Linking arterial biomechanics, contractility, and microstructure: A novel platform for combined structure-function assessment in murine arteries under physiological conditions
BackgroundEx vivo characterization of arterial viscoelastic properties shows arterial stiffness and contractility to depend on both axial stretch and dynamic pressurization. While these arterial properties are the subject of extensive ex vivo research due to their relevance to vascular pathophysiology, only few experimental approaches mimic both physiological axial stretch and dynamic pressurization when characterizing arterial biomechanics, vasoreactivity, and tissue microstructure. To fill this gap, we developed a custom dynamic biaxial pressure myograph compatible with two-photon laser scanning microscopy (TPLSM). MethodsWe studied five murine carotid artery segments. Sample viscoelastic behaviour was characterized by quasi-static and dynamic pressurization experiments at and around physiological axial stretch, as well as quasi-static stretching at physiological pressures. In addition, vasoconstriction in response to 2 {micro}M phenylephrine was measured during dynamic pressurization and with axial loads that mimicked physiological conditions. Lastly, arterial collagen, elastin, and cell nuclei were imaged using TPLSM with the sample at physiological axial stretch and pressurized at 100 mmHg. ResultsThe setup enabled capture of the non-linear biaxial viscoelastic behaviour of the arterial wall as well as the viscoelastic stiffening with dynamic pressurization. Modulation of these characteristics upon stimulated smooth muscle contraction was also captured well. Moreover, the related ultrastructural properties of the collagen-elastin network as well as the transmural cell distribution, were recordable at corresponding loading conditions by TPLSM. ConclusionThe presented multi-modal characterization platform enables comprehensive ex vivo measurements under well-controlled in vivo-like loading conditions, for in-depth studies focusing on arterial stiffening. Our findings emphasize the need for controlling dynamic pressure and axial stretch conditions in investigating mechanistic and constitutive aspects of arterial stiffening.