Hypothesis

Targeted, transient expression of OSK (Oct4, Sox2, Klf4) in hematopoietic stem and progenitor cells (HSPCs) using a TCR‑driven inducible system will rejuvenate the immune compartment, reduce circulating senescent immune cells, and consequently lower systemic senescence burden in non‑lymphoid organs.

Rationale

• Aged immune cells drive inflammaging and paracrine senescence in distant tissues 1.
• Thymic involution forces reliance on peripherally expanded T cells that accumulate epigenetic age 3.
• Senescent immune cells potentiate OSK‑mediated reprogramming via p16^INK4a^ and IL-6, creating oncogenic risk 4.
• Limiting OSK expression to HSPCs and coupling it to transient TCR signaling restricts reprogramming to cells actively engaging antigen, providing a built-in safety switch.

Novel Mechanistic Insight

We propose that TCR-linked OSK activation induces a brief proliferative burst in HSPCs, generating a wave of naive T cells with reset epigenetic clocks. These youthful T cells enhance senescent-cell clearance via perforin/granzyme pathways and secrete IL-10, dampening inflammaging. The reduced inflammatory milieu lowers NF-kB activation in stromal cells, decreasing p21^CIP1^ expression and preventing secondary senescence induction. Thus, immune rejuvenation precedes and drives organ-level rejuvenation.

Testable Predictions

1. In aged mice, TCR-OSK induction will increase the proportion of CD62L^hi^ CD44^lo^ naive T cells by >30% within two weeks, measured by flow cytometry.
2. Epigenetic age of sorted naive T cells (using DunedinPACE) will decrease by >=5 years relative to baseline.
3. Serum IL-6 and TNF-alpha levels will drop >=25% concomitant with reduced p16^INK4a^+ cell counts in lung, liver, and kidney histology.
4. Transplant of TCR-OSK-reprogrammed immune cells into young recipients will confer resistance to accelerated aging induced by hematopoietic DNA damage (as in [1]).
5. Oncogenic incidence (lymphoma formation) will not exceed control groups when OSK expression is limited to <48 hours per pulse and administered no more than once monthly.

Falsifiability

If TCR-OSK induction fails to elevate naive T-cell frequencies or does not attenuate systemic senescence markers despite confirmed transgene expression, the hypothesis is refuted. Likewise, a significant increase in lymphoid malignancies would indicate unacceptable risk, falsifying the safety premise.