Time‐related Histopathologic Analyses of Immunologically Untreated Porcine Valved Conduits Implanted in a Porcine‐to‐Goat Model

Abstract

This study was performed to evaluate the clinical feasibility of use of immunologically nontreated xenogenic valves, using a porcine-to-goat pulmonary valved conduit implantation model. Porcine pulmonary valve conduits were prepared with no specific immunological treatment and implanted in the right ventricular outflow tract of goats under cardiopulmonary bypass. The goats were assigned at predetermined intervals (1 day, 1 week, and 3, 6, and 12 months) as two animals for each interval. Echocardiographic examinations of the valves were performed before sacrifice. Upon retrieving the xenograft specimens, they were inspected visually and microscopically. Ten of the 12 animals survived the predetermined observation periods. Variable degrees of pulmonary regurgitation were the main findings on echocardiographic evaluations. On gross examination of the explanted specimens, all leaflets, except in one animal that prematurely died, were fairly well preserved. They were slightly shortened but free of thrombosis or vegetation. Aneurysmal dilatations of the anterior wall of the implanted pulmonary artery were observed in one of 12-month-survival animals and in another one of 3-month-survival animals. Microscopically, the three components of implanted xenografts (the pulmonary artery, valve, and infundibulum) were shown to be gradually replaced with host cells in time, while maintaining structural integrity. The nuclei of the donor tissue disappeared through pyknosis and karyolysis. In conclusion, immnunologically untreated xenogenic pulmonary valved conduits can be an alternative potential as valve substitutes with distinctive advantages of providing self-healing potential, despite a few problems observed in the current study such as occurrences of pulmonary regurgitation and sporadic cases of aortic aneurysm.

Immunologically Untreated Fresh Xenograft Implantation in a Pig‐to‐Goat Model

“…Mural inflammation was slightly more prevalent in the frozen group. However, neo-intima and neo-media formation, as described in our previous study (12), were identified in both groups. The three layers of the pulmonary artery, that is, intima, media, and adventitia, and its structural integrity were preserved in both groups.…”

“…In our previous study (12), immunologically untreated, frozen-stored xenogenic pulmonary valved conduits did not show severe rejection sequelae clinically, and their three components (pulmonary artery, valve, and infundibulum) were found to be gradually replaced by host cells, while structural integrity was maintained. Thus, we suggested that implanted immunologically untreated xenografts undergo controlled rejection and repair.…”

“…In the present study, to determine whether the frozen preservation technique used might have affected immune reaction, we compared the histologic findings of immunologically untreated xenografts subjected to frozen storage and those of immunologically untreated fresh xenografts in the same animal model used in our previous study (12).…”

Artificial Organs 2007: A Year in Review

“…Won Gon Kim et al. (95) of the Department of Thoracic and Cardiovascular Surgery and Heart Research Institute (Seoul, Korea) reported on their investigation of the clinical feasibility of using immunologically nontreated xenogenic valves using a porcine‐to‐goat pulmonary valved conduit implantation model. Ten of the 12 animals survived the observation periods up to 12 months while exhibiting variable degrees of pulmonary regurgitation.…”

Time‐related Histopathologic Changes in Fresh Frozen Carotid Xenografts in a Pig‐to‐Goat Implantation Model

“…Authors previously reported that immunologically untreated xenogenic pulmonary valves have potential as valve substitutes due to a lack of rejection reactions and the maintenance of self-healing capacity after pig-to-goat transplantation (6).The potential immune privilege of valvular and large vascular tissues after xenotransplantation could be extended to clinically applicable smaller-diameter vessel substitutes. In this regard,we previously conducted a pilot study to evaluate this possibility using immunologically untreated xenogenic carotid artery grafts, and found that untreated xenogenic grafts showed good patency to the same extent as acellularized xenogenic grafts within an observation period of 6 months (7).…”