Osteoclast-targeted delivery of anti-miRNA oligonucleotides by red blood cell extracellular vesicles.

Osteoporosis (OP) affects millions worldwide but currently cannot be cured. Suppressing the level of miR-214 in osteoclasts by the anti-miRNA oligonucleotide (AMO) anti-miR-214 reverses bone absorption and provides a potential treatment. Here we report a peptide-guided delivery strategy using red blood cell extracellular vesicles (RBCEVs) as the vehicle to realize osteoclast-targeted delivery of anti-miR-214. A bi-functional peptide, TBP-CP05, which binds to both the CD63 on RBCEVs and receptors on osteoclasts, acts as the guide. TBP-CP05 binds with RBCEVs through CP05, displays the TRAP-binding peptide (TBP) on the surface of EVs, and endows RBCEVs with osteoclast-targeting capability both in vitro and in vivo. Intravenous injection of the osteoclast-targeting RBCEVs (OT-RBCEVs) led to the enrichment of EVs in the bone skeleton, significant inhibition of the osteoclast activity, elevated osteoblast activity, and improved bone density in osteoporotic mice. Altogether, this work demonstrates efficient guidance of drug-loaded EVs to the targeted cells in vivo using bi-functional fusion peptides, and showcases that targeted delivery of anti-miR-214 by OT-RBCEVs may be a viable method for OP treatment. SIGNIFICANCE STATEMENT. Surface functionalization of EVs endows these nanovesicles cell-specific targeting property which guides the drug cargos to specific tissues and cells with higher accuracy, longer retention, and minimal off-target effects. Methods to functionalize EVs with minimal procedures are highly desired for clinical applications. Here we present a facile method using a bifunctional fusion peptide to guide RBCEVs to osteoclasts. A simple incubation of the bifunctional peptide and RBCEVs results in osteoclast-targeting RBCEVs (OT-RBCEVs) that effectively deliver anti-miR-214 to osteoclasts in vivo in a mouse model of osteoporosis, bringing a potential therapy to osteoporotic patients. This is, to our knowledge, the first report on peptide functionalization of RBCEVs and osteoclast-targeted delivery using RBCEVs.