Immunogenicity, Antigenicity, and Endothelial Viability of Aortic Valves Preserved at 4°C in a Nutrient Medium

Abstract

In patients undergoing aortic valve replacement, allograft valves stored at 4 degrees C in a nutrient medium have been associated with excellent immediate and long-term results. The effects of this method of prolonged storage on the antigenic, immunological and cellular characteristics of these grafts are incompletely understood. This study was designed to study these phenomena in rat aortic valves subjected to antibiotic sterilization and stored for up to 3 weeks in RPMI containing 10% fetal calf serum. Selected valves from Brown Norway rats were implanted heterotopically into the abdominal aorta of Lewis rats. Other valves were studied prior to transplantation. Antigenicity was determined by immunocytochemical staining using monoclonal mouse antibodies directed at Class I and Class II rat antigens. Immunogenicity was determined by duration of second-set skin graft survival following heterotopic aortic valve implant. Endothelial cell viability was determined by flow cytometric analysis of endothelial cells harvested from aortic valve allografts by collagenase digestion. Only fresh valves and valves stored for 1 day were positive for Class I antigens; no valves were positive for Class II antigens. Duration of skin graft survival was prolonged with greater duration of storage, but grafts remained immunogenic after 21 days of storage. Endothelial cell viability declined from 95% in the fresh valves to 64% after 21 days of storage. With prolonged duration of allograft valve storage at 4 degrees C, there is an attenuation of antigenicity, immunogenicity, and endothelial cell viability. Loss of endothelial cells may contribute to the changes in immunological responses to the valve allografts. The expression of antigens on the endothelial surface is not a reliable predictor of immunological response.

Mid- to long-term outcomes of cardiovascular tissue replacements utilizing homografts harvested and stored at Japanese institutional tissue banks

“…However, cryopreserved homografts develop a slow but defi nite allogeneic immunologic reaction leading to SHVD, particularly when implanted in young patients. 12,13 In addition, recent advances in biologic valves may make them more acceptable than homograft valves. 14,15 Despite their negative features, homografts still have a strong appeal to surgeons because of their excellent handling characteristics during fragile tissue reconstruction, particularly in active endocarditis [16][17][18][19] and at the time of the Ross operation.…”

Cryopreservation of Rat Aortic Valves Results in Increased Structural Failure

“…9,10 All of these factors could have an impact on the durability of the allograft after implantation. Some centers continue to advocate the use of fresh valves maintained at 4°C and implanted within hours to a few days.…”

Rat heart-aorta cluster transplantation: a novel model to study transplant rejection

“…These degenerative changes have been largely confirmed in a number of experimental models of large-vessel transplantation that have emerged over the years [lo]. The general theme behind the investigations that followed the application of these models focused on the effects of cold preservation on the immunogenicity and endothelial cell viability of such grafts [7,10,17,181. These studies suggested that these grafts were especially prone to rejection because their recipients did not receive immunosuppression.…”