Effect of Sialic Acid on Platelet Cryopreservation

Sialic acid is a molecule which is responsible for the net negative surface charge of platelets. We investigated the effect of sialic acid on fresh and cryopreserved platelets. Platelet samples were obtained by platelet apheresis from 8 healthy donors. Platelet suspensions with different sialic acid concentrations (0, 1, 2 and 4 mg/mL) were studied for ADP and ristocetin induced platelet aggregation, basal and ADP induced P-selectin and glycoprotein- Ib/IX expression. Then platelet samples were cryopreserved in 5% DMSO with or without 4 mg/mL sialic acid. After thawing, P-selectin expression was compared with the control group. Six samples were also washed after thawing and P-selectin expression was again compared to unwashed samples. Sialic acid suppressed ADP induced platelet aggregation and P-selectin expression in a dose dependent manner. In cryopreserved samples, P-selectin expression of 4 mg/mL sialic acid containing group was found significantly higher than the control group (p< 0.001). In cryopreserved control group, P-selectin expression of thawedwashed group was significantly higher than thawed-unwashed group (p< 0.05). Our results indicate that sialic acid is not a good cryoprotective agent. Washing procedure after thawing to eliminate DMSO causes significant platelet activation.