Abstract
Rationale Aging leads to increased cellular senescence and is associated with decreased potency of tissue-specific stem/progenitor cells.
Objective To determine the impact of ageing and senescence on human cardiac stem/progenitor cell (CPC) biology and regenerative potential, and investigate whether elimination of senescent cells in aged mice enhances CPC activation and cardiomyocyte proliferation.
Methods and Results CPCs were isolated from the right atrial appendage (∼200mg) of human subjects with cardiovascular disease (n=119), aged 32-86 years, and assessed for expression of senescence-associated markers (p16INK4A, SA-β-gal, DNA damage γH2AX, telomere length), Senescence-Associated Secretory Phenotype (SASP), cell growth, differentiation, and regenerative potential following transplantation into the infarcted mouse heart. Senescent cells were eliminated in aged mice (22 – 32 months) in vivo either genetically, using INK-ATTAC mice, which results in inducible elimination of p16INK4A-expressing senescent cells upon the administration of the drug AP20187, or pharmacologically using intermittent oral administration of combined senolytics, Dasatinib (D) and Quercetin (Q). In aged subjects (>74 years old) over half of CPCs are senescent, unable to replicate, differentiate, regenerate or restore cardiac function following transplantation into the infarcted heart. Aged-senescent CPCs secrete SASP factors, which renders otherwise healthy, cycling-competent CPCs to senescence. Elimination of senescent CPCs using senolytics abrogates the SASP and its debilitative effect in vitro. Elimination of senescent cells in aged mice (INK-ATTAC or wildtype mice treated with D+Q) in vivo activates resident CPCs (0.23±0.06% vs. 0.01±0.01% vehicle; p<0.05) and increased the number of small, proliferating Ki67-, EdU-positive cardiomyocytes (0.25±0.07% vs. 0.03±0.03% vehicle; p<0.05).
Conclusions Human CPCs become senescent with age, negatively impacting their regenerative capacity. Therapeutic approaches that eliminate senescent cells may alleviate cardiac deterioration with aging and rejuvenate the regenerative capacity of the heart.