Pathological mechanism of osteoarthritis -analysis of molecules responsing to mechanical stress-

GADD 45 β在人和动物关节软骨组织中的表达，在人网状软骨中GADD 45 β在早期OA软骨簇中表达最高。肥大软骨细胞在OA动物模型中呈阳性表达，而在正常动物中不表达。这些结果表明，GADD 45 β的功能，以支持在OA的过程中的软骨细胞的去分化的机制。为了检查GADD 45 β的软骨细胞表型的机械功能，荧光素酶测定和真实的时间PCR使用软骨细胞系。有趣的是，X型胶原和MMP-13基因表达通过GADD 45 β过表达而增加，但通过使用siRNA抑制GADD 45 β而降低。此外，GADD 45 β过表达可降低II型胶原基因表达，而GADD 45 β抑制可增加II型胶原基因表达。我们还研究了使用ATDC 5细胞的凋亡分析。GADD 45 β具有明显的抗凋亡作用，该蛋白促进X型胶原和MMP-13基因表达，抑制II型胶原基因表达。GAdd 45 β在体外也具有抗软骨细胞凋亡的作用，这些结果表明GAdd 45 β在OA中的重要作用是支持软骨细胞在OA过程中的存活，导致正常软骨细胞的去分化。

In the next step, the expression of GADD45beta was examined using immunohistochemistry of articular cartilage from human and animal samples.GADD45beta was especially highly expressed in cluster of early OA cartilage in human reticular cartilage. The hypertrophic chondrocyte were positive in OA animal model but not in normal animal. These findings suggested GADD45beta functions to support the mechanism of dedifferentitation of chondrocyte during the process of OA.To examine the mechanical function of GADD45beta in terms of phenotype of chondrocyte, luciferase assay and real time PCR were performed using chondrocyte cell line. Interestingly, type X collagen and MMP-13 gene expressions were increased by GADD45beta over-expression, but decreased by GADD45beta suppressing using siRNA. Additionally, type II collagen gene expression was decreased by by GADD45beta over-expression and increased by by GADD45beta suppressing. We also investigated apoptosis analysis using ATDC5 cells. GADD45beta clearly functioned anti-apoptotic way.This protein accelerates Type X collagen and MMP-13 gene expression and suppresses Type II collagen gene expression. GAdd45beta also noble function in terms of anti-apoptosis in chondrocyte in vitro.These results suggest the importance of GADD45beta function in OA to support the survival of chondrocytes during the process of OA, resulting in dedifferentiation from normal chondrocyte.