Erythropoietin mediated bone loss in mice is dose-dependent and mostly irreversible

Recent studies have demonstrated that erythropoietin (EPO) treatment in mice results in trabecular bone loss. Here, we investigated the dose-response relationship between EPO, hemoglobin (Hgb) and bone loss and examined the reversibility of EPO-induced damage. Increasing doses of EPO over two weeks led to a dose-dependent increase in Hgb in young female mice, accompanied by a disproportionate decrease in trabecular bone mass measured by micro-CT (µCT). Namely, increasing EPO from 24 to 540 IU/week produced a modest 12% rise in Hgb (20.2 ± 1.3 mg/dL vs 22.7 ± 1.3 mg/dL), while trabecular bone volume fraction (BV/TV) in the distal femur decreased dramatically (27 ± 8.5% vs 53 ± 10.2% bone loss). To explore the long-term skeletal effects of EPO, we treated mice for two weeks (540 IU/week) and monitored bone mass changes after treatment cessation. Six weeks post-treatment, there was only a partial recovery of the trabecular microarchitecture in the femur and vertebra. EPO-induced bone loss is therefore dose-dependent and mostly irreversible at doses that offer only a minor advantage in the treatment of anemia. Because patients requiring EPO therapy are often prone to osteoporosis, our data advocate for using the lowest effective EPO dose for the shortest period of time to decrease thromboembolic complications and minimize the adverse skeletal outcome.