Expression of matrix metalloproteinases (MMP-2 and MMP-9) in vocal fold polyps

Objective. Vocal fold polyps are the most common benign laryngeal lesions. Matrix metalloproteinases (MMP) play an important role in the physiological and pathological remodeling of tissues. The most important subgroup of MMP family consists of gelatinases A and B (MMP-2 and MMP-9). The objective of this study was investigation of the expression of MMP-2 and MMP-9 in vocal fold polyps and normal tissue of vocal folds.
Material and methods. The immunohistochemical expression of MMP-2 and MMP-9 was investigated in specimens taken by endolaryngeal microsurgery from vocal fold polyps (n=30) and normal tissue of vocal fold (n=13, control group). Expression of MMP-2 and MMP-9, both in epithelium and stroma cells, was graded on a semiquantitative scale, ranging from 0 (no expression) to 6 points (high expression).
Results. A statistically significant increase was observed in the expression of MMP-2 in stroma cells (P=0.0176) of vocal fold polyps compared to control vocal fold group, whereas no significant difference in the expression of MMP-2 was found in epithelium cells (P=0.1487). Comparison of expression of MMP-2 and MMP-9 in epithelium cells revealed a statistically significant increase in MMP-9 expression (P<0.01) in both groups. However, there was no statistically significant difference in the expression of MMP-9 between groups of vocal fold polyps and control vocal folds.
Conclusion. Expression of MMP-2 in stroma was significantly higher in polyps than in normal tissue of vocal folds. Our data draw attention to the role of MMP-2 in the development of vocal fold polyps and necessity of further investigations to define its function in morphogenesis of laryngeal benign, premalignant, and malignant lesions.