Making straps from small movements

To enlarge a drawing, an artist might use a pantograph, a pivoting frame that mechanically amplifies small movements into larger ones. On page 1083, Sawhney and Howard propose that cells use a similar mechanical arrangement to amplify small-scale traction forces into large-scale reorganization of the surrounding matrix. Their model may describe a general mechanism underlying morphogenesis.

When explants of fibroblasts are placed in collagen gels, they exert mechanical forces that lead to the formation of ligament-like straps between explants. Though this system is considered a good model for tissue morphogenesis, it remained unclear how micrometer-scale cellular traction forces generate millimeter-scale structural changes in the matrix.

Using a novel computer algorithm to monitor the patterning of the matrix, the authors found that small cellular movements bring about nearly simultaneous reorganization...