Extracellular Matrix Remodeling by Dynamic Strain in a 3D Tissue Engineered Human Airway Wall Model

Airway wall remodeling is a hallmark of asthma, characterized by subepithelial thickening and extracellular matrix (ECM) remodeling. Mechanical stress due to hyperresponsive smooth muscle cells may contribute to this remodeling, but its extent and relevance in a 3D environment (where the ECM plays an important role in modulating stresses felt by cells) are unclear. To characterize the effects of dynamic compression in ECM remodeling in a physiologically relevant 3D tissue model of the human airway wall, a tissue engineered human airway wall model with differentiated bronchial epithelial cells atop a collagen gel containing lung fibroblasts was developed. Lateral compressive strain of 10% or 30% at 1 or 60 cycles per hour was applied using a novel straining device. ECM remodeling was assessed by immunohistochemistry and zymography. Dynamic strain, particularly at the lower magnitude, induced airway wall remodeling as indicated by increased deposition of types III and IV collagen and increased secretion of matrix metalloproteinase-2 and -9. These changes paralleled increased myofibroblast differentiation. Furthermore, the spatial pattern of type III collagen deposition correlated with that of myofibroblasts; both were concentrated near the epithelium and decreased diffusely away from the surface, indicating some epithelial control of the remodeling response. Thus, in a physiologically relevant 3D model of the bronchial wall, dynamic compressive strain induced tissue remodeling that mimics many features of remodeling seen in asthma, in the absence of inflammation