The washouts of discarded bone marrow collection bags and filters are a very abundant source of hMSCs

Background aims Human multipotent mesenchymal stromal cells (hMSC) are considered good candidates for a growing spectrum of cell therapies. We have validated a protocol that makes use of the washouts of discarded collection sets, left over at the end of the filtration of bone marrow (BM) explants performed for hematopoietic stem cell (HSC) transplantation. Methods The method consists of direct plating of cells without density-gradient isolation followed by two detachment steps and expansion in 5% human platelet lysate (hPL). Results In a median of 26 days, 14 bags for adult patients and nine bags for pediatric patients for a standard dose of 1 x 10(6) hMSC/kg body weight could be prepared from the expansion of a fraction of the cells recovered from seven independent washouts. Moreover, 151 vials could be frozen from the remaining cells. The theoretical full expansion of all the frozen vials (validated by the expansion of two independent vials) could have allowed the production of 173 bags for adults and 348 bags for pediatric patients. Conclusions The washouts of discarded bags and filters left over at the end of routine BM explants filtration are a very abundant source of hMSC precursors that can be easily utilized for clinical applications.