Perfusion decellularization of cadaveric hearts removes cells and generates a cell-free extracellular matrix scaffold containing acellular vascular conduits, which are theoretically sufficient to perfuse and support tissue-engineered heart constructs. However, after transplantation, these acellular vascular conduits clot, even with anti-coagulation. Here, our objective was to create a less thrombogenic scaffold and improve recellularized-left ventricular contractility by re-lining vascular conduits of a decellularized rat heart with rat aortic endothelial cells (RAECs).We used three strategies to recellularize perfusion-decellularized rat heart vasculature with RAECs: retrograde aortic infusion, brachiocephalic artery (BA) infusion, or a combination of inferior vena cava (IVC) plus BA infusion. The re-endothelialized scaffolds were maintained under vascular flow in vitro for 7 days, and then cell morphology, location, and viability were examined. Thrombogenicity of the scaffold was assessed in vitro and in vivo. Both BA and IVC+BA cell delivery resulted in a whole heart distribution of RAECs that proliferated, retained an endothelial phenotype, and expressed endothelial nitric oxide synthase and von Willebrand factor. Infusing RAECs via the combination IVC+BA method increased scaffold cellularity and the number of vessels that were lined with endothelial cells; re-endothelialization by using BA or IVC+BA cell delivery significantly reduced in vitro thrombogenicity. In vivo, both acellular and re-endothelialized scaffolds recruited non-immune host cells into the organ parenchyma and vasculature. Finally, re-endothelialization before recellularization of the left ventricular wall with neonatal cardiac cells enhanced construct contractility.This is the first study to re-endothelialize whole decellularized hearts throughout both arterial and venous beds and cavities by using arterial and venous delivery. The combination (IVC+BA) delivery strategy results in enhanced scaffold vessel re-endothelialization compared to single-route strategies. Re-endothelialization reduced scaffold thrombogencity and improved contractility of left ventricular-recellularized constructs. Thus, vessel and cavity re-endothelialization creates superior vascularized scaffolds for use in whole-organ recellularization applications.
Most previous research on engineered microvessels has been in isotropic systems;1–3 however, aligned microvessels would be advantageous both in terms of mimicking alignment in native tissue (e.g. myocardium4), and in terms of establishing efficient perfusion of the microvessels, as alignment creates natural inlet and outlet sides.
Background: Valve-in-valve transcatheter aortic valve replacement (TAVR) is an option when a surgical valve demonstrates deterioration and dysfunction. This study reports 3-year results following valve-in-valve with self-expanding TAVR. Methods: The CoreValve US Expanded Use Study is a prospective, nonrandomized, single-arm study that evaluates safety and effectiveness of TAVR in extreme risk patients with symptomatic failed surgical biologic aortic valves. Study end points include all-cause mortality, need for valve reintervention, hemodynamic changes over time, and quality of life through 3 years. Patients were stratified by presence of preexisting surgical valve prosthesis-patient mismatch. Results: From March 2013 to May 2015, 226 patients deemed extreme risk (STS-PROM [Society of Thoracic Surgeons Predicted Risk of Mortality] 9.0±7%) had attempted valve-in-valve TAVR. Preexisting surgical valve prosthesis-patient mismatch was present in 47.2% of the cohort. At 3 years, all-cause mortality or major stroke was 28.6%, and 93% of patients were in New York Heart Association I or II heart failure. Valve performance was maintained over 3 years with low valve reintervention rates (4.4%), an improvement in effective orifice area over time and a 2.7% rate of severe structural valve deterioration. Preexisting severe prosthesis-patient mismatch was not associated with 3-year mortality but was associated with significantly less improvement in quality of life at 3-year follow-up ( P =0.01). Conclusions: Self-expanding TAVR in patients with failed surgical bioprostheses at extreme risk for surgery was associated with durable hemodynamics and excellent clinical outcomes. Preexisting surgical valve prosthesis-patient mismatch was not associated with mortality but did limit patient improvement in quality of life over 3-year follow-up. Clinical Trial Registration: URL: http://www.clinicaltrials.gov . Unique identifier: NCT01675440.
The development of engineered microvessels with clinically relevant characteristics is a critical step toward the creation of engineered myocardium. Alignment is one such characteristic that must be achieved, as it both mimics native capillary beds and provides natural inlet and outlet sides for perfusion. A second characteristic that is currently deficient is cross-sectional lumen density, typically under 100 lumens/mm2; the equivalent value for human myocardium is 2000 lumens/mm2. Therefore, this study examined the effects of gel compaction and interstitial flow on microvessel alignment and lumen density. Strong microvessel alignment was achieved via mechanically constrained cell-induced fibrin gel compaction following vasculogenesis, and high lumen density (650 lumens/mm2) was achieved by the subsequent application of low levels of interstitial flow. Low interstitial flow also conferred microvessel barrier function.
