Ovarian thecal cells produce transforming growth factor-beta which can regulate granulosa cell growth.

Ovarian thecal cells in culture were found to synthesize and secrete transforming growth factor-beta (TGF beta). A component in thecal cell-conditioned medium was immunologically similar to TGF beta, as assessed with a RIA, and inhibited specific binding of TGF beta to its cell surface receptors. Thecal cell-secreted proteins also contained TGF beta biological activity, which was determined by stimulation of soft agar colony formation by AKR-2B indicator cells. Specific TGF beta antibodies precipitated a 25 K protein from radiolabeled thecal cell-secreted protein that comigrated with purified platelet-derived TGF beta. Both bovine thecal cell and rat thecal/interstitial cell preparations produced TGF beta, which required acid treatment to obtain fully active samples. The physiological significance of TGF beta production by thecal cells was addressed through an analysis of the effects of TGF beta on bovine granulosa cell growth. TGF beta inhibited epidermal growth factor stimulation of granulosa cell growth, but alone it had no apparent influence. Observations indicate that ovarian thecal cells produce TGF beta, which can regulate granulosa cell growth and differentiation. Discussion of thecal cell-granulosa cell interactions and the possible functions of TGF beta in the ovary is presented.