Vitamin D Receptor Gene Polymorphisms and Risk of Knee Osteoarthritis: Possible Correlations with TNF-α, Macrophage Migration Inhibitory Factor, and 25-Hydroxycholecalciferol Status

Osteoarthritis (OA) etiology and pathogenesis not yet fully understood. We studied the role of vitamin D receptor single-nucleotide polymorphisms (VDR-SNPs), vitamin D3, serum and synovial macrophage migration inhibitory factor (MIF), and tumor necrosis factor-alpha (TNF-alpha) in the development and progression of knee OA (KOA). This study included 205 Egyptian subjects (105 patients with KOA and 100 unrelated, healthy matched subjects selected as controls). The patient group was divided into three groups according to KOA severity (mild, moderate, and severe), with 35 patients in each group. The polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique was used for the ApaI and TaqI SNPs. Vitamin D, serum and synovial TNF-alpha, and MIF assays were performed using ELISA kits. There were significantly lower serum levels of 25-hydroxycholecalciferol with significant increasing TNF-alpha and MIF levels in relation to disease severity among the cases (all: p<0.05).Wild homozygous and heterozygous mutant genotypes (GG+GT) and G allele of ApaI demonstrated risk for KOA development, with odds ratio OR = 6.313 (95% confidence interval (CI) 2.074-19.210) and OR = 1.532 (95%CI 1.013-2.317), respectively. Homozygous mutant CC genotype and C allele of TaqI could be considered a risk factor associated with KOA development, with OR = 2.667 (95%CI 1.270-5.601) and OR = 0.737 (95%CI 0.496-1.095), respectively. VDR-SNPs, vitamin D3, TNF-alpha, and MIF could play an essential role in the pathogenesis and progression of KOA with mechanistic associations.