Abstract 19875: Bone Marrow Stem Cells Mobilized in Response to Ex-vivo Transgenic Overexpression of IGF-1 Differentiate into Functioning Cardiomyocytes and Contribute in Myocardial Regeneration
Objective: Despite extensive preclinical and clinical studies with bone marrow cells (BMCs), ability of BMCs to adopt cardiac phenotype in the ischemic heart remains contentious. This study provides a proof-of-concept that BMCs mobilized into the ischemic heart in response to myocardial ex-vivo transgenic overexpression of IGF-1, developed into mature cardiomyocytes and improved the heart function.
Methods and Results: Forty-eight radiomyoabalated young female Fisher 344 rats received 1×106 BMCs from transgenic GFP+ male rats. Three month later, ischemia/reperfusion model was developed in these animals by 45 minutes ligation of LAD artery followed by reperfusion. The animals were grouped (n=16) for intramyocardial injections of 70μl DMEM without cells (group-1) or containing 1×106 wild type BMCs genetically modified to overexpress IGF-1 (group-2) or adenoviral null vector without therapeutic gene (group-3). The animals were harvested 7 days and 6 weeks after their respective treatment and the hearts were removed for molecular and histological studies. The level of human IGF-1 and SDF-1α was higher in group-2 animal hearts (p<0.05 vs other groups) on day 7 with concomitant mobilization of GFP+ BMCs in and around the ischemic myocardium in groups-2 which positively stained for y-chromosome by FISH. Moreover, the GFP+ BMCs were also identified by immunostaining for ckit, CXCR4, CD44 and GATA4. Double immunostaining for GFP and cardiac actin on 6 weeks post cell engraftment showed that the mobilized cells extensively differentiated into mature muscle fibers. Enzymatic digestion of the rat hearts on 6 weeks yielded single GFP+ rod shaped cardiomyocytes with clear striations in group-2. These isolated GFP+ myocytes were longer as compared to the normal myocytes but showed contractility similar to the normal myocytes. Blood vessel density was markedly enhanced in group-2 (p<0.01 vs group-3) in peri-infarct area. Infarct area was reduced with improved LV-contractile function in group-2 (p<0.05 vs group-3).
Conclusions: BMCs mobilized in response to IGF-1 overexpression in the ischemic heart differentiated into mature and functionally competent cardiomyocytes and improved cardiac function during 6-weeks of observation.
- © 2010 by American Heart Association, Inc.