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Arthritis Rheum. 2007 Feb;56(2):575-85.

Aggrecan degradation in human articular cartilage explants is mediated by both ADAMTS-4 and ADAMTS-5.

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1
Pfizer Global Research and Development, St Louis, MO 63017, USA.

Abstract

OBJECTIVE:

Recent published studies have shown that cartilage from ADAMTS-5-knockout mice, but not ADAMTS-4- or ADAMTS-1-knockout mice, is significantly protected from degradation. The present study was undertaken to evaluate the respective roles of these enzymes in human cartilage breakdown, using a small interfering RNA (siRNA) approach to assess the effects of inhibition of each enzyme in normal and osteoarthritic (OA) explants.

METHODS:

The activities of siRNA specifically targeting ADAMTS-1, -4, and -5 were assessed by transfection into primary human chondrocytes and cultured human cartilage explants. At 24 hours, a cytokine stimulus was applied to normal, but not OA, samples to initiate a catabolic response. At designated times, total RNA was isolated and gene expression was measured by quantitative real-time reverse transcription-polymerase chain reaction. Aggrecan release and aggrecanase-generated neoepitope formation were determined by dye binding analysis and Western blotting, respectively.

RESULTS:

Human chondrocytes and explants were efficiently transfected with siRNA that specifically decreased the expression of each targeted gene. Suppression of ADAMTS-4 and ADAMTS-5, individually or in combination, attenuated the degradation of aggrecan in cytokine-stimulated normal cartilage. A reduction in aggrecan degradation was also observed following siRNA-mediated knockdown of either gene in unstimulated OA cartilage. In contrast, knockdown of ADAMTS-1 failed to inhibit aggrecan loss.

CONCLUSION:

Despite the apparent dominant role of ADAMTS-5 in genetically modified mice, our data suggest that both ADAMTS-4 and ADAMTS-5 contribute to the structural damage that characterizes human OA.

PMID:
17265492
DOI:
10.1002/art.22334
[Indexed for MEDLINE]
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