Study for Effects of Ovarian Thecal Cells on Meiosis-Arresting Activity and Differentiation of Granulosa Cells

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We have successfully developed a co-culture system in which ovarian granulosa and thecal cells are grown on opposite sides of a collagen membrane. Using this co-culture system, we have previously demonstrated that the two follicular cell types reciprocally modulate their proliferation, morphology, structure and function.In the first series of the study, we have examined the effect of granulosa-theca cell communication on oocyte maturation using this culture system. Bovine cumulus-oocyte complexes were incubated with granulosaa cells, with or without theca cells. The time course of germinal vesicle breakdown was assessed. When cultured with granulosa and theca cells, germinal vesicle breakdown was significantly delayd compared when cultured with granulosa cells alone. Breakdown was further delayd when cumulus-oocyte complexes were incubated with FSH- or low-dose of androstenedione-treated granulosa cells with theca cells. While, such effects on germinal vesicle breakdown was not detecte … More d when granulosa cells were incubated with high dose of androstenedione or estradiol.In the second series of the study, the influence of thecal cells on the hormonal producing activity as well as the ultrastructure of granulosa cells from early-, mid-and late-developmental stage follicles in vitro was investigeted. Thecal cells reduced hormonal production by granulosa cells from early stage of follicular development, respectively, while augmented that by cells at late developmental stage. Morphological analysis of granulosa cells co-cultured with thecal cells shows a decrease in the clustering of lysosomes, shrinkage of endoplasmic reticulum and mitochondria of cells from small follicles but an enhancement of these cytodifferentiative features in cells from mature follicles when compared to the cells cultured alone. These results demonstrate that the thecal cells secrete factor (s) which inhibits the differentiation of the immature granulosa cells while promoting that of the matured ones and suggest that the thecal cells play an important role in the control of granulosa cell differentiation during ovarian follicular development. Less