Functional characterization of a novel 3D model of the epithelial-mesenchymal trophic unit

ABSTRACT

Background/Aim: Epithelial-mesenchymal communication plays a key role in tissue homeostasis and abnormal signaling contributes to chronic airways disease such as COPD. Most in vitro models are limited in complexity and poorly represent this epithelial-mesenchymal trophic unit. We postulated that cellular outgrowth from bronchial tissue would enable development of a mucosal structure that recapitulates better in vivo tissue architecture. Materials and Methods: Bronchial tissue was embedded in Matrigel and outgrowth cultures monitored using time-lapse microscopy, electrical resistance, light and electron microscopy. Cultures were challenged repetitively with cigarette smoke extract (CSE). Results: The outgrowths formed as a multicellular sheet with motile cilia becoming evident as the Matrigel was remodeled to provide an air interface; cultures were viable for more than one year. Immunofluorescence and electron microscopy (EM) identified an upper layer of mucociliary epithelium and a lower layer of highly organized extracellular matrix (ECM) interspersed with fibroblastic cells separated by a basement membrane. EM analysis of the mucosal construct after repetitive exposure to CSE revealed epithelial damage, loss of cilia, and ECM remodeling, as occurs in vivo. Conclusions: We have developed a robust bronchial mucosal model. The structural changes observed following CSE exposure suggest the model should have utility for drug discovery and preclinical testing, especially those targeting airway remodeling.

KEYWORDS:

• in vitro model
• epithelium
• fibroblast
• bronchial
• cigarette smoke
• ECM
• electron microscopy

Declaration of interest

Drs. Davies and Holgate report being cofounders and share-holders in the University spin-out company Synairgen. The other authors have no relevant competing interests to declare.

Funding

This work was supported by grants from the National Centre for Reduction, Refinement and Replacement of Animals in Research, Medical Research Council UK, the Asthma, Allergy and Inflammation Research Charity, the University of Palermo “Progetti Innovativi,” the Italian Ministry of Education, University and Research (MIUR, ex60%), and the Euro-Mediterranean Institute of Science and Technology (IEMEST).