Evaluation of survival and functionality in frozen platelets

Prolong platelet survival and functionality up to 28 days.

A sample of apheresis platelets was evaluated, distributed in 3 groups according to the cryopreservative solution used: DMSO5%+2%albumin; DMSO5%+NaCl0,9% and DMSO5%+Dextrose2%. They were then frozen at -80 °C and thawed at 7, 14 and 28 days. The in vitro survival and viability were assessed by the post-thaw platelet count and the CD41, CD61 and CD42a staining percentages by flow cytometry. The functionality was determined with the percentage of post-stimulation aggregation with 1Nm-thrombin using the Chromo-Log490 aggregometer. The control group (CG) consisted of fresh platelets under constant agitation at 22 °C.

A total of 72 platelet aliquots was analyzed. The CG presented a platelet-count of 1934 ± 0.5 × 10⁹/L and a 100% viability. The percentages of CD41, CD61 and CD42a labeling were 99, 98.5 and 96.5%, respectively. The percentage of aggregation was 99%. On day 7 of the post-freezing, the platelet count for groups 1, 2 and 3 was 1,844 ± 102, 1,856 ± 76 and 1,752 ± 226, with the viability of 98, 96 and 95%, respectively. On day 14, the counts were 1,722 ± 238, 1,649 ± 215 and 1,578 ± 223 with the viability of 96, 95 and 94% and, on day 28, they were 1,602 ± 374, 1,438.6 ± 429 and 1,406.6 ± 436, with the viability of 96, 94 and 93%, respectively. Group1 presented a higher expression of membrane antigens. Aggregation percentages were 90, 98 and 89% at day 7, 88%, 98 and 87% at day 14 and 84%, 95 and 82% at day of the 28 post-freezing, respectively, with group2 presenting the best results.

The results support cryopreservation as a reasonable method to prolong platelet survival up to 28 days, maintaining its functionality and viability greater than 50%.