Objective  To investigate the pathological changes of cryopreserved homograft cardiac valves in liquid nitrogen with chondroitin sulfate (CS).   Methods  Forty-eight rabbit aortic valves were randomly divided into control and 5 experiment groups according to different time points (n=8). All the valves were germicidal treated. The experiment groups were cryopreserved in liquid nitrogen contained 7.5% CS for 1

3

5

7 and 9 months respectively. Then

the activities of cells in different groups were examined and the specimens were observed under light and electron microscopy.   Results  Compared with the control

cytoactive of the experiment groups were significantly declined (P0.05)

but there was no significant difference among these experiment groups (P0.05). Compared with 1-month group

cytoactive of 9-month group was significantly declined (P0.05). There were slight morphologic changes in all experiment valves.   Conclusion  The cryoprotectant with 7.5% CS has the protective effect on cryopreserved cardiac valves in liquid nitrogen. Within 7 months after cryopreservation

the cytoactive declined little

histologic structure is preserved better

and valves have better availability.