起生长

目的:探讨激活素A(Activin A)与神经生长因子(Nerve growth factor,NGF)共同刺激鸡胚背根神经节(DRG)神经突起生长作用。方法:采用8 d的鸡胚DRG原代培养法,通过Activin A与NGF联合刺激,观察DRG神经突起生长和DRG神经元存活情况。采用RT-PCR检测钙基因相关肽(CGRP)。结果:Activin A与NGF体外联合培养3 d时DRG神经突起生长比单纯NGF组更明显,DRG神经元存活数量也明显增加,Activin A与NGF联合作用可以明显促进CGRP mRNA表达。结论:Activin A对NGF诱导的鸡胚DRG神经突起生长和维持DRG神经元存活具有增强作用,提示二者的联合应用可能为治疗神经元损伤及变性疾病的应用提供了新的数据和实验依据。     

非悬滴开放式培养法在鸡胚背根节体外培养中的应用

本研究针对悬滴培养法在操作和应用上存在的问题和局限性，改用操作简便、适用范围广的非悬滴开放式培养法培养鸡胚背根节。将数个鸡胚背根节按一定间隔种植在内置生长基质盖玻片的35mm培养皿中，加人适量培养液，置于CO2。孵箱中进行培养。结果显示.从培养24h至60h各时期，培养皿中背根节生长状况均良好，神经突起明显增长，表明用非悬滴开放式培养法培养鸡胚背根节是可行且可靠的。     

备用背根猫脊髓背核组织提取液对鸡胚背根节神经突起生长的影响

应用Liu和Chambers创立的备用背根模型,切除成年雄猫(5只)一侧的L_1～L_5、L_7～S_2背根节,保留L_6背根为备用背根,术后动物存活5d。分别制备脊髓T_(12)～L_3节段手术侧(实验组)、非手术侧(对照组)背核组织及其条件培养液。以Hanks平衡盐溶液的条件培养液作为参照组。用实验组、对照组以及参照组条件培养液对Hamburger 35期Leghorn鸡胚腰段背根部进行悬滴法培养,每只动物进行一批实验。于培养24h,48h观察测量各个背根节神经突起的平均长度。在各组背根节从培养24h到48h神经突起明显增长的基础上,求出每批培养物实验组、对照组背根节平均突起长度与参照组平均突起长度的比值以及5批培养物之平均比值。比较实验组、对照组平均比值在同一观测时间内的差异,发现两个观测时间实验组平均比值都明显大于对照组者。结果提示,猫脊髓经部分去后肢背根传入后,背核组织提取液促进神经突起生长的作用增强。     

备用根大鼠脊髓后角组织神经营养活性物质的分离纯化和生物活性鉴定

<正> 本实验采用凝胶过滤层析法和高效液相色谱技术,分离纯化备用根大鼠部分去传入侧的脊髓后角组织中的神经营养活性物质.1.生物活性检测方法的建立:切除大鼠一侧背根和背根节(DRG),仅保留L-4背根为备用根.术后动物存活5天.分别切取L1-L6节段手术侧和非手术侧脊髓后角组织,制备含手术侧和非手术侧提取液的培养液.用此液分别培养鸡胚DRG,48小时后手术侧组DRG神经突起密度明显大于对照组和非手术侧组,提示去传入纤维支配的脊髓后角组织存在着促神经突起生长的神经营养活性物质.又采用改良的悬滴培养法,发现手术侧脊髓后角组织能支持鸡胚DRG神经元的存活,而且具有促进神经突起生长的作用.2.备用根大鼠脊髓后角组织神经营养活性物质的分离与纯化,部分背根切除术后5天处死动物,切取手术侧脊髓L1-L6节段后角组织,匀浆、离心后,取上清液经Superdex prep grade G-75凝胶过滤层析,呈现Ⅰ、Ⅱ二个洗脱峰,将各洗脱峰浪加入培养基,Ⅰ峰洗脱液表现有神经营养作用.将Ⅰ洗脱峰进行SDS-聚丙烯酰胺凝胶电泳分析,银染后呈现多条明显的蛋白区带,去传入脊髓后角组织呈现神经营养活性的物质是在40-78KD之间.将Ⅰ峰洗脱液浓缩,进行高效液相色谱(HPLC)分析,得到4个不同的洗脱峰(a、b、c、d峰).将各洗脱峰液配制成不同浓度的     

