Frozen blood products: clinically effective and potentially ideal for remote Australia

A deep eutectic solvent is an effective cryoprotective agent for platelets

The most widely used method of platelet cryopreservation requires the addition of dimethyl sulfoxide (DMSO; Me2SO) as a cryoprotective agent (CPA) and pre-freeze removal of Me2SO before freezing to mitigate toxicity. However, alternative CPAs such as deep eutectic solvents (DES), which are less toxic could simplify this process. The aim of this study was to determine the effectiveness of a Proline-Glycerol (Prol-Gly 1:3) DES as a platelet CPA. Platelets were cryopreserved at -80 °C using 10 % Prol-Gly 1:3 (DES; n = 6), or in the absence of a cryoprotectant (no CPA; n = 6). Platelets were also cryopreserved according to the gold-standard blood-banking method using 5.5 % Me2SO (n = 6), with centrifugation and pre-freeze removal of the excess Me2SO. Platelet quality was assessed by flow cytometry and thromboelastography (TEG). Post-thaw recovery was similar between the three groups. The abundance of labile platelet glycoproteins GPIbα and GPVI were highest in the DES group, however, markers of activation (CD62P and annexin-V) were also higher in this group. In terms of function, the strength of the clot (maximum amplitude; TEG) and extent of clot retraction was better with DES platelets compared to no CPA, but lower than Me2SO platelets. DES provides a cryoprotective advantage to platelets when compared to no CPA. Importantly, when compared to Me2SO platelets, most quality parameters were similar in DES platelets. The major advantage with using a DES is biocompatibility, therefore it does not need to be removed prior to transfusion. This greatly simplifies the freezing and thawing process, avoiding the toxic effects of Me2SO.

Cryopreserved platelets washed with a dialysis machine for dimethyl sulphoxide removal

BACKGROUND AND OBJECTIVES

Cryopreserved platelets (cPLTs) can be stored for years and are mainly used in military settings. However, the commonly used cryoprotectant dimethyl sulphoxide (DMSO) has toxic side effects when utilized in high quantities. We developed a novel method to aseptically remove DMSO from thawed cPLTs by dialysis.

MATERIALS AND METHODS

One unit of platelets (N = 6) was mixed with 75 mL of 27% DMSO within 4 days after collection and stored at -80°C for 1 week. The platelet counts, platelet distribution width, mean platelet volume (MPV), platelet activity, platelet release, platelet aggregation, platelet metabolism indicators and platelet ultrastructural features (determined by electron microscopy) of the samples at the pre-freeze, post-thaw wash (post-TW) and 24 h post-thaw wash (24-PTW) stages were determined and compared.

RESULTS

The DMSO clearance rate from the post-TW platelets was 95.56 ± 1.3%, and the platelet recovery rate after washing was 74.66 ± 6.34%. The total count, activity, release factors, aggregation and thrombolytic ability of the post-TW platelets were lower, whereas the MPV and apoptosis rates were higher compared with those of the pre-freeze platelets. The lactic acid, glucose and potassium ions released from the platelets during washing were filtered away by the dialyser, which significantly reduced their concentration. However, 24-PTW platelets were metabolically active, resulting in a decrease in pH and glucose content and an increase in lactic acid content. The level of potassium ions remained low after 24 h of storage and washing. The pre-freeze platelets maintained their normal disc shape and exhibited an open canalicular system (OCS) and a dense tubular system. The cPLTs appeared irregular after washing, with protruding pseudopodia and an extensive OCS, which increased the release of their contents.

CONCLUSION

We developed a novel dialysis method to effectively remove DMSO from cPLTs under aseptic conditions and maintain platelet quality. The clinical efficacy of our method remains to be determined. However, the function of the platelets declined 24 h after washing, making them unsuitable for transfusion.

Identification of platelet subpopulations in cryopreserved platelet components using multi-colour imaging flow cytometry

Cryopreservation of platelets, at  - 80 °C with 5-6% DMSO, results in externalisation of phosphatidylserine and the formation of extracellular vesicles (EVs), which may mediate their procoagulant function. The phenotypic features of procoagulant platelets overlap with other platelet subpopulations. The aim of this study was to define the phenotype of in vitro generated platelet subpopulations, and subsequently identify the subpopulations present in cryopreserved components. Fresh platelet components (n = 6 in each group) were either unstimulated as a source of resting platelets; or stimulated with thrombin and collagen to generate a mixture of aggregatory and procoagulant platelets; calcium ionophore (A23187) to generate procoagulant platelets; or ABT-737 to generate apoptotic platelets. Platelet components (n = 6) were cryopreserved with DMSO, thawed and resuspended in a unit of thawed plasma. Multi-colour panels of fluorescent antibodies and dyes were used to identify the features of subpopulations by imaging flow cytometry. A combination of annexin-V (AnnV), CD42b, and either PAC1 or CD62P was able to distinguish the four subpopulations. Cryopreserved platelets contained procoagulant platelets (AnnV+/PAC1-/CD42b+/CD62P+) and a novel population (AnnV+/PAC1-/CD42b+/CD62P-) that did not align with the phenotype of aggregatory (AnnV-/PAC1+/CD42b+/CD62P+) or apoptotic (AnnV+/PAC1-/CD42b-/CD62P-) subpopulations. These data suggests that the enhanced haemostatic potential of cryopreserved platelets may be due to the cryo-induced development of procoagulant platelets, and that additional subpopulations may exist.

