Matrix metalloproteinases MMP-7, MMP-9 and their tissue inhibitor TIMP-1: expression in chronic sinusitis vs nasal polyposis

Background: Nasal polyps (NP) are characterized by pseudocyst formation, whereas the mucosa in chronic sinusitis (CS) only shows a limited oedema. Matrix metalloproteinases (MMPs) are a family of endopeptidases able to degrade the extracellular matrix. Differences in histological features between CS and NP might be related to the respective expression of MMPs and their tissue inhibitors (TIMPs). Objective: The aim of this study was to investigate MMP-7, MMP-9 and TIMP-1 proteins in NP and CS in comparison with normal mucosa. Methods: Nasal samples, obtained from controls (n = 10), from NP (n = 8) and from CS (n = 10), were analysed by immunohistochemistry and enzyme-linked immunosorbent assay (ELISA). Results: In NP, compared with controls, staining for MMP-9 and MMP-7 appeared in blood vessels. Matrix metalloproteinase-9-positive inflammatory cells could be detected in increased numbers in pseudocyst formations. Concentrations of MMP-9 protein was found significantly increased in both CS and NP compared with controls, while MMP-7 was significantly increased in NP compared with controls and CS. Tissue inhibitors of metalloproteinase-1 protein was significantly increased in CS and NP when compared with controls. Conlcusions: Chronic sinusitis and NP show different pattern of MMP-7/-9 and TIMP-1 expression. We suggest that this difference in regulation of enzymes is related to the respective tissue remodelling observed in both diseases.