Dose-dependent effects of dimethyl sulfoxide (DMSO; Me2SO) for platelet cryopreservation: 10% Me2SO provides superior cryoprotection.

The most widely used method of platelet cryopreservation involves the addition of 5-6% dimethyl sulfoxide (DMSO; Me2SO), followed by pre-freeze centrifugation and hyperconcentration to minimize the content of Me2SO transfused. However, several aspects of platelet quality are negatively affected by cryopreservation, indicating the process could be optimized. The aim of this study was to identify the concentration of Me2SO that provides maximal cryoprotection for platelets. Scaled-down titration experiments were performed in tubes. Me2SO (5% to 20% v/v) was added to apheresis platelets, followed by low-speed centrifugation and removal of the Me2SO-containing supernatant before freezing at -80 °C. Subsequently, platelets were frozen in bags with 10% Me2SO to ensure scalability to standard transfusion practices. All platelets were thawed and reconstituted in plasma prior to testing. In vitro platelet quality was assessed by flow cytometry, aggregometry, viscoelastic testing (TEG), thrombin generation and clot retraction. Titration experiments demonstrated that 10% Me2SO consistently improved platelet quality parameters compared to 5% Me2SO. Higher concentrations (12.5-15% Me2SO) showed similar benefits to 10%, but 20% offered no additional advantage above 5% Me2SO. Freezing platelets in bags in the presence of 10% Me2SO resulted in improvements in platelet recovery, morphology, retention of labile glycoproteins (GPIbα, GPVI), and reduced annexin-V binding and extracellular vesicle formation, compared to 5% Me2SO. TRAP-6-induced aggregation, clot strength and clot retraction were significantly improved in platelets frozen with 10% Me2SO. This study demonstrates that cryopreservation with 10% Me2SO offers superior platelet cryoprotection, at least in the context of in vitro quality parameters.