Ex vivo acidic preconditioning enhances bone marrow ckit+ cell therapeutic potential via increased CXCR4 expression

Triggering CXCR4 receptor signaling is known to enhance the efficacy of cell therapy for cardiovascular regeneration. Here it was examined the effect of ex vivo acidic reconditioning (AP) on CXCR4 expression, in vitro, and on the regenerative potential of mouse bone marrow (BM) ckit+ cells in a mouse model of hindlimb ischemia. AP was obtained by exposing BM ckit+ cells to hypercarbic acidosis (pH 7.0) for 24 hours and subsequently returning them to pH 7.4 throughout the experiments. Control (C) cells were always kept at pH 7.4. Interestingly, AP enhanced CXCR4 and SDF-1 mRNA levels of BM ckit+ cells. AP CXCR4 expression modulation appeared to depend on calcium mobilization and on nitric oxide, as assessed by cytosolic Ca2+ buffering with BAPTA and nitric oxide inhibitor L-NAME treatments. Further, AP increased Stromal Cell-Derived Factor 1 (SDF-1)-driven chemotaxis, transendothelial migration and differentiation toward the endothelial lineage in vitro. In a mouse model of hindlimb ischemia, BM ckit+ cells, subjected to AP, accelerated blood flow recovery, increased capillary and arteriole number as well as the number of regenerating muscle fibres. These effects were abolished by treating AP cells with L-NAME. In summary, AP may constitute a novel strategy to enhance BM ckit+ cell therapeutic potential via NO-dependent increase in CXCR4 expression.