Expression of transforming growth factor-B3 -GF-B3- in the porcine ovary during the oestrus cycle

Abstract

Transforming growth factor-ß (TGF-ß) proteins are growth factors that have been shown to be involved in regulation of ovarian follicular development. Ovarian expression, activity and functional significance of TGF-ß1 and TGF-ß2 isoforms were extensively studied in most species. However, little is known about the biological role of TGF-ß3 previously shown to be expressed independently of the other two isoforms. Therefore, expression of TGF-ß3 mRNA and protein was evaluated by RT-PCR and immunohistochemistry, respectively, in porcine ovaries collected during different phases of the oestrus cycle. Results of RT-PCR analysis showed that TGF-ß3 mRNA is expressed throughout the oestrus cycle. The level of TGF-ß3 mRNA expression was found to be higher at metoestrus and dioestrus. Weak TGF-ß3 immunoreactivity was present in follicular epithelial cells and oocytes of preantral follicles in all stages examined. TGF-ß3 protein expression was exclusively present in theca interna cell layer of antral follicles, and was particularly prominent in large antral follicles. Immediately after ovulation, almost all theca cells outside of the granulosa cell layer were intensively stained with anti-TGF-ß3. Immunostaining of TGF-ß3 in theca lutein cells rapidly decreased during corpus luteum development. It is suggested that TGF-ß3 may play an important role in modulating theca cell function of pre- and postovulatory follicles of the pig.