OBJECTIVETo observe the thick basement membrane-like layer under the damaged epithelium in patients with chronic rhinosinusitis (CRS) and to study its principal components.

METHODSPatients (n = 40) with CRS undergoing functional endoscopic sinus surgery were recruited for the study. Patients (n = 10) with no evidence of sinus disease were used as control subjects. Ethmoidal sinus mucosa specimen were stained by PAS staining to measure the thickness of basement membrane-like layer. Immunohistochemical staining, picrosirius-polarization method and transmission electron microscopy (TEM) were used to analyse the nature of the layer.

RESULTSThe thickness of basement membrane-like layer in CRS type I and CRS type II were significantly increased compared with normal control subjects (t = 5. 426, P < 0. 01; t = 8. 375, P < 0.01). The thickness of CRS type II was significantly greater compared with CRS type I (t = 3. 908, P < 0.01). There was no difference between atopic group and inotropic group (t = 0.803, P> 0.05). There was no expression of fibronectin, laminin, IgA, IgG and IgM in the thick basement membrane-like layer. A thick reticular structure containing collagen fibrils and devoid of cellular elements was observed by TEM.

CONCLUSIONSThis study demonstrates that a long-standing chronic inflammation leads to deposition of collagens type I , III and IV under the damaged epithelium, resulting in an increasingly thick sub-basement membrane layer.