Engineered Plant Virus Complexes with a RANK Motif Modulator and Bone Targeting for Osteoporosis Treatment

Osteoporosis is a systemic skeletal disorder characterized by excessive osteoclastic bone resorption and impaired osteoblastic bone formation. Traditional delivery of antiresorptive drugs lacks a specific biodistribution in the body and may cause adverse effects to the patients. In this study, the peptide BTRM is first synthesized consisting of the bone-targeting peptide Asp8 (BT) and the peptide derived from the amino acid sequences of RANK Motif2/3 (RM), two cytoplasmic RANK motifs (PVQEET560-565 and PVQEQG604-609) that have been reported to play an important role in osteoclastogenesis. Then, BTRM is conjugated on the plant virus-like nanoparticles (VNPs) obtained from cowpea chlorotic mottle viruses (CCMVs), forming the engineered plant viruses BTRM-VNPs. In vitro experiments demonstrate that BTRM-VNPs can effectively and safely inhibit osteoclast differentiation and function. Moreover, after injection into ovariectomized mice, BTRM-VNPs show excellent capability to target bone tissue and improve osteoporotic bone loss. Collectively, the findings may provide a novel and promising strategy in the treatment of osteoporotic defects via targeting bone tissue and regulating the function of RANK Motif2/3.