AB1293 SMAD3 GENE POLYMORPHISMS AND EXPRESSION IN SERUM AND CARTILAGE INFLUENCE THE RISK OF KNEE OSTEOARTHRITIS
Authors: Rajeswar Nath Srivastava, Amar Chandra Sharma, Sudeepti Srivastava, Saloni Raj
Journal: Annals of the Rheumatic Diseases (2019)

<h3>Background:</h3> Knee Osteoarthritis (KOA) is the most common degenerative arthritis, a type of arthritis that is caused by breakdown of articular cartilage with eventual loss of the cartilage of the joints. Smad3 is a key intracellular messenger in the transforming growth factor β signaling pathway. Previous study suggested Smad3 gene mutation is a possible predisposing factor for human OA and found gene mutation in OA, providing insight into the function of SMAD3 mediated TGF-b signals in the development of OA and also suggested that Smad3 gene mutation may be a risk factor for genetic susceptibilities to OA. In this case control study, we investigated the possible correlation between the SNPs SmaI (C/T; rs6494629), FokI (A/C; rs2289263) in Smad3 gene and susceptibility to knee OA and validated in serum and cartilage. <h3>Objectives:</h3> To investigate the possible association between SNPs (rs6494629 and rs2289263) of the Smad3 gene and KOA. <h3>Methods:</h3> In this study cases consisted of men and women ≥40 years that fulfilled American College of Rheumatology (ACR) clinical and radiographic criteria for knee OA. Venous blood samples were obtained from all cases as well as controls for genetic analysis. Polymerase chain reactions were performed for SNP analysis using specific primer. Total protein was measured in serum by an enzyme linked immunosorbent assay according to the manufacturer's Protocol (ELISA) and in cartilage tissue done by western blot. <h3>Results:</h3> A total of 200 cases that confirmed radiographic knee OA and equal number of age and sex matched healthy controls were enrolled. There was no significant difference in demographic characteristics between the cases and controls. A SNP (rs6494629 and rs2289263) mapping to intron 1 of SMAD3 was associated with knee OA (P &lt; 0.013 and P &lt; 0.044, respectively). Within the SNPs (rs6494629) of Smad3 gene, genotype CC and CT was found to be significantly (p&lt;0.013) associated with knee OA as compared with the CC genotype and SNP rs2289263,genotype CC and CA was found to be significantly (p&lt;0.044) associated with knee OA as compared with the AA genotype. In addition when alleles were compared, C allele of both the studied SNP was observed to be significantly associated with knee OA. Serum levels of Smad3 in KOA patients with rs6494629 TT, CT and CC genotypes were significantly higher than healthy subjects with the same rs6494629C/T genotypes (all P &lt; 0.0001, P &lt; 0.0006, P &lt; 0.017 respectively). Increased serum levels of Smad3 were also observed in KOA patients with rs2289263 AA, CA and CC genotypes compared to controls (all P &lt; 0.006, P &lt; 0.0006, P&lt;0.004). We performed Immunoblot analysis on cartilage tissue from 15 cases and 10 controls. The smad3 level in cases was significantly higher than controls (P &lt; 0.006). <h3>Conclusion:</h3> Our data indicate that genetic variation in the SMAD3 gene is involved in the risk of knee OA in North Indian populations, confirming the results from previous studies on the potential importance of this gene in the pathogenesis of OA. Further we also validated these genetic variations at protein level in both blood and tissue and found significant association. <h3>References</h3> [1] Valdes AM, Spector TD, Tamm A, Kisand K, Doherty SA, Dennison EM. Genetic variation in the SMAD3 gene is associated with hip and knee osteoarthritis. Arthritis and rheumatism. 2010;10.1002/art.27530 [2] Su SL, Yang HY, Lee HS, Huang GS, Lee CH, Liu WS. Gene–gene interactions between TGF-b/Smad3 signalling pathway polymorphisms affect susceptibility to knee osteoarthritis. BMJ Open. 2015;5:e007931. <h3>Disclosure of Interests:</h3> None declared