Transient OSK mRNA reprogramming amplifies senomorphic pretreatment to boost senolytic clearance and tissue rejuvenation

Hypothesis

Transient expression of the Yamanaka factors OCT4, SOX2, KLF4 (OSK) via mRNA lipid nanoparticles, administered after a short senomorphic pretreatment, will potentiate senolytic clearance of senescent cells and improve tissue rejuvenation beyond senolytic monotherapy.

Mechanistic Rationale

• Senomorphic agents such as rapamycin (mTOR inhibitor) and JAK inhibitors suppress the SASP, lowering the inflammatory milieu that protects senescent cells from apoptosis [Senolytics and senomorphics overview].
• Partial epigenetic reprogramming with OSK remodels chromatin at senescence‑associated heterochromatin foci and reduces expression of anti‑apoptotic BCL‑2 family members, thereby sensitizing cells to senolytic‑induced death [Network transcriptomic methods].
• OSK also reactivates naïve pluripotency networks that dilute SASP‑driven transcriptional programs, an effect observed with BET inhibitors but acting upstream at the epigenetic level [BET inhibitors repress SASP]
• The combination creates a 'two‑hit' window: first, SASP dampening reduces systemic toxicity; second, OSK‑mediated chromatin loosening lowers the threshold for senolytic apoptosis, allowing lower doses or shorter exposure.

Experimental Design (testable & falsifiable)

1. Animal model: 20‑month‑old C57BL/6 mice (n=10 per group).
2. Groups:
   • Vehicle control
   • Senolytic only (D+Q 5 mg/kg dasatinib + 50 mg/kg quercetin, i.p., days 1 and 3)
   • Senomorphic pretreatment (rapamycin 6 mg/kg + JAK inhibitor ruxolitinib 50 mg/kg, daily days 1‑3) → senolytic (same D+Q schedule)
   • Senomorphic pretreatment → OSK mRNA LNP (2 doses 1 µg each, days 2‑4) → senolytic
   • OSK mRNA LNP alone → senolytic (to control for OSK effect without senomorphics)
3. Readouts (day 7 post‑senolytic):
   • Senescent cell burden via p16^Ink4a^ immunohistochemistry and flow cytometry for Cd9^+Ly6C^- cells [Senolytics and senomorphics overview]
   • SASP cytokines (IL‑6, IL‑8) in serum ELISA [JAK inhibitors block IL‑6/IL-8‑mediated SASP amplification]
   • Tissue‑specific functional assays: grip strength, treadmill endurance, and hippocampal‑dependent memory (novel object recognition)
   • Transcriptomic age using Pasta clock [Pasta transcriptomic age clock]
   • Off‑target apoptosis in liver and kidney (cleaved caspase‑3 IHC) to assess safety

Expected Outcomes

If the hypothesis holds, the OSK‑augmented group will show:

• ≥30 % greater reduction in p16^+ cells vs senolytic alone
• Lower serum SASP levels than senomorphic‑only pretreatment
• Improved physical and cognitive performance exceeding all other groups
• A younger transcriptomic age (ΔPasta <= -1.5) without increased off‑target apoptosis.

Falsifiability

If OSK mRNA does not further decrease senescent cell burden or improve functional outcomes beyond senomorphic‑pretreatment plus senolytic, or if it increases off‑target toxicity, the hypothesis is falsified. This outcome would indicate that transient epigenetic reprogramming does not sensitize senescent cells to senolysis under these conditions.

Broader Impact

Positive results would justify integrating transient epigenetic reprogramming into senotherapeutic protocols, potentially lowering required senolytic doses and expanding the therapeutic window for age‑related diseases such as idiopathic pulmonary fibrosis, Alzheimer’s, and diabetic kidney disease [SToMP-AD trial], [TAME trial], [D+Q improved physical function].