IF synthetic mitochondrial N-formyl peptide (fMLF; 10–100 nM, intracoronary micro-infusion over 60 seconds) is administered as a macropinocytosis-priming pre-treatment, followed immediately by intracoronary delivery of high-quality allogeneic donor mitochondria (10⁸ organelles/mL, isolated from young syngeneic skeletal muscle and quality-filtered by JC-1 membrane potential above 0.9 ΔΨm threshold) to aged (22–24 month) male C57BL/6J mice with documented cardiac mtDNA mutational burden, in the absence of surgical ischemia,

THEN donor mitochondrial retention at 7 and 28 days post-delivery will be significantly greater than in unprimmed allogeneic delivery controls (≥3-fold increase in absolute donor mtDNA copies by droplet digital PCR), and this retention will produce a measurable heteroplasmy shift (≥15% reduction in mutant:wildtype mtDNA ratio by long-range nanopore sequencing) in the left ventricular free wall, alongside ≥20% improvement in left ventricular ejection fraction (LVEF) by echocardiography compared to age-matched vehicle controls,

BECAUSE the following mechanistic cascade is proposed:

1. Aged cardiomyocytes accumulate clonally expanded mutant mtDNA (deletions and point mutations), impairing Complex I/IV activity and reducing ATP synthesis capacity — per the literature synthesis on MitoSENS damage accumulation described in the evidence set (McCully et al., American Journal of Physiology-Heart and Circulatory Physiology, as cited in evidence set).
2. Exogenous mitochondrial transplantation rescues this deficit, but uptake by cardiomyocytes is actin-dependent macropinocytosis, a process that requires cellular priming — (cardiomyocytes internalize exogenous mitochondria via actin-dependent endocytosis/macropinocytosis within 10–30 minutes of exposure, per Cowan et al., 2016, as cited in evidence set).
3. Standard delivery protocols rely on 30-minute LAD ischemia to create the tissue microenvironment that enables this priming — (published studies showing optimal mitochondrial uptake used 30-minute ischemia followed by delivery at reperfusion onset, per Research Context in evidence set) — but this approach inflicts additional damage that is antithetical to a longevity/repair context.
4. The priming mechanism of ischemia is, in significant part, DAMP-mediated: ischemic cardiomyocytes release N-formyl peptides from damaged mitochondria, which activate formyl peptide receptors (FPR1/FPR2) on surviving cardiomyocytes, upregulating macropinocytotic machinery — (allogeneic mitochondria themselves carry DAMPs including N-formyl peptides and unmethylated CpG DNA that activate innate immune pattern recognition, per Ramirez-Barbieri et al., Journal of Thoracic and Cardiovascular Surgery, as cited in evidence set) [SPECULATIVE: that FPR1/FPR2 activation is the dominant upstream signal for macropinocytosis priming, rather than general inflammatory cytokine release].
5. Sub-inflammatory exogenous fMLF (below the threshold that triggers NLRP3 inf...

SENS category: LysoSENS