Abstract 4935: Ex vivo Acidic Preconditioning Modulates Bone Marrow-derived ckit + Cell Function in vitro and Enhances Their Therapeutic Potential in a Mouse Model of Hindlimb Ischemia

Abstract

Background and Objective . Bone marrow-derived cell transplantation may provide a novel strategy for the treatment of cardiac and limb ischemia. However, in some cases cells appear to have lost their therapeutic potential and there is an interest in identifying interventions that are clinically applicable and may enhance cells’ ability to repair damaged tissues. The objective of the present work was to examine whether ex vivo acidic preconditioning (AP) may modulate bone marrow-derived ckit + cell functions in vitro and their regenerative properties in a mouse model of hindlimb ischemia. Methods and results. ckit + cells were obtained from 4-week old mice; AP was achieved by exposing cells to hypercarbic acidosis (buffer pH 7.0) for 24 hours and subsequently returning them to pH 7.4. Control ckit + cells (C) were always kept at pH 7.4. AP enhanced CXCR4 mRNA levels (2.5-fold vs C; n=6; p<0.05). In agreement with this result AP increased SDF-1-driven chemotaxis (2-fold vs C; n=6; p<0.02) and transendothelial migration (10-fold vs C; n=5; p<0.05) as well as SDF-1-driven differentiation toward the endothelial lineage as indicated by DiI-Ac-LDL uptake (2.2-fold vs C; n=10; p<0.005), vWF positivity (2.2-fold vs C; n=4; p<0.005) and KDR positivity (3-fold vs C; n=4; p<0.005). The effect of AP on ckit + cell therapeutic potential was examined in a mouse model of hindlimb ischemia. Either AP or C cells (5 × 10 5 ) were injected into the adductor muscle at the time of femoral artery dissection. AP cells accelerated blood flow recovery vs C cells as determined by laser doppler perfusion imaging at different time points throughout the 14-day time course following acute ischemia (n=8; p<0.01 vs C). Further, 14 days after surgery, AP cells increased capillary (1.3-fold vs C; n=6; p<0.01) and arteriole number (4.6-fold vs C; n=6; p<0.01) as well as the number of regenerating muscle fibers measured 7 days after surgery (4.4-fold vs C; n=6; p<0.05). Conclusions. ckit + cells exposed to AP exhibit enhanced CXCR4 expression and SDF-1-directed cell responses in vitro and regenerative properties in a mouse model of hindlimb ischemia. Thus, AP may represent a simple, unexpensive and clinically applicable strategy to improve the therapeutic efficacy of bone marrow-derived cell transplantation.