Bovine theca and granulosa cell interactions modulate their growth, morphology, and function.

We have developed a culture system in which bovine granulosa and theca cells are allowed to attach to opposite sides of a collagen membrane. We studied the interaction between theca and granulosa cells by investigating the morphology, proliferation, and steroidogenesis of the cells. Granulosa cells cultured alone were flattened and polygonal and formed monolayer sheets. Granulosa cells cocultured with theca cells formed multilayer sheets. The apical surface of each cell appeared convex. Numerous filopodia spread over the cellular surface connecting cells. Theca cells cultured alone were thin, flat, and spindle-shaped. Theca cells cocultured with granulosa cells were also spindle-shaped; however, the apical surface appeared convex. Cocultured cells were more densely packed than theca cells cultured alone. The number of both granulosa and theca cells in the cocultured group increased approximately twofold compared to control cells cultured alone. Progesterone content per 1 x 10(5) granulosa cells in 24-h culture medium of the cocultured group was reduced to 40% of that of the control group. In contrast, androstenedione content per 1 x 10(5) theca cells of the cocultured group increased approximately threefold compared to androstenedione content of control group. These results indicate that communication between these two types of follicular cells results in reciprocal modulation of their proliferation, morphology, and function.