Abstract 16917: Carbon 14 Retrospective Birth Dating Reveals Distinct Rates of Proliferation of Cardiac Cells
The objective of our study was to measure the turnover rate of the three main cell populations of the human heart: myocytes, endothelial cells (ECs) and fibroblasts (FBs). Cells were enzymatically dissociated from donor hearts and explanted failing hearts. Myocytes, ECs, and FBs were separated by differential centrifugation and FACS sorting; the purity of each preparation was determined. The age of cells was determined by the measurement of 14C content in the DNA utilizing accelerator mass spectrometry. Additionally, the proliferation index was obtained by analyzing the expression of Ki67, phospho-histone H3, and aurora B kinase. In donor organs, the age of myocytes and FBs was comparable, varying between 4 and 10 years in adult hearts, and between 1 and 5 years in old hearts. ECs were older than myocytes and FBs, 5-11 and 6-10 years in young and old hearts, respectively. These values, together with the information on the number of cells in the tissue allowed us to compute the turnover rate of each cell class. This parameter was higher in myocytes and FBs than in ECs. Moreover, the turnover rate of myocytes and FBs was increased in the oldest patients, while that of ECs remained relatively constant. This differential response of ECs with aging may be responsible, at least in part, for the rarefaction of coronary vasculature in the old heart. In age-matched failing hearts, the age of all three cell types was younger, and the turnover rate was higher than in control hearts. Our results are in conflict with an early study which, by retrospective 14C birth dating only, claimed that myocyte turnover in the human heart is minimal and decreases with age. In contrast to this previous work, we implemented unbiased collection of cardiac cells, and evaluated the purity of preparations, proportion of mononucleated and multinucleated cells, fraction of polyploid nuclei, and number of cells in the organ. These variables affect significantly the evaluation of cell age and renewal by 14C birth dating. Finally, our 14C data were consistent with those obtained by immunolabeling utilizing various markers of cell cycle. Collectively, our findings indicate that the human heart is characterized by high turnover of myocytes, ECs, and FBs, a phenomenon that increases further with chronic heart failure.
- © 2012 by American Heart Association, Inc.