Research ArticleOsteoarthritis

Inhibition of TET1 prevents the development of osteoarthritis and reveals the 5hmC landscape that orchestrates pathogenesis

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Science Translational Medicine  15 Apr 2020:
Vol. 12, Issue 539, eaax2332
DOI: 10.1126/scitranslmed.aax2332

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Preventing progression

The etiology and progression of osteoarthritis, a disease of joint degeneration, remains incompletely known. Studying epigenetics in a mouse model of osteoarthritis, Smeriglio et al. found that ten-eleven-translocation enzyme 1 (TET1) regulated activation of WNT signaling, metalloproteinases, and mTOR via cytosine hydroxymethylation. Tet1−/− mice were protected from osteoarthritis progression, and similar protection was seen with 2-hydroxyglutarate treatment in chondrocytes from patients with osteoarthritis and a mouse model of surgically induced osteoarthritis. Results suggest that inhibition of TET1 activity could be therapeutic for osteoarthritis.


Osteoarthritis (OA) is a degenerative disease of the joint, which results in pain, loss of mobility, and, eventually, joint replacement. Currently, no disease-modifying drugs exist, partly because of the multiple levels at which cartilage homeostasis is disrupted. Recent studies have highlighted the importance of epigenetic dysregulation in OA, sparking interest in the epigenetic modulation for this disease. In our previous work, we characterized a fivefold increase in cytosine hydroxymethylation (5hmC), an oxidized derivative of cytosine methylation (5mC) associated with gene activation, accumulating at OA-associated genes. To test the role of 5hmC in OA, here, we used a mouse model of surgically induced OA and found that OA onset was accompanied by a gain of ~40,000 differentially hydroxymethylated sites before the notable histological appearance of disease. We demonstrated that ten-eleven-translocation enzyme 1 (TET1) mediates the 5hmC deposition because 98% of sites enriched for 5hmC in OA were lost in Tet1−/− mice. Loss of TET1-mediated 5hmC protected the Tet1−/− mice from OA development, including degeneration of the cartilage surface and osteophyte formation, by directly preventing the activation of multiple OA pathways. Loss of TET1 in human OA chondrocytes reduced the expression of the matrix metalloproteinases MMP3 and MMP13 and multiple inflammatory cytokines. Intra-articular injections of a dioxygenases inhibitor, 2-hydroxyglutarate, on mice after surgical induction of OA stalled disease progression. Treatment of human OA chondrocytes with the same inhibitor also phenocopied TET1 loss. Collectively, these data demonstrate that TET1-mediated 5hmC deposition regulates multiple OA pathways and can be modulated for therapeutic intervention.

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