Haemostatic responsiveness and release of biological response modifiers following cryopreservation of platelets treated with amotosalen and ultraviolet A light

Cryopreservation affects platelet macromolecular composition over time after thawing and differently impacts on cancer cells behavior in vitro

Cryopreservation affects platelets' function, questioning their use for cancer patients. We aimed to investigate the biochemical events that occur over time after thawing to optimize transfusion timing and evaluate the effect of platelet supernatants on tumor cell behavior in vitro. We compared fresh (Fresh-PLT) with Cryopreserved platelets (Cryo-PLT) at 1 h, 3 h and 6 h after thawing. MCF-7 and HL-60 cells were cultured with Fresh- or 1 h Cryo-PLT supernatants to investigate cell proliferation, migration, and PLT-cell adhesion. We noticed a significant impairment of hemostatic activity accompanied by a post-thaw decrease of CD42b+ , which identifies the CD62P--population. FTIR spectroscopy revealed a decrease in the total protein content together with changes in their conformational structure, which identified two sub-groups: 1) Fresh and 1 h Cryo-PLT; 2) 3 h and 6 h cryo-PLT. Extracellular vesicle shedding and phosphatidylserine externalization (PS) increased after thawing. Cryo-PLT supernatants inhibited cell proliferation, impaired MCF-7 cell migration, and reduced ability to adhere to tumor cells. Within the first 3 hours after thawing, irreversible alterations of biomolecular structure occur in Cryo-PLT. Nevertheless, Cryo-PLT should be considered safe for the transfusion of cancer patients because of their insufficient capability to promote cancer cell proliferation, adhesion, or migration.

High fragmentation in platelet concentrates impacts the activation, procoagulant, and aggregatory capacity of platelets

Platelets are transfused to patients to prevent bleeding. Since both preparation and storage can impact the hemostatic functions of platelets, we studied platelet concentrates (PCs) with different initial composition in regard to platelet fragmentation and its impact on storage-induced changes in activation potential. Ten whole blood derived PCs were assessed over 7 storage days. Using flow cytometry, platelet (CD41+) subpopulations were characterized for activation potential using activation markers (PAC-1, P-selectin, and LAMP-1), phosphatidylserine (Annexin V), and mitochondrial integrity (DiIC₁(5)). Aggregation response, coagulation, and soluble activation markers (cytokines and sGPVI) were also measured. Of the CD41+ events, the PCs contained a median of 82% normal-sized platelets, 10% small platelets, and 8% fragments. The small platelets exhibited procoagulant hallmarks (increased P-selectin and Annexin V and reduced DiIC₁(5)). Normal-sized platelets responded to activation, whereas activation potential was decreased for small and abolished for fragments. Five PCs contained a high proportion of small platelets and fragments (median of 28% of CD41+ events), which was significantly higher than the other five PCs (median of 9%). A high proportion of small platelets and fragments was associated with procoagulant hallmarks and decreased activation potential, but, although diminished, they still retained some activation potential throughout 7 days storage.

Platelet Transfusion-Insights from Current Practice to Future Development

Since the late sixties, therapeutic or prophylactic platelet transfusion has been used to relieve hemorrhagic complications of patients with, e.g., thrombocytopenia, platelet dysfunction, and injuries, and is an essential part of the supportive care in high dose chemotherapy. Current and upcoming advances will significantly affect present standards. We focus on specific issues, including the comparison of buffy-coat (BPC) and apheresis platelet concentrates (APC); plasma additive solutions (PAS); further measures for improvement of platelet storage quality; pathogen inactivation; and cold storage of platelets. The objective of this article is to give insights from current practice to future development on platelet transfusion, focusing on these selected issues, which have a potentially major impact on forthcoming guidelines.

Cryopreservation of buffy coat derived platelets: Paired in vitro characterization using uncontrolled versus controlled freezing rate protocols

Background

Cryopreserved platelets show a reduced recovery and viability after freezing and thawing including several ultrastructural and phenotypic deteriorations compared with liquid‐stored platelets. It is suggested that using Controlled‐Rate Freezing (CRF) can reduce variability and optimize the functionality profile for cells. The objective of the study is to compare cellular, metabolic, phenotypic and functional effects on platelets after cryopreservation using different freezing rate protocols.

Study Design and Methods

To evaluate the possible effects of different freezing rate protocols a two‐experimental study comparing diverse combinations was tested with a pool and split design. Uncontrolled freezing of platelets in materials with different thermal conductivity (metal vs cardboard) was evaluated in experiment 1. Experiment 2 evaluated uncontrolled vs a controlled‐rate freezing protocol in metal boxes. All variables were assessed pre and post cryopreservation.

Results

Directly after thawing, no major differences in platelet recovery, LDH, ATP, Δψ, CD62P, CD42b, platelet endothelial cell adhesion molecule and sCD40L were seen between units frozen with different thermal conductivity for temperature. In contrast, we observed signs of increased activation after freezing using the CRF protocol, reflected by increased cell surface expression of CD62P, PAC‐1 binding and increased concentration of LDH. Agonist induced expression of a conformational epitope on the GPIIb/IIIa complex and contribution to blood coagulation in an experimental rotational thromboelastometry setup were not statistically different between the groups.

Conclusion

The use of a uncontrolled freezing rate protocol is feasible, creating a platelet product comparable to using a controlled rate freezing equipment during cryopreservation of platelets.

Platelet Biochemistry and Morphology after Cryopreservation

Platelet cryopreservation has been investigated for several decades as an alternative to room temperature storage of platelet concentrates. The use of dimethylsulfoxide as a cryoprotectant has improved platelet storage and cryopreserved concentrates can be kept at −80 °C for two years. Cryopreserved platelets can serve as emergency backup to support stock crises or to disburden difficult logistic areas like rural or military regions. Cryopreservation significantly influences platelet morphology, decreases platelet activation and severely abrogates platelet aggregation. Recent data indicate that cryopreserved platelets have a procoagulant phenotype because thrombin and fibrin formation kicks in earlier compared to room temperature stored platelets. This happens both in static and hydrodynamic conditions. In a clinical setting, low 1-h post transfusion recoveries of cryopreserved platelets represent fast clearance from circulation which may be explained by changes to the platelet GPIbα receptor. Cryopreservation splits the concentrate in two platelet subpopulations depending on GPIbα expression levels. Further research is needed to unravel its physiological importance. Proving clinical efficacy of cryopreserved platelets is difficult because of the heterogeneity of indications and the ambiguity of outcome measures. The procoagulant character of cryopreserved platelets has increased interest for use in trauma stressing the need for double-blinded randomized clinical trials in actively bleeding patients.