Targeting Inflammatory Mediator Signalling in Pericytes to Resolve Tissue Fibrosis

Abstract

The migration of pericytes from the vasculature towards the inflamed airway is a key contributor to airway remodelling, a hallmark of allergic asthma. However, the mechanisms contributing to this event are not yet known. Various growth factors, cytokines and matrikines have been linked to airway remodelling or allergic asthma, although how they interact with pericytes and effect their migration is yet to be determined. These factors may be useful, druggable targets for future asthma treatments. Pericyte migration was observed via Transwell and scratch assays and the expression of indicators of fibrosis including periostin and N-cadherin were assessed via immunostaining and ELISA and the IL-13 inhibitor cinnamaldehyde was explored as a drug to target this migration. In order to better observe pericyte uncoupling from endothelial cells and their subsequent migration, 3D co-cultures of pericytes and endothelial cells were constructed via magnetic levitation and analysed using immunostaining. As an in vivo corollary, the house dust mite mouse model of allergic asthma was utilised and lung tissue, tracheobronchial whole mounts, bronchoalveolar lavage fluid and whole lung digests were harvested and used to assess the effect of the CXCL12 neutraligand LIT-927 on airway remodelling. The results demonstrate increased pericyte migration following treatment with TGF-β, EGF or periostin and under inflammatory conditions in vivo. The impact of periostin was further explored, with the expression of periostin by pericytes increased by TGF-β and periostin secretion driven by IL-13, which was successfully inhibited with cinnamaldehyde treatment. Spheroids of pericytes and endothelial cells were successfully constructed, although further optimisation of the staining method is needed. CXCL12 neutralization with LIT-927 was found to reduce symptoms of respiratory distress and impede the uncoupling of pericytes while not affecting the immune response or the expression of CXCR4 on pericytes. Overall, cinnamaldehyde and LIT-927 are promising future drugs for treating allergic asthma.