Induction of Osteogenic Protein-1 Expression by Interleukin-1beta in Cultured Rabbit Articular Chondrocytes

Induction of Osteogenic Protein-1 Expression by Interleukin-1b
in Cultured Rabbit Articular Chondrocytes

SATOSHI YOSHIDA,^1,2 YOSHIKO KUBOTA,¹ TAMOTSU TOBA,² SABURO HORIUCHI¹ and TADASHI SHIMAMURA²

¹Department of Biochemistry, and ²Department of Orthopaedic Surgery,
Iwate Medical University, Morioka 020-8505

To elucidate the effects of interleukin-1b (IL-1b) on osteogenic protein-1 (OP-1) gene expression in a polylayer culture of rabbit articular chondrocytes, we measured rabbit OP-1 mRNA using quantitative TaqMan reverse transcriptase-polymerase chain reaction (RT-PCR) techniques. Rabbit articular chondrocytes were isolated and cultured in minimum essential medium eagle a modification containing 10% fetal bovine serum for 7 days. IL-1b was then added and cultures were continued for 48 or 96 hours. OP-1 gene expression was detected in cell cultures both with and without addition of IL-1b. However, the level of expression was very low in the control group. OP-1 gene expression was significantly increased about 450- to 800-fold in IL-1b-treated groups (0.1, 1, and 10 ng/ml) versus the control group. Evaluation of serial changes in OP-1 expression after addition of IL-1b (10 ng/ml) revealed that OP-1 gene expression increased rapidly after addition of IL-1b, reaching a peak at 48 hours, and then decreasing. Simultaneous assay of CD44 expression demonstrated a rapid increase, similar to that of OP-1 expression, following addition of IL-1b: this was followed by a more gradual increase. Assay of hyaluronan synthase-2 (HAS-2) expression following addition of IL-1b showed an increase after OP-1 expression had already reached a peak. Our results demonstrate that OP-1 expression is induced by IL-1b and suggest that this expression, like that of HAS-2, may play a role as a protective mechanism against inflammatory cytokines.

Keywords —— osteogenic protein-1; interleukin-1b; articular chondrocytes

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Tohoku J. Exp. Med., 2002, 197, 101-109

Address for reprints: Satoshi Yoshida, Department of Biochemistry, Iwate Medical University, 19-1 Uchimaru, Morioka 020-8505, Japan.

e-mail: satto@fj8.so-net.ne.jp