Differential biomechanical development of elastic tissues in the bovine fetus

Mechanical loading conditions are important factors in the gestational development of fetal tissues. However, little is known about how mechanical loading during development modulates the structure and function of elastic tissues. We hypothesized that developing elastic tissues functionally adapt to their loading conditions. To test this hypothesis, we assessed the changes in the composition, viscoelasticity, and thermoelastic properties of elastic tissue from bovine aortas (functional during gestation) and nuchal ligaments (nonfunctional during gestation). Clear differences in the developmental timeline of elastic tissue structure and function were observed between aortic and ligament elastic tissue. Elastic tissue in the aorta developed earlier than that of the nuchal ligament, indicating a role for loading conditions in the timeline of development. Ligament elastic tissue, however, underwent rapid remodeling in late gestation-likely as a preadaptation to the sudden-onset of tensile load it experiences at birth. Finally, while the same fundamental structure-mechanical relationships were seen in both tissues, there was a clear difference in mechanical properties between the elastic tissues from the adult nuchal ligament and the adult aorta, indicating that postnatal loading conditions continue to influence tissue structure and mechanical properties, tailoring them to their functional roles in adult life.