Frozen for combat: Quality of deep-frozen thrombocytes, produced and used by The Netherlands Armed Forces 2001-2021

BACKGROUND

The Netherlands Armed Forces (NLAF) are using -80°C deep-frozen thrombocyte concentrate (DTC) since 2001. The aim of this study is to investigate the effect of storage duration and alterations in production/measurement techniques on DTC quality. It is expected that DTC quality is unaffected by storage duration and in compliance with the European guidelines for fresh and cryopreserved platelets.

STUDY DESIGN AND METHODS

Pre-freeze and post-thaw product platelet content and recovery were collected to analyze the effects of dimethyl sulfoxide (DMSO) type, duration of frozen storage (DMSO-1 max 12 years and DMSO-2 frozen DTC max 4 years at -80°C) and type of plasma used to suspend DTC. Coagulation characteristics of thawed DTC, plasma and supernatant of DTC (2× 2500 G) were measured with Kaolin thromboelastography (TEG) and phospholipid (PPL) activity assay.

RESULTS

Platelet content and recovery of DTC is ±10%-15% lower in short-stored products and remained stable when stored beyond 0.5 years. Thawed DTC (n = 1724) were compliant to the European guidelines (98.1% post-thaw product recovery ≥50% from original product, 98.3% ≥200 × 10⁹ platelets/unit). Compared to DMSO-1, products frozen with DMSO-2 showed ±8% reduced thaw-freeze recovery, a higher TEG clot strength (MA 58 [6] vs. 64 [8] mm) and same ±11 s PPL clotting time. The use of cold-stored thawed plasma instead of fresh thawed plasma did not influence product recovery or TEG-MA.

DISCUSSION

Regardless of alterations, product quality was in compliance with European guidelines and unaffected by storage duration up to 12 years of -80°C frozen storage.

The haemostatic effect of deep-frozen platelets versus room temperature-stored platelets in the treatment of surgical bleeding: MAFOD—study protocol for a randomized controlled non-inferiority trial

Background

The Netherlands Armed Forces have been successfully using deep-frozen (− 80 °C) thrombocyte concentrate (DTC) for the treatment of (massive) bleeding trauma patients in austere environments since 2001. However, high-quality evidence for the effectiveness and safety of DTCs is currently lacking. Therefore, the MAssive transfusion of Frozen bloOD (MAFOD) trial is designed to compare the haemostatic effect of DTCs versus room temperature-stored platelets (RSP) in the treatment of surgical bleeding.

Methods

The MAFOD trial is a single-blinded, randomized controlled non-inferiority trial and will be conducted in three level 1 trauma centres in The Netherlands. Patients 12 years or older, alive at hospital presentation, requiring a massive transfusion including platelets and with signed (deferred) consent will be included. The primary outcome is the percentage of patients that have achieved haemostasis within 6 h and show signs of life. Haemostasis is defined as the time in minutes from arrival to the time of the last blood component transfusion (plasma/platelets or red blood cells), followed by a 2-h transfusion-free period. This is the first randomized controlled study investigating DTCs in trauma and vascular surgical bleeding.

Discussion

The hypothesis is that the percentage of patients that will achieve haemostasis in the DTC group is at least equal to the RSP group (85%). With a power of 80%, a significance level of 5% and a non-inferiority limit of 15%, a total of 71 patients in each arm are required, thus resulting in a total of 158 patients, including a 10% refusal rate. The data collected during the study could help improve the use of platelets during resuscitation management. If proven non-inferior in civilian settings, frozen platelets may be used in the future to optimize logistics and improve platelet availability in rural or remote areas for the treatment of (massive) bleeding trauma patients in civilian settings.

Trial registration

ClinicalTrials.gov NCT05502809. Registered on 16 August 2022.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-022-06739-2.

Cryopreservation of apheresis platelets treated with riboflavin and UV light

BACKGROUND

Pathogen reduction technology (PRT) is increasingly used in the preparation of platelets for therapeutic transfusion. As the Czech Republic considers PRT, we asked what effects PRT may have on the recovery and function of platelets after cryopreservation (CP), which we use in both military and civilian blood settings.

