Association of Rs1676486 genetic polymorphism and lumbar disc degeneration in Iranian population

lumbar disc degeneration is a multifactorial degenerative disease which is affected by genetic inheritance and environmental factors. Type XI collagen is important for organization of the extracellular matrix and cartilage collagen construction. Rs1676486 is a SNP that causes the conversion of C-T, resulting in a change in the expression of the collagen 11 alpha chain. The T allele reduces the alpha 1 chain transcription of collagen 11 and ultimately leads to an imbalance in gene expression.

This study aims to determine the genetic variant of alpha1 type11 collagen is associated with the progress of intervertebral disc degeneration. All patients were selected from the AL-Zahra Hospital of medical university of Isfahan, Iran, between April 2016 and September 2017. SNP rs1676486 of alpha1 type11 collagen was genotyped in 100 patients and 100 healthy controls. The inclusion criteria for patients were: individuals who had typical clinical and imaging symptoms and signs of intervertebral disc degeneration. Exclusion criteria were: patients with trauma, metabolic and neuromuscular diseases, and congenital disorder of the spine. The Genomic DNA was extracted from peripheral blood samples by a Whole Blood Genomic DNA Extraction Kit. The chi-square test and fisher’s exact test were evaluated to determine differences of genotype and allele distributions between intervertebral disc degeneration patients and healthy controls. To compare the relationship between genotypes and clinical features the Mann-Whitney U test was used.

The mean age was 39.54±9.52 years for the patients and 28.14±5.32 years for the controls, respectively. The mean BMI were 26.3±3.18 kg/m2 and 27.3±3.52 kg/m2 for the patients and the controls, respectively. In addition, the results showed that the prevalence of surgical disc in patients with L4-L5 levels was 52.1% and L5-S1, with 31.1%. This study showed, rs1676486 in alpha1 type11 collagen gene was associated with modified intervertebral disc degeneration at age ≤50 years and this gene increases intervertebral disc degeneration risk at age >50 years. SNP rs1676486 had the significant association with the intervertebral disc degeneration (P=0.019), and patients were found to have higher frequency of AA than the controls.

This observation shows that type XI collagen is related to age and genetic factor in intervertebral disc degeneration disease.