Culture of bovine preantral follicles in a serum-free system: Markers for assessment of growth and development

Satisfactory development of bovine follicles in vitro remains elusive. This study used a serum-free system to evaluate the effects of insulin-like growth factor-1 (IGF-1) on bovine preantral follicles in culture and to identify the activity of gelatinase matrix metalloproteinases (MMPs) and their endogenous inhibitors (TIMPs) in vitro to assess their potential as markers of development. Preantral follicles were cultured for 6 days in serum-free medium containing insulin and IGF-1 (10 ng/ml). No difference was observed in follicular growth, health, or antrum formation between IGF-1-treated follicles and controls. However, IGF-1 had a negative effect (P < 0.01) on oocyte size and granulosa cell proliferation. When MMP-9 was secreted, the probability of follicles having healthy granulosa or theca cells at the end of the culture period was 0.85 and 0.60, respectively. If TIMP-1 was released, the probability of follicles having healthy somatic cells was 0.79. When TIMP-2 was detected, the probability of granulosa and theca cell health was 0.78 and 0.67, respectively. These results demonstrate no positive effects of IGF-1 on bovine follicles in this system. Furthermore, MMP-9 and TIMPs are related to follicular health and, therefore, can be used as markers of follicular development.