Background: Senescent cells accumulate with ageing, including in the heart, and contribute to tissue deterioration. Due to their senescence-associated secretory phenotype (SASP) they negatively affect an organs’ microenvironment. Clearance of senescent cells, either genetically or pharmacologically using senolytics, has been shown to enhance cardiac function. Our group showed that eliminating senescent cells in aged mice using the senolytics, Dasatanib+Quercetin (D+Q) rejuvenated the heart’s regenerative potential, with progenitor cell activation, new cardiomyocyte formation, and improved cardiac function.

Aim: To investigate the effects of D+Q senolytics on cardiac recovery and remodelling in adult mice following isoproterenol-induced cardiac injury.

Methods: Male mice (~12 weeks) were subcutaneously administered with 150 mg kg^-1 isoproterenol (ISO; n=18) or saline (saline; n=18) for six consecutive days. Next, D (5 mg/kg) and Q (50 mg/kg) or vehicle (5% DMSO, 5% ethanol, 50%, polyethylene glycol, and 40% dH₂O) were administered for 5 consecutive days by oral gavage to each group. D+Q treatment started on day 5 after the last ISO or saline dose. The final groups were: ISO-D+Q, saline-D+Q, ISO-vehicle, saline-vehicle, n=9 per group. Echocardiography was performed at baseline, day 7 after ISO, and day 28 after the last D+Q dose. Excised hearts were analysed to assess the cardiac injury and fibrosis, cardiomyocyte hypertrophy, senescence, and SASP factors. ANOVA or Student's t-test was used to analyse the data between 4 groups or 2 groups, respectively.

Results: Ejection fraction and cardiac output decreased (p<0.05) in the ISO-treated group (n=18) compared to the saline group (n=18) on day 7. On day 28 after the last D+Q dose, ISO-D+Q treated mice had improved (p<0.05) ejection fraction and cardiac output (EF: 64.3 ± 5.4%; CO: 22.5 ± 3.9%; n=9) compared to the ISO-vehicle group (EF: 52.6 ± 5.7%; CO: 16.3 ± 3.4%; n=9). No changes were observed for cardiac function in the saline-vehicle (n=9) or the saline-D+Q (n=9) groups. D+Q treatment decreased (p<0.05) the expression of senescence marker, SA-β-gal in the ISO-D+Q group (0.5 ± 0.2%; n=3), compared to the ISO-vehicle group (2.8 ± 0.8%; n=3). Furthermore, the number of p21 cells decreased in the ISO-D+Q group (0.3 ± 0.1%; n=3), compared to the ISO-vehicle group (2.9 ± 0.4%; n=3). SA-β-gal and p21 were not detected in the saline-vehicle (n=3) or the saline-D+Q (n=3) groups. The mRNA expression of senescence markers, p16, p21 and SASP factors, including TGF-β2, IL-6, IL-1, and CXCL10 were decreased ~2-fold (p<0.05) in the ISO-D+Q group (n=3), compared to the ISO-vehicle group (n=3). Cardiomyocyte cross-sectional area was decreased (p<0.05) in the ISO-D+Q group (464.3 ± 59.9µm²; n=6) compared to the ISO-vehicle group (570 ± 69.9µm²; n=6). ISO-D+Q treatment did not significantly change fibrosis, compared to the ISO-vehicle group (ISO-D+Q:2.8 ± 1.9%; ISO-vehicle:3.9 ± 1.7%).

Conclusion: D+Q senolytics decreased senescence and SASP factors after ISO injury, which resulted in improved cardiac function. These findings support the use of senolytics as a potential therapeutic for cardiac injury and deterioration. Further pre-clinical and clinical studies are warranted.