MicroRNAs: exploring new horizons in osteoarthritis.

INTRODUCTION: Osteoarthritis (OA) is a common disease worldwide leading to significant morbidity. The underlying disease process is multifactorial however there is increasing focus on molecular mechanisms. MicroRNAs are small non-coding segments of RNA that have important regulatory functions at a cellular level. These molecules are readily detectable in human tissues and circulation. They are increasingly recognised as having a major role in many disease processes - including malignancy and inflammatory processes.

OBJECTIVE: This review paper aims to provide a comprehensive update on the evidence for miRNA roles in OA.

DESIGN: A comprehensive literature search was performed using key medical subject headings (MeSH) terms 'microRNA' and 'osteoarthritis'.

RESULTS: Several miRNAs have been identified as having aberrant expression levels in OA. Some of these include miR-9, miR-27, miR-34a, miR-140, miR-146a, miR-558 and miR-602. Many of the dysregulated miRNAs have been shown to regulate expression of inflammatory pathways such as interleukin-mediated or matrix metalloproteinase-13 (MMP-13)-mediated degradation of the articular cartilage extracellular matrix (ECM). MiRNAs may also play a role in pain pathways and hence expression of clinical symptoms.

CONCLUSIONS: Recent evidence has shown that miRNAs in the circulation may reflect underlying disease states and hence serve as potential markers for disease activity. These findings may represent possible future therapeutic applications in the management of OA.