Functional polymorphisms located in FOXP3 intron 1 was recently found to be associated with rheumatoid arthritis (RA). Although RA is an autoimmune disease, there is supporting evidence that activated maladaptive responses including pro-inflammatory pathways play roles in osteoarthritis (OA), similar to RA. The aim of this study was to explore the relationship between rs2232365 (-924A/G) and rs3761548 (-3279A/C) polymorphisms as well as possible changes in the 600 bp promoter region of FOXP3 and knee OA.
Patients with primary knee OA (n = 300) and healthy individuals (n = 300) were examined for rs3761548 and rs2232365 FOXP3 gene polymorphisms by the polymerase chain reaction-restriction fragment-length polymorphism method. The 600 bp promoter region (between -500 and +100) of the gene was also sequenced with direct sequencing in 50 knee OA patients and 50 healthy individuals.
There were no sequence variants in the promoter region tested both in OA patients and healthy controls. The SNP rs2232365 showed no association with OA susceptibility and severity and the results of other genetic models were also nonsignificant. On the other hand, rs3761548 AC (P = 0.003), AA + CC (P = 0.0014) as well as AC + AA (P = 0.40) genotypes showed association with Grade 4 knee OA patients.
Our findings indicated that the association between FOXP3 rs2232365 polymorphism and knee OA tended to yield negative results but the FOXP3 rs3761548 C allele was associated with elevated risk of OA in Grade 4 knee OA patients in a Turkish population.