Abstract
Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, and ultimately fatal interstitial lung disease characterized by the accumulation of scar tissue surrounding alveoli. Currently, there are no effective treatments that stop or reverse IPF progression, largely due to an incomplete understanding of the mechanisms that lead to this pathological wound healing process. While the direct cause of IPF remains unknown, extensive research has identified excessive myofibroblast activation, persistent macrophage-driven inflammation, and aberrant remodeling of the extracellular matrix (ECM) as some of the key drivers of fibrogenesis. While fibroblasts are known to respond to both physical and biochemical cues, the integrated influence of changing tissue mechanics and macrophage crosstalk on fibroblast activation is not fully understood. The goal of this work is to investigate how macrophages and ECM mechanics cooperate to regulate fibroblast behavior in vitro, while also defining the mechanical landscape of fibrotic lung tissue in vivo to inform the design of physiologically relevant hydrogel systems.
Using a hyaluronic acid (HA)-based hydrogel platform that recapitulates the mechanics of healthy and fibrotic lung tissue, we decoupled matrix-derived cues from macrophage signaling to assess their relative contributions to fibroblast activation. This system enabled systematic investigation of substrate mechanics, macrophage phenotype, and the roles of soluble versus contact-dependent crosstalk, while the application of pharmacological inhibitors provided initial insight into the signaling pathways underlying these interactions. We then build upon this finding by further investigating the role of the mechanosensitive channel Piezo1, cell adhesion protein cadherin-11 (CDH11), and inflammatory cytokine interleukin-6 (IL-6) on macrophage-fibroblast crosstalk. Finally, we investigate how fibrosis progression influences bulk and spatially-resolved lung tissue mechanics in vivo utilizing the bleomycin mouse model and recapitulate these mechanical behaviors in our hydrogel system. Overall, this work offers new insight into how immune-stromal crosstalk and tissue mechanics converge to regulate fibroblast activation, while also establishing mechanical benchmarks to guide the design of hydrogel platforms that more accurately model IPF.
