Topically administered Risedronate shows powerful anti-osteoporosis effect in ovariectomized mouse model

We investigated the therapeutic effect of topical Risedronate (RIS) on a mouse model of estrogen-deficient osteoporosis. Fourteen-week-old female mice were ovariectomized and assigned to 4 groups: SHAM-operated (SHAM), OVX mice treated with vehicle (OVX-V), OVX mice treated with 0.2% RIS (OVX-0.2% RIS), and OVX-mice treated with 0.02% RIS (OVX-0.02% RIS). Topical samples containing RIS were prepared in 10% (w/w) polyethylene glycol (PEG, MW 400) and 80 μg of sample was spread on the mice's mid-backs every 3 days for 5 weeks. Micro-CT analysis of femora demonstrated that OVX-0.2% RIS exhibited a 29% greater bone mineral density and 24% greater bone volume fraction than that of OVX-V group. Investigation of the trabecular bone in OVX-0.2% RIS revealed a 24% higher bone volume (BV/TV), 51% higher trabecular number (Tb.N), and 40% lower trabecular separation (Tb.Sp) compared to OVX-V mice. Additionally, bone phenotypes of tibiae were further confirmed by histological analysis. OVX-0.2% RIS group exhibited a 494% greater BV/TV, 464% less Tb.Sp, 81% greater active osteoclast surface (Oc.S/BS) and 26% less osteoclast number (N.Oc/BS) than that of OVX-V group. Collectively, these results indicated that topical delivery of RIS has powerful pharmaceutical effects on the prevention of osteoporosis and bone turnover.