内源性GDNF、NT-4对针刺猫脊髓备用根背根节神经元的作用

为了解部分背根切除和针刺及内源性GDNF和NT-4对体外培养备用背根节(DRG)的作用,本研究对5只成年猫进行双侧备用根手术(切除双侧L1~L5和L7~S2DRG,其中L6DRG作为备用背根)。术后当日开始针刺一侧L6脊神经后肢分布区的两组穴位,即足三里和悬钟、伏兔和三阴交,每天一次,每次30min,连续针刺7d后无菌条件下取出双侧L6DRG进行体外培养,24h后全量换液,并将针刺侧的一部分培养孔的培养液分别用含有200ng/ml抗GDNF和NT-4抗体培养液替换,分别作为抗GDNF和NT-4抗体封闭组。7d后终止培养,于显微镜下用显微测微尺测量神经突起的长度;并用抗NSE抗体行免疫细胞化学ABC法染色进行神经元鉴定。结果显示:(1)免疫细胞化学染色可见体外培养的细胞95%以上为NSE阳性细胞,且为典型的体外培养的DRG神经元;(2)体外培养备用根组和抗GDNF抗体组神经突起的平均长度比针刺组的短(P<0.05);(3)而针刺组神经突起的平均长度与抗NT-4抗体组间无差异(P>0.05);两抗体组平均突起长度比备用根组的突起长(P<0.05)。本研究结果提示,针刺可促进体外培养DRG神经元突起的生长,进而可能与脊髓可塑性密切相关;内源性GDNF有促进DRG神经元突起生长的作用;而内源性NT-4在DRG神经元突起生长中发挥的作用却不明显。     

备用背根猫脊髓Ⅱ板层组织对鸡胚背根节神经突起生长的影响

用１０只存活５ｄ的单侧后肢备用根猫（切除Ｌ１～Ｌ５、Ｌ７～Ｓ２背根节，保留Ｌ６背根），取手术侧（实验组）和非手术侧（对照组）脊髓Ⅱ板层组织块及提取液分别与Ｈａｍｂｕｒｇｅｒ３５期鸡胚背根节进行悬滴培养，并以不加植块的背根节培养作参照。比较各组在同一观测时间的差异．结果：（１）各组背根节从培养２４ｈ到４８ｈ，其神经突起均明显增长；（２）同一观测时间内，对照组与参照组的神经突起少而短，从背根节迁出的细胞较多，而实验组神经突起多且长，迁出的细胞较少；（３）在两个观测时间，植块与提取液培养的实验组背根节神经突起平均长度均显著长于对照组者，而对照组与参照组背根节神经突起长度的差异无显著性．表明部分腰骶背根切除猫，其脊髓Ⅱ板层及其提取液的促神经突起生长活性增强．     

备用根大鼠脊髓后角组织提取液对培养的鸡胚背根节神经突起生长的影响

应用组织培养方法，观察备用根大鼠手术侧和非手术侧脊髓后角组织提取液对鸡胚背根节神经突起生长的影响。结果显示：备用根大鼠手术侧脊髓后角组织提取液作用的背根节神经突起生长密度（１５５．２５±１４．２５）明显高于非手术侧提取液作用的背根节神经突起生长密度（８９．１４±９．６０）。提示部份去传入纤维支配的脊髓后角组织可能存在着促进神经突起生长的神经营养活性物质。     

吗啡备用根大鼠脊髓组织神经营养活性物质的分离纯化和生物活性测定

目的　分离纯化吗啡备用根大鼠脊髓组织提取液 ,以期获得某些神经营养活性物质。　方法　应用SephacrylS 2 0 0HR凝胶层析、高效液相色谱 (HPLC)和组织培养等技术分离和检测神经营养活性物质。　结果　备用根大鼠脊髓组织提取液能够促进体外培养的鸡胚背根节 (DRG)神经突起的生长 ;吗啡作用的大鼠脊髓组织提取液也具有同样的作用 ,但备用根大鼠和吗啡作用的大鼠脊髓组织提取液在促神经突起生长作用方面并没有明显的差异。吗啡备用根大鼠脊髓组织提取液具有明显的神经营养活性作用。吗啡备用根大鼠脊髓组织提取液的SephacrylS 2 0 0HR凝胶层析Ⅱ峰洗脱液和Ⅳ峰洗脱液能够促进DRG神经突起的生长。经SDS PAGE分析 ,Ⅱ峰洗脱液呈现 1条分子量约为 6 5kD的蛋白质主带 ,Ⅳ峰洗脱液的蛋白质成分较为复杂。应用HPLC对凝胶层析Ⅳ峰洗脱液作进一步的分离 ,发现HPLCA峰洗脱液能够促进DRG神经突起的生长。经SDS PAGE显示 ,A峰洗脱液的两条蛋白质主带分子量分别为 30kD和 18kD。　结论　吗啡备用根大鼠脊髓组织提取液中具有神经营养活性作用的物质可能是分子量约为 6 5kD、30kD和 18kD蛋白质     

