Vascular Casting of Adult and Early Postnatal Mouse Lungs for Micro-CT Imaging

“…To evaluate phenotypic features that might influence vascular resistance, we utilized a polymer casting technique we recently optimized ( 21 ) to visualize the length and branching pattern of the pulmonary architecture using μCT at several developmental timepoints. A representative Eln +/+ ( Figure 7A ) and Eln +/− ( Figure 7B ) P90 volume rendering shows the entire PA vascular arcade.…”

Section: Resultsmentioning

confidence: 99%

“…Microfil TM (Flow Tech Inc., Carver, MA) injections were performed as previously described ( 21 ). Approximate postnatal day 1 (P1), 7 (P7), 30 (P30), and 90 (P90) mice were used for these experiments.…”

Section: Methodsmentioning

confidence: 99%

Elastin Insufficiency Confers Proximal and Distal Pulmonary Vasculopathy in Mice, Partially Remedied by the KATP Channel Opener Minoxidil: Considerations and Cautions for the Treatment of People With Williams-Beuren Syndrome

Knutsen

Gober

Kronquist

et al. 2022

Front. Cardiovasc. Med.

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BackgroundWilliams Beuren syndrome (WBS) is a recurrent microdeletion disorder that removes one copy of elastin (ELN), resulting in large artery vasculopathy. Early stenosis of the pulmonary vascular tree is common, but few data are available on longer-term implications of the condition.MethodsComputed tomography (CT) angiogram (n = 11) and echocardiogram (n = 20) were performed in children with WBS aged 3.4–17.8 years. Controls (n = 11, aged 4.4–16.8 years) also underwent echocardiogram. Eln+/− mice were analyzed by invasive catheter, echocardiogram, micro-CT (μCT), histology, and pressure myography. We subsequently tested whether minoxidil resulted in improved pulmonary vascular endpoints.ResultsWBS participants with a history of main or branch pulmonary artery (PA) stenosis requiring intervention continued to exhibit increased right ventricular systolic pressure (RVSP, echocardiogram) relative to their peers without intervention (p < 0.01), with no clear difference in PA size. Untreated Eln+/− mice also show elevated RVSP by invasive catheterization (p < 0.0001), increased normalized right heart mass (p < 0.01) and reduced caliber branch PAs by pressure myography (p < 0.0001). Eln+/− main PA medias are thickened histologically relative to Eln+/+ (p < 0.0001). Most Eln+/− phenotypes are shared by both sexes, but PA medial thickness is substantially greater in Eln+/− males (p < 0.001). Eln+/− mice showed more acute proximal branching angles (p < 0.0001) and longer vascular segment lengths (p < 0.0001) (μCT), with genotype differences emerging by P7. Diminished PA acceleration time (p < 0.001) and systolic notching (p < 0.0001) were also observed in Eln+/− echocardiography. Vascular casting plus μCT revealed longer generation-specific PA arcade length (p < 0.0001), with increased PA branching detectable by P90 (p < 0.0001). Post-weaning minoxidil decreased RVSP (p < 0.01) and normalized PA caliber (p < 0.0001) but not early-onset proximal branching angle or segment length, nor later-developing peripheral branch number.ConclusionsVascular deficiencies beyond arterial caliber persist in individuals with WBS who have undergone PA stenosis intervention. Evaluation of Eln+/− mice reveals complex vascular changes that affect the proximal and distal vasculatures. Minoxidil, given post-weaning, decreases RVSP and improves lumen diameter, but does not alter other earlier-onset vascular patterns. Our data suggest additional therapies including minoxidil could be a useful adjunct to surgical therapy, and future trials should be considered.

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Section: Introductionmentioning

confidence: 99%

“…As an alternative to in vivo contrast-based angiography, casting of vessels with radio-dense polymers has traditionally been combined with tissue or organ dissection, digestion, and dye immersion, along with ex vivo image acquisition ( Walker et al., 2011 ; Ghanavati et al., 2014 ; Knutsen et al., 2020 ; Christoffersonm and Nilsson, 1988 ). Typically, high-density, radio-opaque polymer mixtures used in these methods are not optimized for arterio-venous transit, which limits their use to casting of either the arterial or venous system ( Knutsen et al., 2020 ). Conversely, low-density radio-opaque polymers that cross capillary beds are not well visualized in imaging methods such as micro-computed tomography (micro-CT) without prior isolation of the tissue and clearing or digestion, which can distort and/or destroy the gross or fine anatomy of the vasculature ( Choi et al., 2017 ; Hildebrand, 1968 ; Hong et al., 2020 ).…”

Section: Introductionmentioning

confidence: 99%