Biology subjects

Spronck, B.

Publications and source records attributed to Spronck, B..

6 recordsLinked to original sources

bioRxiv2025

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.

bioengineering↗

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↗

bioRxiv2023

Smooth Muscle Cell Death Drives an Osteochondrogenic Phenotype and Severe Proximal Vascular Disease in Progeria

Hutchinson-Gilford Progeria Syndrome results in rapid aging and severe cardiovascular sequelae that accelerate near end of life. We associate progressive deterioration of arterial structure and function with single cell transcriptional changes, which reveals a rapid disease process in proximal elastic arteries that largely spares distal muscular arteries. These data suggest a novel sequence of progressive vascular disease in progeria: initial extracellular matrix remodeling followed by mechanical stress-induced smooth muscle cell death in proximal arteries, leading a subset of remnant smooth muscle cells to an osteochondrogenic phenotypic modulation that results in an accumulation of proteoglycans that thickens the wall and increases pulse wave velocity, with late calcification exacerbating these effects. Increased pulse wave velocity drives left ventricular diastolic dysfunction, the primary diagnosis in progeria children. Mitigating smooth muscle cell loss / phenotypic modulation promises to have important cardiovascular implications in progeria patients.

bioengineering↗

bioRxiv2019

Genetic Background Dominates Fibrotic Aortic Remodeling During Angiotensin-Induced Hypertension in Mice

Many genetic mutations affect aortic structure and function in mice, but little is known about the influence of background strain. We phenotyped aortas from C57BL/6J and 129SvEv mice before and after continuous infusion of angiotensin II (AngII) for two weeks, which elevated blood pressure similarly in both strains (1.34-fold vs. 1.32-fold, systolic). Excised thoracic aortas were characterized functionally using isobaric vasoactive and cyclic passive stiffness tests whereas immunohistological studies quantified altered medial and adventitial composition as well as the infiltration of pan-inflammatory CD45+ cells. Baseline aortic geometry, composition, and biomechanical properties were similar across strains, consistent with mechanical homeostasis. Yet, aortic remodeling in response to AngII-induced hypertension differed dramatically between strains, with gross maladaptive remodeling in C57BL/6J but not in 129SvEv mice. CD45+ cell density was markedly higher in C57BL/6J than 129SvEv aortas while vasoconstrictive responses to AngII were greater in 129SvEv than C57BL/6J both before and after hypertension; importantly, smooth muscle mediated vasoconstriction reduces pressure-induced wall stress. Bulk RNA sequencing, layer-specific biomechanical modeling, and growth and remodeling simulations support the emergent hypothesis that mechanical stress-mediated immune processes promote maladaptive remodeling while smooth muscle contractile processes reduce wall stress and thereby protect against fibrosis. Differentially expressed mechano-sensitive genes thus play key roles in the distinct hypertensive aortic remodeling in C57BL/6J and 129SvEv mice and must be considered when comparing studies in different background strains, particularly mixed strains that are often used to generate mice with targeted mutations. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=152 SRC="FIGDIR/small/727800v2_ufig1.gif" ALT="Figure 1"> View larger version (33K): org.highwire.dtl.DTLVardef@e9f1d9org.highwire.dtl.DTLVardef@104e221org.highwire.dtl.DTLVardef@19a00bforg.highwire.dtl.DTLVardef@1a70cd5_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