Alarmins S100A8 and S100A9 elicit a catabolic effect in human osteoarthritic chondrocytes that is dependent on Toll-like receptor 4

Arthritis Rheum. 2012 May;64(5):1477-87. doi: 10.1002/art.33495.


Objective: S100A8 and S100A9 are two Ca(2+) binding proteins classified as damage-associated molecular patterns or alarmins that are found in high amounts in the synovial fluid of osteoarthritis (OA) patients. The purpose of this study was to investigate whether S100A8 and/or S100A9 can interact with chondrocytes from OA patients to increase catabolic mediators.

Methods: Using immunohistochemistry, we stained for S100A8 and S100A9 protein, matrix metalloproteinases (MMPs), and a cartilage-breakdown epitope specific for MMPs (VDIPEN) in cartilage from OA donors. Isolated chondrocytes or explants from OA and non-OA donors were stimulated with S100A8 and/or S100A9. Messenger RNA and protein levels of MMPs, cytokines, and cartilage matrix molecules were determined with quantitative reverse transcription-polymerase chain reaction and Luminex techniques, respectively. For receptor blocking studies, specific inhibitors for Toll-like receptor 4 (TLR-4), receptor for advanced glycation end products (RAGE), and carboxylated glycans were used.

Results: In cartilage from OA patients, the expression of S100A8 and S100A9 protein close to chondrocytes was associated with proteoglycan depletion and expression of MMP-1, MMP-3, and VDIPEN. Stimulation of chondrocytes with S100A8 and S100A9 caused a strong up-regulation of catabolic markers (MMPs 1, 3, 9, and 13, interleukin-6 [IL-6], IL-8, and monocyte chemotactic protein 1) and down-regulation of anabolic markers (aggrecan and type II collagen), thereby favoring cartilage breakdown. Blocking TLR-4, but not carboxylated glycans or RAGE, inhibited the S100 effect. The catabolic S100 effect was significantly more pronounced in chondrocytes from OA patients as compared to those from non-OA patients, possibly due to higher TLR-4 expression.

Conclusion: S100A8 and S100A9 have a catabolic effect on human chondrocytes that is TLR-4 dependent. OA chondrocytes are more sensitive than normal chondrocytes to S100 stimulation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biomarkers / metabolism
  • Calgranulin A / administration & dosage
  • Calgranulin A / metabolism*
  • Calgranulin B / metabolism*
  • Calgranulin B / pharmacology
  • Cartilage Oligomeric Matrix Protein
  • Cartilage, Articular / drug effects
  • Cartilage, Articular / metabolism*
  • Cartilage, Articular / pathology
  • Cells, Cultured
  • Chondrocytes / drug effects
  • Chondrocytes / metabolism*
  • Chondrocytes / pathology
  • Cytokines / genetics
  • Cytokines / metabolism
  • Epitopes / metabolism
  • Extracellular Matrix Proteins / genetics
  • Extracellular Matrix Proteins / metabolism
  • Gene Expression
  • Glycoproteins / genetics
  • Glycoproteins / metabolism
  • Humans
  • Matrilin Proteins
  • Matrix Metalloproteinases / genetics
  • Matrix Metalloproteinases / metabolism
  • Oligopeptides / metabolism
  • Osteoarthritis / metabolism*
  • Osteoarthritis / pathology
  • Peptide Fragments / metabolism
  • Receptor for Advanced Glycation End Products
  • Receptors, Immunologic / antagonists & inhibitors
  • Recombinant Proteins
  • Toll-Like Receptor 4 / antagonists & inhibitors
  • Toll-Like Receptor 4 / metabolism*


  • Biomarkers
  • Calgranulin A
  • Calgranulin B
  • Cartilage Oligomeric Matrix Protein
  • Cytokines
  • Epitopes
  • Extracellular Matrix Proteins
  • Glycoproteins
  • Matrilin Proteins
  • Oligopeptides
  • Peptide Fragments
  • Receptor for Advanced Glycation End Products
  • Receptors, Immunologic
  • Recombinant Proteins
  • TLR4 protein, human
  • TSP5 protein, human
  • Toll-Like Receptor 4
  • peptide VDIPEN
  • Matrix Metalloproteinases