| Abstrakt: |
Aim In osteoarthritis chondrocytes, matrix metalloproteases ( MMPs) and their inhibitors are induced by interleukin ( IL)-1beta or tumor necrosis factor ( TNF)-alpha and balanced by inhibitors, but their messenger RNA ( mRNA) expression has not been studied in individual cells. Methods Normal articular chondrocytes (10 donors; age 50 ± 6 years, mean ± SEM) were stimulated in a monolayer for 24 h with IL-1beta, TNF-alpha, or transforming growth factor ( TGF)-beta1 (10 ng/mL each), alone or in combination. m RNA expression for MMP-1, MMP-3 and tissue inhibitor of metalloproteinase ( TIMP)-1 was studied by in situ hybridization (35 S-c RNA) and quantitative reverse transcription polymerase chain reaction ( RT- PCR) ( n ≥ 3 each). Results Whereas < 5% chondrocytes constitutively expressed MMP-1, a higher percentage expressed MMP-3 and TIMP-1 (31.1 ± 1.8%; 36.7 ± 2.8%, respectively). Upon stimulation with IL-1beta, TNF-alpha or IL-1beta/ TNF-alpha, the percentage of cells positive for MMP-1, MMP-3 and TIMP-1 rose significantly ( IL-1beta: 31.5%, 54.5% and 60.2%, respectively; TNF-alpha: 35.4%, 56.6%, 50.9%; IL-1beta/ TNF-alpha: 38.8%, 45.2%, 52.1%). In bulk population ( RT- PCR), m RNA for MMP-1 and MMP-3 was also induced by IL-1beta (11.9-fold, 1.2-fold, respectively), TNF-alpha (4.8-fold, 1.0-fold) or IL-1beta/ TNF-alpha (14.7-fold, 1.4-fold), an effect attenuated by TGF-beta1. TIMP-1 m RNA, in contrast, was down-regulated by IL-1beta, TNF-alpha or IL-1beta/ TNF-alpha, an effect again partially reverted by TGF-beta1. Finally, collagen type II m RNA was down-regulated by IL-1beta, TNF-alpha or IL-1beta/ TNF-alpha (by 90%, 50% and 98%, respectively) and that of collagen type I was up-regulated (5.7-fold, 3.0-fold, 3.7-fold). Conclusions Up-regulation of MMP-1/ MMP-3 by IL-1beta and/or TNF-alpha in a fraction of chondrocytes in vitro suggests that a subpopulation of catabolic cells may also exist in osteoarthritis. These cells may undergo considerable dedifferentiation, as indicated by a decreased collagen- II/collagen- I ratio. [ABSTRACT FROM AUTHOR] |
