Role of ovarian theca and granulosa cell interaction in hormone productionand cell growth during the bovine follicular maturation process

We have investigated the possible role of theca and granulosa cell interact ion in the control of the hormone-producing activity and growth of granulos a and theca cells during bovine ovarian follicular development, using a coc ulture system in which granulosa and theca cells were grown on opposite sid es of a collagen membrane. When follicular cells were isolated from small f ollicles (3-5 mm), theca cells reduced estradiol, progesterone, and inhibin production by granulosa cells to 14 +/- 5%, 64 +/- 6%, and 27 +/- 4%, resp ectively, of the production by granulosa cells cultured alone. On the other hand, when the cells were isolated from large follicles (15-18 mm), theca cells increased these levels to 253 +/- 34%, 156 +/- 24%, and 287 +/- 45%, respectively. Theca cells did not affect the growth of granulosa cells. And rostenedione production by theca cells was augmented by granulosa cells to 861 +/- 190% (in small follicles) and 1298 +/- 414% (in large follicles), r espectively. The growth of theca cells was also augmented by granulosa cell s (small follicle, 210 +/- 43%, and large follicle, 194 +/- 24%, respective ly). These results indicate that theca cells secrete factor(s) inhibiting t he differentiation of immature while promoting that of matured granulosa ce lls; they also suggest that granulosa cells secrete factor(s) promoting bot h the differentiation and growth of theca cells throughout the follicular m aturation process.