Department of Biotechnology, Guru Nanak Dev University, Amritsar 143005, India.
Mol Cell Endocrinol. 2012 Jan 2;348(1):95-103. doi: 10.1016/j.mce.2011.07.040. Epub 2011 Aug 5.
There is abundant evidence to prove that the astrocytes are highly dynamic cell type in CNS and under physiological conditions such as reproduction, these cells display a remarkable structural plasticity especially at the level of their distal processes ensheathing the gonadotropin releasing hormone (GnRH) axon terminals. The morphology of GnRH axon terminals and astrocytes in the median eminence region of hypothalamus show activity dependent structural plasticity during different phases of estrous cycle. In the current study, we have assessed the functional contribution of ∞-2,8-linked polysialic acid (PSA) on neural cell adhesion molecule (PSA-NCAM) in this neuronal-glial plasticity using both in vitro and in vivo model systems. In vivo experiments were carried out after stereotaxic injection of endoneuraminidase enzyme (endo-N) near median eminence region of hypothalamus to specifically remove PSA residues on NCAM followed by localization of GnRH, PSA-NCAM and glial fibrillary acidic protein (GFAP) by immunostaining. Using in vitro model, structural remodeling of GnV-3 cells, (a conditionally immortalized GnRH cell line) co-cultured with primary astrocytes was studied after treating the cells with endo-N. Marked morphological changes were observed in GnRH axon terminals in proestrous phase rats and control GnV-3 cells as compared to endo-N treatment i.e. after removal of PSA. The specificity of endo-N treatment was also confirmed by studying the expression of PSA-NCAM by Western blotting in cultures treated with and without endo-N. Removal of PSA from surfaces with endo-N prevented stimulation associated remodeling of GnRH axon terminals as well as their associated glial cells under both in vivo and in vitro conditions. The current data confirms the permissive role of PSA to promote dynamic remodeling of GnRH axon terminals and their associated glia during reproductive cycle in rats.
有大量证据证明星形胶质细胞是中枢神经系统中高度活跃的细胞类型。在生理条件下，如繁殖过程中，这些细胞表现出显著的结构可塑性，尤其是在其远端突起包绕促性腺激素释放激素（GnRH）轴突末梢的水平。在不同发情周期阶段，下丘脑正中隆起区域的 GnRH 轴突末梢和星形胶质细胞的形态显示出与活动相关的结构可塑性。在本研究中，我们使用体外和体内模型系统评估了神经元-神经胶质可塑性中 ∞-2,8-连接多唾液酸（PSA）对神经细胞黏附分子（PSA-NCAM）的功能贡献。体内实验是在立体定向注射神经氨酸酶（endo-N）到下丘脑正中隆起区域附近进行的，该酶特异性去除 NCAM 上的 PSA 残基，然后通过免疫染色定位 GnRH、PSA-NCAM 和神经胶质纤维酸性蛋白（GFAP）。使用体外模型，研究了 GnV-3 细胞（一种条件永生化 GnRH 细胞系）与原代星形胶质细胞共培养后，用 endo-N 处理后的结构重塑。与 endo-N 处理相比，发情前期大鼠和对照 GnV-3 细胞的 GnRH 轴突末梢观察到明显的形态变化，即 PSA 去除后。Western blot 研究显示，用和不用 endo-N 处理培养物后 PSA-NCAM 的表达证实了 endo-N 处理的特异性。用 endo-N 从表面去除 PSA 可防止 GnRH 轴突末梢及其相关胶质细胞在体内和体外条件下与刺激相关的重塑。目前的数据证实了 PSA 促进 GnRH 轴突末梢及其相关胶质细胞在大鼠生殖周期中动态重塑的许可作用。
