The role of histone deacetylase 3 in chondrogenesis and osteoarthritis

Abstract

Histone deacetylases (HDACs) regulate the acetylation pattern of chromatin to control gene expression. Previous studies reported class I HDACs and specifically HDAC3 as a key regulator of MMP1/13 expression, the major collagenases in cartilage. Moreover, HDAC inhibitors were shown to have a chondroprotective role in in vivo models of osteoarthritis. The aim of this study was to examine the role of HDAC3 in catabolic gene expression in osteoarthritis and in chondrocyte differentiation in vivo and in vitro. Chemical inhibitors against all HDACs (e.g. TSA) and specifically against HDAC3 (Apicidin) were used in conjunction with HDAC3 RNAi in human SW1353 chondrocytes, stimulated with IL-1 and in a mesenchymal stem cell (MSC) chondrogenic differentiation model. Gene expression was quantified using qRT- PCR and protein by western blotting, immunohistochemistry and biochemical methods. RNA microarray analysis was performed following RNAi or Apicidin treatment, across a time-course of IL-1 stimulation in chondrocytes to identify critical regulators of catabolic gene expression. Subsequently the role of E2F-1 transcription factor was studied with gain or loss of function experiments. E2F-1 activity on MMP1/13 was assessed by luciferase reporter gene activation and interaction with HDAC3 determined by immunoprecipitation. The role of HDAC3 in murine development was determined by generating a cartilage specific conditional knockout mouse model. HDAC3 is essential for IL-1- induced MMP1/13 and FRA1 expression in chondrocytes. Microarray analysis suggests the E2F-1 transcription factor may mediate the effect of HDAC3 on gene expression regulation. Accordingly, modulation of E2F1 levels alters IL-1 induced MMP1/13 expression and HDAC3 appears to interact with E2F1. Additionally, HDAC3 regulates anabolic gene expression, including COL2A1 and ACAN, during MSC chondrogenesis and is required for normal endochondral ossification, since conditional deletion resulted in embryonic lethality. We propose a novel role for HDAC3 in the regulation of catabolic and anabolic gene expression.