Effects of varying gonadotrophin dose and timing on antrum formation and ovulation efficiency of mouse follicles in vitro

BACKGROUND: This study tested factors affecting mouse follicle growth in vitro, to determine end-points marking follicle function in vitro. METHODS: Pre-antral follicles (mean 137 μm) from B6CBF1 mice were cultured in a substrate-adherent system for ≤14 days. FSH (0–1000mIU/ml) day of HCG (1.5 IU/ml days 9–14) protein supplement [fetal calf serum (FCS) (×2) mouse serum (×2) hypogonadal (hpg) mouse serum or human serum albumin (HSA)] were varied. Follicle survival timing of antrum formation incidence of ovulation within 16 24 40 48 h of HCG oocyte growth were assessed. RESULTS: FSH (100 mIU/ml) produced the best antral development (P < 0.001 versus 10 1000 mIU/ml). Antra were observed from day 5. Transient antra formed occasionally in the absence of FSH. By 14 days significant senescence had occurred (P < 0.001) but the proportion of follicles ovulating within 16 h of HCG declined from day 9 onwards indicating this to be a more sensitive marker of follicle responsiveness. Optimal growth occurred in 5% FCS (×2) or hpg mouse serum although fewer follicles ovulated in hpg serum (P < 0.05). No normal growth occurred in normal mouse serum (×2) or HSA. Oocytes grew to full size within 9 days with 100 mIU/ml FSH FCS. CONCLUSIONS: These data provide sensitive end-points for assessing follicle growth in vitro.