ABSTRACT
BACKGROUND: Tissue engineering using in vitro-cultivated autologous vascular wall cells is a new approach to biological heart valve replacement. In the present study, we analyzed a new concept to process allogenic acellular matrix scaffolds of pulmonary heart valves after in vitro seeding with the use of autologous cells in a sheep model. METHODS AND RESULTS: Allogenic heart valve conduits were acellularized by a 48-hour trypsin/EDTA incubation to extract endothelial cells and myofibroblasts. The acellularization procedure resulted in an almost complete removal of cells. After that procedure, a static reseeding of the upper surface of the valve was performed sequentially with autologous myofibroblasts for 6 days and endothelial cells for 2 days, resulting in a patchy cellular restitution on the valve surface. The in vivo function was tested in a sheep model of orthotopic pulmonary valve conduit transplantation. Three of 4 unseeded control valves and 5 of 6 tissue-engineered valves showed normal function up to 3 months. Unseeded allogenic acellular control valves showed partial degeneration (2 of 4 valves) and no interstitial valve tissue reconstitution. Tissue-engineered valves showed complete histological restitution of valve tissue and confluent endothelial surface coverage in all cases. Immunohistological analysis revealed cellular reconstitution of endothelial cells (von Willebrand factor), myofibroblasts (alpha-actin), and matrix synthesis (procollagen I). There were histological signs of inflammatory reactions to subvalvar muscle leading to calcifications, but these were not found in valve and pulmonary artery tissue. CONCLUSIONS: The in vitro tissue-engineering approach using acellular matrix conduits leads to the in vivo reconstitution of viable heart valve tissue.
Subject(s)
Extracellular Matrix/transplantation , Heart Valve Prosthesis , Pulmonary Valve/transplantation , Animals , Antigens, Differentiation/metabolism , Calcinosis/pathology , Culture Techniques/methods , Echocardiography , Endothelium, Vascular/cytology , Endothelium, Vascular/metabolism , Extracellular Matrix/metabolism , Heart Valve Prosthesis Implantation , Immunohistochemistry , Inflammation/pathology , Lung/cytology , Pulmonary Valve/diagnostic imaging , Pulmonary Valve/pathology , Sheep , Transplantation, HomologousABSTRACT
BACKGROUND: Recently, homocysteine (HCY) levels have been suggested to be a risk factor in cardiac allograft vascular disease (CAVD). As plasma levels are partially under genetic control, we investigated the influence of the methylenetetrahydrofolate reductase (MTHFR) polymorphism on HCY levels and development of CAVD in heart transplant (HTX) recipients. METHODS: Genotyping and assessment of fasting HCY levels were performed in a cohort of 146 HTX recipients and correlated to the onset and progression of CAVD, assessed by serial angiography. RESULTS: Actuarial freedom from CAVD did not differ significantly between the genotypes. However, patients positive for CAVD presented with higher HCY levels than CAVD-negative individuals (21.0+/-9.4 vs. 18.2+/-6.6 micromol/L, P=0.046). CONCLUSIONS: There is some evidence that plasma HCY might be involved in development of CAVD. However, polymorphism of the MTHFR gene could not be shown to be related to severity of allograft vascular disease.
