Human Non-hematopoietic CD271(pos)/CD140a(low/neg) Bone Marrow Stroma Cells Fulfill Stringent Stem Cell Criteria in Serial Transplantations.

Human bone marrow contains a population of non-hematopoietic stromal stem/progenitor cells (BMSCs), which play a central role for bone marrow stroma and the hematopoietic microenvironment. However, the precise characteristics and potential stem cell properties of defined BMSC populations have not yet been thoroughly investigated. Using standard adherent colony-forming unit fibroblast (CFU-F) assays, we have previously shown that BMSCs were highly enriched in the nonhematopoietic CD271(pos)/CD140a(low/neg) fraction of normal adult human bone marrow. In this study, we demonstrate that prospectively isolated CD271(pos)/CD140a(low/neg) BMSCs expressed high levels of hematopoiesis supporting genes and signature mesenchymal and multipotency genes on a single cell basis. Furthermore, CD271(pos)/CD140a(low/neg) BMSCs gave rise to non-adherent sphere colonies (mesenspheres) with typical surface marker profile and trilineage in vitro differentiation potential. Importantly, serial transplantations of CD271(pos)/CD140a(low/neg) BMSC-derived mesenspheres (single cell and bulk) into immunodeficient NOD scid gamma (NSG) mice showed increased mesensphere numbers and full differentiation potential after both primary and secondary transplantations. In contrast, BMSC self-renewal potential decreased under standard adherent culture conditions. These data therefore indicate that CD271(pos)/CD140a(low/neg) BMSCs represent a population of primary stem cells with MSC phenotype and sphere-forming capacity that fulfill stringent functional stem cell criteria in vivo in a serial transplantation setting.