Abstract 860: Phenotypic Characterization Of Murine And Human Cardiac-resident Progenitor Cells Isolated On Basis Of Aldehyde-dehydrogenase Activity

Abstract

Identification of stem cells based on hematopoietic stem cell (HSC) surface markers, such as stem cell antigen-1 (Sca-1) and the c-kit receptor, has limited specificity. High aldehyde-dehydrogenase (ALDH) activity is a general cellular property of stem cells shared by HSC, neural, and intestinal stem cells. The presence of cells with high ALDH activity in the adult heart has not been investigated. Methods: Cells were isolated from adult mouse hearts, and from atrial appendage samples from humans with ischemic or valvular heart disease. Myocyte-depleted mouse Sca-1+, and lineage (Lin)-negative/c-kit+ human heart cells were purified with immunomagnetic beads. ALDH-high cells were identified using a specific fluorescent substrate, and sorted by FACS. Cell surface marker analysis was performed by flow cytometry. Results: Myocyte-depleted mouse heart cells contained 4.8+/−3.2% ALDH-high/SSC-low and 32.6+/−1.6% Sca-1+ cells. ALDH-high cells were Lin-negative, Sca-1+ CD34+ CD105+ CD106+, contained small CD44+ (27%) and CD45+ (15%) subpopulations, and were essentially negative for c-kit (2%), CD29, CD31, CD133 and Flk-1. After several passages in culture, ~20% of ALDH-high cells remained ALDH-high. Myocyte-depleted human atrial cells contained variable numbers of ALDH-high cells ranging from 0.5% to 11%, and 4% Lin-negative/c-kit+ cells. ALDH-high cells were CD29+ CD105+, contained a small c-kit+ subpopulation (5%), and were negative for CD31, CD45 and CD133. After 5 passages in culture, the majority of ALDH-high cells remained ALDH-high. Conclusions: Adult mouse and human hearts contain significant numbers of cells with high ALDH activity, a general cellular property that stem cells possess in different organs, and express stem cell markers (Sca-1 and CD34 in the mouse). The immunophenotype of cardiac-resident ALDH-high cells differs from that previously described for bone marrow ALDH-high HSC, and suggests that this cell population may be enriched in mesenchymal progenitors. Analysis of lineage differentiation potential of ALDH-high cells is in progress. ALDH activity provides a new, practical approach to purifying cardiac-resident progenitor cells.