Osteophyte deposition and subchondral bone damage are notable features of osteoarthritis (OA). Deregulated mineralization contributes to osteophyte and subchondral irregularity. The microRNA-29 (miR-29) family is associated with arthritic disorders. This study is aimed to investigate miR-29a function to OA osteophyte formation and subchondral integrity. Intact and damaged articular cartilage in patients with end-stage knee OA who required total knee arthroplasty were harvested to probe miR-29a, cartilage, and mineralized matrix expression using RT-PCR and in situ hybridization. Osteophyte volume and subchondral morphometry of collagenase-induced OA knees in mice were quantified using μCT and histomorphometry. Increased bone matrix expression (collagen I and bone alkaline phosphatase) and reduced cartilage matrix (collagen II and aggrecan) along with low miR-29a expression existed in human OA specimens. Aged miR-29a knockout mice showed spontaneous osteophyte formation and articular cartilage erosion. In primary articular chondrocytes, miR-29a deficiency significantly reduced cartilage matrix synthesis, whereas von Kossa staining-positive mineralized matrix production was increased. Of interest, the severity of collagenase-induced osteophyte accumulation and subchondral damage along with serum cartilage breakdown products CTX-II and COMP levels were significantly compromised in mice overexpressing miR-29a. Intra-articularly injecting miR-29a significantly reduced osteophyte volume and subchondral integrity and retained cartilage morphology in collagenase-injured knees. Reduced miR-29a signalling worsens osteophyte and subchondral destruction in OA through increasing mineralized matrix formation of chondrocytes. Restoring miR-29a shields joints from cartilage degradation, osteophyte and subchondral destruction. This study conveys new mechanistic underlying OA osteophyte pathogenesis and shines light on the remedial potential of miR-29a to OA.

Introduction

Excessive bone mass and microarchitecture loss exacerbate the risk of osteoporotic fracture, a skeletal disorder attributable to disability in the elder. Excessive marrow adipose development at the expense of osteoblastic bone acquisition is a prominent feature of aging-induced osteoporotic skeletons. MicroRNA-29a (miR-29a) modulates osteogenic and adipogenic commitment of mesenchymal progenitor cells. The purposes of this study were to test if miR-29a overexpression changed bone mass or microstructure in aged skeletal tissues.

Introduction

Osteoarthritis (OA) of the knee, a prevalently degenerative joint disorder provoked by articular cartilage loss, accounts for the leading cause of total knee arthroplasty. Autophagy is an indispensable intracellular event that maintains chondrocyte survival and metabolism. MicroRNAs are non-coding small RNAs participating in tissue morphogenesis, remodeling, and homeostasis. This study was undertaken to investigate the effect of microRNA-128 (miR-128) knockdown on the development of OA knees.