Bone-Targeting AAV-Mediated Gene Silencing in Osteoclasts for Osteoporosis Therapy

Yeon-Suk Yang,Jun Xie,Sachin Chaugule,Dan Wang,Jung-Min Kim,Jihea Kim,Phillip W.L Tai,Seok-Kyo Seo,Ellen Gravallese,Guangping Gao,Jae-Hyuck Shim

doi:10.1016/j.omtm.2020.04.010

Abstract

Improper activity of bone-resorbing osteoclasts results in low bone density and deterioration of bone structure, which increase the risk of fractures. Anti-resorptive therapies targeting osteoclasts have proven effective in preserving bone mass, but these therapeutic agents lead to defective new bone formation and numerous potential side effects. In this study, we demonstrate that recombinant adeno-associated virus, serotype 9 (rAAV9) can deliver to osteoclasts an artificial microRNA (amiR) that silences expression of key osteoclast regulators, RANK (receptor activator for nuclear factor κB) and cathepsin K (rAAV9.amiR-rank, rAAV9.amiR-ctsk), to prevent bone loss in osteoporosis. As rAAV9 is highly effective for the transduction of osteoclasts, systemic administration of rAAV9 carrying amiR-rank or amiR-ctsk results in a significant increase of bone mass in mice. Furthermore, the bone-targeting peptide motif (Asp)14 or (AspSerSer)6 was grafted onto the AAV9-VP2 capsid protein, resulting in significant reduction of transgene expression in non-bone peripheral organs. Finally, systemic delivery of bone-targeting rAAV9.amiR-ctsk counteracts bone loss and improves bone mechanical properties in mouse models of postmenopausal and senile osteoporosis. Collectively, inhibition of osteoclast-mediated bone resorption via bone-targeting rAAV9-mediated silencing of ctsk is a promising gene therapy that can preserve bone formation and mitigate osteoporosis, while limiting adverse off-target effects.

Highlights

Osteoporosis is an aging-associated disease marked by bone loss and deterioration of the bone microstructure.[1]
RAAV9 Can Effectively Transduce OCs Our previous study demonstrated that systemic delivery of rAAV9 in mice can transduce osteoblast-lineage cells and OCs residing on the bone surface (BS).[26]
Since OCs originate from hematopoietic stem cells (HSCs) in the bone marrow, we explored the ability of rAAV9 to transduce other HSClineage cells. rAAV9.EGFP was intravenously (i.v.) injected into 2-month-old mice and the tissue distribution of rAAV9 was assessed by EGFP expression using IVIS optical imaging (Figure S1)

Summary

Introduction

Osteoporosis is an aging-associated disease marked by bone loss and deterioration of the bone microstructure.[1]. Most existing therapeutic agents for osteoporosis are anti-resorptive agents, such as bisphosphonates and anti-RANKL (receptor activator of nuclear factor kB ligand) antibody, inhibitors of osteoclast (OC) differentiation and bone resorption. Their effectiveness is limited by an inability to promote new bone formation, as OC-mediated bone resorption is coupled with osteoblast-mediated bone formation during remodeling.[2,3] these agents are accompanied by potential adverse effects, including atypical fractures and osteonecrosis of the jaw.[4,5] the development of anti-resorptive therapies that can preserve osteoblast function while limiting off-target side effects is still an unmet need

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