Mitochondrial ROS‑NLRP3 Axis Drives c‑Kit+ Cardiac Progenitor Senescence and Can Be Reversed by Mitophagy Induction

Hypothesis

We propose that mitochondrial ROS accumulation in aged c‑Kit+ cardiac progenitors activates the NLRP3 inflammasome, driving a senescent state marked by p16INK4A upregulation and a pro‑inflammatory SASP. This axis creates a feed‑forward loop that impairs progenitor function and sabotages the regenerative niche. Enhancing mitophagy (e.g., with Urolithin A or genetic PINK1 overexpression) will break this loop, reduce senescence, and restore regenerative capacity.

Mechanistic Rationale

1. Mitochondrial stress as the primary trigger – Aged myocardium shows increased ROS and mtDNA damage in stem‑like cells [https://www.nhlbi.nih.gov/events/2026/inflammation-associated-hsc-senescence-and-dysfunction-blood-and-cardiovascular]. In c‑Kit+ progenitors, ROS can oxidize cardiolipin, leading to NLRP3 inflammasome assembly.
2. NLRP3‑driven SASP – Active NLRP3 cleaves caspase‑1, processing IL‑1β and IL‑18, which reinforce senescence via NF‑κB signaling and sustain p16INK4A expression [https://doi.org/10.1111/acel.12931].
3. Mitophagy as a brake – PINK1/PARKIN‑mediated mitophagy removes damaged mitochondria, lowering ROS and NLRP3 activation. Evidence from hematopoietic stem cells shows that boosting mitophagy rescues senescence [https://www.nhlbi.nih.gov/events/2026/inflammation-associated-hsc-senescence-and-dysfunction-blood-and-cardiovascular]; we extrapolate this to cardiac progenitors.
4. Feedback amplification – Senescent c‑Kit+ cells secrete IL‑1α and TGF‑β that further impair mitochondrial function in neighboring progenitors, expanding the senescent pool.

Testable Predictions

• Prediction 1: In hearts from 24‑month‑old mice, c‑Kit+ cells will show higher mitochondrial ROS, NLRP3 activity, and p16INK4A+ frequency compared with 3‑month‑old controls.
• Prediction 2: Genetic overexpression of PINK1 specifically in c‑Kit+ cells (using c‑Kit‑CreERT2;Rosa26‑LSL‑PINK1) will reduce ROS, NLRP3 cleavage, and p16INK4A+ cells, and improve ejection fraction after myocardial infarction.
• Prediction 3: Pharmacological mitophagy inducer Urolithin A administered to aged mice will phenocopy the genetic rescue, decreasing SASP cytokines (IL‑1β, IL‑6) in cardiac interstitial fluid.
• Prediction 4: NLRP3 inhibition (MCC950) will similarly lower senescence markers, confirming the inflammasome’s mediating role.

Experimental Approach

• Isolation: Flow‑sort c‑Kit+ cells from young and aged mouse hearts; assess MitoSOX fluorescence, NLRP3 ASC speck formation, and western blot for p16INK4A and cleaved caspase‑1.
• Genetic model: Generate c‑Kit‑CreERT2;Rosa26‑LSL‑PINK1 mice; tamoxifen induce at 20 months; evaluate senescence and function 4 weeks post‑MI.
• Pharmacology: Treat aged mice with Urolithin A (50 mg/kg/day) or MCC950 for 4 weeks; measure same endpoints.
• Functional readouts: Echocardiography (EF, FS), scar size (Masson’s trichrome), and progenitor colony‑forming unit‑fibroblast (CFU‑F) assays.
• SASP profiling: Luminex assay of IL‑1β, IL‑6, TGF‑β in cardiac interstitial fluid collected via perfusion.

If predictions hold, the mitochondrial ROS‑NLRP3‑mitophagy axis would be a mechanistically justified target for rejuvenating the c‑Kit+ progenitor pool in aged myocardium, directly addressing the current knowledge gap.