[Potential of hematopoietic stem cells marked with retrovirus: dependence on stimulation with growth factors]

Lethally irradiated mice were reconstituted with hematopoietic cells retrovirally marked by human ADA sequence. Before and during gene transfer adult bone marrow cells were pre-stimulated by a combination of exogenous growth factors, IL-6 and kit-ligand, or by culture on irradiated adherent cell layer of long-term bone marrow culture. Twelve-day-old embryonic liver cells were transduced without prestimulation with exogenous growth factors. In mice reconstituted with growth factors stimulated adult bone marrow cells during 4 months after transplantation 200-300 hematopoietic cell clones were functioning simultaneously. Five months and later after reconstitution oligo-monoclonal hematopoiesis was revealed. The findings suggest that growth factors induce long-lasting proliferation of quiescent pHSC as a result of which clone(s) with proliferative advantage replace all others and only this clone(s) persists during long time, up to 11 months. Vice versa, in mice reconstituted with adult or embryonic hematopoietic cells which were transduced without growth factors prestimulation, the phase of polyclonal hematopoiesis was never observed and hematopoietic cell clonal succession was revealed. The data obtained for the first time demonstrate artifactual influence of high-concentration IL-6 and kit-ligand on the developmental potential of hematopoietic stem cell. The model can be useful for the study of mechanism of hematopoiesis regulation, proliferative and developmental potential of primitive HSC and growth factors effect on them.