Human airway smooth muscle
- Publisher: Erasmus University Rotterdam
mesheuropmc: respiratory system | respiratory tract diseases
textabstractThe function of airway smooth muscle in normal subjects is not evident. Possible physiological roles include maintenance of optimal regional ventilation/perfusion ratios, reduction of anatomic dead space, stabilisation of cartilaginous bronchi, defense against impurities and, less likely, squeezing mucus out of mucous glands and pulling open the alveoli next to the airways1 . Any role of airway smooth muscle is necessarily limited, because an important degree of contraction will lead to airway narrowing and to an increased work of breathing. There is, however, no doubt that in asthma the acute bronchoconstriction following exposure to nonspecific or allergic stimuli is due to airway smooth muscle contraction. Most research on airway smooth muscle function has therefore concentrated on clarifying its role in bronchial hyperresponsiveness, airway obstruction and allergy. From the foregoing chapters it can be concluded that many factors may be involved in the pathogenesis of the abnormal responsiveness of airway smooth muscle in patients with asthma or chronic bronchitis. One of these factors is an intrinsic abnormality of the airway smooth muscle cells. In order to examine this, several animal models have been developed, most of which have features in common with human allergic bronchoconstriction2 • Because of important differences between species, and because there is no satisfactory animal model of spontaneous, non-allergic asthma, it is crucial to study human airway smooth muscle from subjects with and without airway hyperresponsiveness. The research on human lung tissue in vitro has been limited by the supply, and by difficulties in obtaining stable and reproducible responses of airway smooth muscle in vitro. Moreover, it is very difficult to obtain lung tissue from asthmatic subjects. This chapter will give a summary of the research on airway smooth muscle hyperresponsiveness in experimental animals and man. From these data, the aims of the studies to be presented in parts II and III will be derived and briefly outlined.