Meeting Abstract

100.1  Sunday, Jan. 6  Muscle-collagen interactions at the fiber bundle level. DANOS, N*; AZIZI, E; Univ. of California, Irvine; Univ. of California, Irvine ndanos@uci.edu

The passive force-length properties of muscle fibers are thought to be important determinants of a muscle’s operating length and force production. The extra-cellular collagen surrounding muscle fibers (endomysium) and fascicles (perimysium) have long been considered the structures responsible for passive elasticity in muscle. However, few studies to date have developed a direct link between the mechanical properties of these intramuscular connective tissues and the passive elasticity of muscle fibers. In addition, it remains unclear how connective tissue structures within muscle impact contractile performance. We explore the role of collagen in the extracellular matrix of muscle fibers and bundles by first comparing collagen density and passive stiffness in the anconeus muscle of three species of anurans with divergent loading regimes: the bullfrog Rana catesbiana, the cane toad Bufo marinus and the African clawed frog Xenopus laevis. We then examine the in vitro passive and active properties of muscle fiber bundles before and after a collagenase treatment that partially digests extracellular collagen. We find that the fiber bundles begin to develop tension at longer lengths after collagenase treatment. Active tetanic contractions after collagenase treatment reach lower maximum forces and develop force more slowly compared with pre-collagenase contractions. The results indicate that endomysium and perimysium collagen contributes both to passive stiffness and to the profile of active force production in muscle.