ADENINE-NUCLEOTIDE DEPLETION IN CRYOPRESERVED HUMAN CARDIAC VALVES - THE STUNNED LEAFLET INTERSTITIAL CELL-POPULATION

Preparation protocols for human cardiac valves are intended to minimiz e cytotoxicity because it has been thought that viable leaflet interst itial cells may enhance homograft durability. Preimplantation factors influencing the status of these cells at the time of transplantation i nclude ischemia, disinfection, and cryopreservation freezing programs. In these experiments, ade:nine nucleotide quantitation was undertaken to assess metabolic consequences of preparation; preharvest ischemia served as an independent variable to examine the relationship between time of procurement (postmortem) and high-energy phosphate status of t he cryopreserved leaflets at thaw. Nucleotides were measured using hig h-performance liquid chromatography performed on extracts of semilunar cusps from 25 cryopreserved human valves with documented ischemic tim es. Results indicate total adenine nucleotides (TAN; [ATP] + [ADP] + [ AMP], in nmol TAN/mg leaflet protein) are higher (P < 0.05) after <2 h of harvest ischemia (1.16 +/- 0.36) than with ischemic times of 3-6 h (undetected), 7-12 h (0.18 +/- 0.07), and 13-20 h (0.06 +/- 0.06). De pletion of ATP was similar, with many leaflets devoid of detectable le vels. Net utilization of leaflet energy stores demonstrates time depen dency when assayed after completed processing. However, relatively ele vated catabolites, even with brief ischemia, and infrequently identifi ed ATP, ADP, and AMP, suggest a consumption so accelerated that the fo llowing cryopreservation it is virtually independent of procurement-as sociated ischemia. We conclude resumption of a functional cell populat ion obligates significant de novo, phosphoanhydride boned reformation or a repopulation of dead/dying interstitial cells from a subset survi ving the apparently severe rigors of valve preparation. (C) 1995 Acade mic Press, Inc.