The leading edge is the primary force producing component of migrating fibroblasts

To examine how cells generate force at the level of single extracellular matrix fibers, a miniature force-transducer system was created around a novel microfabricated silicon device. We characterize the development of isometric force on single collagen type-I fibers. We show that cells remodel individual collagen fibers by moving them inward using a hand-over-hand cycle of binding, movement, and release. This remodelling is caused by only a 2-3 micrometer region of active lamellapodium. We also show that movement of individual fibers is rapid at low restrictive forces, and this velocity quickly decreases as forces approach 60 pN. A single cell is capable of generating between 180-250 pN of force on a single fiber. This data supports the hypothesis that the leading edge of migrating cells is primarily responsible for generating force on the substrate.