Abstract: Objective To evaluate the effect of lyophilization on the morphological feature, ultrastructure and apoptosis of platelets. Methods The lyophilized platelets were rehydrated after preserved 30 days. The changes of the morphology and ultrastructure of platelets were observed under the light microscope and transmission electron microscope (TEM) respectively. The survival rate and apoptosis rate of platelets were analyzed by flow cytometry (FCM). The aggregation rates of rehydrated lyophilized platelets were measured by using 1U/ml thrombin. Results The morphology of rehydrated lyophilized platelets keeps normal. There were no evident cell aggregation in rehydrated lyophilized platelets，but the refractive index of them was relative weak compared with fresh platelets. The result of ultrastructure observation indicated that the intracellular elementary structures of rehydrated lyophilized platelets were clear and the cell membrane keeps intact. According to the result of FCM analysis, the apoptosis rate of the fresh platelets and lyophilized platelets was(0.44±0.19)％ and (3.25±1.68)％ respectively, and there was a significant difference between the two groups（P＜0.05).The maximum aggregation rates of rehydrated lyophilized platelets were(93.28±2.3)％. Conclusion The rehydrated lyophilized platelets keep intact cellular structure. The study provides an evidence for successful building the method of lyophilized platelet in our lab.

Key words: lyophilized platelet, rehydrated, ultrastructure, apoptosis