EX-VIVO EXPANSION OF HUMAN HEMATOPOIETIC STEM-CELLS - IMPLICATIONS FOR THE MODERN BLOOD-BANK

Pluripotent hematopoietic stem cells (PHSC) are rare cells within the marrow that are capable of self-renewal and differentiation into multi ple hematopoietic lineages. Following myeloablative chemotherapy and r adiation therapy and marrow transplantation, hematological reconstitut ion occurs after a period of 2-3 weeks. Recently, a number of laborato ries have shown that both early and delayed phases of engraftment are mediated by PHSC within a graft and that engraftment can be accelerate d by transplanting greater numbers of PHSC. Increasing efforts have be en directed, therefore, towards developing methods to expand PHSC ex v ivo. In this report, we describe an endothelial cell-based culture sys tem to which exogenous cytokines are added which appears to permit the ex vivo expansion of PHSC. Refinement of these technologies will pote ntially have a major impact on the ability of blood banks to improve t he quality of hematopoietic stem cell grafts.