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

Arthritis Rheum. 2007 Feb;56(2):575-85. doi: 10.1002/art.22334.


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.

MeSH terms

  • ADAM Proteins / genetics
  • ADAM Proteins / metabolism*
  • ADAMTS1 Protein
  • ADAMTS4 Protein
  • ADAMTS5 Protein
  • Adult
  • Aged
  • Aged, 80 and over
  • Aggrecans / metabolism*
  • Cartilage, Articular / cytology
  • Cartilage, Articular / metabolism*
  • Cartilage, Articular / pathology
  • Cells, Cultured
  • Chondrocytes / cytology
  • Chondrocytes / metabolism
  • Chondrocytes / pathology
  • Gene Expression Regulation
  • Gene Silencing
  • Humans
  • Male
  • Middle Aged
  • Osteoarthritis / metabolism*
  • Osteoarthritis / pathology
  • Procollagen N-Endopeptidase / genetics
  • Procollagen N-Endopeptidase / metabolism*
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • RNA, Small Interfering / genetics
  • RNA, Small Interfering / metabolism
  • Transfection


  • Aggrecans
  • RNA, Messenger
  • RNA, Small Interfering
  • ADAM Proteins
  • ADAMTS1 Protein
  • ADAMTS1 protein, human
  • ADAMTS5 Protein
  • ADAMTS5 protein, human
  • Procollagen N-Endopeptidase
  • ADAMTS4 Protein
  • ADAMTS4 protein, human
  • Adamts4 protein, mouse