The effects of prestrain and collagen fibril alignment on in vitro mineralization of self-assembled collagen fibers

Collagen fibers are under tension in most extracellular matrices both prior to and during normal loading. This tension not only provides mechanical advantages, but also appears to establish a loading basis for the stimulation of mechanochemical transduction processes. The presence of tensile loads applied to collagen fibers also results in physical alignment of the collagen fibrils along the tensile axis. This alignment may influence biological processes such as mineralization. In this study we report a comparison between elastic and viscous stress-strain curves and mineral contents of self-assembled collagen fibers that were strained to 30% of their original lengths and then mineralized, and self-assembled collagen fibers that were not strained before being mineralized. We concluded that the application of strain changes the organization of the collagenous matrix and alters the calcium phosphate nucleation and/or growth in the matrix. In addition, when the mechanical behavior of collagen fibers is compared with mechanical data from mineralized turkey tendon, the results indicate that collagen fibril-to-fibril interactions present in turkey tendon appear to be more organized compared with self-assembled aligned collagen fibers. We concluded that organized collagen-collagen interactions appear to be an important characteristic required for elastic energy storage in tendon.