STUDY DESIGN AND METHODS

16 Group O apheresis platelets units were treated with PRT (Mirasol, Terumo BCT, USA) before freezing; 15 similarly collected units were frozen without PRT as controls. All units were processed with 5-6% DMSO, frozen at - 80 °C, stored > 14 days, and reconstituted in thawed AB plasma. After reconstitution, all units were assessed for: platelet count, mean platelet volume (MPV), platelet recovery, thromboelastography, thrombin generation time, endogenous thrombin potential (ETP), glucose, lactate, pH, pO2, pCO2, HCO3, CD41, CD42b, CD62, Annexin V, CCL5, CD62P, and aggregates > 2 mm and selected units for Kunicki score.

RESULTS

PRT treated platelet units had lower platelet number (247 vs 278 ×10⁹/U), reduced thromboelastographic MA (38 vs 62 mm) and demonstrated aggregates compared to untreated platelets. Plasma coagulation functions were largely unchanged.

CONCLUSIONS

Samples from PRT units showed reduced platelet number, reduced function greater than the reduced number would cause, and aggregates. While the platelet numbers are sufficient to meet the European standard, marked platelets activation with weak clot strength suggest reduced effectiveness.

In-vitro thromboelastographic characterization of reconstituted whole blood utilizing cryopreserved platelets

Conducting in-vitro thrombosis research presents numerous challenges, the primary of which is working with blood products, whether whole blood or fractionated whole blood, that have limited functional shelf-lives. As a result, being able to significantly prolong the clotting functionality of whole blood via fractionation and recombination promises greater accessibility via resource minimization in the realm of thrombosis research. Whole blood with CPDA1 from healthy volunteers was fractionated and stored as frozen platelet-free plasma (PFP, -20°C), refrigerated packed red blood cells (pRBCs, 4°C) and cryopreserved platelets (-80°C). Subsequent recombination of the above components into their native ratios were tested via thromboelastography (TEG) to capture clotting dynamics over a storage period of 13 weeks in comparison to refrigerated unfractionated WB+CPDA1. Reconstituted whole blood utilizing PFP, pRCBs and cryopreserved platelets were able to maintain clot strength (maximum amplitude) akin to day-0 whole blood even after 13 weeks of storage. Clots formed by reconstituted whole blood exhibited quicker clotting dynamics with nearly two-fold shorter R-times and nearly 1.3-fold increase in fibrin deposition rate as measured by TEG. Storage of fractionated whole blood components, in their respective ideal conditions, provides a means of prolonging the usable life of whole blood for in-vitro thrombosis research. Cryopreserved platelets, when recombined with frozen PFP and refrigerated pRBCs, are able to form clots that nearly mirror the overall clotting profile expected of freshly drawn WB.

Epidemiology of Massive Transfusion - A Common Intervention in Need of a Definition

While massive transfusion (MT) recipients account for a small proportion of all transfused patients, they account for approximately 10% of blood products issued. Furthermore, MT events pose organizational and logistical challenges for health care providers, laboratory and transfusion services. Overall, the majority of MT events are to support major bleeding in surgical patients, trauma and gastrointestinal hemorrhage. The clinical context in which the bleeding event occurred, the number of blood products required, patient age and comorbidities are the most important predictors of outcomes for short- and long-term survival. These data are important to inform blood services, clinicians and health care providers in order to improve care and outcomes for patients with major bleeding. There is no standard accepted definition of MT, with most definitions based on number of blood components administered within a certain time-period or activation of MT protocol. The type of definition used has implications for the clinical characteristics of MT recipients included in epidemiological and interventional studies. In order to understand trends in incidence of MT, variation in blood utilization and patient outcomes, and to harmonize research outcomes, a standard and universally accepted definition of MT is urgently required.

Cryopreservation of platelets treated with riboflavin and UV light and stored at -80°C for 1 year

BACKGROUND

The combination of pathogen reduction technologies (PRTs) and cryopreservation can contribute to building a safe and durable platelet (PLT) inventory. Information about cryopreserved riboflavin and UV light-treated PLTs is scarce.

STUDY DESIGN AND METHODS

Twenty-four buffy coat (BC) PLT concentrates were grouped into 12 type-matched pairs, pooled, and divided into 12 non-PRT-treated control units and 12 riboflavin and UV light PRT-treated test units. Both were cryopreserved with 5% DMSO and stored at -80°C for 1 year. The cryopreservation method used was designed to avoid the formation of aggregates. PLT variables (PLT recovery, swirling, pH, MPV, and LDH) and hemostatic function measured by thromboelastography (TEG) were analyzed before cryopreservation (day 1) and post-cryopreservation at day 14 and months 3, 6, and 12 of storage at -80°C. The analyses were carried out within 1-h post-thaw.

