Differential Expression of Extracellular Matrix Components in Nasal Polyp Endotypes

Chronic rhinosinusitis is a difficult-to-treat disease that is often characterized by recurrent nasal polyp (NP) growth following surgical removal. The disease has been separated into distinct phenotypes based on cellular infiltrate or underlying physiological mechanisms. NPs are composed in part of an inflammatory cellular infiltrate, blood vessels, and a large amount of extracellular matrix (ECM). Despite the recognition of prominent ECM deposition, few studies have examined the components in detail and how they might differ with disease state.

The purpose of this study was to quantitate the expression of ECM components in NPs.

NPs were stained with pico-sirius red to determine total collagen content, and immunofluorescence was used to detect collagen I, collagen III, collagen IV, fibronectin, and laminin. Expression of each was quantitated and analyzed in relation to rhinosinusitis phenotype and separately as a function of polyp eosinophil number.

When analyzed by phenotype, collagen I, collagen III, and fibronectin were expressed at the highest levels in noneosinophilic sinus disease. Collagen IV was not different among any groups, and its location was found predominately around vessels. When analyzed as a function of polyp eosinophil number, total collagen and collagen III showed a significant inverse correlation.

NP ECM composition differs with disease state with higher expression in cases where eosinophil levels are low. This suggests that in eosinophilic polyps there is a loss of matrix deposition either through break down or a failure to produce the essential components. Understanding these differences may identify new therapeutic targets.