Epithelial activation in chronic obstructive pulmonary disease (COPD)

`Background:` Early on I identified that reticular basement membrane (Rbm) in current smokers with COPD was highly fragmented, with cracks termed “clefts” containing cells. This looked like the described hallmark of EMT (epithelial mesenchymal transition). I followed this preliminary observation with a comprehensive cross-sectional study in which I hypothesized that the airway epithelium is activated in smokers, and that this may promote EMT, but that this will be especially active in COPD. As a part of my thesis, I also investigated the expression and activity of the anti-inflammatory enzyme HDAC2 (histone deacetylase 2) which is reported to be reduced in COPD lungs and may account for associated pulmonary inflammation. I hypothesised that the current literature is correct in stating that HDAC2 is down-regulated in COPD airways and also that these reduced HDAC2 levels are normalised by aggressive inhaled corticosteroid (ICS) therapy and smoking cessation in patients with COPD. \(Methods\) \(and\) \(results:\) Endobronchial biopsies (ebb) from current smokers with COPD (COPD-CS) and ex-smokers with COPD (COPD-ES), smokers with normal lung function (NS) and never-smoking controls (NC) stained for markers of EMT, matrix metalloproteinase-9 (MMP-9), fibroblast protein (S100A4), epidermal growth factor receptor (EGFR), vimentin and cytokeratins. To confirm the extent of suppressed HDAC2 ebb were immuno-stained for HDAC2. In a double-blind, randomized, placebo-controlled study, I assessed the effects of ICS on Rbm fragmentation and HDAC2. Compared to NC, there was significant fragmentation of the Rbm in COPD-CS, COPD-ES and NS groups. COPD-CS, NS and COPD-ES demonstrated increases in staining for: basal epithelial S100A4, epithelial EGFR and MMP-9 and S100A4 for cells in Rbm ``clefts`` compared to NC. Dual staining revealed that vimentin (a mesenchymal marker) co-stained with cytokeratin (an epithelial marker). ICS normalised Rbm fragmentation. Compared to NC there was significant increase in HDAC2 positive cells in NS in the lamina propria (LP) but a decrease in COPD-CS. However, this latter abnormality was due to a reduction in total LP cells and not % cell HDAC2 staining. There were significantly more HDAC2 positive cells in COPD-ES compared to COPD-CS, but again due to an increase in total cell numbers. ICS made no difference to HDAC2 staining. `Conclusions:` This is the first description of likely EMT in smoking and COPD. ICS reversed Rbm fragmentation. HDAC2 expression was reduced in smokers but confounded by changes in cellularity. Quitting does seem to have a real effect on upregulating HDAC2, but it is not affected by ICS.