MMP-9 microsatellite polymorphism and susceptibility to exudative form of age-related macular degeneration

Purpose: To assess if a polymorphism (PM) of the microsatellite (CA13–27) in the promoter region of Matrix Metalloproteinase 9 (MMP-9) was associated with the exudative form of age-related macular degeneration (AMD) and to its risk factors. Methods: In 107 patients with AMD (AMD Group) and 223 age- and gender-matched controls (Control Group) with cataract, demographic, clinical data, and MMP-9 PM have been compared. Results: The comparison of allelic frequencies showed a different pattern of CA repeats between AMD and Control Group (P < 0.00005), in particular the prevalence of longer microsatellites (≥ 22 CA repeats) was higher in AMD than in Control Group (O.R. 2.49, 95% CI 1.71 - 3.37, P < 0.001). Analyses of genetic frequencies gave similar results. Logistic regression confirmed that 22 or more CA repeats are associated to AMD. The only association between MMP-9 PM and other risk factors for AMD was with BMI (Spearman’s R = 0.298, P < 0.00005): all patients with both microsatellites ≥ 22 CA repeats were overweight or obese (χ2 test P < 0.0005, compared to other genotypes). Conclusions: Longer microsatellites in the promoter of MMP-9 are associated to the exudative form of AMD and to body mass index, a well-known risk factor for the disease.