In vitro culture and in vitro maturation of mouse preantral follicles with recombinant gonadotropins

OBJECTIVE: To develop an effective method for in vitro maturation of preantral follicles isolated from mice ovarian tissue. DESIGN: Isolated preantral follicles were randomly allocated to designed experimental groups for study. SETTING: University-based research lab. PATIENT(S): Healthy, normal mice. INTERVENTION(S): Superovulation with pregnant mare serum gonadotropin and hCG. MAIN OUTCOME MEASURE(S): Morphological changes and E(2) production were assessed. RESULT(S): To obtain competent oocytes, preantral follicles must be cultured with medium containing insulin and recombinant gonadotropins (i.e., recombinant FSH and recombinant LH), with a change of medium daily. A high initial recombinant LH or recombinant FSH facilitates E(2) secretion, enhances granulosa cell outgrowth, and has earlier antral formation. However, prolonged culture in high-recombinant LH or recombinant FSH triggers early differentiation and luteinization of granulosa cells, which results in low metaphase II oocyte and blastocyst formation. CONCLUSION(S): We have developed a culture system that allows the successful maturation of preantral follicles in vitro. The matured follicles are a physiologically functional unit that not only secrete E(2) but also generate competent oocytes. In a special condition, 90% of the cultured follicles survived, 53.5% of them produced MII oocytes, and 50% of the derived MII oocytes were fertilized and reached the blastocyst stage after culture in vitro.