RESULTS

No aggregates were found in either PLT group at any time. Swirling was observed in both groups. MPV increased and mean pH values decreased over time (p < .001), but the mean pH value was never below 6.4 in either group after 12 months of storage at -80°C. PLT recovery was good and clotting time became significantly shorter over the storage period in both groups (p < .001).

CONCLUSION

Our cryopreservation and thawing method prevented aggregate formation in cryopreserved riboflavin-UV-light-treated PLTs, which exhibited good recovery, swirling, pH > 6.4, and procoagulant potential, as evidenced by a reduced clotting time after 12 months of storage at -80°C. The clinical relevance of these findings should be further investigated in clinical trials.

Frozen Blood Reserves

Frozen blood reserves are an important component in meeting blood needs. The idea behind a frozen blood reserve is twofold: to freeze units of rare blood types for later use by patients with special transfusion needs and for managing special transfusion circumstances. The permeating additive glycerol is used as a cryoprotectant to protect red blood cells (RBCs) from freezing damage. The use of thawed RBCs has been hampered by a 24-h outdating period due to the potential bacterial contamination when a functionally open system is used for addition and removal of the glycerol. The introduction of an automated, functionally closed system for glycerolization and deglycerolization of RBCs improved the operational practice. More importantly, the closed process allowed for extended shelf life of the thawed RBCs. In the current chapter, a cryopreservation procedure for RBCs using a functionally closed processing system is described.

Prolonged (post-thaw) shelf life of -80°C frozen AB apheresis plasma

BACKGROUND

Early plasma transfusion is important in the treatment of patients with major hemorrhage. Prolonged shelf life of AB type frozen −80°C and cold‐stored (4°C) deep frozen plasma (DFP) will improve strategic stock management, minimize need for resupply, and make pre‐hospital implementation more feasible.

METHODS AND MATERIALS

Plasma products type AB of different age and origin (−30°C Fresh Frozen [(FFP], −80°C DFP [short (±1 year) and long (±7 year)] stored) were thawed (Day 0), stored at 4°C, and sampled on Days 7 and 14. Additionally, samples of plasma containing blood products (Octaplas LG®, whole blood and platelets) were compared for coagulation factor activity, phospholipid clotting time (PPL), and kaolin TEG during 4°C or 22°C storage.

RESULTS

Coagulation profiles of FFP, short‐ and long‐stored −80°C DFP were not significantly different after thaw. Cold storage did not affect fibrinogen, Protein C, and Antithrombin III activities whereas factor V, VII, VIII, and Protein S decreased in all blood products. After 14 days DFP still meets the guidelines for clinical use, except for Protein S (0.4 IU/mL). With exception of Octaplas LG®, phospholipid activity and TEG coagulation were similar between plasma containing blood components during storage.

CONCLUSION

AB DFP quality was unaffected by almost 7 years of frozen storage. Quality of thawed 14‐day stored AB DFP met, with exception of Protein S, all minimal guidelines which implies that its quality is sufficient for use in the (pre)‐hospital (military) environment for treatment of major hemorrhage.

Characterizing the ability of an ice recrystallization inhibitor to improve platelet cryopreservation

Improving aspects of platelet cryopreservation would help ease logistical challenges and potentially expand the utility of frozen platelets. Current cryopreservation procedures damage platelets, which may be caused by ice recrystallization. We hypothesized that the addition of a small molecule ice recrystallization inhibitor (IRI) to platelets prior to freezing may reduce cryopreservation-induced damage and/or improve the logistics of freezing and storage. Platelets were frozen using standard conditions of 5-6% dimethyl sulfoxide (Me₂SO) or with supplementation of an IRI, N-(2-fluorophenyl)-d-gluconamide (2FA), prior to storage at -80 °C. Alternatively, platelets were frozen with 5-6% Me₂SO at -30 °C or with 3% Me₂SO at -80 °C with or without 2FA supplementation. Supplementation of platelets with 2FA improved platelet recovery following storage under standard conditions (p = 0.0017) and with 3% Me₂SO (p = 0.0461) but not at -30 °C (p = 0.0835). 2FA supplementation was protective for GPVI expression under standard conditions (p = 0.0011) and with 3% Me₂SO (p = 0.0042). Markers of platelet activation, such as phosphatidylserine externalization and microparticle release, were increased following storage at -30 °C or with 3% Me₂SO, and 2FA showed no protective effect. Platelet function remained similar regardless of 2FA, although functionality was reduced following storage at -30 °C or with 3% Me₂SO compared to standard cryopreserved platelets. While the addition of 2FA to platelets provided a small level of protection for some quality parameters, it was unable to prevent alterations to the majority of in vitro parameters. Therefore, it is unlikely that ice recrystallization is the major cause of cryopreservation-induced damage.

