Cytokine modulation of murine stem cell engraftment: the role of adherence to plastic surfaces.

Murine marrow stem cells acquire an engraftment defect when cultured for 48 hours in cytokines, whereas the number of progenitor cells expands. Stem or progenitor cells have been noted to adhere to various surfaces, including plastic. Despite vigorous harvesting by cell scraping, the possibility existed that cytokines might induce selective adhesion of the rare engraftable stem cells to plastic surfaces. We have evaluated whether loss of engraftability by cytokine-treated marrow cells could be due to adhesion to plastic culture vessels. BALB/c marrow cells were cultured in the presence of interleukin 3 (IL-3), IL-6, IL-11, and steel factor for 48 hours in plastic tissue culture flasks from which cells were harvested by standard scraping and washing or after 5 or 10 minutes of additional exposure to trypsin (0.25%), or they were cultured with the same cytokines in nonadherent polytetrafluoroethylene (Teflon) culture bottles. Harvested cultured or fresh-starting male cells were then engrafted into nonirradiated female hosts or were placed in competition with fresh female BALB/c marrow in lethally irradiated female hosts. Defective engraftment was seen in nonmyeloablated or irradiated female hosts 7 to 24 weeks after marrow infusion in all cultured cell groups. These data indicate that cytokine-treated engraftable stem cells do not show significant adherence to plastic surfaces.