A Stro-1+ human universal stromal feeder layer to expand/maintain human bone marrow hematopoietic stem/progenitor cells in a serum-free culture system

Objective To compare the ability of allogeneic versus autologous purified human Stro-1+ mesenchymal stem cell (MSC) populations from different human donors to support the ex vivo expansion and maintenance of human hematopoietic stem/progenitor cells (HSCs). Furthermore, we compared the results obtained with MSC as a feeder layer to traditional allogeneic stromal layers grown in long-term bone marrow culture media (LT-ST). Methods Adult human bone marrow CD34+-enriched cells were cultured in serum-free medium for 2 to 3 weeks over the respective MSC-irradiated feeder layers or over traditional allogeneic LT- ST stromal layers in the presence of stem cell factor, basic fibroblast growth factor, leukemia inhibitory factor, and Flt-3 and analyzed every 2 to 4 days for expansion, phenotype, and clonogenic ability. Results There was a progressive expansion of total numbers of cells in all the experimental groups; however, allogeneic MSCs were more efficient at expanding CD34+CD38− cells and showed a higher clonogenic potential than both allogeneic LT-ST and autologous MSCs. The differentiative potential of cells cultured on both MSC and LT-ST was primarily shifted toward myeloid lineage; however, only MSCs were able to maintain/expand a CD7+ population with lymphocytic potential. Importantly, transplantation into preimmune fetal sheep demonstrated that the HSCs cultured over MSCs retained their engraftment capability. Conclusion These results indicate that purified Stro-1+ MSCs may be used as a universal and reproducible stromal feeder layer to efficiently expand and maintain human bone marrow HSCs ex vivo.