Abstract 16327: Aging and Senescence of Endogenous Cardiac Stem Cells (eCSCs) Determines Their Growth and Differentiation Potential
The adult myocardium harbours resident (endogenous) multi-potent cardiac stem cells (eCSCs). Manipulation of eCSCs ex-vivo and in situ has opened new therapeutic avenues for anatomical and functional myocardial regeneration. However, if aging/senescence of the eCSCs determines their function and regenerative capacity, their state might determine the success of regenerative procedures. c-kitpos CD45neg eCSCs were isolated from young (4-wks) and old (22-months) mouse hearts, and young (<40 yrs) and old (>65 yrs) human right atria appendage (∼200mg). eCSCs were characterised for co-expression of ageing and senescence markers (p16INK4a, hyperphos-RB, p53, p21, p27, senescence-associated β-galactosidase) with known stemness/multipotency (Oct-4, Nanog, Bmi-1, TERT, Sox-2) and proliferation (Ki67) markers. The growth (BrdU labelling), clonogenicity and differentiation potential of young and old eCSCs was also assessed. c-kitpos CD45neg eCSCs were isolated with similar efficiency from both murine hearts (8±2% of the small cell population depleted of cardiomyocytes) and human myocardial samples (5±2%). The number of eCSCs isolated was similar regardless of age, gender and pathology (∼45,000/gram of tissue). c-kitpos CD45neg eCSCs isolated from young and old hearts showed age-correlated increased expression of ageing and senescence markers and decreased expression of stemness/multipotency and proliferation markers. Moreover, ‘aged’ eCSCs showed limited cloning and growth capacity and impaired cardiac differentiation capacity. When eCSCs isolated from old hearts were grown in Wnt3A conditioned media or transfected with a lentivirus driving Bmi-1 expression, the ‘aged/senescent’ impairment in proliferation was corrected. Importantly, although the cloning efficiency was inversely age-related, single-cell derived eCSC clones obtained from young and old hearts were indistinguishable by their gene expression and differentiation potential, strongly suggesting that eCSC aging is a stochastic process. eCSCs stochastically develop a senescent phenotype with age impacting their growth and differentiation potential. Furthermore, these results provide evidence for a role of the Wnt/β-catenin and Bmi-1 pathways on eCSC senescence.
- © 2012 by American Heart Association, Inc.