RESUMO
Although widely used as a preclinical model for studying venous diseases, there is a scarcity of in vivo characterizations of the naïve murine venous system. Additionally, previous studies on naïve veins (ex vivo) have not included the influence of surrounding structures and biomechanical forces. Using MRI, we noninvasively quantified the cross-sectional area, cyclic strain, and circularity of the venous system in young and old, male and female C57BL/6 mice. We investigated the most common venous locations used to perform venous disease research: the common jugular vein, suprarenal inferior vena cava (IVC), infrarenal IVC, common iliac vein, and common femoral vein. Our results elucidate age-dependent changes in venous cross-sectional area, which varied by location. Maximum cyclic strain, a parameter of lumen expansion, showed 10% change across the cardiac cycle, approximately half the magnitude of arteries. Veins demonstrated noncircular shapes, particularly in the core vasculature. The cardiovascular stressor dobutamine had only a small impact on the venous system. Also, our data demonstrate that the peripheral veins tend to decrease in cross-sectional area and circularity with age. Conversely, the IVC tends to increase in size and circularity with age, with males exhibiting larger variability in response to dobutamine compared to females. This work provides a foundation for drawing age and sex comparisons in disease models, and represents the first in vivo characterization of the murine venous system at rest and during the application of a pharmacological exercise surrogate.
