Culture of human cd34 progenitor cells in conditioned medium from primary porcine endothelial cells maintains a primitive and highly proliferative progenitor cell population

Recently, we have shown that serum-free conditioned medium from untreated porcine microvasular endothelial cells (PMVEC CM, concentrated 70X, >50,000 kDa) contains hematopoietic growth factor activity that promotes the in yjjro. proliferation, differentiation, and colony cell formation of primitive human hematopoietic progenitor cells in the absence of other hematopoietic growth factors In this study, we evaluated the replating potential of individual day-14 colonies generated in cultures treated wilh PMVEC CM alone (-7% cloning efficiency) Individual primary colonies were harvested, dispersed, and replatcd in secondary methylcellulose cultures containing optimal sources of colonystimulating activity. Colonies were scored on day 14 after replating and repetitive replating of secondary, tertiary and fourth generation colonies were performed under the identical conditions When primary colonies initiated in PMVEC CM alone were transferred to secondary cultures, 100% of these transferred colonies gave rise to an average of 18.8±2 6 secondary colonies of multiple lineages (CPU-Mix, CFU-GM, BFÜ-E) 48% of the 2" colonies gave rise to an average of 16.8± 2 9 3rd generation colonies and 6.3% of the 3° colonies gave rise to an average of 2 7± 2.1 fourth generation colonies Formation of third and fourth generation colonies suggests that initial culture in PMVEC CM supports primitive progenitor cells with extensive proliferative and self-renewal capacity.