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Derepression of MicroRNA‐138 Contributes to Loss of the Human Articular Chondrocyte Phenotype
Author(s) -
Seidl Christine I.,
MartinezSanchez Aida,
Murphy Christopher L.
Publication year - 2016
Publication title -
arthritis and rheumatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.106
H-Index - 314
eISSN - 2326-5205
pISSN - 2326-5191
DOI - 10.1002/art.39428
Subject(s) - chondrocyte , chromatin immunoprecipitation , microrna , microbiology and biotechnology , cartilage , gene silencing , transcription factor , phenotype , biology , aggrecan , luciferase , gene expression , gene , transfection , promoter , genetics , pathology , articular cartilage , osteoarthritis , anatomy , medicine , alternative medicine
Objective To investigate the function of microRNA‐138 (miR‐138) in human articular chondrocytes (HACs). Methods The expression of miR‐138 in intact cartilage and cultured chondrocytes and the effects of miR‐138 overexpression on chondrocyte marker genes were investigated. Targets of miR‐138 relevant to chondrocytes were identified and verified by overexpression of synthetic miRNA mimics and inhibitors, luciferase assays, chromatin immunoprecipitation, and RNA immunoprecipitation of native argonaute 2, using quantitative polymerase chain reaction, Western blotting, and luciferase assays. Results Expression levels of miR‐138 were maintained at relatively low levels in intact human cartilage but were greatly increased upon loss of the differentiated phenotype in culture, with a concomitant decrease in the major cartilage extracellular matrix component COL2A1. We showed that miR‐138 is able to repress the expression of COL2A1 by directly targeting Sp‐1 and hypoxia‐inducible factor 2α (HIF‐2α), 2 transcription factors that are essential for COL2A1 transcription. We further demonstrated a direct association of these targets with miR‐138 in the RNA‐induced silencing complex and confirmed binding of Sp‐1 to the COL2A1 promoter region in HACs. Conclusion We propose that an evolutionary pressure helps to suppress expression levels of miR‐138 in human cartilage, thus enabling expression of appropriate tissue‐specific matrix genes. Inhibition of miR‐138 may serve as a potential therapeutic strategy to maintain the chondrocyte phenotype or reduce the progression of dedifferentiation in cultured HACs.