Homing of in vitro expanded Stro-1- or Stro-1+ human mesenchymal stem cells into the NOD/SCID mouse and their role in supporting human CD34 cell engraftment

The Stro-1 antigen potentially defines a mesenchymal stem cell (MSC) progenitor subset. We here report on the role of human ex vivo-expanded selected Stro-1+ or Stro-1- MSC subsets on the engraftment of human CD34+ cord blood cells in the nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mouse model. The data show that cotransplantation of expanded Stro-1- cells with CD34+ cells resulted in a significant increase of human CD45, CD34, CD19, and CD11b cells detected in blood or in bone marrow (BM) and spleen as compared with the infusion of CD34+ cells alone. Infusion into mice of expanded Stro-1+ and Stro-1- cells (without CD34+ cells) showed that the numbers of Stro-1+-derived (as assessed by DNA analysis of human β-globin with quantitative polymerase chain reaction [PCR]) were higher than Stro-1--derived cells in spleen, muscles, BM, and kidneys, while more Stro-1--derived than Stro-1+-derived cells were found in lungs. The transduction of expanded Stro-1+ cells with an enhanced green fluorescent protein (eGFP) gene did not modify their cytokine release and their homing in NOD/SCID mouse tissues. The difference between the hematopoietic support and the homing capabilities of expanded Stro-1+ and Stro-1- cells may be of importance for clinical therapeutic applications: Stro-1+ cells may rather be used for gene delivery in tissues while Stro-1- cells may rather be used to support hematopoietic engraftment. (Blood. 2004;103:3313-3319)