Study for Effects of Ovarian Thecal Cells on Granulosa Cell Diferentiation during Follicular Maturation.

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We have developed a co-culture system in which granulosa and thecal cells were maintained on the opposite surface of a collagen membrane. Using this system, we have investigated the possible role of thecal cells in the conrol of the hormonal producing activity and the ultrastructure of granulosa cells during bovine ovarian follicular development. Thecal cells reduced estradiol, inhibin and progester one production by granulosa cells from early stage of follicular development, respectively, while augmented those by cells at late developmental stage. Morphological analysis of granulosa cells co-cultured with thecal cells shows a decreasein 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.