Remodeling of a collagenous tissue at fixed lengths

Mature tissues can often adapt to changes in their chemical, mechanical, or thermal environment. For example, in response to sustained increases or de creases in mechanical loads, some tissues grow and remodel so as to restore the stress or strain to its homeostatic state. Whereas most previous work addresses gross descriptors of tissue growth, this paper introduces a possi ble cell-mediated mechanism by which remodeling may occur in a soft connect ive tissue-that the kinetics of collagen deposition and degradation is simi lar regardless of the configuration of the body at which it occurs. The pro posed theoretical framework applies to three-dimensional settings, but it i s illustrated by focusing on the remodeling of a uniaxial collagenous tissu e that is maintained at a fixed length for an extended period. It is shown that qualitative features expected of such remodeling (e.g., an increased c ompliance and increased stress-free length when remodeling occurs at an ext ended length) are easily realized. Growth and remodeling are complex phenom ena, however, and are likely accomplished via multiple complementary mechan isms. There is a need, therefore, to identify other candidate mechanisms an d, of course, to collect experimental data suitable for testing and refinin g the possible theories.