In vitro survival and multiplication of chicken myeloblasts promoted for several weeks by chick embryo extract

Growth of hemopoietic cells from chick embryonic aorta, spleen, and bone marrow was obtained in a serum-free culture medium containing 10-d-old chick embryo extract. When cells were cultured in semi-solid medium (plasma clot), they proliferated and differentiated to generate colonies committed to the granuloid or erythroid lineage. Mixed colonies composed either of granulocytes and macrophages or granulocytes and erythroblasts were also obtained. In addition, two different types of colonies composed of immature cells (blast cells) could be distinguished by the size of the cells. These colonies were composed of larger cells originating from the more immature progenitors, because they developed after a longer incubation period. Growth of bone marrow cells up to 3 wk in liquid culture was also obtained in the serum-free culture supplemented with chick embryo extract. These cells retained a very immature phenotype and the ability to differentiate when reseeded in an appropriate medium. These results indicate for the first time that chick embryo extracts contain hematopoietic growth factors that are active in differentiation and proliferation of chick hematopoietic cells.