Introduction: Female mammals are born with a finite reserve of primordial follicles which dictates the reproductive lifespan. Despite this the factors responsible for primordial follicle activation remain largely unknown. The transforming growth factor beta (TGFβ) superfamily has been implicated in early follicle development however little attention has been given to the effects of TGFβ2, expression of which has been demonstrated in the ovary. This study aimed to examine the role of TGFβ2 on follicle activation and preantral follicle growth.
Materials and methods: Neonatal (PND4) mouse ovaries (C57BL/6) were treated with TGFβ2 (1, 10, and 100 ng/ml) for 6 days in a whole-ovary culture system. Cultured ovaries were fixed for immunohistochemical localization of vasa and laminin and image analysis was performed to classify and quantify follicle proportions. In addition, preantral follicles (two or more layers of granulosa cells) were mechanically isolated from PND15 mouse ovaries. Single follicles were cultured in 96-well plates with TGFβ2 (0.01, 0.1, and 1 ng/ml). Follicle area was measured at 0, 24, 48, and 72 h (ImageJ).
Results and discussion: TGFβ2 induced a dose-dependent suppression of follicle activation in whole ovary as demonstrated by reduced depletion of primordial follicles and fewer growing follicles. No observational differences in caspase-3 staining were demonstrated between treatment groups eliminating TGFβ2 toxicity. By contrast, TGFβ2 promoted a significant increase in growth of isolated preantral follicles at all concentrations after 48 h (two-way, ANOVA P <0.0001). These results highlight differential effects of TGFβ2 during primordial follicle activation and preantral follicle growth.
02 Sep 2014 - 04 Sep 2014