Preservation of myocyte structure and mitochondrial integrity in subzero cryopreservation of XXXX hearts for transplantation using antifreeze proteins--an electron microscopy study.

@entity1 @entity160 @entity35
OBJECTIVE: Freeze tolerant fish and insects in nature are able to survive subzero temperatures by noncolligatively lowering the freezing temperature of their body fluids using a family of thermal hysteresis proteins (antifreeze proteins, AFPs) specific for each species. Past efforts to cryopreserve @entity1 hearts using these proteins were unsuccessful. We report the first successful subzero cryopreservation of @entity35 hearts using fish derived antifreeze proteins with preservation of myocyte structure. METHODS: Heterotopic heart transplantations were performed in isoimmunic @entity35 . Donors' hearts were arrested using University of Wisconsin (UW) solution and preserved in UW solution containing @entity160 I (six experiments) or @entity160 III (six experiments) at concentrations of 15-20 mg/cc for 2-6 h at subzero temperatures ranging from -1.1 to -1.3 degrees C. Four control experiments were performed by preserving harvested hearts in UW solution alone at -1.3 degrees C for 6 h. In all experiments ice was added in the solution for crystallization. Heterotopic transplantations were performed in the abdomen of the recipient @entity35 . Viability was visually assessed and graded on a scale of 1 (poor contraction) to 6 (excellent contraction). The hearts were then fixed in vivo and processed for electron microscopy study. RESULTS: All hearts preserved at subzero temperatures using @entity160 I or @entity160 III survived displaying viability scores of 4-6 1 h after transplantation. Three of the four control hearts that were preserved at -1.3 degrees C without the protective effect of @entity160 froze and died upon reperfusion. Electron microscopy study of hearts preserved with @entity160 demonstrated preservation of myocyte structure and mitochondrial integrity. CONCLUSION: Subzero cryopreservation of @entity1 hearts for transplantation using @entity160 I or @entity160 III is feasible with preservation of myocyte structure and mitochondrial integrity.
