Hypothesis

In rheumatoid arthritis (RA), senescent osteocytes accumulating in periarticular bone secrete IL-6 that activates JAK/STAT3 trans-signaling in neighboring synovial fibroblasts, leading to transcriptional suppression of DNMT3a. This DNMT3a deficit causes progressive CpG hypomethylation at Horvath clock loci, accelerating biological aging by 5–8 years beyond chronological age.

Testable Predictions

Selective clearance of p16^INK4a+ osteocytes using dasatinib + quercetin (D+Q) in collagen-induced arthritis (CIA) mice will:

1. Reduce synovial IL-6 trans-signaling measured by soluble gp130 levels (>50% reduction vs vehicle)
2. Restore DNMT3a expression in synovial tissue by >40%
3. Decelerate the epigenetic clock (murine Horvath-equivalent methylation arrays) by ≥2 predicted years over 12 weeks

Rationale

While senolytic therapy shows promise in osteoarthritis, the specific mechanism linking senescent osteocytes to epigenetic aging acceleration through IL-6/DNMT3a crosstalk remains unexplored. RA patients exhibit both accelerated epigenetic aging (Horvath & Raj, 2018) and elevated senescent cell burden, but no causal chain has been dissected.

This hypothesis bridges geroscience and autoimmune rheumatology by proposing osteocyte senescence as the upstream driver of biological age acceleration — not merely a consequence of chronic inflammation.

Key Controls

• Positive control: IL-6 receptor blockade (tocilizumab analog) to confirm the signaling axis
• Mechanistic control: DNMT3a conditional knockout in synovial fibroblasts to test whether epigenetic effects are independent of inflammation reduction
• Aging control: Non-arthritic aged mice to distinguish disease-driven from age-driven senescence

Falsification Criteria

The hypothesis is falsified if D+Q clears senescent osteocytes but fails to restore DNMT3a or decelerate epigenetic aging, suggesting alternative pathways dominate clock acceleration in RA.