EFFECTS OF STORAGE-TEMPERATURE AND FETAL CALF SERUM ON THE ENDOTHELIUM OF PORCINE AORTIC VALVES

Endothelial integrity and function may be an important determinant for long-term success of allograft heart valves. To determine the optimal storage temperatures for preservation of long-term endothelial functi on in porcine aortic valves, different storage temperatures and times were investigated, Fresh valves were either (1) stored at 4 degrees C, with or without 10% fetal calf serum supplement, for 1, 2, 4, 7, 14, 21, or 28 days; (2) cryopreserved for 2, 4, or 8 weeks at -80 degrees C or -170 degrees C; (3) cryopreserved in long-term storage (as long a s 1 year),,vith or without fetal calf serum, at -170 degrees C. Viabil ity of endothelial cells was assessed through measurement of the produ ction of prostacyclin in basal and bradykinin-stimulated conditions, d uring in vitro incubation of the valve cusps at 37 degrees C. Endothel ial morphologic variations in valves stored at 4 degrees C were evalua ted by scanning electron microscopy. With storage at 4 degrees C, afte r 4 days the valves already produced significantly less (p < 0.05) pro stacyclin than fresh preparations in both basal (0.21 +/- 0.01 versus 3.56 +/- 0.03 ng . ml(-1) . cm(-2)) and stimulated conditions (4.17 +/ - 0.36 vs 24.23 +/- 1.83). Morphologic changes could not yet be distin guished with scanning electron microscopy at that time. When the stora ge period was extended, the levels of prostacyclin further diminished; after 14 days, prostacyclin release could no longer be detected. In c ryopreserved valves, prostacyclin production was similar for as long a s 2 weeks of storage either at -80 degrees C or at -170 degrees C in b asal (2.69 +/- 0.63 vs 2.93 +/- 0.51) and stimulated (16.43 +/- 3.19 v s 16.50 +/- 2.57, = 6) conditions, After 8 weeks, no prostacyclin rele ase could be detected in valves stored at -80 degrees C. After 6 month s storage at -170 degrees C, the prostacyclin production was significa ntly (p < 0.05) reduced compared with fresh valves; it then remained c onstant for as long as 1 year, The valves stored with fetal calf serum produced significantly (p < 0.05) less prostacyclin than did those wi thout fetal calf serum. For longer cryopreserved banking, we recommend storing heart valves at -170 degrees C instead of at -80 degrees C to maintain viability of endothelial cells. Fetal calf serum would harm endothelial viability during long-term cryopreservation.