Abstract
IntroductionTo investigate if decreased histone deacetylase 4 (HDAC4) is associated with human osteoarthritis (OA) cartilage degeneration by releasing HDAC4 inhibition of runt-related transcription factor-2 (Runx2) resulting in increase of OA cartilage degeneration-related genes.MethodsThe mRNA and protein levels of HDAC4, Runx2, matrix metalloproteinase (MMP)-13, Indian hedgehog (Ihh) and type X collagen were detected by performing real-time PCR (RT-PCR), western blotting and immunohistochemistry on specimens from human OA and normal cartilage. To further explore the mechanism of regulation of Runx2 and OA-related genes by HDAC4, changes in these OA-related genes were further quantified by RT-PCR after overexpression of HDAC4 and knockdown of HDAC4 by siRNA. Runx2 and MMP-13 promoter activities were measured by dual luciferase assays.ResultsThe levels of HDAC4 in the cartilage from OA patients and healthy 40- to 60-year-old donors were decreased to 31% and 65% compared with specimens from 20- to 40-year-old healthy donors, respectively (P <0.05). Decreased HDAC4 was associated with increased Runx2 and other OA-related genes in human OA cartilage, specifically: MMP-13, Ihh and type X collagen. Exogenous HDAC4 decreased the mRNA levels of Runx2, MMP1, MMP3, MMP-13, type X collagen, Ihh, ADAMTS-4 and -5, and increased the mRNA of type II collagen. In addition, the data also shows that overexpression of HDAC4 not only decreased the expression of interleukin (IL)-1β, Cox2 and iNos and increased the expression of aggrecan, but also partially blocked the effect of IL-1β on expression of catabolic events in human OA chondrocytes. HDAC4 also inhibited Runx2 promoter activity and MMP13 promotor activity in a dose-dependent manner. In contrast, inhibition of HDAC4 by TSA drug had an opposite effect.ConclusionsOur study is the first to demonstrate that decreased HDAC4 contributes, at least in part, to the pathogenesis of OA cartilage degeneration. Thus, HDAC4 may have chondroprotective properties by inhibiting Runx2 and OA-related genes.Electronic supplementary materialThe online version of this article (doi:10.1186/s13075-014-0491-3) contains supplementary material, which is available to authorized users.
Highlights
To investigate if decreased histone deacetylase 4 (HDAC4) is associated with human osteoarthritis (OA) cartilage degeneration by releasing HDAC4 inhibition of runt-related transcription factor-2 (Runx2) resulting in increase of OA cartilage degeneration-related genes
Western blotting analysis showed that expression of HDAC4 were decreased in the 40- to 60-year-olds and further decreased in the OA specimens, compared with the specimens obtained from the 20- to 40-year-olds (Figure 1B). β-actin and Coomassie Blue staining confirmed equal loading of total proteins from cartilage samples (Figure 1B)
Quantification of western blots showed that the concentration of Runx2 in the cartilages of OA patients was increased 212% compared with the normal cartilages (P
Summary
To investigate if decreased histone deacetylase 4 (HDAC4) is associated with human osteoarthritis (OA) cartilage degeneration by releasing HDAC4 inhibition of runt-related transcription factor-2 (Runx2) resulting in increase of OA cartilage degeneration-related genes. Studies have demonstrated that aging, genetics and mechanical factors are associated with the development of OA. Recent studies have demonstrated that changes observed in the behavior of chondrocytes in OA cartilage resemble those undergone by chondrocytes undergoing differentiation during embryogenesis [1,2,3,4,5,6]. Hypertrophic chondrocytes express matrix metalloproteases (MMPs) and type X collagen, which cause cartilage degradation as part of the endochondral ossification process of growth plate development [7,8,9,10]. During OA, chondrocytes lose the stable phenotype and enter hypertrophic differentiation, as demonstrated by increased expression of type X collagen, Ihh, and MMP-13. Cartilage degeneration in OA is similar to cartilage degradation in the growth plate [12,13]
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