Hypothesis

Immune-targeted partial reprogramming of hematopoietic stem and progenitor cells (HSPCs) will restore mitochondrial NAD+ biosynthesis, thereby reversing the senescence-associated secretory phenotype (SASP) of circulating leukocytes and attenuating systemic aging.

Mechanistic rationale

• Senescent immune cells exhibit defective mitochondrial oxidative phosphorylation and reduced NAD+ levels, which drive a pro-inflammatory SASP via NF‑κB activation [3].
• Partial expression of Yamanaka factors (Oct4, Sox2, Klf4, c‑Myc) in HSPCs has been shown to rejuvenate cellular metabolism without erasing lineage identity [5].
• Restoring NAD+ flux through upregulation of the salvage pathway enzyme NAMPT suppresses SASP by deacetylating NF‑κB p65, reducing cytokine production and senescence spread [4].
• Because immune cells continuously traffic through all tissues, rejuvenating the hematopoietic compartment should dilute senescent leukocyte burden and interrupt the propagation of senescence to parenchymal organs.

Testable predictions

1. Mouse model: HSPC‑specific, doxycycline‑inducible expression of OCT4/SOX2/KLF4/c‑Myc (OSKM) for 48 h weekly will increase NAD+/NADH ratio in bone‑marrow‑derived leukocytes by ≥30 % after 4 weeks [1].
2. SASP attenuation: Plasma levels of IL‑6, TNF‑α, and CXCL10 will drop ≥25 % relative to control aged mice, correlating with reduced p16^INK4a^ expression in liver, kidney, and muscle [2].
3. Functional rejuvenation: Treated aged mice will exhibit improved grip strength (+15 %) and treadmill endurance (+20 %) compared with vehicle controls after 8 weeks of intervention.
4. Falsification: If NAD+ restoration fails to lower SASP markers despite HSPC reprogramming, the hypothesis that immune mitochondrial NAD+ drives systemic senescence is refuted.

Experimental approach

• Generate Vav‑iCreERT2; Rosa26‑LSL‑OSKM mice; administer tamoxifen to induce Cre in hematopoietic lineage, then doxycycline pulses for transient OSKM expression.
• Control groups: Vav‑iCreERT2; Rosa26‑LSL‑GFP + doxycycline, and wild‑type aged mice receiving vehicle.
• Measure NAD+ metabolites by LC‑MS/MS in sorted CD45^+ leukocytes, SASP cytokines by ELISA, senescence burden by p16^INK4a^ immunohistochemistry, and physiological aging markers.

Impact: Demonstrating that rescuing mitochondrial NAD+ in circulating immune cells reprograms systemic aging would shift gerotherapeutic focus from tissue‑specific senolytics to a rejuvenating immune hub, offering a single‑cell‑type intervention with organism‑wide benefits.