Evidence of a Novel Aggrecan-Degrading Activity in Cartilage: Studies of Mice Deficient in Both ADAMTS-4 and ADAMTS-5

Arthritis Rheum. 2008 Jun;58(6):1664-73. doi: 10.1002/art.23458.

Abstract

Objective: To characterize aggrecan catabolism and the overall phenotype in mice deficient in both ADAMTS-4 and ADAMTS-5 (TS-4/TS-5 Delta-cat) activity.

Methods: Femoral head cartilage from the joints of TS-4/TS-5 Delta-cat mice and wild-type mice were cultured in vitro, and aggrecan catabolism was stimulated with either interleukin-1alpha (IL-1alpha) or retinoic acid. Total aggrecan release was measured, and aggrecanase activity was examined by Western blotting using neoepitope antibodies for detecting cleavage at EGE 373-374 ALG, SELE 1279-1280 GRG, FREEE 1467-1468 GLG, and AQE 1572-1573 AGEG. Aggrecan catabolism in vivo was examined by Western blotting of cartilage that had been extracted immediately ex vivo.

Results: TS-4/TS-5 Delta-cat mice were viable, fertile, and phenotypically normal. TS-4/TS-5 Delta-cat cartilage explants did not release aggrecan in response to IL-1alpha, and there was no detectable increase in aggrecanase neoepitopes. TS-4/TS-5 Delta-cat cartilage explants released aggrecan in response to retinoic acid. There was no retinoic acid-stimulated cleavage at either EGE 373-374 ALG or AQE 1572-1573 AGEG. There was a low level of cleavage at SELE 1279-1280 GRG and major cleavage at FREEE 1467-1468 GLG. Ex vivo, cleavage at FREEE 1467-1468 GLG was substantially reduced, but still present, in TS-4/TS-5 Delta-cat mouse cartilage compared with wild-type mouse cartilage.

Conclusion: An aggrecanase other than ADAMTS-4 and ADAMTS-5 is expressed in mouse cartilage and is up-regulated by retinoic acid but not IL-1alpha. The novel aggrecanase appears to have different substrate specificity from either ADAMTS-4 or ADAMTS-5, cleaving E-G bonds but not E-A bonds. Neither ADAMTS-4 nor ADAMTS-5 is required for normal skeletal development or aggrecan turnover in cartilage.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ADAM Proteins / deficiency*
  • ADAMTS4 Protein
  • ADAMTS5 Protein
  • Aggrecans / metabolism*
  • Animals
  • Blotting, Western
  • Cartilage / metabolism
  • Endopeptidases / metabolism*
  • Femur Head / metabolism
  • Mice
  • Mice, Knockout
  • Procollagen N-Endopeptidase / deficiency*

Substances

  • Aggrecans
  • Endopeptidases
  • ADAM Proteins
  • ADAMTS5 Protein
  • Adamts5 protein, mouse
  • Procollagen N-Endopeptidase
  • ADAMTS4 Protein
  • Adamts4 protein, mouse
  • aggrecanase