Mesenchymal stromal cells improve the transplantation outcome of CRISPR-Cas9 gene-edited human HSPCs (NHEJ)

Mesenchymal Stromal Cells (MSCs) have been employed in vitro to support HSPC expansion and in vivo to promote Hematopoietic Stem and Progenitor Cells (HSPCs) engraftment. Based on these studies, we developed an MSC-based co-culture system to optimize transplantation outcome of CRISPR-Cas9 gene-edited (GE) human HSPCs. We show that bone marrow (BM)-MSCs produce several hematopoietic supportive and anti-inflammatory factors capable to alleviate the proliferation arrest and mitigate the apoptotic and inflammatory programs activated in GE-HSPCs, improving their expansion and clonogenic potential in vitro. The use of BM-MSCs resulted in superior human engraftment and increased clonal output of GE-HSPCs contributing to the early phase of hematological reconstitution in the peripheral blood of transplanted mice. In conclusion, our work poses the biological bases for a novel clinical use of BM-MSCs to promote engraftment of GE-HSPCs and improve their transplantation outcome. CRISPR-Cas9 gene-edited (GE)-HSPCs cultured in presence or not with Mesenchymal Stromal Cells (MSCs) and transplanted into NSG mice. Non-Homologous End Joining (NHEJ) tracking performed on samples from peripheral blood (PB) and bone marrow (BM) of xenotransplanted mice.