oa Ice-Free-Cryopreservation Attenuates Calcification in Allograft Heart Valves

The objective of the study was to attenuate calcification in allogeneic ovine pulmonary heart valves. Six valves of white face sheep were ice-free-cryopreserved (STUDY) in 12.6 mol/L cryoprotectant (4.65, 4.65, and 3.31 mol/L of DMSO, formamide and 1,2-propanediol) and stored at -80°C. 6 control valves were cryopreserved by controlled slow rate freezing in 1.4 mol/L DMSO and stored in vapor-phase nitrogen (CONTROL). After 7 months in vivo explanted valves were processed for histopathology. Gross morphology showed significantly thickened leaflets in the CONTROL group. Histopathology revealed a marked calcification in the leaflet stroma and conduit wall. STUDY valves in contrast demonstrated well preserved ECM structures, no leaflet thickening, inflammation and only neglectable calcification in the conduit wall. Only discrete panus formation was noted migrating from the ventricularis onto the leaflet. Ice-free-cryopreservation enables attenuation of calcification in ovine allografts valves. The observed decreased calcification warrant improved long-term function.