Mechanical adaptation and tissue remodeling

Abstract

The adaptive response of connective tissue to mechanical loading includes an increased synthesis and turnover of matrix proteins, including the collagen. Collagen formation and degradation increases with acute loading of tendon and skeletal muscle, in vivo. This increased activity is associated with local and systemic release of growth factors (e.g., IGF-1, TGF-beta, IL-6) that is temporally coupled with a rise in procollagen expression. Chronic loading of tissue, such as with physical training, will lead to increased collagen turnover and a net collagen synthesis which are together associated with a modification of the mechanical properties, including a reduction in tendon stress. Altogether this likely yields a more load-resistant tissue. The adaptation time to chronic loading is longer in tendon tissue compared to contractile elements of skeletal muscle or heart, and it is only with very prolonged loading that significant changes in gross dimensions of the tendon can be observed. Current observations support the notion that mechanical loading leads to collagen-rich tissue adaptation, and that this requires an intimate interplay between mechanical signaling and biochemical changes in the matrix, such that chemical changes can be converted into adaptations in morphology, structure and material properties. © 2008 Springer Science+Business Media, LLC.