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 bo ne marrow was obtained in a serum-free culture medium containing 10-d- old chick embryo extract. When cells were cultured in semi-solid mediu m (plasma clot), they proliferated and differentiated to generate colo nies committed to the granuloid or erythroid lineage. Mixed colonies c omposed either of granulocytes and macrophages or granulocytes and ery throblasts were also obtained. In addition, two different types of col onies 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 develope d 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 sup plemented with chick embryo extract. These cells retained a very immat ure phenotype and the ability to differentiate when reseeded in an app ropriate medium. These results indicate for the first time that chick embryo extracts contain hematopoietic growth factors that are active i n differentiation and proliferation of chick hematopoietic cells.