Abstract
<b>Introduction:</b> We have previously observed an inverse relationship between FEV<sub>1</sub> and the volume fraction of extracellular matrix (V<sub>VECM</sub>) within the layer of airway smooth muscle (ASM) in smokers with airflow obstruction. Many patients with asthma have a degree of fixed airflow obstruction. We hypothesized that fixed and variable obstruction may differ with regard to V<sub>VECM</sub> within the ASM layer. <b>Aim:</b> To compare the V<sub>VECM</sub> within the ASM layer in asthmatic subjects with (n=7, FEV<sub>1</sub><80% predicted) or without (n=8, FEV<sub>1</sub>>80% predicted) fixed airflow obstruction. <b>Methods:</b> The FEV<sub>1</sub>, measured pre-operatively in patients undergoing lobectomy (n=12), or obtained from medical records from post-mortem cases (n=3), was recorded. Airways were paraffin embedded and thin (0.5µm) transverse sections were cut and stained using the Masson’s trichrome technique. Point counts were made within the ASM layer to estimate the V<sub>VECM</sub> and the correlation between FEV<sub>1</sub> and V<sub>VECM</sub> was estimated using Spearman’s correlation coefficient. <b>Results:</b> Mean ± SD, *=p<0.001. V<sub>VECM</sub> negatively correlated with FEV<sub>1</sub> (r=0.62, p=0.02) but not in non-smoking asthma cases analyzed separately (r=0.81, p=0.09). <b>Conclusion:</b> The V<sub>VECM</sub> within the ASM layer negatively correlated with FEV<sub>1</sub> in asthmatic subjects, with a similar trend seen in non-smoking asthma subjects. These data suggest that, as seen in smokers, fixed airflow obstruction in asthma is related to increased ECM within the ASM layer.
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