-80 °C deep frozen erythrocytes during military operations. The Dutch frozen concept

The Dutch military uses frozen blood products for the treatment of bleeding trauma patients during military deployments. With -80 °C frozen blood products it is possible to follow operational demand while reducing the number of resupply transports and loss of products due to expiration. In this paper lessons learned are described on efficient blood management with -80 °C deep-frozen erythrocytes (DEC).

Calcium chelation: a novel approach to reduce cryopreservation-induced damage to frozen platelets

BACKGROUND

Cryopreserved platelets are phenotypically and functionally different to conventionally stored platelets. Calcium may be released from internal stores during the freeze-thaw process, initiating signaling events which lead to these alterations. It was hypothesized that the addition of a calcium chelator prior to cryopreservation may mitigate some of these changes.

METHODS

Buffy coat-derived platelets that had been pooled and split were tested fresh and following cryopreservation (n = 8 per group). Platelets were cryopreserved using 5%-6% dimethylsulfoxide (DMSO) or were supplemented with increasing concentrations of the internal calcium chelator, BAPTA-AM (100 μM, 200 μM, or 400 μM), prior to storage at -80°C.

RESULTS

Supplementation of platelets with BAPTA-AM prior to freezing improved platelet recovery in a dose response manner (400 μM: 84 ± 2%) compared to standard DMSO cryopreserved platelets (70 ± 4%). There was a loss of GPIbα, GPVI, and GPIIb/IIIa receptors on platelets following cryopreservation, which was rescued when platelets were supplemented with BAPTA-AM (400 μM: p < 0.0001 for all). Platelet activation markers, such as phosphatidylserine and P-selectin, were externalized on platelets following cryopreservation. However, the addition of BAPTA-AM significantly reduced the increase of these activation markers on cryopreserved platelets (400 μM: p < 0.0001 for both). Both cryopreserved platelet groups exhibited similar functionality as assessed by thromboelastography, forming clots at a faster rate than fresh platelets.

CONCLUSIONS

This study demonstrates that calcium plays a crucial role in mediating cryopreservation-induced damage to frozen platelets. The addition of the calcium chelator, BAPTA-AM, prior to cryopreservation reduces this damage.

Optimizing the supply of whole blood-derived bioproducts through the combined implementation of cryopreservation and pathogen reduction technologies and practices: An overview

The essential historical knowledge and expertise developed over the past 5-6 decades on the safety / efficacy of conventional blood components therapy by blood transfusion establishments have guided the development of validated methods which have ensure optimal safety margins for frozen blood and its bioproducts with or even without pathogen reduction. Newer generations of pathogen reduced frozen red blood cell, plasma and platelet products and the standardised and safer pooling of human platelet lysate are now become available for potential clinical use. These types of whole blood-derived bioproducts not only reduce the risk of transmission of range of pathogenic blood-borne pathogen. As cryopreservation can be combined with PRT without significantly compromising in vitro quality characteristics or physiological capabilities, it allows us to maximize the available inventory of these blood products in both civil and military trauma settings. The main objective of this overview is to update readers and scientific / medical communities of the various building blocks needed to optimally grantee the pathogen safety of whole blood-derived bioproducts, with minimal untoward events to the recipients. While this is an emerging area, we are seeing the numerous potential opportunities that cryopreservation and pathogen inactivation can have on the transfused patient outcomes. This manuscript is informed by recent publications on this topic.

The Lipid Composition of Platelets and the Impact of Storage: An Overview

Lipids and bioactive lipid mediators are essential for platelet function. The lipid profile of platelets is highly dynamic due to free exchange of lipids with the plasma, release of extracellular vesicles, and both enzymatic and nonenzymatic lipid conversion. The lipidome of platelets changes in response to activation to accommodate the functional requirements of platelets, particularly for maintenance of hemostasis. Furthermore, when stored at room temperature as a component for transfusion, the lipid profile of platelets is altered. Although there is a growing interest in alternate storage conditions, such as refrigeration and cryopreservation, few contemporary studies have examined the impact of these storage modes on the lipid profile. However, evidence exists that bioactive lipid mediators produced over the storage of blood products may have functional implications once these products are transfused. As such, there is a need to determine the changes occurring to the lipid profile of these products over storage. This review outlines the role of lipids in platelets and discusses the current state of lipidomics for studying platelet components for transfusion in an effort to highlight the necessity for additional transfusion-focused investigations.

Freezing expired platelets does not compromise in vitro quality: An opportunity to maximize inventory potential

BACKGROUND AND OBJECTIVES

Cryopreservation provides an option for long-term storage of platelet concentrates. While platelets are usually frozen as soon as practical after collection (within 2 days), the ability to freeze units at a later stage of the shelf life may improve inventory management. As such, the aim of this study was to determine the impact of freezing platelets approaching expiry (Day 5/6).

