Directed differentiation of chick embryonic germ cells into neural cells using retinoic acid induction in vitro

Embryonic germ cells (EG) are undifferentiated stem cells isolated from cultured primordial germ cells (PGC). Like embryonic stem cells (ES), EG are also capable of proliferation and self-renewal and have the capacity to differentiate in vitro into all cell types. To date, it has been proven that ES are capable of directed differentiation into neural precursors and progenies in mammals. However, similar studies on EG in mammals and other species are few. This investigation aimed to induce chick EG to differentiate into neural cells and compare the difference of efficiency between directed differentiation and spontaneous differentiation. EG were isolated and identified from 5.5-day chick gonadal PGC, incubated and passaged in conditioned medium. After the formation of embryoid bodies (EB), EB were grown in suspension and induced by retinoic acid (RA), using a protocol named 4-/4+, to make the formation of neurospheres and progenies. RT-PCR and immunocytochemistry analysis demonstrated that neural-specific markers can be detected after directed induction. Moreover, EG differentiated into neural lineage cells using 4-/4+ protocol much more efficiently than that in the spontaneous differentiation with fluorescence-activated cell sorting (FACS) analysis. The results revealed that RA can obviously promote the directed differentiation of chick EG into neural lineage.