Bioactive Lipid Mediators Predict Platelet Function in Transfusion Recipients: A Phase 1 Randomized Clinical Trial in Healthy Humans

Background: Platelets are stored at room temperature for 5-7 days (RSP) and are transfused to patients who are bleeding or at risk of bleeding. Due to frequent and severe shortages, the FDA recently approved cold-stored platelets in plasma (CSP) for up to 14 days despite a lack of post-transfusion data. It is also unclear which donors are best suited to provide platelets for either RSP or CSP and which in vitro markers accurately predict post-transfusion RSP or CSP platelet function. Objective: To evaluate the post-transfusion function and predictors of post-transfusion function of platelets stored for the maximum approved storage times (7-day RSP, 14-day CSP) in healthy volunteers on acetylsalicylic acid (ASA). Methods: We conducted a randomized cross-over study in ten healthy humans. Subjects on ASA were randomized to receive either autologous RSP or CSP first. We obtained blood from recipients before and after transfusion for platelet function testing and samples from the storage bag before and after storage for lipid metabolite analysis. The first round was followed by a second round with transfusion of the alternative product and the same testing sequence. Results: RSP reversed platelet inhibition significantly better in αIIbβ3 integrin activation-dependent assays. In contrast, CSP led to significantly more thrombin generation in recipients. Overall, RSP contained more pro-inflammatory lipid mediators while CSP had more anti-inflammatory lipid mediators. In particular, LPC species including LPC-O species (formerly known as Lyso-platelet activating factor [LPAF]), LPE, and LPI were significantly more abundant in RSP than in CSP, while LPS was more abundant in CSP than in RSP. Similarly, the relative increase of LPC, LPE, and LPI, and linoleic acid-dependent oxylipins, such as diHOMEs and HODEs were higher in RSP recipients than in CSP recipients. Linoleic acid-dependent oxylipins correlated positively with platelet aggregation in units and recipients of RSP and CSP. Polyunsaturated fatty acids (PUFAs) showed a negative correlation with platelet aggregation in both RSP and CSP units and recipients. Most importantly, LPC-O (LPAF) species showed a strong negative correlation with endogenous thrombin generation potential in CSP units after collection (pre-storage), post-storage, and in transfusion recipients. Conclusion: Results from our trial provide the first efficacy data of autologous and extended-stored CSP in plasma. We report the first correlational data between unit and recipient lipid mediators and post-transfusion platelet function. Taken together, we show that the main mechanism of post-transfusion CSP function appears to be based on procoagulant properties. In the future, testing platelet donors for LPC-O (LPAF) species could identify donors whose platelets are better suited for cold storage than room-temperature storage.