Airway Smooth Muscle Layer Has Key Role in Asthma

Extracellular matrix in ASM layer influences airway function in patients with asthma

TUESDAY, Jan. 17 (HealthDay News) -- Although extracellular matrix (ECM) expression in the airway smooth muscle (ASM) layer is not different for patients with asthma and controls, it is associated with the dynamics of airway function in patients with asthma, according to a study published online Jan. 9 in Allergy.

Ching Yong Yick, from the Academic Medical Center in Amsterdam, Netherlands, and colleagues conducted a cross-sectional study on airway dynamics of 19 patients with atopic mild asthma, 15 healthy atopic controls, and 12 healthy nonatopic controls. Tests performed included spirometry, methacholine responsiveness, deep-breath-induced bronchodilation (ΔRrs), and bronchoscopy with endobronchial biopsies. Biopsy samples were analyzed using histochemical and immunohistochemical assays.

The researchers found that there were no significant differences in the ECM expression in ASM between patients with asthma and controls. The fractional area and mean density of collagen I and III were significantly associated with the slope of methacholine dose-response and with ΔRrs. In patients with asthma, there was a significant association for both ASM collagen III and laminin with forced expiratory volume in one second.

"In asthma, ECM in ASM is related to the dynamics of airway function in the absence of differences in ECM expression between asthma and controls. This indicates that the ASM layer in its full composition is a major structural component in determining variable airways obstruction in asthma," the authors write.

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