IF a sequential two-phase intervention — Phase A: systemic senolytic preconditioning with dasatinib (5 mg/kg) plus quercetin (50 mg/kg, oral gavage, days 3–4 and 11–12 post-MI, mirroring established D+Q dosing protocols) (Senolytics reduce coronavirus-related mortality)[https://doi.org/10.1126/science.abe4832], followed by Phase B: intramyocardial AAV6-GMT (Gata4, Mef2c, Tbx5) vector delivery at day 14 post-MI — is administered to aged (20–24 month) C57BL/6J male mice subjected to permanent left anterior descending (LAD) coronary artery ligation, with Tcf21-CreERT2; Rosa26-tdTomato dual-reporter lineage tracing to identify converted fibroblasts,

THEN the rate of Tcf21-lineage+ fibroblast-to-induced cardiomyocyte (iCM) conversion will increase by ≥3-fold compared to GMT-alone controls in aged mice (as measured by co-expression of tdTomato with cardiac troponin T [cTnT] and α-actinin at 4 weeks post-vector delivery, quantified by flow cytometry and confocal imaging), accompanied by a ≥5 percentage-point improvement in left ventricular ejection fraction (LVEF by echocardiography), ≥20% reduction in infarct scar area (Masson's trichrome), and suppression of SASP cytokines (IL-6, IL-1β, TGFβ1) in the peri-infarct zone,

BECAUSE the following mechanistic chain operates:

1. LAD ligation in aged mice triggers accumulation of p16^INK4a+/p21+/SA-β-gal+ senescent cardiac fibroblasts in the peri-infarct zone at densities far exceeding those seen in young infarcted hearts; these cells constitutively secrete a SASP dominated by TGFβ1, IL-6, and IL-1β (Aged-senescent cells contribute to impaired heart regeneration)[https://doi.org/10.1111/acel.12931], creating a non-permissive molecular environment for lineage conversion. [SPECULATIVE: the quantitative SASP burden in aged post-MI mouse hearts specifically has not been directly benchmarked against young controls in the 2023–2025 literature.]

2. Even small numbers of senescent cells are sufficient to impose systemic and local dysfunction by inducing bystander senescence and amplifying inflammation in neighboring cells (Senolytics Improve Physical Function and Increase Lifespan in Old Age)[https://doi.org/10.1038/s41591-018-0092-9]; in the infarct border zone, this means that a minority population of senescent fibroblasts can dysregulate the entire fibroblast pool, including the Tcf21+ subpopulation that represents the primary reprogramming substrate (Tcf21-CreERT2 lineage tracing validates fibroblasts as reprogramming source)[https://pmc.ncbi.nlm.nih.gov/articles/PMC3357908/].

3. D+Q at the established protocol (5 mg/kg dasatinib + 50 mg/kg quercetin) selectively eliminates Bcl-2/Bcl-xL-dependent senescent cells — including senescent cardiac progenitor cells and senescent fibroblasts — while sparing proliferating or quiescent cells; critically, candidate senolytics including dasatinib, quercetin, fisetin, and navitoclax were validated in dose-response studies to selectively clear senescent CPCs and abrogate t...

SENS category: GlycoSENS

Key references: • doi.org/10.1126/science.abe4832], • doi.org/10.1111/acel.12931], • doi.org/10.1038/s41591-018-0092-9]; • doi.org/10.1111/acel.12931]. • doi.org/10.1007/s11357-022-00542-2]