Developmental potential of mouse follicular epithelial cells and cumulus cells after nuclear transfer

The developmental potential after nuclear transfer of mouse follicular epit helial cells cultured in vitro was examined. Follicular epithelial cells su rrounding growing oocytes (type 5, diameter of oocytes, 62.6 +/- 5.9 mu m; n = 14) were obtained from ovaries of adult mice. Before nuclear transfer, cells were cultured for several passages and subjected to serum starvation for several days. When the nuclear-transfer oocytes were at the 2-cell stag e, serial nuclear transfer was performed. Additionally, cumulus cells surro unding ovulated oocytes were used as nuclear donors, with or without therma l stimulation (from -25 degrees C to 60 degrees C for 10 min) before nuclea r transfer. Nuclear-transfer oocytes with follicular epithelial cells devel oped into blastocysts (34%) after serial nuclear transfer, and 4 living fet uses on Day 10.5 (25%, 16 transferred) and 1 dead fetus on Day 19.5 of preg nancy (3%, 30 transferred) were obtained after transfer to recipients. Alth ough blastocysts (20%) were obtained after serial nuclear transfer of cumul us cells, only one implantation site without a fetus was observed on Day 10 .5 of pregnancy. Thermal stimulation of cumulus cells before nuclear transf er did not enhance the ability to develop into fetuses or blastocysts.