Study On The Function Of Smad3 Gene And Its Correlative Factors In The Development Of Human Osteoarthritis

Osteoarthritis (OA) is the most common joint disease worldwide, with multifactorial disorder .affecting many positions,occuring at a very high frequency, and has enormous socialand economic consequences, but the molecular mechanism of the development of OA is largely unknown. Recently, Yang et al founded mutant mice homozygous for a targeted disruption ofSmad3-exon8 (Smac3e*8/e*8) by gene targeting, which sufferedsymptoms mimicking typical human osteoarthritis, and till now, it is the only report on single gene targeted disruption leading to the development of OA and it suggested that the smad3 gene mutations are associated with the pathogenesis of OA. Further, Wu et al found that the expression level of MMP-9 in serum ofthe mutuant mice is significantly higher than that of wild type, and these data suggested that MMP-9 also play an important role in the development of OA. At the same time, its hinted tous that it was necessary to study the association between the Smad3 gene, MMPs and the development of human OA. In this study, to reveal the association between the Smad3gene mutation and human OA, we employed polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) silver staining and sequencing in 32 patients with knee OA to detect mutation of all exons (exon1-9) of the Smad3 gene. We found a single base mutation (656A@T) in one patient accompanied by amino acid substitution (197N@I) locating inthe linker region of the SmadS protein, which showing thatmutations in the SmadS gene are associated with the pathogenesis of human OA, and may play an important role in the development of human OA.At the same time, to clarify the correlation between the MMP-2&MMP-9 and the development of human OA, the expression level of MMP-2&MMP-9 were detected in serum in patients with OA by zymographic analysis of gelatinases. It was found that the expression level of both MMP-2 and MMP-9 of patients with OA were significantly higher than that of controls (P<0.05), and we also found that the expression level of both MMP-2 and MMP-9 of the patient with the mutation obviously higher than mean expression level of patients and controls. This data suggested that both MMP-2 and MMP-9, cooperating with SmadS gene mutation correlated to the pathogenesis of OA, and may play an important role in the development of OA. All together, our study had showed that Smad3 gene cooperating with MMP-2 and MMP-9 may plays an important role in the development of human OA. We are the first one who found the Smad3 gene mutation in patients with OA and this is the fist report showing that the Smad3 gene mutations are6associated with the pathogenesis of human OA. And this is needed to be further studied.