MATERIALS AND METHODS

Two ABO-matched buffy coat-derived platelets (30% plasma/70% platelet additive solution) were pooled and split to produce matched pairs (n = 8 pairs). Platelets were frozen on Day 1 after collection (cryopreserved platelets [CPPs]) or Day 5 or 6 (expired-CPPs) at -80°C with 5% to 6% dimethyl sulfoxide. In vitro platelet quality was tested before freezing and after thawing and reconstitution in plasma.

RESULTS

The majority of prefreeze parameters were equivalent for all platelet units (Day 1 vs. Day 5 or 6). Expired-CPPs had a higher mean postthaw platelet recovery (82 ± 4%) compared to CPPs (75 ± 4%; p = 0.0021). Cryopreservation resulted in a loss of surface glycoproteins (glycoprotein (GP) Ibα, GPIIb, GPVI), an increase in activation markers (phosphatidylserine and P-selectin) and microparticle release, compared to unfrozen platelets. However, the cryopreservation-induced changes were equivalent in CPPs and expired-CPPs. Functionality was measured by thromboelastography and was similar between expired-CPPs (R-time: 5.3 ± 0.3) and CPPs (R-time: 5.4 ± 0.5; p = 0.7094).

CONCLUSION

The phenotype and functional profile of platelets frozen at expiry were similar to platelets frozen 1 day following collection. These data suggest that expired platelets may represent a suitable starting material for cryopreservation.

Maximising platelet availability by delaying cold storage

BACKGROUND AND OBJECTIVES

Cold-stored platelets may be an alternative to conventional room temperature (RT) storage. However, cold-stored platelets are cleared more rapidly from circulation, reducing their suitability for prophylactic transfusion. To minimise wastage, it may be beneficial to store platelets conventionally until near expiry (4 days) for prophylactic use, transferring them to refrigerated storage to facilitate an extended shelf life, reserving the platelets for the treatment of acute bleeding.

MATERIALS AND METHODS

Two ABO-matched buffy-coat-derived platelets (30% plasma/70% SSP+) were pooled and split to produce matched pairs (n = 8 pairs). One unit was stored at 2-6°C without agitation (day 1 postcollection; cold); the second unit was stored at 20-24°C with constant agitation until day 4 then stored at 2-6°C thereafter (delayed-cold). All units were tested for in vitro quality periodically over 21 days.

RESULTS

During storage, cold and delayed-cold platelets maintained a similar platelet count. While pH and HSR were significantly higher in delayed-cold platelets, other metabolic markers, including lactate production and glucose consumption, did not differ significantly. Furthermore, surface expression of phosphatidylserine and CD62P, release of soluble CD62P and microparticles were not significantly different, suggesting similar activation profiles. Aggregation responses of delayed-cold platelets followed the same trend as cold platelets once transferred to cold storage, gradually declining over the storage period.

CONCLUSION

The metabolic and activation profile of delayed-cold platelets was similar to cold-stored platelets. These data suggest that transferring platelets to refrigerated storage when near expiry may be a viable option for maximising platelet inventories.

Refrigeration, cryopreservation and pathogen inactivation: an updated perspective on platelet storage conditions

Conventional storage of platelet concentrates limits their shelf life to between 5 and 7 days due to the risk of bacterial proliferation and the development of the platelet storage lesion. Cold storage and cryopreservation of platelets may facilitate extension of the shelf life to weeks and years, and may also provide the benefit of being more haemostatically effective than conventionally stored platelets. Further, treatment of platelet concentrates with pathogen inactivation systems reduces bacterial contamination and provides a safeguard against the risk of emerging and re-emerging pathogens. While each of these alternative storage techniques is gaining traction individually, little work has been done to examine the effect of combining treatments in an effort to further improve product safety and minimize wastage. This review aims to discuss the benefits of alternative storage techniques and how they may be combined to alleviate the problems associated with conventional platelet storage.

Characterization of biologic response modifiers in the supernatant of conventional, refrigerated, and cryopreserved platelets

BACKGROUND

Alternatives to room temperature storage of platelets (PLTs) are of interest to support blood banking logistics. The aim of this study was to compare the presence of biologic response modifiers (BRMs) in PLT concentrates stored under conventional room temperature conditions with refrigerated or cryopreserved PLTs.

STUDY DESIGN AND METHODS

A three-arm pool-and-split study was carried out using buffy coat-derived PLTs stored in 30% plasma/70% SSP+. The three matched treatment arms were as follows: room temperature (20-24°C), cold (2-6°C), and cryopreserved (-80°C with DMSO). Liquid-stored PLTs were tested over a 21-day period, while cryopreserved PLTs were tested immediately after thawing and reconstitution in 30% plasma/70% SSP+ and after storage at room temperature.

