[Follicle structure regulates cellular interaction between granulosa and thecal cells in follicular development]

To study ovarian follicular development, we established a procedure to reconstruct a follicular wall in vitro by using three-dimensional collagen gel. Granulosa cells and thecal cells were dissociated from median follicles of porcine ovaries. Isolated thecal cells were embedded in collagen gel and a medium containing isolated granulosa cells was overlaid. A monolayer culture of recombined granulosa and thecal cells in collagen gel was used for the control. To examine the synergism of granulosa cells and thecal cells in this culture system, isolated granulosa and thecal cells were cultured either singly or in combination. The culture media were assayed for steroids by RIA. Cultured granulosa cells in this culture system were epitheloid and grown in multilayer aggregates. In contrast, cells cultured by the conventional method were as flat as a monolayer sheet. Ultrastructural findings for these cells showed abundant organella. Gap junctions were often observed between these cells and the basal lamina-like structure. Estradiol production by both culture methods was significantly higher than the sum of that produced by granulosa and thecal cells cultured separately. Androstenedione accumulation was increased by this culture system, but was suppressed by the conventional culture system. These findings suggest that the constitution of the ovarian follicular wall plays an important role in morphological and functional interaction between granulosa and thecal cells.