 The proposed mechanism for this fiber aggregation is protein extension and elongation under mechanical shear force, which leads to lateral packing and protein aggregation of fibers.Phillips et al.showed that mechanical shear produced by stretching a high viscosity fibronectin gel causes substantial changes in its structure and that when applied through uniaxial extension, a viscous fibronectin gel forms oriented fibrous fibronectin aggregates; additionally, the fibrous aggregates have a decreased solubility and can support the various cell types in vitro.