Mimicking Dynamic Changes in the Lung Extracellular Matrix with Visible Light-Responsive Materials to Understand Lung Injury and Fibrosis

Microinjuries to cells and extracellular matrix (ECM) in the lung can induce maladaptive wound healing that lead to disease, from fibrosis to late cancer recurrence. These events are associated with changes in the mechanical properties of the cellular microenvironment that are known to greatly impact cellular functions although underlying mechanisms are not fully understood. Cell culture platforms that synthetically mimic these changes in mechanical properties are needed to study and understand these diseases toward ultimately designing improved treatment strategies. Using visible light as an external stimulus, this work aims to fabricate a platform that mimics the mechanical property changes associated with maladaptive wound healing, from injury to subsequent stiffening, to study the cellular responses to these dynamic changes in the microenvironment. Strain-promoted azide-alkyne cycloaddition hydrogels were formed using a coumarin-containing linker to enable injury-mimetic properties. The stiffening mimetic properties were then enabled by triggering thiol-yne reactions via visible-light photoinitiation. Changes in viscoelastic properties were also triggered. The biomechanical properties of this hydrogel-based synthetic ECM were modulated to mimic injury and repair processes via selective photodegradation and subsequent photoreactions. Assessment of these mechanical changes was performed with rheometry and confocal imaging. Relevant cell types (e.g., epithelial cells, macrophages) were cultured on these synthetic ECMs and then subjected to injury, stiffening, and injury-stiffening, and cellular responses were assessed via immunostaining and imaging. The use of this photoresponsive hydrogel-based synthetic ECM platform to probe cellular response to injury and fibrosis aims to provide new tools for probing cellular responses to dynamic biomechanical changes and mechanistic insights toward modulating these complex processes and preventing disease.