Effect of storage duration on the mechanical behavior of mouse carotid artery.

Determining arterial mechanical properties is important for understanding the work done by the heart and how it changes with cardiovascular disease. Ex vivo tests are necessary to apply various loads to the artery and obtain data to model and predict the behavior under any load. Most ex vivo tests are performed within 24 h of dissection, so the tissue is still "alive." For large elastic arteries; however, the passive mechanical behavior is attributed mostly to the very stable proteins, elastin, and collagen. If the testing equipment fails, is in use, or is located at another facility, it would be useful to store the vessels and postpone the tests until the equipment is available. The goal of this study is to determine the effects of storage time on the mechanical behavior of the common carotid artery from adult mice. Each artery was tested after storage for 1-28 days in physiologic saline at 4°C. There were no significant effects of storage time on the arterial diameter or force at each pressure, but there were significant effects on the stretch ratio and stress at each pressure. The significant effects on the stretch ratio and stress were due to decreases in the unloaded dimensions with storage time, when measured from cut arterial rings. When the unloaded dimensions were measured instead from histology sections, there were no significant changes with storage time. We conclude that histology sections yield a more consistent measurement of the unloaded dimensions and that there are no significant changes in the mechanical behavior of mouse carotid artery with storage up to 28 days.

Mechanical testing of mouse carotid arteries: from newborn to adult.

The large conducting arteries in vertebrates are composed of a specialized extracellular matrix designed to provide pulse dampening and reduce the work performed by the heart. The mix of matrix proteins determines the passive mechanical properties of the arterial wall(1). When the matrix proteins are altered in development, aging, disease or injury, the arterial wall remodels, changing the mechanical properties and leading to subsequent cardiac adaptation(2). In normal development, the remodeling leads to a functional cardiac and cardiovascular system optimized for the needs of the adult organism. In disease, the remodeling often leads to a negative feedback cycle that can cause cardiac failure and death. By quantifying passive arterial mechanical properties in development and disease, we can begin to understand the normal remodeling process to recreate it in tissue engineering and the pathological remodeling process to test disease treatments. Mice are useful models for studying passive arterial mechanics in development and disease. They have a relatively short lifespan (mature adults by 3 months and aged adults by 2 years), so developmental(3) and aging studies(4) can be carried out over a limited time course. The advances in mouse genetics provide numerous genotypes and phenotypes to study changes in arterial mechanics with disease progression(5) and disease treatment(6). Mice can also be manipulated experimentally to study the effects of changes in hemodynamic parameters on the arterial remodeling process(7). One drawback of the mouse model, especially for examining young ages, is the size of the arteries. We describe a method for passive mechanical testing of carotid arteries from mice aged 3 days to adult (approximately 90 days). We adapt a commercial myograph system to mount the arteries and perform multiple pressure or axial stretch protocols on each specimen. We discuss suitable protocols for each age, the necessary measurements and provide example data. We also include data analysis strategies for rigorous mechanical characterization of the arteries.