Late-Breaking Developments in Stem Cell Biology and Cardiac Growth Regulation

Abstract

### 5000 Characterization and Growth of Human Cardiac Stem Cells Claudia Bearzi, Stefano Cascapera, Angelo Nascimbene, Claudia Casarsa, Raffaella Rastaldo, Toru Hosoda, Antonella De Angelis, Marcello Rota, Federico Quaini, Konrad Urbanek, Annarosa Leri, Piero Anversa, New York Medical College Cardiovascular Research Inst, Valhalla, NY; Roberto Bolli, University of Louisville Division of Cardiology, Louisville, KY; Jan Kajstura, New York Medical College Cardiovascular Research Inst, Valhalla, NY The human heart contains a subpopulation of replicating myocytes that is enhanced in pathologic states characterized by acute and chronic cardiac failure. On the assumption that these dividing cells represent amplifying myocytes originated from a pool of undifferentiated cells, effort was made to establish the conditions for the isolation and expansion of potential progenitor cells from surgical specimens of human myocardium. Because of the small size of the samples, we have cultured slices of human atrial and ventricular myocardium by the primary explant technique. The presence of stem cell surface antigens in the outgrowing cardiac cells was determined by immuno-cytochemistry and FACS analysis; c-kitPOS, MDR1POS and Sca-1-likePOS cells were found in 1.8±1.7%, 0.5±0.7% and 1.3±1.9% of the unsorted myocardial cell population, respectively. The fraction of c-kitPOS cells included lineage negative, 52±12%, and early committed cells, 48±12%. After plating, c-kitPOS cells attached rapidly and continued to grow up to P8 undergoing ∼25 population doublings. Ki67 labeling showed that the number of cycling cells remained constant from P1 to P8, 48±10%. For clonal assay, single c-kitPOS cells were deposited in individual wells of a Terasaki plate. After 2–3 weeks, clones were generated and the number of cells in the clones varied from 500 to 1,500. Doubling time was ∼28 hours and ∼90% of cells were labeled by BrdU after 5 days of exposure. In differentiation medium, clonogenic cells gave rise to myocytes, endothelial cells and vascular smooth muscle cells. When …