Objective: To analyse the distribution patterns of tenascin and proteoglycans in normal and osteoarthritic cartilage, and to determine the effect of interleukin 1β (IL1β) on aggrecan and tenascin expression by human articular chondrocytes in vitro.
Methods: Normal and osteoarthritic cartilage and bone samples were obtained during total knee replacements or necropsies. After fixation and decalcification, paraffin embedded specimens were sectioned perpendicular to the surface. Specimens were graded according to Mankin and subdivided into those with normal, and mild, moderate, and severe osteoarthritic lesions. Serial sections were immunostained for tenascin. Tenascin expression by healthy and osteoarthritic chondrocytes was quantified by real time polymerase chain reaction (PCR). Furthermore, in cell culture experiments, human articular chondrocytes were treated with 0.1 or 10 ng/ml IL1β. Real time PCR analyses of aggrecan and tenascin transcripts (normalised 18S rRNA) were conducted to determine the effect of IL1β on later mRNA levels.
Results: Tenascin was immunodetected in normal and osteoarthritic cartilage. In osteoarthritic cartilage increased tenascin staining was found. Tenascin was found specifically in upper OA cartilage showing a strong reduction of proteoglycans. Greatly increased tenascin transcript levels were detected in osteoarthritic cartilage compared with healthy articular cartilage. IL1β treatment of articular chondrocytes in vitro significantly increased tenascin transcripts (~200% of control) and strongly reduced aggrecan mRNA levels (~42% of control).
Conclusions: During progression of osteoarthritis the switch in matrix synthesis occurs mainly in upper osteoarthritic cartilage. Furthermore, changes in synthesis patterns of osteoarthritic chondrocytes may be significantly influenced by IL1β, probably diffusing from the joint cavity within the upper osteoarthritic cartilage.
- interleukin 1β
- HBSS, Hanks’s buffered salt solution
- IL, interleukin
- OA, osteoarthritis
- PBS, phosphate buffered saline
- PCR, polymerase chain reaction
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- [View PDF] - Figure W1. Additional serial sections of normal and OA cartilage are demonstrated. A Healthy articular cartilage with a smooth surface and a high content of proteoglycans (safranin-o staining). B Tenascin immunostaining reveals tenascin deposition at the surface lining, in the superficial zone and middle zone in a territorial and interterritorial staining pattern (normal cartilage with the strongest staining found in our study, same specimen shown in A). C Mild OA lesion with pannus-like tissue on the surface (safranin-o staining). D Immunohistochemical analysis of tenascin in the same section shown in C (note the strong immunostaining of pannus-like tissue indicated by arrows). E Moderate OA cartilage lesion with a reduction of proteoglycans, loss of the superficialzone, fissuring of the surface and chondrocyte clusters next to the surface (safranin-o staining). F Immunohistochemical detection of tenascin in the same section shown in E (note the strong tenascin staining in cartilage areas with a strong reduction of safranin-o staining indicated by arrowheads). G Proteoglycan staining of severely affected cartilage with great reduction of cartilage substance and small clusters next to the joint space. H Immunostaining for tenascin revealed a strong tenascin deposition in the upper OA cartilage (note the strong tenascin staining in cartilage areas with a total loss of proteoglycans indicated by arrows). Bar in A represents 100��m in A-F and 200��m in G-H.
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