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Title: The role of histone deacetylases in cartilage gene regulation and chondroprotection
Author: Culley, Kirsty Leesa
ISNI:       0000 0004 2735 196X
Awarding Body: University of East Anglia
Current Institution: University of East Anglia
Date of Award: 2010
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The expression of cartilage-degrading metalloproteinases (MMPs or ADAMTSs) is regulated in part via changes in acetylation mediated by histone acetyltransferases and histone deacetylases (HDACs). Classical HDACs can be divided into class I (HDAC1, 2, 3 and 8), class II (HDAC4, 5, 6, 7, 9 and 10) and Class IV (HDAC11). Broad spectrum HDAC inhibitors (HDACi) block cytokine-induction of key proteases in SW1353 chondrosarcoma cells and primary human articular chondrocytes (HACs), resulting in chondroprotection. This study aimed to elucidate the role of HDACs in chondroprotection using selective chemical HDACi and siRNA technology. Trichostatin A (TSA) (broad spectrum) and valproic acid (VPA) (class I selective at <1mM) repressed all cytokine-induced metalloproteinase genes in SW1353 cells, and MMP13 expression in HACs. MS-275 (class I selective) failed to repress cytokine-induced MMP1 and MMP13 expression in SW1353 cells, but repressed MMP13 expression in HACs. Tubacin (HDAC6 specific) decreased cytokine-induced MMP1 and MMP13 in SW1353 cells. All inhibitors prevented cytokine-induced degradation of bovine nasal cartilage, where MS-275 was also able to repress cytokine-induced MMP expression, including MMP1 and MMP13. A profile of HDAC expression showed that the majority have reduced expression in OA cartilage compared to normal. TSA increased HDAC3 expression and decreased HDAC7 expression in SW1353 cells, suggesting that HDACi may both inhibit HDAC catalytic activity, and regulate HDAC expression. Knockdown of individual HDACs in SW1353 cells using siRNA showed that inhibition of all HDACs, except HDAC1, caused a repression of basal and IL-1α-induced MMP13 expression, with HDAC1 knockdown potentiating IL-1α-induced MMP13 expression. In HACs, HDAC3 or HDAC8 knockdown resulted in reduced basal and IL-1α-induced MMP13 expression, HDAC1 or HDAC11 knockdown potentiated both of these and HDAC5 or HDAC6 knockdown potentiated only IL-1α-induced MMP13 expression. Problems with non-targeting control siRNAs made interpretation of experiments difficult. HDACs therefore play a key role in metalloproteinase expression, with inhibition of class I HDACs, or separately HDAC6, capable of altering metalloproteinase expression to confer chondroprotection.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available