Vitamin D Receptor Gene Polymorphism in Egyptian Patients with Knee Osteoarthritis

Abstract

Introduction : Several polymorphisms have been implicated and associated with osteoarthritis (OA), including vitamin D receptor (VDR). VDR is present in many tissues, including chondrocytes. Vitamin D has been found to increase synthesis of proteoglycan in vitro , suggesting that it may affect the cartilage metabolism. Objective: to investigate the frequency of the VDR gene polymorphism in Egyptian patients with knee OA, and compared them with controls. Subjects and Methods : 200 patients with primary knee OA according to the American College of Rheumatology criteria and 200 matched controls who had no OA. Clinical impact of OA were assessed using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) questionnaire. VDR gene polymorphism Bsm I, Apa I, FokI and Taq I restriction fragment length polymorphisms (RFLPs) were determined by the polymerase chain reaction (PCR). Results : The frequency of ApaI genotype and alleles did not differ significantly between the knee OA patients and the controls. However, three genotypes where significantly higher in knee OA patients than in controls: the bb genotype of BsmI, TT genotype of TaqI and FF genotype of FokI. Knee OA patients with osteophytes had significantly more frequent bb genotype of BsmI, TT genotype of TaqI and FF genotype of FokI. BsmI, TaqI and FokI genotypes or alleles did not show any association with the presence of joint space narrowing (JSN). Knee OA patients who had bb genotype of BsmI, TT genotype of TaqI and FF genotype of FokI are associated with significantly higher WOMAC scores. Conclusion : The current study suggests that VDR gene polymorphism may be associated knee OA in the studied group of Egyptian patients. Association was mostly with severe clinical manifestation and osteophyte formation but not with JSN.