Embryonic fibroblast-conditioned medium enhances viability and proliferation of chick circulating primordial germ cells (cPGCs) in suspension culture

Primordial germ cells circulating in the embryonic vascular system (cPGCs) were isolated from 2.5-day-old chick embryos and cultured individually in suspension for 5 days in embryonic stem-cell medium (ESM) adjusted to pH 8.0 supplemented with fetal bovine serum. Most cells died within 5 days, during which time only a few cells (16-23%) underwent mitosis once, and only a very few cells (less than 3%) twice. The use of conditioned medium (CM) derived from embryonic fibroblasts enhanced the viability and proliferation of the cPGCs, resulting in survival of up to one-third of the cells for 5 days. A fraction of the cells (3-5%) even divided 3 times. The in vitro cultured cPGCs maintain the capacity to migrate into the gonadal area. The chick cPGCs cultured in vitro for up to 5 days in the CM produced germ-line chimeras upon injection into the bloodstream of 2-day-old quail embryos.