Aging and freezing of active nematic dynamics of cancer-associated fibroblasts by fibronectin matrix remodeling

Cancer-associated fibroblasts (CAFs) are one of the most abundant cell types in tumor stroma. Exhibiting an elongated morphology, CAFs align with each other, closely resembling nematic ordering in liquid crystal physics. CAFs play a pivotal role in the genesis and remodeling of the extracellular matrix (ECM), with ECM proteins, especially fibronectin, reciprocally modulating CAF alignment and coherence. Yet, the intricate feedback loops between fibronectin deposition and CAF structuring remain largely unexplored. Here, we combined CAF live imaging, traction force microscopy, ECM microfabrication, and theoretical modeling to assess how the ECM influences the dynamics of nematically ordered CAFs. We found that CAFs dynamically orchestrate a fibronectin network that mirrors their nematic ordering. Over time, this passive nematic ordering of fibronectin, in turn, steers CAF rearrangement. Contrary to most cellular systems, where defects remain dynamic at a steady state, the ECM/CAF interplay profoundly alters the behavior of both CAF and ECM nematics, leading to aging-massive slowdown, and even freezing of defect dynamics. This results in a CAFs capsule where aligned areas and defects are spatially and temporally fixed, yet active, exerting forces at the substate and transmitting forces between cells. Functionally, while defects may be permissive, it is the fibronectin loss-induced fluidization of the CAF capsule that critically undermines its barrier function.