备用根大鼠脊髓后角组织神经营养活性物质的分离纯化和生物活性测定

目的　进一步分离纯化备用根大鼠部分去传入纤维支配 (手术侧 )的脊髓后角组织提取液 ,以获得某种神经营养活性物质。　方法　用 Superdex G- 75 prep grade凝胶层析、高效液相色谱 (HPL C)层析和细胞培养等技术分离和检测神经营养活性物质。　结果　手术侧脊髓后角组织提取液经 Superdex G- 75 prep grade凝胶层析和 HPL C层析后 ,得到的 A峰洗脱液具有促进体外培养鸡胚背根节 (DRG)分离神经元存活及其神经突起生长的神经营养活性作用。经 SDS-聚丙烯酰胺凝胶电泳 (PAGE)显示 ,A峰洗脱液呈现一条分子量约为 6 0 k D的蛋白质主带。　结论　结合生物活性检测结果 ,分子量约 6 0 k D的蛋白质可能是手术侧脊髓后角组织的神经营养活性物质     

Agarose gel stiffness determines rate of DRG neurite extension in 3D cultures

The optimization of scaffold mechanical properties for neurite extension is critical for neural tissue engineering. Agarose hydrogels can be used to stimulate and maintain three-dimensional neurite extension from primary sensory ganglia in vitro. The present study explores the structure-function relationship between dorsal root ganglion (DRG) neurite extension and agarose gel mechanical properties. A range of agarose gels of differing concentrations were generated and the corresponding rate of E9 DRG neurite extension was measured. Rate of neurite extension was inversely correlated to the mechanical stiffness of agarose gels in the range of 0.75-2.00% (wt/vol) gel concentrations. In addition, we postulate a physical model that predicts the rate of neurite extension in agarose gels, if gel stiffness is a known parameter. This model is based on Heidemann and Buxbaum's model of neurite extension. These results, if extended to scaffolds of other morphological and chemical features, would contribute significantly to the design criteria of three-dimensional scaffolds for neural tissue engineering.     

Characterization of cortical neuron outgrowth in two- and three-dimensional culture systems

To improve the ability of regeneration by grafting living cells or by adding growth factor to a lesion site, it is important to find good biomaterials for neuron survival and regeneration. This study focused on two- and three-dimensional cultures in a matrix using biomaterials such as agarose, collagen, fibrin, and their mixtures, because these are considered to be suitable biomaterials for neuron outgrowth. Cortical neurons were dissected from E17 rat embryos and cultured in agarose gel, collagen gel, fibrin glue, and mixtures of collagen and fibrin. Results showed that neurons cultured in collagen gel and fibrin glue had longer periods of survival (more than 3 weeks) and better neurite extension than those observed in agarose gels. As to the survival rate according to the MTT and lactate dehydrogenase assays, fibrin glue was the most suitable biomaterial for neuron survival among the biomaterials examined. With two-dimensional fibrin plating, neuron cells exhibited cell aggregation and stress fibers, but the same results were not observed with collagen gel. There were no differences in neurite extension and survival in the mixtures of collagen and fibrin. The results suggest that collagen and fibrin can provide a suitable substrate for a three-dimensional culture matrix for neuronal survival and differentiation.     

Anisotropic scaffolds facilitate enhanced neurite extension in vitro

Tissue engineering (TE) techniques to enhance nerve regeneration following nerve damage have had limited success in matching the performance of autografts across short nerve gaps (< 10 mm). For regeneration over longer nerve gaps, TE techniques have been less successful than autografts. Most engineered scaffolds do not present directional cues to the regenerating nerves. In our efforts to design a TE scaffold to replace the autograft, we hypothesize that anisotropic hydrogel scaffolds with gradients of a growth-promoting glycoprotein, laminin-1 (LN-1), may promote directional neurite extension and enhance regeneration. In this study we report the engineering of three-dimensional (3D) agarose scaffolds with photoimmobilized gradients of LN-1 of differing slopes. Dorsal root ganglia (DRG) from chicken embryos were cultured in the agarose scaffolds and their neurite extension rate was determined. DRG neurite extension rates were significantly higher in the anisotropic scaffolds, with a maximal growth rate in an anisotropic scaffold twice that of the maximal growth rate in isotropic scaffolds of LN-1. We suggest that these anisotropic scaffolds, presenting an optimal gradient of LN-1, may significantly impact nerve regeneration. Such anisotropic scaffolds may represent a new generation of tissue engineered materials with built-in directional cues for guided tissue or nerve regeneration.     

