Controlled-rate versus uncontrolled-rate freezing as predictors for platelet cryopreservation efficacy

Cryobiologic variables responsible for cell injuries and freezing techniques applicable in medical cryopractice should be revised and/or reengineered for minimizing cryoinjuries and maximizing cell recovery. In this study, the efficacy of different cryopreservation protocols based on platelet (PLT) recovery was evaluated.

PLTs (n = 33) were prepared from whole-blood units. Cell count and viability, PLT morphologic score (PMS), and hypotonic shock response were determined. PLT surface antigens were measured by flow cytometry. Controlled-rate (with compensated fusion heat) and uncontrolled-rate freezing methods combined with 6 percent dimethyl sulfoxide were used.

PLT recovery was superior in the controlled-rate setting (91.0 +/- 5.5 vs. 86.0 +/- 6.5; p < 0.05). PMS was significantly better in controlled-rate freezing (p < 0.01). GPIb/CD42b expression was reduced in both freezing groups versus control. GP140/CD62p expression was significantly (p < 0.05) lower in the controlled-rate group and in both frozen groups was significantly higher than in the control groups.

The use of strictly equalized (1 degrees C/min) controlled-rate freezing, combined with an intensified cooling rate (2 degrees C/min) during the liquid-to-solid-phase transition period, allows advanced quantitative and qualitative PLT recovery, even though the minor intergroup differences for some variables were observed.