Cell surface receptors transmit sufficient force to bend collagen fibrils

To better understand the dynamic interaction of cells with their surroundin g extracellular matrix, chondrocytes and rat embryo fibroblasts were overla id with individual collagen fibrils and observed with high-resolution video -enhanced differential interference contrast microscopy. Although the cells had a polygonal shape characteristic of nonmotile cells, they used process es usually associated with cell locomotion to acquire the collagen fibrils. Instead of being transported in a retrograde direction, fibrils on the dor sal cell surface were bent, and regions of the bent fibrils were shifted in diverse directions. A blocking antibody to the beta(1) integrin subunit si gnificantly inhibited collagen fibril acquisition and bending. Enhanced act in assembly was only occasionally associated with fibrils undergoing rearra ngement. Considering that the relatively stiff collagen fibrils require the application, of force to be bent, this study shows that cells with a polyg onal morphology (as opposed to a polarized, motile shape) are capable of ex erting force through the beta(1) integrins on the dorsal surface of the cel l. Analysis of the bending patterns indicates that fibril buckling was indu ced by retrograde force combined with regions held stationary and/or the fi brils were bent by forces acting in opposing directions. (C) 1999 Academic Press.