Passively sensitized human organotypic tissue as asthma model to study mast cell-nerve interaction

Background: In the pathogenesis of asthma mast cells play a key role. It is well known that mast cell activation and degranulation is mediated through the aggregation of their high-affinity IgE-receptor (FceRI) by IgE and antigen. But, newly evidences suggest that mast cells can also respond to stimuli that are independent of FceRI, such as tachykinin peptides. The tachykinin substance P has been referred as a pivotal neuropeptide involved in activation and degranulation of mast cells. But, there is a lack of in vitro models to study the local mast cell-nerve interaction. Thus, we aimed to analyze, if C-fibers activation and the release of neuropeptides lead to mast cell degranulation and bronchoconstriction, using passively sensitized human Precision-Cut Lung Slices (PCLS) as an ex vivo model. Moreover, the role of key molecules such as substance P receptor, histamine 1 receptor and soluble IgE were evaluated. Method: To mimic an acute allergic phase, human precision cut lung slices (PCLS) were passively sensitized with plasma from allergic patients. Subsequently, bronchoconstriction was provoked with the allergen house dust mite (HDM) or with C-fiber agonist capsaicin histamine 1 receptor antagonist, NK1 receptor inhibi tor and IgE antagonist. Bronchoconstriction was visualized by videomicroscopy and the reduction of the airway area [% of initial airway area] was analysed. Additionatly, cryosection preparations from human bronchus were immunostained using antibodies against the mast cell tryptase. Mast cell morphology after capsaicin stimulation was illustrated in confocal images. Results: HDM– and capsaicin-induced bronchoconstriction showed reduction of the airway area to 30% and 47% respectively. PCLS incubated with allergic plasma the histamine 1 receptor antagonist, the NK1 receptor inhibitor and IgE antagonist and stimulated with capsaicin showed no reduction of the airway area. Regarding cryosection preparations from human bronchus, immunostaining of mast cells revealed degranulation as evidenced by loss of cell-stored and appearance of freely located mast cell tryptase. Conclusion: Here we show a functional communication of C-fiber nerves and mast cell mediators in human lung tissue leading to strong bronchoconstriction from passively sensitized human PCLS in response to capsaicin. Thus, passively sensitized human organotypic tissue expose the importance of neuroimmunologic characteristics involved in allergic asthma