5.4 HIGH PWV IS ASSOCIATED WITH NANO-SCALE CHANGES IN THE MEDIAL LAYER OF THE INTERNAL MAMMARY ARTERY

Abstract

Background: Arterial stiffening occurs as part of the natural ageing process. Degradation of the extracellular matrix (ECM) in the medial layer is typically implicated in arterial stiffening. However, little is known about how localised changes in arteries in terms of both structure and mechanical properties contribute to the overall stiffening of arteries. Aim: To determine localised differences in the nano-structure and mechanical properties in the medial layer of internal mammary arteries (IMA) in patients with high and low pulse wave velocity (PWV). Methods: IMAs were collected form coronary bypass operations from 7 patients with high (13.8 3.3 m/s) and 7 patients with low (8.6 0.7 m/s) PWV. The samples were cryo-sectioned to a nominal thickness of 5 μm for atomic force microscopy (AFM) measurement. All the samples were tested hydrated. Histological analysis was used to determine collagen and elastin content. Data are presented as means SEMs. Results: The medial layers of IMAs in the high PWV group were significant stiffer than in the low PWV group (Low 228.4 15.6 kPa, High 735.8 108.8 kPa,) (p < 0.0001). Topographical features as visualised with AFM were similar in both groups but the higher nanomechanical stiffness was found to correlate with histological data. Conclusions: Nanomechanical properties of the medial layer in the IMA associate with PWV data. Changes in composition in the ECM drive the profound localized changes in tissue stiffness.