Osteonecrosis of the femoral head (ONFH) is a severe pathological state with multiple etiologies. Steroid hormone metabolism-related genes play an important role in ONFH. The aim of this study was to investigate the relationships between polymorphisms of the drug-metabolizing enzyme gene, cytochrome P450 (CYP450), and the drug transporter gene, ATP-binding cassette subfamily B member 1 (ABCB1), as well as their DNA methylation status with the pathogenesis of steroid-induced ONFH. Methods: In this case-control study, we evaluated five single nucleotide polymorphisms (SNPs) in two genes in a Han Chinese population, including 79 patients with steroid-induced ONFH and 114 persons who took steroids but did not develop steroid-induced ONFH. SNPs were genotyped by the improved multiplex ligation detection reaction. MethylTarget technology was used to ascertain the methylation status at two CpG islands in the ABCB1 gene for statistical analysis. Finally, interactions between the SNPs and the CpG site's methylation levels were statistically analyzed by methylation quantitative trait locus. Results: We found that the T allele of the CYP450 rs2242480 locus was associated with steroid-induced ONFH risk reduction (odds ratio [OR] = 0.598, 95% confidence interval [CI]: 0.360-0.992, p = 0.046). In the genetic model analysis, the T allele of the rs2032582 locus in the ABCB1 gene was associated with a reduced risk of steroid-induced ONFH under the dominant model (OR = 0.465, 95% CI: 0.223-0.972, p = 0.042). The CpG sites with significant differences (p < 0.05) in methylation levels between the cases and controls were ABCB1_1_192 .ABCB1_2_43. A total of 14 pairs of linear regression tests between SNPs and methylation sites demonstrated statistical significance ( p < 0.05). Conclusions: This study provides evidence for two steroid-induced ONFH susceptibility genes (ABCB1, CYP450) in the Han Chinese population.

Background: Although the precise etiology of osteonecrosis of the femoral head (ONFH) has yet to be fully elucidated, it is known that nuclear receptor subfamily3, group C, member 1 (NR3C1), 5, 10-methylenetetrahydrofolate reductase (MTHFR) and insulin-like growth factor-binding protein 3 (IGFBP3) are related to the pathophysiology of steroid-induced osteonecrosis of the femoral head (SONFH). The expression of NR3C1, MTHFR and IGFBP3 are regulated by epigenetics and genetic profiles. Objective: The primary objective of this study was to investigated the association between NR3C1, MTHFR and IGFBP3 gene polymorphisms and DNA methylation status and SONFH.Methods: This case-control study included 79 patients with SONFH and 114 patients who took steroids but did not develop SONFH. We evaluated 5 single-nucleotide polymorphisms (SNPs) out of 3 genes in Chinese Han population. These SNPs were genotyped by improved multiplex ligation detection reaction (iMLDR). Methyltarget was used to test the methylation level of positive sites, the interaction between SNPs and DNA methylation level was analyzed using eQTLD technique.Results: We identified rs3110697 in the IGFBP3 gene that was potentially associated with a reduced risk of SONFH in the genotype (P=0.008; odds ratio [OR]: 0.741; 95% confidence intervals [CI]: 0.456–1.205) and in the recessive model (P=0.003; OR: NA; 95% CI: NA–NA). Furthermore, CpG sites with significant differences in methylation levels were screened as follows: IGFBP3_2-143, MTHFR_1-36, MTHFR_1-77, MTHFR_1-139, MTHFR_2-42, NR3C1_2-163, NR3C1_4-47, and the differences were statistically significant compared with the control group (p<0.05). A total of 10 pairs of linear regression tests of SNP and methylation sites were statistically significant (p<0.05).Conclusions: SONFH is a polygenic disorder in which a wide range of interactions between SNPs and DNA methylation levels may dominate the course of the disease.