Adipocyte differentiation of human marrow mesenchymal stem cells reduces the supporting capacity for hematopoietic progenitors but not for severe combined immunodeficiency repopulating cells

Bone marrow stromal cells provide a microenvironment for hematopoiesis. Adipocytes are the major stromal cell phenotype in bone marrow, but their function in hematopoiesis is poorly understood. In this study, we compared the hematopoietic-supporting capacity of adipocytes and their progenitor, mesenchymal stem cells (MSCs), by culturing human cord blood (CB) CD34+CD38- hematopoietic progenitor cells (HPCs) on a layer of adipocytes or MSCs. CB CD34+CD38- cells cultured on MSCs generated higher proportions of CD34+CD38- HPCs and colony-forming cells than those cultures on a layer of adipocytes, indicating an inferior hematopoietic support by adipocytes. However, CB CD34+CD38- HPCs cultured on MSCs and adipocytes were equally capable of reconstituting human hematopoiesis in non-obese diabetic/severe combined immunodeficient disease (NOD/SCID) mice. These findings show that differentiation of MSCs into adipocytes is accompanied by the loss of capacity to support mature HPCs, but not transplantable SCID-repopulating cells.