An in vivo model of in situ implantation using pulmonary valved conduit in large animals under off-pump condition.

BACKGROUND: The application of pulmonary valved conduit to reconstruct the continuity between right ventricles and pulmonary artery is one of the major surgeries. This study aimed to establish an in vivo model of in situ implantation using pulmonary valved conduit in large animals under off-pump condition to validate the long-term effects of artificial pulmonary valved conduit. METHODS: Domesticate juvenile male sheep and tissue-engineered porcine pulmonary valved conduit were used for the experiment: 30 sheep, weighing (15 ± 3) kg (range 13 to 17 kg) were randomly divided into two groups which were all operated under general anesthesia by off-pump surgery (group 1) and left thoracotomy (group 2). Two different off-pump surgical methods were used to perform cannulation in sheep pulmonary artery to replace part of sheep pulmonary artery with pulmonary valved conduit which will work together with sheep pulmonary artery and valves. During the experiments, animal survival, complication rates, operating time and blood loss were recorded to compare the results between groups and to establish a surgical method with minimal invasion, simplicity, safety, and high success rates. RESULTS: In group 1, a total of 15 cases of surgeries were performed, in which two sheep died; the operative mortality was 13.3% (2/15). In group 2, a total of 15 cases of surgeries were performed, and the surgical mortality rate was 0 (0/15). The operation time and blood loss in group 2 was significantly better than that in group 1. The postoperative echocardiograms showed that, after the surgeries by these two methods, the blood flows were normal, and the valves can open and close freely. Autopsy after 6 months showed that the inner wall and the valves of pulmonary valved conduit were smooth with no thrombus formation. CONCLUSION: These two off-pump methods are feasible and safe with fewer traumas; but the second method is better and particularly suitable for the establishment of a juvenile animal model.

Decellularized porcine pulmonary arteries cross-linked by carbodiimide.

The physical properties of the tissues are weakened after decellularization, and the exposed collagen fibers are prone to thrombogenesis. Several studies have proven that the use of carbodiimide (EDC) as a cross-linking agent can improve the properties of decellularized xenogeneic scaffold materials. We adopted EDC for the treatment of porcine pulmonary arteries in an effort to improve the physical properties of these arteries following decellularization. Twenty porcine pulmonary arteries were randomly divided into 3 groups. The control group (group A) consisted of fresh porcine pulmonary arteries with no further processing; group B was treated with trypsin and the detergent Triton X-100 to remove cells; and group C was cross-linked with EDC after trypsin and Triton X-100 treatment, as in group B. The pulmonary arteries were assessed based on water content, thickness, tensile strength, and thermal shrinkage temperature, to evaluate the physical properties of all of the samples. The scaffolds were then subcutaneously embedded in rabbits. These constructs were removed after 4 weeks and checked. The cells and matrix components of the arterial walls were removed and the fibrous scaffolds were retained. In group B, the moisture content of the pulmonary arterial walls was increased; and the thickness of the walls and the tensile strength of the pulmonary arteries were decreased in comparison with group A. In subcutaneous embedding of the group B samples in rabbits, after 4 weeks, fibroblasts had grown into the scaffolds and regenerated the tissue. The water content was decreased in the pulmonary arterial walls, there was an increase in the tensile strength and the thermal shrinkage temperature in group C compared with group B. The EDC-based cross-linking procedure can enhance the tensile strength of decellularized pulmonary arteries and decrease scaffold rejection and degradation and promote tissue regeneration in vivo.