Neuroplasticity and neuroimmune interactions in fatal asthma.

Background: Alteration of airway neuronal function and density and bidirectional interaction between immune cells and sensory peripheral nerves have been proposed to trigger and perpetuate inflammation that contribute to asthma severity. To date, few studies analysed neuroplasticity and neuroinflammation in tissue of asthmatic individuals. We hypothesized that the presence of these phenomena would be a pathological feature in fatal asthma.

Methods: We have quantified the expression of the pan-neuronal marker PGP9.5 and the neuronal sensory-derived neuropeptide calcitonin gene-related peptide (CGRP) in the large airways of 12 individuals deceased due to an asthma attack and compared to 10 control lung samples. The proximity between nerve bundles to eosinophils, mast cells and CADM1⁺ cells was also quantified. We have additionally developed a hPSC-derived sensory neuron/mast cell co-culture model, from where mast cells were purified and differences in gene expression profile assessed.

Results: Fatal asthma patients presented a higher PGP9.5 and CGRP positive area in the airways, indicating sensory neuroplasticity. Eosinophils, mast cells and CADM1⁺ cells were observed in close contact or touching the airway nerve bundles, and this was found to be statistically higher in fatal asthma samples. In vitro co-culture model showed that human mast cells adhere to sensory neurons and develop a distinct gene expression profile characterized by upregulated expression of genes related to heterophilic adhesion, activation and differentiation markers, such as CADM4, PTGS2, C-KIT, GATA2, HDC, CPA3, ATXN1 and VCAM1.

Conclusions: Our results support a significant role for neuroplasticity and neuroimmune interactions in fatal asthma, that could be implicated in the severity of the fatal attack. Accordingly, the presence of physical neuron and mast cell interaction leads to differential gene expression profile in the later cell type.