Dictionary of Allergies .. Airway epithelium in asthma

Airway epithelium in asthma

The recognition of changes in the airway epithelium, even of living asthmatic patients whose disorder is a fairly mild one, has led to studies of airway structure in asthma by means of the application of endoscopical bronchial biopsing techniques. When the structure of the airway epithelium in these asthmatics without previous continuous medication was compared to that of non-smoking, non-allergic control subjects, the major difference was a clear decrease in the number of ciliated cells and an increase in the number of goblet cells in the asthmatics. The asthma patients were further randomised into two parallel study groups in a double-blind manner, one group receiving inhaled steroid 600μg bid and the other inhaled β2-agonist 375μg bid, for three months. Bronchial biopsies were taken both before and after treatment. After inhaled steroid treatment they showed an increased number of ciliated cells in the epithelium the ciliated/goblet cell ratio being similar to that of the healthy control group. This was accompanied by decreased numbers of inflammatory cells; these changes were not seen in specimens from terbutaline treated patients. These findings suggest that in asthmatic patients a slow "destructive" process of the epithelium with some kind of a regeneration process may be going on. Ciliated cells are probably the first to disappear on injury, and they may not be replaced with its own kind until the injurious stimulation is over. Perhaps a more important aspect than actual epithelial shedding may be a more continuous replacement of the ciliated epithelium by another type of epithelium in asthmatic airways in early stage of the disease. To conclude, bronchial biopsies in living mild asthmatics have revealed that normal ciliated epithelium is altered to an epithelium where goblet or other non-matured epithelial cells predominate. The epithelium in asthma is further characterized by the presence of abnormally high numbers of inflammatory cells particularly eosinophils and lymphocytes.

References

Laitinen, A., and Laitinen, L.A.: Structural changes and cell findings in the airway epithelium in asthmatic patients. Symposium at the XVth EAACI Congress. Airway inflammation, May 11, Paris, 1992