Role of combinations of polymorphisms of cytokine genes in the diagnosis of Legg–Calve–Perthes disease in children

Abstract

Background. LeggCalvePerthes disease (LCPD) is an idiopathic avascular femoral head osteonecrosis. The early disease stage is associated with the development of synovitis of the hip joint linked to the overproduction of factors induced by hypoxia as well as of interleukin (IL)-6. Associations of individual polymorphic variants of cytokine genes with LCPD have been shown. Moreover, alterations in the cytokine regulatory cascade are considered an important link in the pathogenesis of synovial inflammation in the early stages of LCPD. Accordingly, this process may be associated with a certain combination of polymorphic variants of the genes for pro-inflammatory and anti-inflammatory cytokines.
 Aim. This study aimed to study the associations of polymorphic variants of the genes for pro-inflammatory and anti-inflammatory IL with LCPD.
 Materials and methods. In this casecontrol study, the main and control groups were composed of 26 children with LCPD and 40 healthy children (all aged 311 years), respectively. Genotyping of IL10 (rs1800896), IL13 (rs20541), IL18 (rs187238), IL18 (rs5744292), IL1a (rs1800587), IL1RA (POL_GF_58), IL-1Ra (rs4251961), IL1B (rs16944), IL1B (rs1143634), IL4 (POL_GF_59), IL4 (rs2243250), IL6 (rs1800796), IL6 (rs1800795), INF (rs2430561), TGF (rs1800469), and TNF (rs1800629) was performed by polymerase chain reaction (PCR) using TaqMan probes to the corresponding polymorphic variants of genes produced by Thermo Fisher Scientific (USA) on an amplifier ViiATM 7 RealTime PCR System (Life Technologies, USA). Statistical processing of the results was carried out using the SNPstats program and multifactor dimensionality reduction.
 Results. The study revealed three separate LCPD-potentiating genotypes of polymorphic variants of cytokine genes: IL10 (rs1800896; TC)*T/C (OR 6.50), IL4 (POL_GF_49, VNTR, Intron4)*2R/2R (OR 12.32), and IL-6 (rs1800796; GC)*G/C (OR 4.08). Two polymorphic variants of the IL4 gene (POL_GF_49, VNTR, Intron4, and rs2243250; CT) had a pronounced synergism with respect to the diagnosis of LCPD. Moderate synergy with respect to the diagnosis of LCPD demonstrated the intergenic interaction of IL6 (rs1800796, GC) with tumor necrosis factor- (rs1800629, GA). Moderate antagonism between LCPD and intergenic interactions was obtained for polymorphic variants of IL18 (rs5744292, TC) and transforming growth factor- (rs1800469, AG) genes.
 Conclusions. The pathogenesis of synovitis and subsequent osteonecrosis in LCPD is associated with a combination of polymorphic variants of the genes of pro-inflammatory and anti-inflammatory cytokines, as well as of DNA variants of the pro-allergic IL4 gene.