Induction of apoptosis in rat thecal/interstitial cells by transforming growth factor α plus transforming growth factor β in vitro

Abstract

In each estrous cycle dominant follicles are selected from a growing pool to develop to the preovulatory stage and to ovulate. Those follicles that do not ovulate must be eliminated in order to maintain the constant mass and homeostasis of the ovary. Granulosa cells are lost by apoptosis at the onset of follicular atresia, whereas apoptotic thecal cells are identified at later stages of atresia. Since transforming growth factor (TGF) alpha and TGF beta 1 have been implicated in the regulation of thecal cell physiology we have localized these growth factors by immunohistochemistry in sections of ovaries from 25-day-old rats, an age at which the ovary exhibits a wave of atresia of preantral follicles. Thecal cells contained TGF alpha and TGF beta 1 throughout the entire process of follicular atresia. To determine if these growth factors could influence thecal cell death, thecal/interstitial cells were isolated from 25-day-old rats, and maintained in culture with growth factors. Subconfluent cultures treated with TGF alpha or TGF beta 1 alone remained healthy whereas in the presence of both TGF alpha and TGF beta 1 there was light microscopical evidence of rounding up of cells and detachment from the monolayer. Chromatin condensation and internucleosomal fragmentation, characteristic of apoptosis, were observed by nucleic acid staining and fluorescence microscopy of thecal/interstitial cells treated with TGF alpha plus TGF beta 1. Further evidence that these cells were undergoing apoptosis came from DNA analysis and the demonstration of DNA laddering. This response of thecal/interstitial cells to TGF alpha plus TGF beta 1 was density dependent; confluent cultures were protected from the induction of apoptosis under these conditions. We conclude that thecal cells are eliminated from atretic follicles by the active and strictly regulated process of involving the combined actions of TGF alpha and TGF beta 1.

Increased cell survival by inhibition of BRCA1 using an antisense approach in an estrogen responsive ovarian carcinoma cell line

“…During estrous, many hormones and growth factors interact in a complex manner as survival factors and inducers of cell proliferation, which are then balanced with growth inhibitors [36,37,38,39,40]. The mechanism by which BRCA1 can regulate or influence these processes has not yet been identified.…”

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“…The decreased content of DNA observed following culture could be related to a suppression of granulosa cell proliferation or survival. Since TGF-β can stimulate apoptotic pathways in concert with other factors [48,49], a role for TGF-β in regulating apoptosis of ovarian cells has been proposed.…”

Prostaglandin F2α-Induced Functional Regression of the Corpus Luteum and Apoptosis in Rodents

“…TGFb alters the capacity of steroidogenesis directly (27,28) and localizes in the corpus luteum in rats (29) and humans (30) in addition to the theca / interstitial cells of rats (28). Induction of apoptosis in ovarian thecal and interstitial cells is enhanced by combined treatment with TGF-a and TGF-b (31,32); the changes are accompanied by the increased expression of interleukin1b converting enzyme (caspase-1) mRNA 5 h after the combined treatment. TGF-b triggers apoptosis in aortic smooth muscle cells (33).…”