P1.3 A NEW DYNAMIC ORGAN BATH SETUP TO ASSESS ISOBARIC STIFFNESS PARAMETERS OF PERIODICALLY STRETCHED ISOLATED MOUSE AORTIC SEGMENTS

Abstract

Cyclic stretch is a major contributor of vascular function. However, isolated mouse aortas are frequently studied at low stretch frequency or even isometric conditions. Pacing experiments done in rodents and humans show that arterial compliance is highly cyclic stretch frequency-dependent. The Rodent Oscillatory Tension Set-up to study Arterial Compliance (ROTSAC) is an in-house developed organ bath that clamps aortic segments (width 2mm, diameter 0.5–3mm) to imposed preloads at physiological rates up to 600bpm. The technique enables us to acquire pressure-diameter loops (derived from simultaneous force-displacement measurements) and calculate biomechanical parameters such as Peterson’s modulus (Ep) and compliance. To our knowledge, this is the first set-up that facilitates the study of active vessel wall components, physiological stretch frequency and pressure variations and its effect on the biomechanical properties of the aorta. Arterial stiffness is generally considered to be determined mainly by structural components. However, using this device, we were able to show – by isobaric determination of compliance and Ep while changing pressure and vascular smooth muscle cells (VSMCs) tone – that active vessel wall components are highly important in determining biomechanical properties of the aorta. Ep values for WT mouse aorta (350.3 ± 8.2 mmHg) were in accordance with literature data and increased 29% upon a rise in diastolic pressure of 40 mmHg, while isobaric Ep increased 47% upon maximal contraction of the VSMCs. We believe that this set-up can significantly contribute to a better understanding how active vessel wall components influence arterial stiffening, hypertension and its associated cardiovascular complications.