Arthritis & Rheumatism, Volume 63,
November 2011 Abstract Supplement
Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Chicago, Illinois November 4-9, 2011.
Alarmins s100a8 and s100a9 Elicit a Higher Catabolic Response in Osteoarthritic Chondrocytes Compared to Normal Chondrocytes That Is Toll Like Receptor 4 Dependent.
Schelbergen1, Rik, Blom1, Arjen B., van den Bosch1, Martijn H.J., Sloetjes1, Annet, Vogl2, Thomas, Roth2, Johannes, van den Berg1, Wim B.
S100A8 and S100A9 are classified as damage associated molecular patterns (DAMPs) or alarmins and are found in high amounts in the synovial fluid of rheumatoid arthritis (RA) and osteoarthritis (OA) patients. Previously, we found that S100A8 and S100A9 are associated with cartilage degradation in murine collagenase-induced OA. We also showed that S100A8 and S100A9 stimulate expression and activity of matrix metalloproteinases (MMPs) and pro-inflammatory cytokines in murine chondrocytes.
In the current study, we investigated whether and via which receptor S100A8 and/or S100A9 can have a catabolic effect on chondrocytes from OA patients. Furthermore, we compared the S100-effect on OA chondrocytes with non-OA chondrocytes.
In cartilage from end stage OA, we stained for S100A8 and S100A9 protein, MMP-1 and -3 and a cartilage breakdown epitope specific for MMPs (VDIPEN) using immunohistochemistry. Isolated chondrocytes from OA and non-OA donors were stimulated with S100A8 and S100A9 protein. mRNA levels of MMPs, cytokines and cartilage matrix molecules were determined with RT-qPCR, protein levels of MMPs and cytokines with Luminex. For receptor blocking studies, specific inhibitors for Toll-like receptor 4 (TLR4) (intracellular TAK242) and RAGE and carboxylated glycans (blocking antibodies) were used.
In cartilage of OA patients, localisation of S100A8 and S100A9 protein was found close to chondrocytes and was associated with proteoglycan (PG) depletion, MMP1 and -3 and VDIPEN expression.
Stimulation of OA chondrocytes with S100A8 and S100A9 caused a significant upregulation of MMP1, -3, -9 and -13 at the mRNA level (5.7, 5.0, 4.0, and 3.1-fold respectively). The upregulation was confirmed on protein level for MMP-1, -3 and -13 (2.3, 3.1 and 3.6-fold respectively). Moreover, S100A8 and S100A9 caused a huge increase in cytokine and chemokine expression. IL-6, IL-8 and MCP-1 were all greatly increased by S100A8 and S100A9 at both the mRNA (15.1, 24.0 and 3.7-fold respectively) as well as the protein level (29.1, 49.7 and 7.7-fold respectively). Moreover, the expression of anabolic markers (aggrecan and collagen type II) was significantly reduced at the mRNA level (2.7 and 2.7-fold decrease respectively).
Blocking TLR4 almost completely inhibited the upregulation of MMP-3, IL-6, IL-8, MCP-1 and collagen type II by S100A9 in OA chondrocytes. In contrast, blocking of carboxylated glycans and RAGE did not alter the S100-effects.
Finally, the catabolic effect of S100A8 and S100A9 was significantly more pronounced in chondrocytes from OA patients when compared to non-OA. TLR4 mRNA expression was enhanced in OA chondrocytes, which might explain the increased sensitivity.
S100A8 and S100A9 have a catabolic effect on human chondrocytes that is dependent on TLR4. OA chondrocytes are more sensitive for S100-stimulation than normal chondrocytes.
This study underlines the potential of S100A8 and S100A9 as mediators of cartilage damage during OA.
To cite this abstract, please use the following information:
Schelbergen, Rik, Blom, Arjen B., van den Bosch, Martijn H.J., Sloetjes, Annet, Vogl, Thomas, Roth, Johannes, et al; Alarmins s100a8 and s100a9 Elicit a Higher Catabolic Response in Osteoarthritic Chondrocytes Compared to Normal Chondrocytes That Is Toll Like Receptor 4 Dependent. [abstract]. Arthritis Rheum 2011;63 Suppl 10 :1793