Hypothesis

Clonal hematopoiesis (CH)–derived myeloid skewing elevates IL‑1β production, which in turn upregulates RANKL on osteo‑hematopoietic niche cells. This heightened RANKL drives osteoclast activation and bone resorption, releasing TGF‑β and calcium sequestrants that suppress erythropoietin (EPO) receptor signaling on erythroid progenitors. Consequently, EPO resistance in aged marrow stems from a CH‑IL‑1β–RANKL–osteoclast axis rather than solely from HSC‑intrinsic defects.

Mechanistic Rationale

Aged HSCs show myeloid bias and CH–associated TET2/DNMT3A mutations increase inflammasome activity, boosting IL‑1β secretion 2. IL‑1β stimulates stromal osteoblasts and mesenchymal stromal cells to express RANKL, a key osteoclast differentiation factor 5. Activated osteoclasts resorb bone matrix, liberating sequestered TGF‑β and extracellular calcium, both known to dampen EPOR‑JAK2‑STAT5 signaling in erythroid precursors 6. This creates a feedback loop where niche‑derived suppressive signals blunt EPO efficacy, independent of HSC intrinsic aging.

Testable Predictions

1. In aged mice with CH (e.g., Vav‑Cre Tet2fl/fl), serum IL‑1β and bone marrow RANKL levels will be elevated compared with age‑matched wild‑type controls.
2. Pharmacologic blockade of IL‑1β (using anakinra) or RANKL (using denosumab) will reduce osteoclast activity, lower trabecular bone loss, and restore erythroid response to a sub‑maximal EPO dose.
3. Ex vivo co‑culture of sorted erythroid progenitors with osteoclast‑conditioned medium will show decreased EPOR phosphorylation and STAT5 activation, an effect reversible by TGF‑β neutralizing antibodies.
4. CH‑mutant mice treated with IL‑1βR antagonist will exhibit improved hemoglobin levels without increasing malignancy incidence over a 6‑month period.

Experimental Approach

• Model: Use Tet2‑deficient CH mice aged 18–20 months; include WT littermates and CH mice receiving IL‑1βR or RANKL inhibitors.
• Readouts: Flow cytometry for HSC subsets, CFU‑E colonies, serum EPO, hemoglobin, bone micro‑CT for trabecular volume, TRAP staining for osteoclasts, ELISA for IL‑1β, RANKL, TGF‑β.
• Interventions: Sub‑maximal EPO (1 U/g) administered twice weekly; parallel groups receive anakinra (100 mg/kg i.p.) or denosumab (5 mg/kg s.c.) weekly.
• Analysis: Two‑way ANOVA with post‑hoc Tukey test to assess interaction between CH status and inhibitor treatment on erythropoietic output and bone parameters.

Potential Impact

Confirming this niche‑mediated EPO resistance mechanism would redirect therapeutic focus from escalating EPO doses—which exacerbate bone loss—to targeting the IL‑1β–RANKL–osteoclast axis. Such strategies could improve anemia correction while preserving skeletal integrity in elderly patients with CH, reducing fracture risk and healthcare burden.