Influence of thyroid hormone on mouse preantral follicle development in vitro

OBJECTIVE: To evaluate the role of 3,3',5-triiodothyronine (T(3)) on ovarian follicle development in vitro. DESIGN: Experimental study. SETTING: University reproductive biology unit. ANIMAL(S): CD1 mice (female). INTERVENTION(S): In vitro culture. MAIN OUTCOME MEASURE(S): Assessment of follicle and oocyte development following a 6-day culture with FSH (100 mU/mL), (Bu)(2)cAMP (0.5 mM), and T(3) (1-100 nM), alone or in combination. RESULT(S): A high percentage of in vitro grown (IVG) FSH-stimulated follicles formed an antral cavity (AC), while the addition of T(3) (100 nM) significantly reduced this response in a statistically significant manner. A statistically significant recovery of AC formation was obtained by limiting exposure to 4 days of culture. Formation of AC was induced by (Bu)(2)cAMP, which prevented T(3)-mediated suppression of AC formation. Under different conditions, high proportions of germinal vesicle-arrested IVG oocytes displayed condensed chromatin configuration. The capacity to undergo germinal vesicle breakdown (GVBD) was similar in all groups, and a statistically significant reduction in the percentage of oocytes with PB1 was recorded when T(3) was added to FSH or (Bu)(2)cAMP. This ability was partially recovered by removing T(3) on day 4 of culture. CONCLUSION(S): Exposure to high T(3) concentrations can impair preantral follicle development, but this effect can be partly reverted by restoring a physiological hormonal milieu before follicle commitment to antral development