Integrative Physiology Tracking Chromatid Segregation to Identify Human Cardiac Stem Cells That Regenerate Extensively the Infarcted Myocardium

Rationale: According to the immortal DNA strand hypothesis, dividing stem cells selectively segregate chromosomes carrying the old template DNA, opposing accumulation of mutations resulting from nonrepaired replication errors and attenuating telomere shortening. Objective: Based on the premise of the immortal DNA strand hypothesis, we propose that stem cells retaining the old DNA would represent the most powerful cells for myocardial regeneration. Methods and Results: Division of human cardiac stem cells (hCSCs) by nonrandom and random segregation of chromatids was documented by clonal assay of bromodeoxyuridine-tagged hCSCs. Additionally, their growth properties were determined by a series of in vitro and in vivo studies. We report that a small class of hCSCs retain during replication the mother DNA and generate 2 daughter cells, which carry the old and new DNA, respectively. hCSCs with immortal DNA form a pool of nonsenescent cells with longer telomeres and higher proliferative capacity. The self-renewal and long-term repopulating ability of these cells was shown in serial-transplantation assays in the infarcted heart; these cells created a chimeric organ, composed of spared rat and regenerated human cardiomyocytes and coronary vessels, leading to a remarkable restoration of cardiac structure and function. The documentation that hCSCs divide by asymmetrical and symmetrical chromatid segregation supports the view that the human heart is a self-renewing organ regulated by a compartment of resident hCSCs. Conclusions: The impressive recovery in ventricular hemodynamics and anatomy mediated by clonal hCSCs carrying the " mother " DNA underscores the clinical relevance of this stem cell class for the management of heart failure in humans. Key Words: immortal DNA strand hypothesis Ⅲ asymmetrical stem cell division Ⅲ asymmetrical chromatid segregation Ⅲ symmetrical chromatid segregation Ⅲ adult stem cells Ⅲ myocardial infarction Ⅲ myocardial regeneration Ⅲ cell cycle Ⅲ proliferation T he controversy concerning the growth reserve of the adult heart has not been resolved, and questions continue to be raised about the actual existence of cardiac stem cells (CSCs) and their function in tissue homeostasis and repair. 1,2 The claim has been made that the myocardial origin of stem cells has only been partially clarified, and the mechanism by which the CSC pool is preserved in their cardiac niches has not been completely understood. The possibility that stem cells migrate from the bone marrow to the heart and continuously repopulate the niche structures is favored by some, 3,4 whereas others consider asymmetrical CSC division the biological system controlling the …