星形胶质细胞在凝胶环境下的三维培养

目的:制备不同浓度的三维琼脂糖凝胶以进行星形胶质细胞的体外培养,从而寻找适合细胞生长的理想环境。方法:分别制备1%、2%、3%的琼脂糖凝胶,利用纳米压痕仪测量其弹性模量。星形胶质细胞在凝胶中培养1、3、5、7 d,观察细胞活性以及细胞骨架的变化。结果:随着凝胶浓度的增加,琼脂糖凝胶弹性模量逐渐增加。2%的琼脂糖凝胶的弹性模量最接近筛板组织的弹性模量;在2%、3%琼脂糖凝胶环境下,细胞活性具有较高水平。随着细胞在凝胶中培养的时间增加,星形胶质细胞的突起逐渐伸出,细胞从球形向梭形或星形转变,更接近细胞真实的生长状态。结论:2%琼脂糖凝胶最接近星形胶质细胞在体内的生长环境,细胞成活率较高,是细胞体外三维培养的理想环境。 【关键词】星形胶质细胞;琼脂糖凝胶;三维培养;力学特性     

Three-dimensional nanofibrillar surfaces covalently modified with tenascin-C-derived peptides enhance neuronal growth in vitro

Current methods to promote growth of cultured neurons use two-dimensional (2D) glass or polystyrene surfaces coated with a charged molecule (e.g. poly-L-lysine (PLL)) or an isolated extracellular matrix (ECM) protein (e.g. laminin-1). However, these 2D surfaces represent a poor topological approximation of the three-dimensional (3D) architecture of the assembled ECM that regulates neuronal growth in vivo. Here we report on the development of a new 3D synthetic nanofibrillar surface for the culture of neurons. This nanofibrillar surface is composed of polyamide nanofibers whose organization mimics the porosity and geometry of the ECM. Neuronal adhesion and neurite outgrowth from cerebellar granule, cerebral cortical, hippocampal, motor, and dorsal root ganglion neurons were similar on nanofibers and PLL-coated glass coverslips; however, neurite generation was increased. Moreover, covalent modification of the nanofibers with neuroactive peptides derived from human tenascin-C significantly enhanced the ability of the nanofibers to facilitate neuronal attachment, neurite generation, and neurite extension in vitro. Hence the 3D nanofibrillar surface provides a physically and chemically stabile cell culture surface for neurons and, potentially, an exciting new opportunity for the development of peptide-modified matrices for use in strategies designed to encourage axonal regrowth following central nervous system injury.     

The influence of physical structure and charge on neurite extension in a 3D hydrogel scaffold

Understanding neural cell differentiation and neurite extension in three-dimensional scaffolds is critical for neural tissue engineering. This study explores the structure-function relationship between a 3D hydrogel scaffold and neural cell process extension and examines the role of ambient charge on neurite extension in 3D scaffolds. A range of agarose hydrogel concentrations was used to generate varied gel physical structures and the corresponding neurite extension was examined. Agarose gel concentration and the corresponding pore radius are important physical properties that influence neural cell function. The average pore radii of the gels were determined while the gel was in the hydrated state and in two different dehydrated states. As the gel concentration was increased, the average pore radius decreased exponentially. Similarly, the length of neurites extended by E9 chick DRGs cultured in agarose gels depends on gel concentration. The polycationic polysaccharide chitosan and the polyanionic polysaccharide alginate were used to incorporate charge into the 3D hydrogel scaffold, and neural cell response to charge was studied. Chitosan and alginate were covalently bound to the agarose hydrogel backbone using the bi-functional coupling agent 1,1'carbonyldiimldazole. DRGs cultured in chitosan-coupled agarose gel exhibited a significant increase in neurite length compared to the unmodified agarose control. Conversely, the alginate-coupled agarose gels significantly inhibited neurite extension. This study demonstrates a strong, correlation between the ability of sensory ganglia to extend neurites in 3D gels and the hydrogel pore radius. In addition, our results demonstrate that charged biopolymers influence neurite extension in a polarity dependent manner.     

