Abstract 19154: A Combinatorial Approach for Bone Marrow Stem Cell Mobilization, Homing-in and Retention for De Novo Cardiac Regeneration: Gcsf Treatment Combined with Ex Vivo Transgenic Sdf-1α Delivery in the Heart

Abstract

Objective: We have already shown that bone marrow stem cells (BMC) mobilized into the infarcted heart developed into mature cardiomyocytes and improved the heart function. Granulocyte colony stimulating factor (GCSF) reduces stromal cell derived factor-1 α (SDF-1α) in the bone marrow to support extravasation of BMC from their niches. We hypothesized that GCSF treatment combined with a favorable SDF-1α gradient in the infracted heart would promote homing-in and retention of mobilized BMC for angiomyogenic repair of the infracted myocardium. Methods and Results: Radiomyoabalated young female Fisher 344 rats received 1×10 6 BMC from transgenic GFP + male rats. Two month later, animals were used to develop experimental model of acute LAD artery ligation. The animals were grouped (n=16) to receive following intramyocardial injection of 70μ l DMEM without cells (G1) or containing 1×10 6 wild type BMC with (G2 and G3) or without SDF-1α overexpression (G4). Besides G1 and G3 had intraperitoneal injection of DMEM without GCSF whereas G2 and G4 received 10µg/kg body weight GCSF treatment starting 3 days prior to and until 2 days after intramyocardial injection of cells. Animals were harvested 4 days and 4 weeks after their respective treatment and the hearts were removed for molecular and histological studies. SDF-1α expression was higher in G2 and G4 animal hearts ( p <0.05 vs all groups) on day 4 with. Highest mobilization of GFP + BMC was observed in and around the infarcted myocardium in G2. GFP + BMC were also identified by immunostaining for ckit, CXCR4 and CD44 which showed highest propensity in G2. Fluorescence immunostaining for GFP and cardiac actin at 4 weeks showed that mobilized cells extensively differentiated into mature muscle fibers. Similarly, vascular density was markedly increased in G2 ( p <0.01 vs all groups) in peri-infarct area. Infarct size was significantly attenuated with improved LV contractile function in G2 ( p <0.05 vs all groups). Conclusions: Concomitant ex vivo expression of SDF1α in the infarcted heart combined with intraperitoneal GCSF treatment is more effective and efficient approach to mobilize BMC for participation in myocardial repair. Mobilized BMC homed-in to the infarcted heart and supported extensive angiomyogenic repair.