Regulation of plasticity and biological features of endothelial progenitor cells by MSC-derived SDF-1

Bone marrow (BM) is a source of mesenchymal stromal cells (MSCs) and endothelial progenitor cells (EPCs). MSCs provide a specific niche in the BM and biological features of EPCs may be changed with this niche. Stromal cell-derived factor 1 (SDF-1) secreted from primary BM-MSCs and biological features of this niche on EPC development are still yet to be understood. The aim of this study was to evaluate the role of SDF-1 produced by MSCs on EPC development. We applied the CRISPR/Cas9 system for the knock-out of the SDF-1 gene in BM-derived MSCs. BM-derived EPCs were then cocultured with MSCs^SDF-1-/- or MSCs^SDF-1+/+ to identify the role of MSC-derived SDF-1α on proliferation, migration and angiogenic activity of EPCs. Next, pre-expanded EPCs were harvested and co-transplanted with MSCs^SDF-1-/- or MSCs^SDF-1+/+ into sublethally irradiated mice to analyze the potency of these cells for marrow reconstitution. Our results revealed that proliferation, colony formation, migration and angiogenic activity of EPCs was significantly increased after coculture with MSCs^SDF-1+/+. We also found that co-transplantation of EPCs with MSCs^SDF-1+/+, in contrast to MSCs^SDF-1-/-, into irradiated mice resulted in marrow repopulation and hematologic recovery, leading to improved survival of transplanted mice. In conclusions, MSC-derived SDF-1 niche plays an important role in the development of EPCs and this niche is essential for bone marrow repopulation by these cells and can enhance the efficiency of EPC therapy for ischemic diseases.