Biochemical characteristics and functional performance of cold-stored platelets: an in-vitro comparative study

Background: Platelet refrigeration could eliminate bacterial contamination and improve the hemostatic function even better than already-used room-temperature storage. This study aimed to assess the effect of cold storage, with and without agitation, on the apheresis platelets' hemostatic, metabolic, and functional activity. Materials and methods: The study included 10 healthy volunteer donors to collect Apheresis PLT. They were submitted to careful clinical examination and standard laboratory workup. Collected samples were processed in accordance with American Association of Blood Banks (AABB) guidelines. Every aliquot collected from each volunteer was stored for up to 5 days at one of the following storage conditions: 1. In an FDA-approved-PLT incubator with agitation at room temperature (RT + AG as a group; GI), 2. In an FDA-approved-refrigerator at 4 oC with agitation (4 oC + AG as a group; GII), 3. In an FDA-approved- refrigerator at 4 oC without agitation (4 oC – AG as a group; GIII). The following PLT workup was done; PLT count and mean platelet volume (MPV), metabolic variables, PLT aggregation studies, PLT receptors expression, and PLT pro-inflammatory mediator’s release.Results:All samples had a significant PLT count decline compared to baseline data. No changes in MPV were observed in all groups on day 3 and day 5, meaning that single PLT size remained unchanged. In addition, GI showed a mark of significant increase in metabolic activity when compared to baseline PLTs in contrast to GII, and GIII, which were more metabolically stable and less active.Comparison between the studied groups regarding PLT aggregation revealed significantly higher PLT aggregation response to ADP and collagen in GII and GIII compared to GI on the 3rd and 5th days. Moreover, it was shown that GII and GIII samples had significantly higher CD62p expression when compared with GI on the 3rd and 5th days despite being less active and more stable. While it was found that TXB2 levels were significantly higher, nearly 3-fold, in GI as compared to GII and GIII.Conclusions: Apheresis platelets (AP) cold storage provides a clear advantage over standard conditions regarding biochemical balance and hemostatic performance, which could markedly improve AP's clinical and economic value in different scenarios.  Keywords: Platelet aggregation, P-selectin, Thromboxane B2.