Article Text

Up regulation of cathepsin K expression in articular chondrocytes in a transgenic mouse model for osteoarthritis
  1. J P Morko,
  2. M Söderström,
  3. A-M K Säämänen,
  4. H J Salminen,
  5. E I Vuorio
  1. Skeletal Research Programme, Department of Medical Biochemistry and Molecular Biology, University of Turku, FIN-20520 Turku, Finland
  1. Correspondence to:
    Dr E Vuorio
    Department of Medical Biochemistry and Molecular Biology, University of Turku, FIN-20520 Turku, Finland; eero.vuorioutu.fi

Abstract

Objectives: To study the expression of cysteine proteinases, particularly cathepsin K, and their extracellular inhibitor cystatin C in articular cartilage of transgenic Del1 mice which harbour a short deletion mutation in a type II collagen transgene and are predisposed to early onset osteoarthritis.

Methods: Northern analysis was used to measure mRNA levels of cathepsins B, H, K, L, and S, and cystatin C in total RNA extracted from knee joints of Del1 mice, using their non-transgenic litter mates as controls. Immunohistochemistry and morphometry was used to study the distribution of cathepsin K and cystatin C in the knee joints.

Results: Up regulation of cathepsin K mRNA expression was seen in the knee joints of transgenic Del1 mice at the onset of cartilage degeneration. Cathepsin K was found near sites of matrix destruction in articular chondrocytes, particularly in clusters of proliferating cells, and in calcified cartilaginous matrix. In intact articular cartilage of control animals, cathepsin K was only seen in a small number of chondrocytes. Upon aging, control animals also developed osteoarthritis, which was accompanied by increased cathepsin K expression. Cystatin C was mostly localised in and around chondrocytes located in calcified cartilage, with no obvious association with the onset of cartilage degeneration.

Conclusion: The temporospatial distribution of cathepsin K in osteoarthritic cartilage suggests a role for this enzyme in the pathogenesis of osteoarthritis. Because cathepsin K can digest cartilage matrix components it may contribute to the development of osteoarthritic lesions. These data may provide new clues for the development of treatments aimed at preventing cartilage degeneration.

  • cathepsin K
  • cystatin C
  • osteoarthritis
  • synovial tissue
  • transgenic mice
  • MMPs, matrix metalloproteinases
  • PBS, phosphate buffered saline
  • SDS, sodium dodecyl sulphate
  • SSC, saline-sodium citrate
View Full Text

Statistics from Altmetric.com

Supplementary materials

  • Web-only Figures

    Three web-only figures accompany this article. They are provided below.

    Files in this Data Supplement:

    • [View Figure] - Figure W1 Progression of articular cartilage degeneration in knee joints of transgenic Del1 mice and nontransgenic controls. Grading of osteoarthritic changes was performed as described earlier. 5 33 34 Closed symbols denote Del1 samples and open circles their control litter mates. (Mann-Whitney U test; n = 5�30; *** p <_0.001-- end="end" desc="desc" _636649figurew1.gif="_636649figurew1.gif" _--="_--">
    • [View Figure] - Figure W2 Temporal expression of cysteine cathepsins and cystatin C mRNAs in developing, growing and aging mouse knee joints. Total RNAs were extracted from entire knee joints of Del1 and control mice at birth and at the age of 4 and 9 months (marked above lines; nb, newborn; mo, month; , control; +, Del1). The hybridisations were performed with cDNA probes detecting mRNAs for cathepsin B (Ctsb), cathepsin H (Ctsh), cathepsin K (Ctsk), cathepsin L (Ctsl) and cathepsin S (Ctss), as well as for cystatin C (Cst3) (marked on the left, respectively). The lowest panel 28S demonstrates the hybridisation of the filter with a probe for 28S rRNA. Hybridisation intensity was analysed using a phosphoimager. Transcript sizes are shown on the right.
    • [View Figure] - Figure W3 Immunohistochemical detection of cathepsin K and cystatin C in the mouse synovial tissue at the age of 4 months. Tissue distribution is shown in sagittal sections of knee joints obtained from control (A, D, F) and Del1 mice (B, C, E). Immunostaining for cathepsin K (A, B) and cystatin C (D, E) is identified as a brown precipitate. There was no staining for cathepsin K (C) or cystatin C (F) when primary antibodies were omitted or replaced by normal mouse serum. The bar in panel A corresponds to 15 m for panels A-F. Paraffin sections; biotin-streptavidin complex with horseradish peroxidase label and diaminobenzidine detection, counterstaining with hematoxylin.

Footnotes

    Request Permissions

    If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.