The Role of Micrornas in Osteoarthritis and Ageing-Related Functional Decline in Joint Tissue Homeostasis

Abstract

Purpose: Osteoarthritis is a degenerative disease associated with changes in the articular cartilage and bone, severely affecting patients' mobility and quality of life. A similar, but less acute decline is also seen during ageing. microRNAs (miRs) are novel post-transcriptional regulators of gene expression. microRNAs have been implicated in different aspects of musculoskeletal ageing through their differential expression, however the functional consequences of this are still not fully understood. Methods: Wild type C57BL6/J adult (3–6 months old) mice and human cartilage explants from knee replacement surgeries were used. To study microRNA function in vivo, modified microRNA antagomiR was delivered via intraarticular injection into knee joints of mice or via transfection into the human explants. Knee joints were dissected for histological assessment or RNA isolation. Human cartilage explants were cultured with IL-1β, miR mimic and/or antagomiR. Fixed joints and explants were subsequently decalcified and processed for wax embedding. Serial coronal sections were stained with Safranin O at regular intervals across the joint, and scored for articular cartilage degradation severity, using the OARSI grading system (from grades 0–6). RNA was used for microRNA and mRNA profiling using high-throughput sequencing and subsequently qPCR. Results: Our data shows dysregulation of miR-199 in human and mouse models of OA. Using qPCR and luciferase assays, we validated a selection of the microRNAs target genes differentially expressed in mouse femorotibial joints and human cartilage explants models of OA. miR-199 was further analysed using in vitro and in vivo gain- and loss-of-function approaches. Conclusions: In summary, we have shown the regulation of OA-associated target genes by miR-199 in the in vitro and in vivo models of OA and have shown that dysregulation of miR-199 expression may contribute to the pathogenic phenotype in the OA models. The authors would like to acknowledge financial support from the MRC-Arthritis Research UK Centre for Integrated research into Musculoskeletal Ageing (CIMA) and BBSRC.