Co-culture of cord blood CD34+ cells with human BM mesenchymal stromal cells enhances short-term engraftment of cord blood cells in NOD/SCID mice

Background The major challenge for cord blood transplantation (CBT) is higher rates of delayed and failed engraftment. In an attempt to broaden the application of CBT to more candidates, ex vivo expansion of hematopoietic stem/progenitor cells in CB is a major area of investigation. The purpose of this study was to employ human BM mesenchymal stromal cells (hBM-MSC) as the feeding-layer to expand CB cells ex vivo. Methods In this study, hBM-MSC were isolated and characterized by morphologic, mmunophenotypic and RT-PCR analysis. The hBM-MSC at passage 3 were employed as the feeding-layer to expand CB CD34+ cells in vivo in the presence of thrombopoietin, flt3/flk2 ligand, stem cell factor and G-CSF. The repopulating capacity of the ex vivo -expanded CB cells was also evaluated in a NOD/SCID mice transplant experiment. Results After 1 or 2 weeks of in vitro expansion, hBM-MSC supported more increasing folds of CB in total nucleated cells, CD34+ cells and colony-forming units (CFU) compared with CB without hBM-MSC. Furthermore, although NOD/SCID mice transplanted with CB cells expanded only in the presence of cytokines showed a higher percentage of human cell engraftment in BM than those with unexpanded CB CD34+ cells, expanded CB cells co-cultured with hBM-MSC were revealed to enhance short-term engraftment further in recipient mice. Discussion Our study suggests that hBM-MSC enhance in vitro expansion of CB CD34+ cells and short-term engraftment of expanded CB cells in NOD/SCID mice, which may be valuable in a clinical setting.