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

点击翻译按钮获取中文摘要

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.