3D printed ascending aortic simulators with physiological fidelity for surgical simulation.

Introduction: Three-dimensional (3D) printed multimaterial ascending aortic simulators were created to evaluate the ability of polyjet technology to replicate the distensibility of human aortic tissue when perfused at physiological pressures.

Methods: Simulators were developed by computer-aided design and 3D printed with a Connex3 Objet500 printer. Two geometries were compared (straight tube and idealised aortic aneurysm) with two different material variants (TangoPlus pure elastic and TangoPlus with VeroWhite embedded fibres).

Wall stresses of early remodeled pulmonary autografts.

Objective: The Ross procedure is an excellent option for children or young adults who need aortic valve replacement because it can restore survival to that of the normal aged-matched population. However, autograft remodeling can lead to aneurysmal formation and reoperation, and the biomechanics of this process is unknown. This study investigated postoperative autograft remodeling after the Ross procedure by examining patient-specific autograft wall stresses.

Autograft remodeling after the Ross procedure by cardiovascular magnetic resonance imaging: Aortic stenosis versus insufficiency.

Background: Studies suggest that patients undergoing the Ross procedure for aortic insufficiency are at greater risk of autograft dilatation than those with aortic stenosis. By using a tailored Ross technique to mitigate autograft dilatation in patients with aortic insufficiency, we aimed to compare the biomechanical and morphologic remodeling of the autograft at 1 year between patients with aortic insufficiency and patients with aortic stenosis.

Methods: A total of 210 patients underwent a Ross procedure (2011-2016).

Distinct Expression of Nonmuscle Myosin IIB in Pulmonary Arteries of Patients With Aortic Stenosis vs Insufficiency Undergoing a Ross Procedure.

Background: Clinical studies have revealed a greater risk of pulmonary autograft dilation after the Ross procedure in patients with preoperative aortic insufficiency (AI). The present study examined whether the morphologic, biomechanical, and cellular properties of the pulmonary artery (PA) from patients with AI were phenotypically different compared with patients diagnosed with aortic stenosis (AS).

Methods: PA segments were harvested from patients undergoing the Ross procedure for AS (n = 16) and AI (n = 6).

Increased MMP activity in curved geometries disrupts the endothelial cell glycocalyx creating a proinflammatory environment.

Wall shear stress gradients (WSSGs) induce an inflammatory phenotype in endothelial cells (ECs) which is hypothesized to be mediated by mechanotransduction through the EC glycocalyx (GCX). We used a three-dimensional in vitro cell culture model with a 180o curved geometry to investigate if WSSGs created by curvature can cause EC inflammation and disruption of the GCX. The hydrodynamics of the model elicited a morphological response in ECs as well as a pattern of leukocyte adhesion towards the inner wall of curvature that was attenuated with enzymatic removal of GCX components.

Transesophageal echocardiographic strain imaging predicts aortic biomechanics: Beyond diameter.

Background: Clinical guidelines recommend resection of ascending aortic aneurysms at diameters 5.5 cm or greater to prevent rupture or dissection. However, approximately 40% of all ascending aortic dissections occur below this threshold.

Investigation on the Regional Loss Factor and Its Anisotropy for Aortic Aneurysms.

An aortic aneurysm is a lethal arterial disease that mainly occurs in the thoracic and abdominal regions of the aorta. Thoracic aortic aneurysms are prevalent in the root/ascending parts of the aorta and can lead to aortic rupture resulting in the sudden death of patients. Understanding the biomechanical and histopathological changes associated with ascending thoracic aortic aneurysms (ATAAs), this study investigates the mechanical properties of the aorta during strip-biaxial tensile cycles.

Histopathological and biomechanical properties of the aortic wall in 2 patients with chronic type A aortic dissection.

Type A aortic dissection is an acute condition that requires urgent surgical intervention. However, in a subset of patients, aortic dissections go undiagnosed and become chronic, thereby allowing the dissected wall to undergo a distinct remodeling process from that of the surrounding intact wall. Here, we observe the biomechanical and histological changes in the aortic wall of two patients with chronic Type A aortic dissection.

Obtaining the biomechanical behavior of ascending aortic aneurysm via the use of novel speckle tracking echocardiography.

Introduction: Ex vivo measurement of ascending aortic biomechanical properties may help understand the risk for rupture or dissection of dilated ascending aortas. A validated in vivo method that can predict aortic biomechanics does not exist. Speckle tracking transesophageal echocardiography (TEE) has been used to measure ventricular stiffness; we sought to determine whether speckle TEE could be adapted to estimate aortic stiffness in vivo and compare these findings with those obtained by ex vivo tissue measurements.

Evaluating ascending aortic aneurysm tissue toughness: Dependence on collagen and elastin contents.

Ascending thoracic aortic aneurysms (ATAAs) can lead to a dissection or rupture of the aorta, causing death or disability of the patients. Surgical interventions used to treat this disease are associated with risks of mortality and morbidity. Several studies have investigated the rupture mechanisms of ATAAs; however, underlying reasons behind aortic rupture (failure) have not been fully elucidated and further investigations are necessary.

The Ross procedure: biomechanical properties of the pulmonary artery according to aortic valve phenotype.

Objectives: The aim of this study is to determine whether patients undergoing the Ross procedure with bicuspid aortic valves have pulmonary artery biomechanical properties different from those with tricuspid valves.

Methods: Thirty-two pulmonary arteries and 20 aortas were obtained from patients undergoing the Ross procedure at the time of surgery, from a cohort of 32 patients. The aortic valve was tricuspid in 5 patients (16%), bicuspid in 18 patients (56%) and unicuspid in 9 patients (28%).

Biomechanics of the Ascending Thoracic Aorta: A Clinical Perspective on Engineering Data.

Aneurysms of the ascending thoracic aorta often require prophylactic surgical intervention to resect and replace the aortic wall with a synthetic graft to avoid the risk of dissection or rupture. The main criterion for surgical intervention is the size of the aneurysm, with elective surgery recommended with a maximal aortic diameter of 4.2-5.

Efficient processing of procathepsin K to the mature form.

The proteolysis of collagen fibrils by cathepsin K is a hallmark of bone catabolism and tissue degeneration. The production of active recombinant cathepsin K is central for our ability to study the mechanisms by which these processes occur. Here we report an efficient processing method for the preparation of recombinant cathepsin K expressed in Pichia pastoris.

Laminar shear stress prevents simvastatin-induced adhesion molecule expression in cytokine activated endothelial cells.

In addition to lowering cholesterol, 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, or statins, have been shown to modulate gene expression in endothelial cells. The effect of statins on cell adhesion molecule expression is unclear and largely unexplored in endothelial cells exposed to shear stress, an important regulator of endothelial cell function. In this study, the effect of simvastatin on vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) expression was evaluated in human abdominal aortic endothelial cells (HAAEC) conditioned with various levels of laminar wall shear stress with or without tumor necrosis factor alpha (TNFα).