Association of TIMP-1 and COL4A4 Gene Polymorphisms with Keratoconus in an Iranian Population

Keratoconus (KC) is a bilateral and noninflammatory disease, characterized by progressive thinning and anterior protrusion of the cornea and may result in severe visual impairment due to irregular astigmatism. Matrix metalloproteinases (MMP) are the main group of enzymes that degrade extracellular matrix proteins including collagens; Type IV collagen is found in the corneal stroma. MMP enzymatic activity is inhibited by tissue inhibitor of metalloproteinase-1 (TIMP-1). A decrease in TIMP-1 level is associated with the development of KC. In the present study, we investigated the impact of COL4A4 rs2228557 C/T and TIMP-1 rs4898 C/T (X-chromosome) variants on the odds of KC development in a sample of Iranian population.

This case–control study was conducted on 140 patients with KC and 150 healthy control subjects. We used modified methods of Nested-PCR and ARMS-PCR in combination (Nested- ARMS-PCR) and confirmed their validity with RFLP–PCR.

Significant differences were noticed between KC patients and healthy individuals regarding the genotype TY or T allele frequencies of rs4898 in the male subjects (OR = 0.43, 95%CI: 0.20–0.92, P = 0.03), whereas no significant differences were identified in the female subjects (OR = 1.07, 95%CI: 0.52–2.20, P = 0.85). The rs2228557, T allele was associated with KC (OR = 0.69, 95% CI: 0.50–0.97, P = 0.035).

In the rs2228557 variant, T allele acts as a protective factor from the disease and decreases the risk of KC compared with the C allele. Also, in our investigation about rs4898, we found that TY genotype or T allele decreased the risk of KC compared with the C allele in males and was a protective factor for KC in our population.