The success of percutaneous coronary intervention (PCI) has been limited by restenosis and stent thrombosis. Delayed or incomplete endothelial regeneration is believed to be a key factor responsible for these events. Developing a stent with an accelerated healing profile may be of benefit. We aimed to evaluate the feasibility and safety of seeding a bare metal stent (BMS) with human trophoblastic endovascular progenitor cells (hTEC) derived from human embryonic stem cells. A porcine coronary artery model was used to compare the rate and extent of endothelial regeneration and the degree of neointimal proliferation. Characterisation of hTEC confirmed a mixed progenitor and endothelial cell phenotype. The biodistribution and fate of hTEC were studied using radiolabelled 111Indium oxine and fluorescent in situ hybridisation. Scanning electron microscopy showed earlier endothelial coverage in hTEC-seeded stents as compared to similar BMS. hTEC-seeded BMS achieved complete stent coverage in three days. Quantitative coronary angiography, intravascular ultrasound assessment and histomorphometry showed no difference in neointimal hyperplasia between hTEC-seeded and control BMS. hTEC seeding of coronary stents is a novel and safe approach to accelerate endothelial regeneration without increasing neointimal proliferation.
A model that combines the results of in vivo experiment, 3D image data, and computer simulation has been developed. Twelve identical stents were implanted into six healthy pigs and explanted at a range of different post-recovery periods from 6 h to 28 days. The stented vessel segments were embedded in methacrylate resin for the preparation of transverse histological sections and imaged using ultra-high resolution micro-CT. The resulting CT data was used to reconstruct the 3D geometry of the stents and one case was used to inform a 3D computational fluid dynamic model. Derived hemodynamic parameters such as wall shear stress (WSS), axial WSS, and oscillatory shear index were correlated with the distribution of neointimal hyperplasia, assessed from histomorphometric analyses. The direct comparison of hemodynamic parameters and biological response supports the hypothesis that low and oscillatory WSS lead to a greater neointimal response within the stented region. Moreover, the realistic geometry obtained from micro-CT images, characterized by proximal overexpansion and asymmetric deployment of the stent, leads to a markedly non-uniform distribution of WSS values and correlates with asymmetric neo-intimal growth. This correlation cannot be appreciated from studies of idealized geometries.
Inflammatory mechanisms are proposed to play a significant role in the pathogenesis of pulmonary arterial hypertension (PAH). Previous studies have described PAH in fat-fed apolipoprotein E knockout (ApoE(-/-)) mice. We have reported that signaling in interleukin-1-receptor-knockout (IL-1R1(-/-)) mice leads to a reduction in diet-induced systemic atherosclerosis. We subsequently hypothesized that double-null (ApoE(-/-)/IL-1R1(-/-)) mice would show a reduced PAH phenotype compared with that of ApoE(-/-) mice. Male IL-1R1(-/-), ApoE(-/-), and ApoE(-/-)/IL-1R1(-/-) mice were fed regular chow or a high-fat diet (Paigen diet) for 8 weeks before phenotyping for PAH. No abnormal phenotype was observed in the IL-1R1(-/-) mice. Fat-fed ApoE(-/-) mice developed significantly increased right ventricular systolic pressure and substantial pulmonary vascular remodeling. Surprisingly, ApoE(-/-)/IL-1R1(-/-) mice showed an even more severe PAH phenotype. Further molecular investigation revealed the expression of a putative, alternatively primed IL-1R1 transcript expressed within the lungs but not aorta of ApoE(-/-)/IL-1R1(-/-) mice. Treatment of ApoE(-/-) and ApoE(-/-)/IL-1R1(-/-) mice with IL-1-receptor antagonist prevented progression of the PAH phenotype in both strains. Blocking IL-1 signaling may have beneficial effects in treating PAH, and alternative IL-1-receptor signaling in the lung may be important in driving PAH pathogenesis.
Pulmonary arterial hypertension (PAH) is a life-threatening disease characterized by the progressive narrowing and occlusion of small pulmonary arteries. Current therapies fail to fully reverse this vascular remodeling. Identifying key pathways in disease pathogenesis is therefore required for the development of new-targeted therapeutics. We have previously reported tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) immunoreactivity within pulmonary vascular lesions from patients with idiopathic PAH and animal models. Because TRAIL can induce both endothelial cell apoptosis and smooth muscle cell proliferation in the systemic circulation, we hypothesized that TRAIL is an important mediator in the pathogenesis of PAH. We demonstrate for the first time that TRAIL is a potent stimulus for pulmonary vascular remodeling in human cells and rodent models. Furthermore, antibody blockade or genetic deletion of TRAIL prevents the development of PAH in three independent rodent models. Finally, anti-TRAIL antibody treatment of rodents with established PAH reverses pulmonary vascular remodeling by reducing proliferation and inducing apoptosis, improves hemodynamic indices, and significantly increases survival. These preclinical investigations are the first to demonstrate the importance of TRAIL in PAH pathogenesis and highlight its potential as a novel therapeutic target to direct future translational therapies.
The death receptor ligand tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) shows considerable clinical promise as a therapeutic agent. TRAIL induces leukocyte apoptosis, reducing acute inflammatory responses in the lung. It is not known whether TRAIL modifies chronic lung injury or whether TRAIL has a role in human idiopathic pulmonary fibrosis (IPF). We therefore explored the capacity of TRAIL to modify chronic inflammatory lung injury and studied TRAIL expression in patients with IPF.
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