Embryonic stem cell lines derived from blastocysts by a simplified technique.

We have isolated euploid, pluripotent stem cell lines directly from mouse blastocysts by a simple culture technique. Our method permits cell lines to be derived from individual embryos, without the use of ovariectomy, immunosurgery and conditioned medium. We cultured individual intact blastocysts in MicroTest plates on top of a feeder layer of lethally irradiated STO mouse fibroblasts in a 10-microliters volume of Dulbecco's modified Eagle's medium (DMEM) supplemented with 10% fetal calf serum (FCS). The cell lines maintain a stable complement of 40 chromosomes, form embryoid bodies and differentiate both in culture and in solid tumors.