Arthritis & Rheumatism, Volume 62,
November 2010 Abstract Supplement

Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Atlanta, Georgia November 6-11, 2010.


Alarmins S100A8 and S100A9 Skew Human Chondrocytes towards a Cartilage Breakdown Phenotype.

Schelbergen4,  Rik F. P., van Lent5,  Peter L., Blom5,  Arjen B., Sloetjes5,  Annet, Vogl2,  Thomas, Roth1,  Johannes, Van Den Berg3,  Wim B.

Children's Hospital Eastern Ontario, Ottawa, ON, Canada
Institute of Immunology, Muenster
Radboud Univ Nijmegen Med Cntr, Nijmegen, The Netherlands
Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
Radboud University Nijmegen Medical Centre

Background:

Alarmins S100A8 and S100A9 are members of the S100 family of Ca2+-binding proteins that are associated with inflammation and cartilage and bone erosion during human rheumatoid arthritis (RA). Recently, we found that S100A8 and S100A9 are also associated with cartilage degradation in murine collagenase-induced osteoarthritis (OA). We also showed that S100A8 and S100A9 stimulate expression and activity of matrix metalloproteinases (MMPs) and pro-inflammatory cytokines in murine chondrocytes. We now investigated whether S100A8, S100A9 and/or the S100A8/S100A9 complex could also activate human chondrocytes from OA patients and skew them towards a cartilage breakdown phenotype.

Methods:

Cartilage was collected from human OA patients undergoing joint replacement. Immunostaining was performed on paraffin sections of OA cartilage using antibodies against S100A8 and S100A9 and against VDIPEN and NITEGE, which are MMP- and A disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)-induced cartilage breakdown neoepitopes. Chondrocytes were isolated from OA cartilage and stimulated with recombinant S100A8, S100A9, S100A8/A9 heterodimer and/or interleukin 1b (IL-1b). mRNA levels of MMPs, cytokines and cartilage matrix molecules were determined with RT-qPCR and protein levels of MMP and cytokine using Luminex.

Results:

Immunostaining on OA cartilage showed that both S100A8 and S100A9 protein were expressed in and around chondrocytes. Furthermore, immunostaining of breakdown neoepitopes VDIPEN and NITEGE was found in the same areas as the S100 proteins.

Stimulation of OA chondrocytes with the monomers S100A8 and S100A9 for 24 hours strongly stimulated cartilage degrading molecules like MMPs and cytokines. mRNA expression of MMP1, -3, -9 and -13 was upregulated 6.0, 5.2, 4.3, and 2.8-fold respectively. Protein levels of MMP1, -3 and -13 were upregulated 3.4, 1.3 and 2.4-fold respectively. Moreover, particularly interleukin 6 (IL-6) levels were strongly upregulated on mRNA level (11-fold) and protein levels reached 10 ng/ml.

Apart from stimulating cartilage degradation, S100A8 and S100A9 monomers also inhibited new formation of cartilage matrix molecules. mRNA levels of aggrecan and collagen type II were significantly decreased 2- to 3-fold, suggesting that these proteins inhibit repair.

The S100A8/A9 heterodimer neither had effect on cartilage degradation nor on cartilage matrix production.

The effect of S100A8 and S100A9 was similar to IL-1b effects, but there was no additive effect of S100 with IL-1b, suggesting independent mechanisms.

Conclusions:

S100A8 and S100A9 expression is found in areas with cartilage breakdown. Moreover these proteins inhibit new formation of matrix molecules and stimulate production of cartilage degrading molecules in vitro thereby skewing human chondrocytes towards a cartilage breakdown phenotype.

S100A8 and/or S100A9 may serve as therapeutic targets for the treatment of cartilage damage.

To cite this abstract, please use the following information:
Schelbergen, Rik F. P., van Lent, Peter L., Blom, Arjen B., Sloetjes, Annet, Vogl, Thomas, Roth, Johannes, et al; Alarmins S100A8 and S100A9 Skew Human Chondrocytes towards a Cartilage Breakdown Phenotype. [abstract]. Arthritis Rheum 2010;62 Suppl 10 :1472
DOI: 10.1002/art.29238

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