The nanoformula of zoledronic acid and calcium carbonate targets osteoclasts and reverses osteoporosis

Osteoporosis is known as an imbalance in bone catabolism and anabolism. Overactive bone resorption causes bone mass loss and increased incidence of fragility fractures. Antiresorptive drugs are widely used for osteoporosis treatment, and their inhibitory effects on osteoclasts (OCs) have been well established. However, due to the lack of selectivity, their off-target and side effects often bring suffering to patients. Herein, an OCs' microenvironment-responsive nanoplatform HA-MC/CaCO3/ZOL@PBAE-SA (HMCZP) is developed, consisting of succinic anhydride (SA)-modified poly(β-amino ester) (PBAE) micelle, calcium carbonate shell, minocycline-modified hyaluronic acid (HA-MC) and zoledronic acid (ZOL). Results indicate that HMCZP, as compared with the first-line therapy, could more effectively inhibit the activity of mature OCs and significantly reverse the systemic bone mass loss in ovariectomized mice. In addition, the OCs-targeted capacity of HMCZP makes it therapeutically efficient at sites of severe bone mass loss and allows it to reduce the adverse effects of ZOL, such as acute phase reaction. High-throughput RNA sequencing (RNA-seq) reveals that HMCZP could down-regulate a critical osteoporotic target, tartrate-resistant acid phosphatase (TRAP), as well as other potential therapeutical targets for osteoporosis. These results suggest that an intelligent nanoplatform targeting OCs is a promising strategy for osteoporosis therapy.