Neurite bridging across micropatterned grooves

After injury, regenerating axons must navigate complex, three-dimensional (3D) microenvironments. Topographic guidance of neurite outgrowth has been demonstrated in vitro with culture substrates that contain micropatterned features on the nanometer-micron scale. In this study we report the ability of microfabricated biomaterials to support neurite extension across micropatterned grooves with feature sizes on the order of tens of microns, sizes relevant to the design of biomaterials and tissue engineering scaffolds. Neonatal rat dorsal root ganglion (DRG) neurons were cultured on grooved substrates of poly(dimethyl siloxane) coated with poly-L-lysine and laminin. Here we describe an unusual capability of a subpopulation of DRG neurons to extend neurites that spanned across the grooves, with no underlying solid support. Multiple parameters influenced the formation of bridging neurites, with the highest numbers of bridges observed under the following experimental conditions: cell density of 125,000 cells per sample, groove depth of 50 microm, groove width of 30 microm, and plateau width of 200 microm. Bridges were formed as neurites extended from a neuron in a groove, contacted adjacent plateaus, pulled the neuron up to become suspended over the groove, and the soma translocated to the plateau. These studies are of interest to understanding cytoskeletal dynamics and designing biomaterials for 3D axon guidance.     

A laminin and nerve growth factor-laden three-dimensional scaffold for enhanced neurite extension.

Agarose hydrogel scaffolds were engineered to stimulate and guide neuronal process extension in three dimensions in vitro. The extracellular matrix (ECM) protein laminin (LN) was covalently coupled to agarose hydrogel using the bifunctional cross-linking reagent 1,19- carbonyldiimidazole (CDI). Compared to unmodified agarose gels, LN-modified agarose gels significantly enhanced neurite extension from three-dimensionally (3D) cultured embryonic day 9 (E9) chick dorsal root ganglia (DRGs), and PC 12 cells. After incubation of DRGs or PC 12 cells with YIGSR peptide or integrin beta1 antibody respectively, the neurite outgrowth promoting effects in LN-modified agarose gels were significantly decreased or abolished. These results indicate that DRG/PC 12 cell neurite outgrowth promoting effect of LN-modified agarose gels involves receptors for YIGSR/integrin beta1 subunits respectively. 1,2-bis(10, 12-tricosadiynoyl)-sn-glycero-3-phosphocholine (DC(8,9)PC)-based lipid microcylinders were loaded with nerve growth factor (NGF), and embedded into agarose hydrogels. The resulting trophic factor gradients stimulated directional neurite extension from DRGs in agarose hydrogels. A PC 12 cell-based bioassay demonstrated that NGF-loaded lipid microcylinders can release physiologically relevant amounts of NGF for at least 7 days in vitro. Agarose hydrogel scaffolds may find application as biosynthetic 3D bridges that promote regeneration across severed nerve gaps.     

Electrical and Neurotrophin Enhancement of Neurite Outgrowth Within a 3D Collagen Scaffold

Electrical and chemical stimulation have been studied as potent mechanisms of enhancing nerve regeneration and wound healing. However, it remains unclear how electrical stimuli affect nerve growth, particularly in the presence of neurotrophic factors. The objective of this study was to explore (1) the effect of brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) supplementation to support neurite outgrowth in a 3D scaffold, and (2) the effect of brief, low voltage, electrical stimulation (ES) on neurite outgrowth prior to neurotrophin supplementation. Dissociated E11 chick dorsal root ganglia (DRG) were seeded within a 1.5 mg/mL type-I collagen scaffold. For neurotrophin treatments, scaffolds were incubated for 24 h in culture media containing NGF (10 ng/mL) or BDNF (200 ng/mL), or both. For ES groups, scaffolds containing neurons were stimulated for 10 min at 8–10 V/m DC, then incubated for 24 h with neurotrophin. Fixed and labeled neurons were imaged to measure neurite growth and directionality. BDNF supplementation was not as effective as NGF at supporting DRG neurite outgrowth. ES prior to NGF supplementation improved DRG neurite outgrowth compared to NGF alone. This combination of brief ES with NGF treatment was the most effective treatment compared to NGF or BDNF alone. Brief ES had no impact on neurite directionality in the 3D scaffolds. These results demonstrate that ES improves neurite outgrowth in the presence of neurotrophins, and could provide a potential therapeutic approach to improve nerve regeneration when coupled with neurotrophin treatment.