Fibroblast contractility drives network reorganization and epithelial proliferation in intestinal polyposis

Fibroblasts are critical regulators of epithelial homeostasis through mechanics and signaling. However, the regulatory principles governing fibroblast behaviors are largely unknown. Fibroblast dysregulation has emerged as a pathological contributor in epithelial diseases such as intestinal polyposis. Here, using an inducible Bmp-loss-of-function polyposis model, we define stepwise mechanisms unraveling how dysregulated signaling perturbs fibroblast behaviors, which in turn, disrupt their function to regulate epithelial homeostasis. Intriguingly, the first initiating event leading to epithelial polyps was architectural and impacted the fibroblasts, not the epithelium. Bmp signaling inhibition caused fibroblasts to become hypercontractile, leading to their reorganization from an elaborate network into collapsed clusters beneath crypts. Disrupted fibroblast mechanics and compartmentalization preceded epithelial hyperproliferation in polyps. Using in vitro models, we show that fibroblast hypercontractility not only disrupted fibroblast organization, but also enhanced the ability of fibroblasts to support epithelial growth, leading to epithelial dysregulation. Overall, our studies reveal stepwise regulatory mechanisms underlying fibroblast signaling, mechanics and organization critical for their function to regulate epithelial homeostasis.