Biology subjects

Giudici, A.

Publications and source records attributed to Giudici, A..

3 recordsLinked to original sources

bioRxiv2024

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.

bioengineering↗

bioRxiv2023

Evaluating flash freezing for preservation of rat abdominal aorta for delayed biomechanical characterization

Most studies investigating arterial stiffening use animal rather than human arteries. This is because human tissue becomes available in small amounts and at irregular times, which complicates planning of experimental work. Suitable tissue preservation methods for delayed biomechanical testing prevents the need for testing fresh tissue and alleviates some of the logistical challenges of human ex vivo studies. Therefore, the present study aimed to investigate whether the existing method of flash freezing and subsequent cryostorage provides is suitable for delaying the characterization of arterial biomechanics. Fresh and flash frozen abdominal aortas (n=16 and 14, respectively) were quasi- statically and dynamically tested using a biaxial testing set-up with dynamic pressurization capabilities. The acquired biomechanical data was modeled using a constituent-based quasi-linear viscoelastic modeling framework, deriving directional stiffness parameters, individual constituent biomechanical contributions, and viscoelastic stiffening under dynamic pressurization conditions. Flash freezing reduced arterial wall thickness, increased circumferential stiffness, as well as reduced viscoelastic stiffening at higher pressures. These findings reflected those in the modeled contribution of collagen to arterial biomechanics, showing increased collagen load bearing at higher pressures. However, despite the above mentioned detectable changes, flash freezing did not alter the mechanical relation between elastin and collagen, maintaining a non-linear response to pressurization and stretch. Flash freezing may thus be suitable for studies requiring delayed characterization of passive arterial biomechanics, assuming care is taken to ascert that the impact of flash freezing on study groups can be approached as a systematic error.

bioengineering↗

bioRxiv2023

Instability in computational models of vascular smooth muscle cell contraction

PurposeThrough their contractile and synthetic capacity, vascular smooth muscle cells play a key role in regulating the stiffness and resistance of the circulation. To model the contraction of blood vessels, an active stress component can be added to the (passive) Cauchy stress tensor. Different constitutive formulations have been proposed to describe this active stress component. Notably, however, the ex vivo measurement of the biomechanical behaviour of contacted blood vessels presents several experimental challenges, which complicate the acquisition of comprehensive data sets to inform complex active stress models. In this work, we examine formulations for use with limited experimental contraction data as well as those developed to capture more comprehensive data sets. MethodsWe prove analytically that a subset of these formulations exhibits unstable behaviours (i.e., a non-unique diameter solution for a given pressure) in certain parameter ranges, particularly when contractile deformations are large. Furthermore, using experimental literature data, we present two case studies where these active stress models are used to capture the contractile response of vascular smooth muscle cells in the presence of 1) limited and 2) extensive contraction data. ResultsOur work shows how limited contraction data complicates the selection of an appropriate active stress model for vascular applications, potentially resulting in unrealistic modelled behaviours. ConclusionAs such, the data presented herein provide a useful reference for the selection of an active stress model which balances the trade-off between accuracy and the available biomechanical information.

biophysics↗