Development and characterization of an in vitro wound healing model of chronic bronchial asthma

Chronic bronchial asthma afflicts more than 15 million people in the U.S., and as many as 150 million people worldwide. The disease is characterized by chronic repetitive exacerbations of bronchial narrowing and permanent structural changes to the airway wall. The increasing prevalence, morbidity, and healthcare costs associated with asthma have made therapies the focus of intense research. Although attempts have been made to understand the cellular and molecular mechanisms underlying the structural remodeling in asthma, the complex association of factors of this phenomenon is poorly understood. A comprehensive understanding of human wound repair is limited by accessibility to the airways and difficulties in isolating in vivo each mechanism of the wound healing process. These limitations have inspired the development of an in vitro model of the bronchial mucosa. This engineered “tissue” allows the study of cell-cell and cell-matrix interactions that has previously been impeded by physiological limitations.; Cell culture, imaging techniques and biological assays were utilized in this study to develop and characterize an engineered human lung tissue model to study the mechanisms underlying chronic bronchial asthma. An engineered tissue model of the human airway mucosa was developed using a co-culture of normal fibroblasts and small airway epithelial cells in a 3-D collagen gel. Consistent with previous studies, the contractile properties of the tissue were found to be modulated by the presence of the epithelium. The engineered tissue construct was then developed into a wound healing model by implementing a series of different wound types (chemical or mechanical) and wound patterns (single or chronic) that are characteristic of bronchial asthma. Upon injury, the expression of ECM proteins, chemical mediators and growth factors in the ECM was found to depend on the wound pattern and type. These data suggest that the repair response to different wounds occurs via distinct mechanisms. Additionally, two-photon laser scanning microscopy (TPLSM) was determined to be a valid tool to probe fibrillar collagen in the ECM, and to detect changes in the repair response in the context of the in vitro wound healing model.