The interaction between aggrecan gene VNTR polymorphism and cigarette smoking in predicting incident symptomatic intervertebral disc degeneration

Abstract

An association between the aggrecan variable number of tandem repeat (VNTR) polymorphism and the disc degeneration has been previously reported in Finnish men, and smoking had previously been suspected of causing disc degeneration. However, the interaction between aggrecan gene VNTR polymorphism and smoking in symptomatic intervertebral disc degeneration (IDD) has not been well studied. To examine the interaction between aggrecan gene VNTR and smoking in the susceptibility of symptomatic IDD of Chinese Han in northern China, intervertebral discs of 132 participants were evaluated on magnetic resonance imaging, using decreased signal intensity. After harvesting the blood samples, the aggrecan gene VNTR region was analyzed using polymerase chain reaction (PCR). The data indicated that between the two groups, participants carrying one or two alleles ≤25 repeats who did not smoke showed a 1.102-fold increased risk for symptomatic IDD (p= 0.855; 95% confidence interval 0.389–3.119), and participants carrying two alleles >25 repeats who smoked more than 1 pack-year showed a 1.013-fold higher risk (p = 0.982; 95% confidence interval 0.333–3.084), whereas participants carrying one or two alleles ≤25 repeats who smoked more than 1 pack-year showed a 4.5-fold increased risk for symptomatic IDD (p = 0.005; 95% confidence interval 1.589–12.743). Overall, we observed an underlying additive and multiplicative interaction between the aggrecan gene VNTR polymorphism and smoking in symptomatic IDD.

KEYWORDS:

• aggrecan gene
• magnetic resonance imaging
• proteoglycans
• smoking
• symptomatic intervertebral disc degeneration