The MAASWERP study: An international, comparative case study on measuring biomechanics of the aged murine aorta

Arterial stiffening is a hallmark of vascular ageing, and unravelling its underlying mechanisms has become a central theme in the field of cardiovascular disease. While various techniques and experimental setups are accessible for investigating biomechanics of blood vessels both in vivo and ex vivo, comparing findings across diverse methodologies is challenging. In the present study, we aimed to compare arterial stiffness measurements of two distinct ex vivo setups for measuring aortic mechanics. First, we measured arterial stiffness in the aorta of adult (5 months) and aged (24 months) wild-type C57Bl/6J mice in vivo, after which ex vivo biomechanical evaluation was performed using the Rodent Oscillatory Tension Setup to study Arterial Compliance (ROTSAC; University of Antwerp, Belgium) and the DynamX setup (Maastricht University, The Netherlands). Measurements in both setups were conducted in parallel with matched protocols and identical buffers and chemicals. Overall, both methods revealed age-related increased stiffness, although parameters of aortic mechanics showed different numerical values, suggesting that results are not directly interchangeable between methods. Surprisingly, smooth muscle cell contraction had opposing effects between the setups. Indeed, smooth muscle cell contraction increased arterial stiffness in the ROTSAC but decreased stiffness in the DynamX. These opposing effects could be attributed to how the two setups differentially load the collagen fibres in the arterial wall, ex vivo. In conclusion, the observed differences between the two ex vivo setups highlight the necessity to report findings on (altered) aortic mechanics in the context of the used methodology.