Characterization of cardiac-resident progenitor cells expressing high aldehyde dehydrogenase activity

High aldehyde dehydrogenase (ALDH) activity has been associated with stem and progenitor cells in various tissues. Human cord blood and bone marrow ALDH-bright (ALDH^br) cells have displayed angiogenic activity in preclinical studies and have been shown to be safe in clinical trials in patients with ischemic cardiovascular disease. The presence of ALDH^br cells in the heart has not been evaluated so far. We have characterized ALDH^br cells isolated from mouse hearts. One percent of nonmyocytic cells from neonatal and adult hearts were ALDH^br. ALDH ^very-br cells were more frequent in neonatal hearts than adult. ALDH^br cells were more frequent in atria than ventricles. Expression of ALDH1A1 isozyme transcripts was highest in ALDH^very-br cells, intermediate in ALDH^br cells, and lowest in ALDH^dim cells. ALDH1A2 expression was highest in ALDH^very-br cells, intermediate in ALDH^dim cells, and lowest in ALDH^br cells. ALDH1A3 and ALDH2 expression was detectable in ALDH^very-br and ALDH^br cells, unlike ALDH^dim cells, albeit at lower levels compared with ALDH1A1 and ALDH1A2. Freshly isolated ALDH^br cells were enriched for cells expressing stem cell antigen-1, CD34, CD90, CD44, and CD106. ALDH ^br cells, unlike ALDH^dim cells, could be grown in culture for more than 40 passages. They expressed sarcomeric α-actinin and could be differentiated along multiple mesenchymal lineages. However, the proportion of ALDH^br cells declined with cell passage. In conclusion, the cardiac-derived ALDH^br population is enriched for progenitor cells that exhibit mesenchymal progenitor-like characteristics and can be expanded in culture. The regenerative potential of cardiac-derived ALDH^br cells remains to be evaluated.