Abstract 19048: Clonal Analysis of Cardiac Tissue Formation Reveals Limited Proliferative Capacity of Mature Cardiomyocytes During Development
Strong evidence supports the ability of the heart to generate new cardiomyocytes during development and in response to injury albeit at a very low rate. However, it still remains unclear whether the newly formed cells originate from cardiac progenitor/stem cells or pre-existing cardiomyocytes capable of proliferation. Identification of the cell populations responsible for new cardiomyocyte formation is imperative towards the development of novel clinical strategies. Herein, we hypothesized that cardiac progenitor cells are the main source of the new cardiomyocytes generated during development while contribution of pre-existing cardiomyocytes is limited. For clonal analysis of cardiomyocyte formation we utilized a stochastic multicolor reporter system called Rainbow that allows random marking of cells with the fluorescent proteins Cerulean (CFP), mOrange or mCherry upon Cre-mediated recombination. Selective labeling of cardiomyocytes was achieved by crossing Rainbow mice αMHC-CreER mice. As control Actin-CreER;Rainbow mice were used where all types of cells can be labeled. Rare recombination events were induced at embryonic day E12.5 and clone formation and expansion were retrospectively analyzed at different time-points from E15.5 to postnatal day P30. To determine at which developmental stage cardiac cells lose their ability to proliferate, recombination was induced at different time-points from early embryonic to postnatal life and analysis was performed at P30. αMHC-CreER;Rainbow hearts exhibited mainly single colored cells randomly distributed within the tissue. A few doublets and some rare four-cell clones were observed. In Actin-CreER;Rainbow mice, we observed clones ranging from two to more than twenty cells. Clone formation and expansion decreased with age. Interestingly we observed clones consisting of more than one cell types indicating the existence of a common progenitor cell. We show that αMHC-positive cardiomyocyte proliferation is limited during development while non-αMHC expressing cells exhibit clonal expansion. Our results suggest a possible contribution of cardiac progenitor cells even during late cardiovascular development.
- © 2013 by American Heart Association, Inc.