Measurement of Mechanical Properties of Soft Tissues In Vitro Under Controlled Tissue Hydration

Alterations in tissue hydration that accompany inflammation or chronic remodeling of the Extracellular Matrix (ECM) have significant impact on the biomechanics of vascular tissue in health and disease. Examination of tissue behavior under controlled hydration in vitro could be helpful in better understanding the effects of tissue water content on its mechanical properties where in vivo tissue conditioning could not be possible. This study explains a multistage experimental protocol that allows both to prepare the tissue specimens with specific water content and to measure their mechanical behavior while maintaining the water content constant during the laboratory experimentation. Stress relaxation behaviors of the bovine aortic specimens-extracted from native, collagen-denatured and elastin-isolated tissues-were obtained within a water content range of 100-400 %. Using this method, distinct relaxation behaviors were obtained from tissue specimens with changing ECM treatments and hydration levels. The relaxation behavior was found to conform to a 4-parameter linear-viscoelastic macromechanical model consisting of two Maxwell components in parallel. The macromechanical model was able to distinguish between the morphological mechanisms associated with ECM elastin and collagen.