BIOCHEMICAL AND CELLULAR CHARACTERIZATION OF CARDIAC-VALVE TISSUE AFTER CRYOPRESERVATION OR ANTIBIOTIC PRESERVATION

It has been reported that aortic homografts that have been cryopreserv ed before transplantation remain viable longer as an allograft than ti ssue stored at 4 degrees C in an antibiotic solution. In the present s tudy, we tested the hypothesis that storage of cardiac valve tissue by cryopreservation or by antibiotic preservation may alter the metaboli c status of the tissue. Initially,,ve collected aortic valves composed of cardiac tissue, aortic root, and valvular tissue from cadaver dono rs. These specimens were divided into three equal portions, and one po rtion was analyzed before storage while the other two parts were store d for 3 weeks at either 4 degrees C in an antibiotic solution or at -1 96 degrees C in liquid nitrogen. All specimens were examined with rega rd to the following parameters: tissue structure, tissue viability, ce ll proliferative capacity, metabolic function, and identification of c ell-specific antigens. We found no significant alterations in the stru cture of any of the three tissue components after antibiotic preservat ion or cryopreservation; however, cell viability and cell number were decreased in all three groups. Ah tissue samples grew in culture befor e storage. When we compared activities of the following organellar mar ker enzymes-lysosomal acid lipase, plasma membrane 5' nucleotidase, mi tochondrial cytochrome oxidase, and microsomal neutral alpha-glucosida se-we observed no major differences between tissues stored by either t echnique. In addition, we observed no loss of enzymic activity as a re sult of storage. Finally, when cell lines isolated from each tissue sp ecimen were incubated with monoclonal antibodies against cell-specific antigens in an immunoperoxidase assay, all the cell cultures proved t o be endothelial cells. These results suggest that although cardiac va lve tissue stored by cryopreservation or by antibiotic preservation re tained its normal structure and metabolic capabilities, both storage t echniques produced significant decreases in cell numbers and viability . However, only endothelial cells from tissue stored by cryopreservati on retained the capacity to proliferate in vitro. These findings have important implications for the function of aortic homografts transplan ted after storage.