Senolytics and Exercise Both Clear Aging Heart Cells and Restore Cardiac Function

Cardiac aging is driven in large part by the accumulation of senescent cells — cardiomyocytes, fibroblasts, and endothelial cells that have entered irreversible cell-cycle arrest, secrete pro-inflammatory factors (the SASP), and impair ventricular relaxation and contractility. Despite growing evidence that senolytics and aerobic exercise independently reduce senescence in various tissues, no study had evaluated either as a long-term preventive cardiac strategy, and none had combined them. This study from McMaster and Brock universities is the first to do both, running interventions for 9 months in aging mice — the longest senolytic cardiac study to date.

Male and female C57BL/6N mice aged 12 months were randomized into four groups and treated until 21 months: vehicle control (VEH, n=12), aerobic treadmill exercise (EX, n=11), dasatinib + quercetin senolytics (SEN, n=15), or both combined (SENEX, n=16). A separate cohort of young mice (4 months) served as a reference. Senescence was quantified at the single-cell level using immunofluorescence for p16, p21, and γ-H2AX in cardiomyocytes and interstitial cells. Cardiac function was assessed by high-frequency ultrasound including ejection fraction, fractional shortening, E/A ratio (diastolic index), and myocardial performance index (MPI). Whole-heart protein expression of p16, p21, and SASP components was also measured by Western blot.

All three interventions — EX, SEN, and SENEX — significantly reduced the proportion of p16+, p21+, and γ-H2AX+ cardiomyocytes and interstitial cells compared to VEH mice (p<0.05 for all). For example, senescent cardiomyocyte burden was substantially lower in treated groups, approaching levels seen in young mice. Diastolic function, measured by E/A ratio, was significantly higher in EX, SEN, and SENEX compared to VEH (p<0.05), reflecting improved ventricular relaxation. Ejection fraction and fractional shortening were also significantly improved in all intervention groups versus VEH (p<0.05). The myocardial performance index — a composite of systolic and diastolic timing — was significantly better in treated groups, indicating overall preserved myocardial efficiency.

A key null finding was that combining senolytics with exercise (SENEX) did not produce additive or synergistic improvements over either intervention alone across any outcome measured. This challenges the hypothesis that the two strategies operate through sufficiently distinct mechanisms to compound their effects. At the whole-heart level, Western blot analysis showed that p16 and p21 protein expression increased with age in VEH mice but was not significantly altered by any intervention, and SASP markers (IL-6, TNF-α, NF-κB, TGF-β) were similarly unchanged. This dissociation between cellular-level senescence clearance and whole-tissue protein expression is an important methodological caveat: immunofluorescence cell-counting detected intervention effects that bulk protein assays missed, underscoring the value of single-cell resolution in senescence research.

Anthropometric data showed no significant differences in body weight, relative heart weight, or left ventricular mass among the aged intervention groups, ruling out cardiac hypertrophy as a confound. Heart rate was slightly elevated in SENEX versus young mice but otherwise consistent. The study's 9-month duration — more than four times longer than prior D+Q cardiac studies — provides novel evidence that chronic senolytic treatment is both feasible and effective without apparent adverse structural remodeling. These findings firmly establish long-term aerobic exercise and D+Q senolytics as mechanistically grounded strategies to mitigate age-related cardiac dysfunction, and set the stage for translational trials in humans.