BACKGROUND: The shelf life of liquid-stored platelet concentrates is limited to 5 days. Therefore, much work has been carried out in an attempt to establish the optimum method for cryopreservation. Among the various cryoprotectants, dimethyl sulfoxide (DMSO) has been shown to be the most effective. However, DMSO-frozen platelets are characterized by a number of cell lesions. This report describes metabolic and functional changes that should give rise to some concern about the functional integrity of these cells.
STUDY DESIGN AND METHODS: Single- donor platelet concentrates were frozen in liquid nitrogen by use of DMSO (5%). After thawing, the cells were washed and resuspended in autologous plasma. Before, during, and after the freezing process, samples for analysis of metabolic measures (e.g., pH; calcium, potassium, and lactate dehydrogenase concentrations; plasma complement factors) and functional measures (e.g., aggregometry, in vitro bleeding time, alpha-granule membrane protein-140 expression) were taken.
RESULTS: Mean platelet volume increases during the deep-freezing process. Potassium, calcium, and lactate dehydrogenase are released from the intracellular space to the extracellular space. A strong activation of complement, which is mainly due to the addition of DMSO, is observed. Platelets become activated as indicated by the expression of alpha-granule membrane protein-140. Accordingly, decreased platelet function can be observed.
CONCLUSION: DMSO-frozen platelets are characterized by several metabolic and functional changes. Although these cells have been shown to exert hemostatic effects in vivo, it is conceivable that those effects could be improved by further development of platelet-freezing techniques.