Effect of nitric oxide on the cryopreservation of platelets

Background : To determine whether nitric oxide (NO) could inhibit activation of platelets stored in a cold or frozen state, we measured platelet P-selectin expression and platelet-bound fibrinogen in platelet-rich plasma (PRP) with S-nitrosoglutathione (GSNO) (Sigma, USA) by flow cytometry. Methods : PRP was prepared by centrifuging venous blood collected in a 3.2% sodium citrate tube from 10 healthy donors. It was aliquotted into 4 groups (no cryoprotectant, GSNO, GSNO/ dimethyl sulfoxide [DMSO] [Sigma], and DMSO), and stored at room, cold and freezing temperatures for 24 hrs. We performed a flow cytometric analysis of all specimens stained with FITC-fibrinogen and PE-CD62P monoclonal antibodies (Becton Dickinson, USA). The results were compared according to the storage temperature and agonist among 4 groups. Results : GSNO inhibited significantly the activation of frozen platelets, but not in the presence of DMSO. GSNO was also shown to preserve the aggregability of frozen platelets because in the presence of GSNO the delta percent change of P-selectin expression and fibrinogen binding of frozen platelets increased significantly irrelevant to DMSO. Conclusions : GSNO inhibited the activation of frozen platelets and preserved the platelet aggregability; therefore, it may be used as a protectant for platelet cryopreservation.