Studies on the mechanism of rapid repair and degradation of post-ovulatory follicular tissues in the vertebrate ovary80197152

卵巢是生殖器官，其主要功能是产生生殖细胞（卵母细胞）。在成熟脊椎动物的卵巢中，卵泡生长、排卵、排卵后卵泡组织修复及其随后的降解以一种动物特有的周期性方式反复发生。本研究旨在探讨脊椎动物卵巢排卵后卵泡组织快速修复和降解的机制。medaka是一种小型淡水硬骨鱼，它是解决这个问题的一个很好的实验模型，因为在适当的培养条件下，这种鱼每天都会排卵。我们在研究中的发现如下：我们从形态学上检查了排卵时释放卵母细胞的卵泡的结构。排卵后留在卵巢内的卵泡组织在一段时间内似乎保留了基本的卵泡层结构，但随后发现该组织降解并消失。检查了I型和IV型胶原蛋白的分布，它们是排卵后卵泡组织的卵泡层的标志物。通过原位杂交分析，证实两种胶原mRNA均定位于卵泡层。随着完整的滤泡层结构消失，胶原mRNA信号无法检测到。使用胶原蛋白特异性抗体的免疫组织化学分析也得出了类似的结果。在试图寻找参与这种降解过程的蛋白酶时，发现尿激酶型纤溶酶原激活剂（uPA）和明胶酶B都是候选蛋白，它们在medaka中都表现出卵巢特异性表达。纤溶酶是由纤溶酶原在uPA作用下产生的活性蛋白酶，它和明胶酶B在体外降解多种ECM蛋白，包括I型和IV型胶原。这些结果表明，uPA/纤溶酶系统和明胶酶B可能在排卵后的快速降解过程中起作用。

The ovary is a reproductive organ whose main function is to generate germ cells (oocytes). In ovaries of mature vertebrate animals, a sequential event of follicular growth, ovulation, post-ovulatory follicular tissue repair and its subsequent degradation repeatedly occurs in a periodic manner unique for animal species. The aim of this study was to define the mechanism of rapid repair and degradation of the post-ovulatory follicular tissues in the vertebrate ovary. The medaka, a small fresh-water teleost, is a good experimental model to approach the problem because the fish ovulates everyday under appropriate culture conditions. Our findings in the research are as follows.1. We morphologically examined the structure of the follicle that had released its oocyte on ovulation. The post-ovulatory follicular tissue remaining in the ovary appeared to retain basic follicle layer structure for some time, but the tissue was found to degrade and disappear thereafter.2. Distribution of collagen type I and IV, which are markers for the follicular layer of the post-ovulatory follicular tissue, was examined. By in situ hybridization analysis, both collagens' mRNA was demonstrated to be localized to the follicle layer. Concomitant with disappearance of intact follicular layer structure, mRNA signals of the collagens became undetectable. Immunohistochimical analysis using specific antibodies for the collagens gave similar results.3. In attempts to search for proteases involved in such a degradation process, urokinase-type plasminogen activator (uPA) and gelatinase B, both of which exhibited ovary-specific expression in the medaka, were found to be candidate proteins. Plasmin, which is active protease generated from plasminogen by the action of uPA, and gelatinase B degraded various ECM proteins including collagens type I and IV in vitro.These results indicate that uPA/plasmin system and gelatinase B may play a role in the post-ovulatory rapid degradation process.