The Contagious Stiffness

Fibrosis — the excessive scarring that stiffens lungs, livers, and hearts — is driven by myofibroblasts, cells that produce collagen and contract tissue. The standard model says fibroblasts become myofibroblasts through biochemical signals: growth factors like TGF-β, or the mechanical stiffness of an already-fibrotic matrix. Remove the signals, stop the transition.

Chandar, Goykadosh, and Parameswaran (arXiv:2503.01834) show that direct physical contact between fibroblasts and myofibroblasts is sufficient to drive the transition — no growth factors, no stiff matrix required. Touch a normal fibroblast with a myofibroblast, and the normal cell transforms. The disease spreads by contact, like an infection, through a mechanism that bypasses every known biochemical pathway.

The structural implication is that fibrosis is self-propagating at the cellular level. Once a critical mass of myofibroblasts exists, they recruit their neighbors by touch, independent of the original injury signal. This explains why fibrosis persists long after the wound that caused it has healed — the myofibroblasts don’t need the wound anymore. They only need each other.

The authors identify FR900359, a G-alpha inhibitor, as capable of blocking this contact-mediated activation, suggesting the pathway runs through G-protein-coupled signaling at the cell surface. But the deeper point is architectural: the disease found a transmission channel that doesn’t require the molecular infrastructure everyone was targeting. The therapeutics aimed at growth factors were intercepting the wrong mail.