Full physiological maturation in vitro of immature mouse oocytes induced by sequential treatment with follicle-stimulating hormone and luteinizing hormone.

Cumulus cell-enclosed immature mouse oocytes were matured in medium supplemented with various combinations of follicle-stimulating hormone (FSH), luteinizing hormone (LH), and estradiol. FSH or LH alone stimulated oocyte maturation, resulting in a significant increase in the rate of development to blastocysts following fertilization in vitro and embryo culture. There was no significant difference between FSH and LH. The effect of FSH was neutralized by FSH antiserum, while that of LH was not, indicating that the stimulation of maturation by LH was not due to FSH contamination in the LH preparation. When LH was added after 2 hr of culture with FSH (sequential combination), blastocyst development was significantly increased compared with FSH alone, reaching the same level as the in vivo matured oocytes. The addition of estradiol, 0.1 ng/ml, to the sequential combination of FSH and LH had no effect, while 0.01 and 1 ng/ml produced a negative effect. The birth rate of normal live offspring following embryo transfer showed no significant difference between embryos derived from oocytes matured in vivo and in vitro (sequential combination with or without 0.1 ng/ml estradiol) or between the two in vitro treatment groups.