Epigenetics of cartilage diseases

Osteoarticular diseases, such as arthritis or osteoarthritis, are multifactorial diseases with an underlying genetic etiology that are challenging to study. Genome-Wide Association studies (GWAS) have identified several genetic loci associated with these diseases. Epigenetics is a complex mechanism of chromatin and gene modulation through DNA methylation, histone deacetylation or microRNA, which might contribute to the inheritability of disease. Some of these mechanisms have been studied for decades in other diseases or as part of the aging process, where epigenetic changes seem to play an important role. With the implementation of better technological tools, such as the Illumina next generation sequencing, altered methylation of DNA has been linked to articular diseases and these mechanisms have been shown to regulate metalloprotease (MMP) expression and cartilage matrix integrity. Some miRNA have also been identified and more extensively characterized, such as delineation of the role played by miR-140 in chondrogenesis, followed by the discovery of numerous miRNA potentially involved in the epigenetic regulation of osteoarthritic disease. Histone deacetylases have long been linked to aging, particularly with respect to the Sirtuin family with Sirt1 as the major player. Because aging is the major risk factor for osteoarthritis, the involvement of Sirtuins in the etiology of osteoarthritis has been suggested and investigated. All of these fine regulations together shed new light on cartilage disease pathophysiology. We present in this short review an update of the role of these pathways in articular diseases.