Ovarian Thecal Cells Produce Transforming Growth Factor-β Which Can Regulate Granulosa Cell Growth*

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Abstract
Ovarian thecal cells in culture were found to synthesize and secrete transforming growth factor-β (TGFβ). A component in thecal cell-conditioned medium was immunologically similar to TGFβ, as assessed with a RIA, and inhibited specific binding of TGFβ to its cell surface receptors. Thecal cell-secreted proteins also contained TGFβ biological activity, which was determined by stimulation of soft agar colony formation by AKR-2B indicator cells. Specific TGFβ antibodies precipitated a 25 K protein from radiolabeled thecal cell-secreted protein that comigrated with purified platelet-derived TGFβ. Both bovine thecal cell and rat thecal/interstitial cell preparations produced TGFβ, which required acid treatment to obtain fully active samples. The physiological significance of TGFβ production by thecal cells was addressed through an analysis of the effects of TGFβ on bovine granulosa cell growth. TGFβ inhibited epidermal growth factor stimulation of granulosa cell growth, but alone it had no apparent influence. Observations indicate that ovarian thecal cells produce TGFβ, which can regulate granulosa cell growth and differentiation. Discussion of thecal cell-granulosa cell interactions and the possible functions of TGFβ in the ovary is presented. (Endocrinobgy121: 786– 792,1987)