RESULTS

Coagulation factor activity was comparable between room temperature and cold PLTs, with the exception of protein S, while cryopreserved PLTs had reduced Factor (F)V and FVIII activity. Cold-stored PLTs retained α-granule proteins better than room temperature or cryopreserved PLTs. Cryopreservation resulted in 10-fold higher microparticle generation than cold-stored PLTs, but both groups contained significantly more microparticles than those stored at room temperature. The supernatant from both cold and cryopreserved PLTs initiated faster clot formation and thrombin generation than room temperature PLTs.

CONCLUSION

Cold storage and cryopreservation alter the composition of the soluble fraction of stored PLTs. These differences in coagulation proteins, cytokines, and microparticles likely influence both the hemostatic capacity of the components and the auxiliary functions.

Immunomodulatory effect of cryopreserved platelets: altered BDCA3+ dendritic cell maturation and activation in vitro

BACKGROUND

Cryopreservation of platelets (PLTs) is useful in remote areas to overcome logistic problems associated with supply and can extend the shelf life to 2 years. During cryopreservation, properties of PLTs are modified. Whether changes in the cryopreserved PLT (CPP) product are associated with modulation of recipients' immune function is unknown. We aimed to characterize the immune profile of myeloid dendritic cells (mDCs) and the specialized blood DC antigen (BDCA)3⁺ subset after exposure to CPPs.

STUDY DESIGN AND METHODS

Using an in vitro whole blood model of transfusion, the effect of CPPs on mDC and BDCA3⁺ DC surface antigen expression and inflammatory mediator production was examined using flow cytometry. In parallel, polyinosinic:polycytidylic acid (poly(I:C)) or lipopolysaccharide (LPS) was utilized to model processes activated in viral or bacterial infection, respectively.

RESULTS

Cryopreserved PLTs had minimal impact on mDC responses but significantly modulated BDCA3⁺ DC responses in vitro. Exposure to CPPs alone up regulated BDCA3⁺ DC CD86 expression and suppressed interleukin (IL)-8, tumor necrosis factor (TNF)-α, and interferon-γ inducible protein (IP)-10 production. In both models of infection-related processes, exposure to CPPs down regulated BDCA3⁺ DC expression of CD40, CD80, and CD83 and suppressed BDCA3⁺ DC production of IL-8, IL-12, and TNF-α. CPPs suppressed CD86 expression in the presence of LPS and IP-10 and IL-6 production with poly(I:C).

CONCLUSION

Cryopreserved PLTs may be immunosuppressive, and this effect is more evident when processes associated with infection are concurrently activated, especially for BDCA3⁺ DCs. This suggests that transfusion of CPPs in patients with infection may result in impaired BDCA3⁺ DC responses.

Cryopreserved platelets demonstrate reduced activation responses and impaired signaling after agonist stimulation

BACKGROUND

Room temperature-stored (20-24°C) platelets (PLTs) have a shelf life of 5 days, making it logistically challenging to supply remote medical centers with PLT products. Cryopreservation of PLTs in dimethyl sulfoxide (DMSO) and storage at -80°C enables an extended shelf life up to 2 years. Although cryopreserved PLTs have been widely characterized under resting conditions, their ability to undergo agonist-induced activation is yet to be fully explored.

STUDY DESIGN AND METHODS

Buffy coat PLTs were cryopreserved at -80°C with 5% to 6% DMSO and sampled before freezing and after thawing. PLTs were analyzed under resting conditions and after agonist stimulation with adenosine diphosphate, collagen, or thrombin receptor-activating peptide-6. The expression of activation markers, microparticle formation, and calcium mobilization were analyzed by flow cytometry. Soluble PLT proteins present in the PLT supernatant were examined by enzyme-linked immunosorbent assay. Protein phosphorylation was investigated with Western blotting.

RESULTS

After cryopreservation, PLTs displayed increased surface activation markers and higher basal calcium levels. Cryopreserved PLTs demonstrated diminished aggregation responses. Additionally, cryopreserved PLTs showed a limited ability to become activated (as measured by CD62P and phosphatidylserine exposure and cytokine release) after agonist stimulation. A reduction in the abundance and phosphorylation of key signaling proteins (Akt, Src, Lyn, ERK, and p38) was seen in cryopreserved PLTs.

CONCLUSIONS

Cryopreservation of PLTs induces dramatic changes to the basal PLT phenotype and renders them largely nonresponsive to agonist stimulation, likely due to the alterations in signal transduction. Therefore, further efforts are required to understand how cryopreserved PLTs achieve their hemostatic effect once transfused.

Strengthening Health Systems Through International Blood Product Sharing Agreements

Blood products are critical to the success of both routine healthcare delivery and emergency response efforts. Ensuring the safety and availability of blood products presents nations with considerable collection, screening, and distribution challenges that are often exacerbated by public health crises, particularly mass-casualty events involving traumatic injuries. However, recent outbreaks of Ebola and Zika virus disease have also illustrated the importance of securing blood product supplies during ongoing infectious disease emergencies. The United States and other nations should consider enhancing existing mechanisms for sharing medical countermeasures by creating formal agreements for sharing blood products during public health emergencies.

