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

Abstract

Immunologically untreated frozen-stored xenografts show controlled rejection and repair due to reduced cellularity in our previous study. To clarify the issue, we compared results obtained using fresh and frozen-stored xenografts. Porcine pulmonary valved conduits were prepared without immunologic treatment and implanted in the right ventricular outflow tract of goats under cardiopulmonary bypass immediately after harvest without frozen storage (the fresh group) or after frozen storage (-70 degrees C for 3 - 7 days) (the frozen group). Four goats were assigned to be raised for 3 (N = 1) or 6 (N = 3) months postoperatively in each group. One goat in the frozen group assigned for the 6-month observation expired at 2 months postoperatively because of thrombotic occlusion of the pulmonary valve. The other goats survived until the scheduled sacrifice. According to echocardiographic findings, one animal sacrificed at 3 months in the frozen group showed more than a moderate degree of pulmonary regurgitation, but all animals in the fresh group showed less than a mild degree. On gross examination, leaflets were slightly better preserved in the fresh group and aneurysmal dilatation of the pulmonary artery was observed at 3 months only in the frozen group. Microscopically, pulmonary arteries showed less severe degenerative changes in the fresh group. Moreover, in the fresh group, viable donor valve cells were still present until 3 months postoperatively (though it disappeared at 6 months postoperatively) and a linear endothelial lining of viable host cells was prominent on all leaflets, whereas this was not the case in the frozen group. In conclusion, fresh xenografts preserved cellular viability and showed fewer degenerative changes than frozen-stored xenografts. Thus, immunologically untreated fresh xenografts could provide a potential valve substitute with distinctive advantages in terms of self-healing potential as compared with frozen-stored xenografts.

Transplantation of a Fresh Cadaveric Iliac Homograft After Celiac Artery Aneurysmectomy

“…In a large study reported by a European Collaborative Vascular Homograft Group, no significant differences in long-term patency rates were observed in patients receiving fresh versus cryopreserved homografts for infected vascular prostheses. Of note, in this as well as in more recent reports, 11,15 no immunosuppression was used in patients who received fresh homografts.…”

A review of the immune response stimulated by xenogenic tissue heart valves

“…Cryopreserved xenografts had increased T cell infiltration; however, the fresh xenografts had lost cellularity, implying cryopreservation might influence the morphological changes in valve xenotransplantation 38 . In contrast, others have found preserved cellular viability and fewer degenerative changes using a fresh‐storage protocol, compared to frozen‐stored xenografts 39 . The modulatory effects of ice‐free cryopreservation (IFC) of xenogeneic heart valve leaflet matrices, without decellularization, on the adaptive human immune response in vitro have been assessed.…”

Artificial Organs 2008: A Year in Review

“…Kiick Sung et al. (127) of the Sungkyunkwan University School of Medicine, Seoul, Korea studied immunologically untreated fresh xenograft implantation in a pig‐to‐goat model. Porcine pulmonary valved conduits were prepared without immunologic treatment and implanted in the right ventricular outflow tract of goats under CPB immediately after harvest without frozen storage (the fresh group) or after frozen storage (−70°C for 3–7 days) (the frozen group).…”