Senescent c-Kit+ CPCs trigger NLRP3 inflammasome activation via mtDNA release, amplifying PANoptosis and blocking cardiac regeneration

Hypothesis: Senescent c‑Kit+ cardiac progenitor cells (CPCs) release mitochondrial DNA (mtDNA) into the extracellular space, which acts as a danger‑associated molecular pattern (DAMP) that activates the NLRP3 inflammasome in neighboring cells. This NLRP3‑driven PANoptosis creates a vicious cycle: inflammasome signaling reinforces senescence in CPCs, amplifies the senescence‑associated secretory phenotype (SASP), and impairs the regenerative potential of the residual progenitor pool. Clearing senescent CPCs or blocking mtDNA‑NLRP3 signaling should break this loop and restore cardiac repair.

Mechanistic Rationale

1. mtDNA as a DAMP – Damaged mitochondria in senescent CPCs release mtDNA through vesicles or necrosis. Extracellular mtDNA engages TLR9 and the NLRP3 inflammasome, leading to caspase‑1 activation and IL‑1β/IL‑18 maturation (4).
2. NLRP3 inflammasome fuels PANoptosis – NLRP3 activation triggers caspase‑1‑dependent pyroptosis, apoptosis and necroptosis (PANoptosis) in adjacent CPCs and cardiomyocytes, expanding the senescent burden (4).
3. Feedback to SASP – Inflammasome‑derived cytokines (IL‑1β, IL‑18) amplify NF‑κB signaling, reinforcing SASP production (e.g., IL‑6, CXCL1) from senescent CPCs (1).
4. Impact on c‑Kit signaling – Chronic inflammasome activity induces oxidative stress that further impairs MAPK/ERK and AKT phosphorylation downstream of c‑Kit, limiting progenitor activation (2).

Testable Predictions

• Prediction 1: Aged hearts will show elevated extracellular mtDNA in the interstitial space, co‑localized with NLRP3 specks and caspase‑1 activity in CPCs.
• Prediction 2: Genetic or pharmacologic inhibition of NLRP3 (e.g., MCC950) in aged mice will reduce PANoptosis markers (cleaved caspase‑3, MLKL phosphorylation, GSDMD cleavage) and lower SASP levels without altering senescent CPC numbers.
• Prediction 3: Combined senolytic treatment (dasatinib+quercetin) with NLRP3 inhibition will produce synergistic improvements in CPC proliferation (Ki67+, EdU+), cardiomyogenic differentiation, and functional recovery after ischemia‑reperfusion injury compared with either intervention alone.
• Prediction 4: Neutralizing extracellular mtDNA with anti‑mtDNA antibodies or using TLR9 antagonists will phenocopy NLRP3 inhibition, confirming mtDNA as the upstream trigger.

Experimental Approach

• Isolate CPCs from young (3 mo) and aged (24 mo) mouse hearts; measure mtDNA release via qPCR of cytosolic fractions and extracellular vesicles.
• In vivo: Treat aged mice with (i) senolytics, (ii) NLRP3 inhibitor MCC950, (iii) both, (iv) vehicle. Assess senescence (p16, SA‑β‑gal), inflammasome activation (ASC specks, caspase‑1), PANoptosis markers, SASP cytokine panel, and cardiac function (echocardiography, pressure‑volume loops) after MI.
• In vitro: Co‑culture senescent CPCs with healthy CPCs; add mtDNA or TLR9/NLRP3 inhibitors; read out proliferation, differentiation, and SASP.
• Human relevance: Examine atrial appendage samples from patients ≥70 yr for extracellular mtDNA and NLRP3 activation; correlate with senescent CPC burden.

If extracellular mtDNA‑NLRP3 signaling drives a feed‑forward loop that locks CPCs into senescence and blocks regeneration, interrupting this axis should rescue the aged heart’s repair capacity, providing a mechanistic bridge between cellular senescence and inflammasome‑mediated cell death.