Abstract: Objective To investigate the influence of cryopreservation on cellular viability of latepregnancy fetal valved allografts in human. Methods The fetal valved allografts with gestational ages ranged from 24 to 40 weeks were sterilely procured within 6 hours after brain death. Each sample was bisected into control group and experiment group. The cellular viability of control group was directly tested and that of experiment group was examined after being storaged in liquid nitrogen for a week through a programmed frozen procedure. The light microscopy, tissue culture and Methylthiazol tetrazolium assay (MTT assay) were used to determine the cellular viability. Results Twelve latepregnancy fetal valved aortic allografts were procured. Light microscopy showed the integrity of the basic structure of the thawed aorta, the normal structure of the collagen and elastic fibers, with part of vascular endothelium lost. There were lots of cells deriving from both groups,but the cellular growing rate of the experiment group was relatively slower. At 490 nm, MTT assay valve of control group was 0.442±0.046, and that of experiment group was 0.424±0.041. The difference between two groups failed to statistically significance(t=1.617, P=0.328). Conclusion There were viable cells in latepregnancy fetal valved allografts after cryopreservation.
Objective To explore the biomechanic effects of multi ple freeze-thaw on human allograft tendons. Methods Thirty tendons (24 flexor digitorum superficial is tendons and 6 flexor poll icis longus tendons) were harvested from 3 fresh cadaver donors and were divided into 6 groups randomly (fresh group; 1 cycle, 2 cycle, 3 cycle, 5 cycle, and 10 cycle freeze-thaw groups). There was 4 flexor digitorum superficial is tendons and 1 flexor poll icis longus tendon in each group. The structural and mechanical properties as well as viscoelastic change were estimated. Results The results of the structural and mechanical properties in 1 cycle, 2 cycle, and 3 cycle freeze-thaw groups were similar to that of the fresh group (P gt;0.05). The tendons in 5 cycle and 10 cycle freeze-thaw groups showed a significantly lower ultimate load and maximum stress when compared with those of fresh group (P lt; 0.05), but there was no significant difference in maximum tensile or maximum strain (P gt; 0.05). Moreover, the tendons in 5 cycle and 10 cycle freeze-thaw groups had a significant increase in viscoelastic properties when compared with fresh group (P lt; 0.05). Conclusion In the cryopreservation of tendon allografts, the cycle of freeze-thaw should not exceed 3 times. Multiple cycle freeze-thaw will weaken the biomechanical properties of tendon allografts, which make grafts easier to fatigue or even rupture.