Immunohistochemical localization of transforming growth factor β1 and β2 in the fetal and neonatal rat ovary

Abstract

The localization of transforming growth factor β (TGFβ) in the differentiating ovary (from fetal day 13.5 to postnatal day 14) was investigated immunohistochemically using polyclonal antibodies for TGFβ1 and TGFβ2. Immunostaining was undetectable in the gonadal primordium on fetal day 13.5. From fetal day 14.5 and throughout fetal life, there was intense immunostaining for TGFβ1 and faint staining for TGFβ2 in some ovarian somatic cells which were identified as epithelial cells at the end of fetal life. This pattern of staining was also found in the presumptive granulosa cells present between the oocytes on postnatal day 1. The staining for TGFβ2 persisted while the staining for TGFβ1 decreased in the granulosa cells of primordial and primary follicles of older rats. In the subsequent stages of follicular development, the staining for TGFβ1 disappeared while faint staining for TGFβ2 persisted in the granulosa cells of secondary and small antral (postnatal day 14) follicles. On day 14, the newly functional thecal/interstitial cells were moderately stained for TGFβ2 and intensely stained for TGFβ1. These results plus our previous immunolocalization of TGFβ1 in the fetal testis [13] show that, in both sexes: (1) TGFβ1 is detectable in the gonads on the same fetal age (day 14.5); (2) TGFβ1 is present in the somatic cells which are the precursors of Sertoli and granulosa cells, at the time of their organization in seminiferous tubules or in primordial follicles; and (3) TGFβ1 is largely present in cells synthesizing androgens, from the onset of their steroidogenic capacity (fetal day 16.5 for Leydig cells and postnatal day 14 for thecal/interstitial cells).