Objective: To identify the association between the interleukin (IL) 6 (IL-6) rs1800795 (-174 G>C), IL-8 rs4073 (-251T>A), and matrix metalloproteinase-13 (MMP-13) rs2252070 (-77G>A) gene polymorphisms and knee osteoarthritis (KOA) susceptibility in the Chinese Han population. Methods: Genomic DNA was extracted from a total of 400 KOA patients and 400 healthy subjects. Sanger sequencing was performed to determine the genotypes of the IL-6 rs1800795 (-174 G/C), IL-8 rs4073 (-251A/T), and MMP-13 rs2252070 (-77A/G) loci. The mRNA expression levels of IL-6, IL-8, and MMP-13 in osteoblasts and the protein expression levels of IL-6, IL-8, and MMP-13 in the synovial fluids of KOA patients were analyzed. Results: The recessive model of IL-6 rs1800795 locus was found to be associated with KOA risk (adjusted odds ratio (OR) = 1.657, 95% confidence interval (CI) = 1.396-1.866, P<0.001). The IL-8 rs4073 locus dominant and recessive model showed no significant association with KOA risk (P>0.05). The dominant and recessive models of the MMP-13 rs2252070 locus showed higher risk for developing KOA (dominant model: adjusted OR = 1.271, 95%CI = 1.095-1.480, P=0.001; recessive model: adjusted OR = 1.361 95%CI = 1.151-1.569, P<0.001). The G>C mutation in IL-6 rs1800795 and the G>A mutation in MMP-13 rs2252070 were associated with significantly higher KOA disease severity. The G>C mutation in the IL-6 rs1800795 locus was associated with up-regulation of IL-6 expression. The G>A mutation in the MMP-13 rs2252070 locus was associated with up-regulation of MMP-13 expression. Conclusion: The IL-8 rs4073 (-251T>A) mutation was not associated with KOA susceptibility. The IL-6 rs1800795 (-174 G>C) and MMP-13 rs2252070 (-77G>A) mutations were associated with KOA susceptibility, increased disease severity, and up-regulation of IL-6 and MMP-13 expression levels.

Ren Gao

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