University of Helsinki, Helsinki 2006
Microbiological, environmental and proteolytic aspects in chronic rhinosinusitis with nasal polyposis
Doctoral dissertation, April 2006.
Chronic rhinosinusitis is one of the most common chronic respiratory tract diseases affecting up to 15% of the adult population in the Western world. It may be perpetuated by factors predisposing to sinus ostial obstruction together with inflammatory changes in the sinus mucosa. Chronic rhinosinusitis is associated with asthma, and it may represent the same disease process. Chronic rhinosinusitis with nasal polyposis (CRSwNP) and asthma share also the characteristic inflammatory features and histopathologic feature of airway remodelling. Remodelling is considered as a key event in the pathogenesis of asthma. It is controlled by a delicate balance between the matrix metalloproteinases (MMPs) and their regulators.
The purpose of the present study was to evaluate the microbiological findings, inflammatory features and MMP and tissue inhibitor of metalloproteinases-1 (TIMP-1) expression in CRSwNP. The results were related to the patient history, exposure to moisture and clinical outcome in order to find out possible explanations for the etiology and chronicity of CRSwNP.
Bacterial culture results were similar in patients and in controls and do not explain the chronic course of CRSwNP. The presence of fungi seems to be more common in CRSwNP than chronic rhinosinusitis in general, and they should be actively searched for using microbiological as well as histological methods. Typical outdoor fungal species were found in nasal lavage samples taken from controls in the autumn but not in the winter, reflecting environmental exposure. Exposure to moisture was reported by 46% of the CRSwNP patients, which is in accordance to the Finnish general population. Exposed patients did not differ significantly from non-exposed subjects with regards to microbiological findings, tissue eosinophilia and clinical outcome.
Significantly elevated levels of collagenase-2 (MMP-8) and interleukin (IL)-8 but not tumour necrosis factor-α were found in CRSwNP patients. In particular, the activation of mesenchymal-type MMP-8 but not polymorphonuclear-type MMP-8 was associated with elevated IL-8 levels. IL-8 and MMP-8 may form an inductive cytokine-proteinase cascade in CRSwNP pathogenesis and provide a target for novel therapies and a diagnostic tool for monitoring CRSwNP treatment. The proteolytic spectrum is different in eosinophilic and non-eosinophilic CRSwNP with the up-regulation of MMP-8 and MMP-9 in non-eosinophilic CRSwNP, suggesting different pathophysiology in these subgroups. The lack of MMP up-regulation was associated with a poor prognostic factor and worse clinical outcome, representing a possible synergic anti-inflammatory function of MMP-8 and MMP-9 in CRSwNP.
This study provides new information about possible immunologic mechanisms in the pathogenesis of CRSwNP. The recently discovered anti-inflammatory/ defensive properties of MMP-8 and MMP-9 in animal models are reported for the first time in a clinical setting in human inflammatory diseases.
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© University of Helsinki 2006
Last updated 13.04.2006