In the current research, we studied the correlation between CXCR4 polymorphism at rs1804029 and rs17848060 loci and the susceptibility to KOA in 305 cases of KOA patients and 305 healthy controls in Chinese Han population. The results revealed that individuals harboring G allele or T allele at CXCR4 rs1804029 site were more susceptible to KOA. Moreover, subjects with G allele at rs1804029 site had lower level of hsa-miR-146a-3p in the plasma, while hsa-miR-20a-3p was highly expressed in subjects with T allele at rs17848060 locus. Dual-luciferase assays further proved that hsa-miR-146a-3p could bind to CXCR4 carrying G at rs1804029 locus, and CXCR4 with A genotype at rs17848060 site was one of the target genes of hsa-miR-20a-3p. Therefore, it was inferred that SNPs at CXCR4 rs1804029 and rs17848060 loci were significantly associated with KOA susceptibility in the Chinese Han population.
CXCR4 is located on chromosome 2q21 and contains two exons and one intron (Federsppiel et al. 1993; Herzog et al. 1993; Wegner et al. 1998). Generally, the 3′-UTR of a gene has a regulatory region for gene expression. Gene mutations in the regulatory region can affect regulation of gene expression; therefore, SNPs in regulatory region are related to the occurrence and development of several diseases (An et al. 2006; Hashemi et al. 2018; Revathidevi et al. 2016; Seegers et al. 2002). The rs1804029 site is located at the 3′-UTR targeted binding site of hsa-miR-146a-3p on CXCR4. The G to T allele mutation at this site can break the interaction between hsa-miR-146a-3p and the 3′-UTR of CXCR4. Similarly, the rs17848060 site is within the binding site of the hsa-miR-20a-3p and CXCR4. The A > T allele mutation can affect the binding between hsa-miR-20a-3p and 3′-UTR of CXCR4. After adjusting for age, gender, BMI, smoking history, drinking history, knee injury history, and KOA family history, the KOA susceptibility of heterozygosity (TG) at the CXCR4 rs1804029 locus and dominant model was significantly increased.
Although there was no significant increase in KOA susceptibility of homozygosity (GG), additive model and recessive model, the overall analysis showed that the KOA susceptibility of carriers with G allele at CXCR4 rs1804029 locus was statistically increased. The reason may be that the sample size of the G allele carrier of the CXCR4 rs1804029 locus was small, especially the sample size of the subjects carrying GG genotype was small, which led to a large error in statistical analysis. The KOA susceptibility of the heterozygous, homozygous, dominant model, and recessive model of CXCR4 rs17848060 locus had significantly increased. Although the KOA susceptibility of the additive model was not significantly increased, CXCR4 with T allele at rs17848060 locus was a susceptible gene for KOA.
Stratified analysis is very important in analyzing the correlation between gene SNPs and development of disease (Wang et al. 2018; Wang et al. 2017; Wu et al. 2015). In the present study, stratified analysis was conducted for the baseline information of enrolled subjects. As expected, stratified analysis of factors including gender, age, BMI, smoking history, drinking history, knee injury history, and KOA family history had a great impact on the correlation between the SNPs at CXCR4 rs17848060 locus and KOA susceptibility, indicating the necessity of stratified analysis for different groups of subjects. In addition, in the stratified analysis, compared with subjects with TT genotype at rs1804029 locus, the KOA susceptibility was significantly higher in the subjects who carried TG and GG genotypes and had drinking history. When the prior probability was 0.1, the FPRP was less than 0.2, suggesting that the sample size was small and the results of the analysis may be biased.
MDR was applied to analyze the interaction between SNPs at CXCR4 rs1804029 and rs17848060 loci and the factors including age, gender, BMI, smoking history, drinking history, knee injury history, and KOA family history. The results showed that the interaction between drinking, knee injury history, and knee osteoarthritis family history and SNPs at rs1804029 and rs17848060 loci had the greatest predictive value for KOA susceptibility, indicating that the occurrence of KOA may be induced by multiple factors.
To probe the potential mechanism, dual-luciferase experiments and bioinformatic assays were conducted to investigate the interaction between SNPs at CXCR4 rs1804029 and rs17848060 sites and predicted miRNAs; experimental data demonstrated the presence of CXCR4 with G allele at rs1804029, and CXCR4 with A allele at rs17848060 locus. Although the levels of miRNA in plasma were consistent with the results of dual-luciferase assay, we did not have data on the expression level of CXCR4 protein in articular cartilage tissue, and further experiments were needed for further verification.
In summary, there are still some limitations in this study that need to be overcome; in particular, the limitation of the sample size affects the objectivity of the results, which need to be further verified in a large sample size. In addition, potential mechanisms need to be deeply explored in both in vitro and in vivo models.