To examine the ability of a broad-spectrum histone deacetylase (HDAC) inhibitor to protect cartilage in vivo, and to explore the effects of class-selective HDAC inhibitors and small interfering RNA (siRNA)-induced knockdown of HDACs on metalloproteinase expression and cartilage degradation in vitro.
A destabilization of the medial meniscus (DMM) model was used to assess the in vivo activity of the HDAC inhibitor trichostatin A (TSA). Human articular chondrocytes (HACs) and SW-1353 chondrosarcoma cells were treated with cytokines and TSA, valproic acid, MS-275, or siRNA, and quantitative reverse transcription-polymerase chain reaction was performed to determine the effect of treatment on metalloproteinase expression. HDAC inhibitor activity was detected by Western blotting. A bovine nasal cartilage (BNC) explant assay was performed to measure cartilage resorption in vitro.
Systemically administered TSA protected cartilage in the DMM model. TSA, valproic acid, and MS-275 repressed cytokine-induced MMP1 and MMP13 expression in HACs. Knockdown of each class I HDAC diminished interleukin-1-induced MMP13 expression. All of the HDAC inhibitors prevented degradation of BNC, in which TSA and MS-275 repressed cytokine-induced MMP expression.
Inhibition of class I HDACs (HDAC-1, HDAC-2, HDAC-3) by MS-275 or by specific depletion of HDACs is capable of repressing cytokine-induced metalloproteinase expression in cartilage cells and BNC explants, resulting in inhibition of cartilage resorption. These observations indicate that specific inhibition of class I HDACs is a possible therapeutic strategy in the arthritides.