Adhesion of myocytes: cytoskeletal contributions assessed by peeling from micropatterned collagen

To quantitatively elucidate myocyte-matrix adhesion, muscle cells were controllably peeled from narrow strips of collagen. Initial growth of myoblasts on collagen strips led to cell elongation and end-on fusion. Cell branching and lateral contact were minimized, enabling detailed study of myocyte-matrix adhesion. A micropipette was used to pull back one end of a cell; along the resulting detachment front, peeling velocity fluctuated as focal roughness, microns in scale, was encountered. Nonetheless, mean velocity generally increased with detachment force, consistent with forced disruption of adhesion bonds. Beta1-integrin distributions correlated with the focal roughness. In addition, the peeling forces and rates were found to be moderately well-described by a dynamical peeling model for receptor-based adhesion. Estimates were thereby obtained for the spontaneous, molecular off-rate and the receptor complex stiffness (0.01 to 0.001 mN/m) of adherent myocytes. Such a local stiffness is in the range of flexible proteins of the spectrin superfamily which includes the myocyte membrane protein dystrophin. Preliminary results with dystrophin-null myocytes, indicate that dystrophin's absence leads to a less adherent, faster peeling cell under a given load.