Transfer of human adenine deaminase gene into murine hematopoietic stem cells: sequential study of spleen colony-forming units from bone marrow of living mice and the requirement of the microenvironment.

Irradiated female mice were reconstituted with male hematopoietic stem cells (HSCs) retrovirally marked with human adenine deaminase (hADA) complimentary DNA. HSCs were incubated with interleukin-6 and stem cell factor before coculture with GP+E86-producing cells. Bone marrow HSCs were infused intravenously to irradiated mice and spleen colony-forming units (CFU-S) were evaluated for hADA marked clones by Southern blot analysis. 45 of 54 CFU-S were marked by the hADA gene sequence with multiple copies integrated per genome. Oligoclonal hematopoiesis evolved over time with 1-2 clones demonstrated 5-11 months after reconstitution. Comparable results were obtained with embryonic fetal liver HSCs. Incubation of bone marrow HSCs with adherent stromal cells rather than growth factors produced less efficient gene transfer, and polyclonal hematopoiesis was not observed. Donor origin was established by the Y chromosome probe. These results support the clonal succession model of hematopoiesis.