Optimizing Recellularization of Whole Decellularized Heart Extracellular Matrix

Abstract

RationalePerfusion 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).Methods and ResultsWe 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.ConclusionsThis 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.

Recent Developments in Cardiovascular Stem Cells

“…125,126 The so-called environmentally responsive systems are designed to match the release of the functional molecular with a patient's physiological need at the appropriate time or the correct site. 127,128 They are constituted of sensitive hydrogels that can control the release of drugs by changing the gel structure according to environmental stimulation, such as temperature, pH, or ion concentration. 127,128 Poly N-isopropylacrylamide hydrogel is a typical example of temperature-sensitive hydrogels, which shows sol-to-gel transformation at a critical solution temperature of ≈35°C.…”

“…127,128 They are constituted of sensitive hydrogels that can control the release of drugs by changing the gel structure according to environmental stimulation, such as temperature, pH, or ion concentration. 127,128 Poly N-isopropylacrylamide hydrogel is a typical example of temperature-sensitive hydrogels, which shows sol-to-gel transformation at a critical solution temperature of ≈35°C. 129 This polymer releases the drug when it transforms from gel-to sol-and is of particular interest in those clinical situations, such as tissue ischemia, characterized by low temperature in the tissue.…”

Maximizing Cardiac Repair

“…Based on this premise, we and others derived decellularized ECM from cadaveric heart for use in cardiac repair. 10,11 In preclinical studies, infarcted pigs treated with percutaneous transendocardial injections of the hydrogel 2 weeks after myocardial infarction showed improvement in cardiac function and increased ventricular volume at 3 months when compared with controls. 12 A phase 1 study is underway in the United States to evaluate the safety and feasibility of VentriGel, a hydrogel of decellularized pig myocardial ECM delivered transendocardially to subjects with ventricular dysfunction secondary to myocardial infarction (NCT02305602).…”

“…Furthermore, decellularized ECM retains its vascular tree, facilitating angiogenesis and blood flow and allowing for perfusion and nutritional support. 10 Decellularized porcine small intestinal submucosa has been successfully used to surgically correct anatomic heart defects under low pressure conditions.…”

Coming to terms with tissue engineering and regenerative medicine in the lung

“…The ultimate goal is to achieve complete recellularization by distributing cells throughout the branches of the airway and vasculature, which is currently still under investigation. Nonetheless, it is also clear that for clinical success an engineered lung will be dependent on establishing a stable, functional blood supply, especially given that denuded vasculature in scaffolds is highly thrombogenic (11,140,165). These issues raise the question of how to best prepare the engineered lung for eventual transplant.…”