Genes encoding for cytokines have been associated with susceptibility for joint osteoarthritis (OA) and interleukin (IL)-1 gene is supposed to be involved in the cartilage destruction process. In this regard, interleukin-1 receptor antagonist (IL-1RA) competing with IL-1 for binding to its receptor may act as an inhibitor of cartilage breakdown. We assessed the association of primary knee OA with IL-1RA region as a putative factor of susceptibility to knee OA in Egyptian patients.
Eighty patients with primary knee OA and 40 aged-matched healthy controls were included into the study. DNA samples were used to study genotypes of IL-1RN gene by polymerase chain reaction (PCR) in both groups.
An increased frequency of the IL-1RN*1 and IL-1RN*2 alleles was found in OA patients relative to controls (60.5% vs. 39.5%, P=0.039, 85.4% vs. 14.6%, P=0.002, respectively) however, only the carriage rate of IL-1RN*2 allele was found to be significant when OA patients were compared to the controls. Significant higher frequencies of IL-1RN*1/*2 and IL-1RN*2/*2 genotypes in OA patients were observed as compared with controls. Both visual analogue scale (VAS) {and radiographic score revealed} significant correlation with both the allelic frequency and the carriage rate of IL-1RN*2 allele. Moreover, absolute frequency of IL-1RN*1/*2 genotype OA patients revealed severe VAS and high radiographic score.
These results suggest that IL-1RN*2 allele represent a significant factor influencing the severity and course of knee OA; thereby supporting the potential role of IL-1 in the pathogenesis of this disease.