Transfusion: -80°C Frozen Blood Products Are Safe and Effective in Military Casualty Care

INTRODUCTION

The Netherlands Armed Forces use -80°C frozen red blood cells (RBCs), plasma and platelets combined with regular liquid stored RBCs, for the treatment of (military) casualties in Medical Treatment Facilities abroad. Our objective was to assess and compare the use of -80°C frozen blood products in combination with the different transfusion protocols and their effect on the outcome of trauma casualties.

MATERIALS AND METHODS

Hemovigilance and combat casualties data from Afghanistan 2006-2010 for 272 (military) trauma casualties with or without massive transfusions (MT: ≥6 RBC/24hr, N = 82 and non-MT: 1-5 RBC/24hr, N = 190) were analyzed retrospectively. In November 2007, a massive transfusion protocol (MTP; 4:3:1 RBC:Plasma:Platelets) for ATLS® class III/IV hemorrhage was introduced in military theatre. Blood product use, injury severity and mortality were assessed pre- and post-introduction of the MTP. Data were compared to civilian and military trauma studies to assess effectiveness of the frozen blood products and MTP.

RESULTS

No ABO incompatible blood products were transfused and only 1 mild transfusion reaction was observed with 3,060 transfused products. In hospital mortality decreased post-MTP for MT patients from 44% to 14% (P = 0.005) and for non-MT patients from 12.7% to 5.9% (P = 0.139). Average 24-hour RBC, plasma and platelet ratios were comparable and accompanying 24-hour mortality rates were low compared to studies that used similar numbers of liquid stored (and on site donated) blood products.

CONCLUSION

This report describes for the first time that the combination of -80°C frozen platelets, plasma and red cells is safe and at least as effective as standard blood products in the treatment of (military) trauma casualties. Frozen blood can save the lives of casualties of armed conflict without the need for in-theatre blood collection. These results may also contribute to solutions for logistic problems in civilian blood supply in remote areas.

Cryopreservation alters the membrane and cytoskeletal protein profile of platelet microparticles

BACKGROUND

Cryopreservation of platelets (PLTs) in dimethyl sulfoxide (DMSO) and storage at -80 °C extends the PLT shelf life to at least 2 years, allowing greater accessibility in military and rural environments. While cryopreserved PLTs have been extensively characterized, the microparticles formed as a result of cryopreservation are yet to be fully described.

STUDY DESIGN AND METHODS

Apheresis PLTs were cryopreserved at -80 °C with 5% DMSO and sampled before freezing and after thawing. Microparticle number, size, surface receptor phenotype, and function were assessed by microscopy, flow cytometry, dynamic light scattering, and thrombin-generating capacity. Proteomic changes were examined using two-dimensional gel electrophoresis and Western blotting.

RESULTS

PLT cryopreservation resulted in a 15-fold increase in the number of microparticles compared to fresh PLTs. The surface receptor phenotype of these microparticles differed to microparticles from fresh PLTs, with more microparticles expressing glycoprotein (GP)IV, GPIIb, and the GPIb-V-IX complex. Cryopreservation drastically altered the abundance of many cytoskeletal proteins in the PLT microparticles, including actin, filamin, gelsolin, and tropomyosin. Despite these changes, PLT microparticles were functional and contributed to phosphatidylserine- and tissue factor- induced thrombin generation.

CONCLUSION

This study demonstrates that PLT microparticles formed by cryopreservation are phenotypically distinct from those present before freezing. These differences may be associated with the procoagulant properties of cryopreserved PLTs.

Freezing of Apheresis Platelet Concentrates in 6% Dimethyl Sulfoxide: The First Preliminary Study in Turkey

Objective:

Transfusion of platelet suspensions is an essential part of patient care for certain clinical indications. In this pioneering study in Turkey, we aimed to assess the in vitro hemostatic functions of platelets after cryopreservation.

Materials and Methods:

Seven units of platelet concentrates were obtained by apheresis. Each apheresis platelet concentrate (APC) was divided into 2 equal volumes and frozen with 6% dimethyl sulfoxide (DMSO). The 14 frozen units of APCs were kept at -80 °C for 1 day. APCs were thawed at 37 °C and diluted either with autologous plasma or 0.9% NaCl. The volume and residual numbers of leukocytes and platelets were tested in both before-freezing and post-thawing periods. Aggregation and thrombin generation tests were used to analyze the in vitro hemostatic functions of platelets. Flow-cytometric analysis was used to assess the presence of frozen treated platelets and their viability.

Results:

The residual number of leukocytes in both dilution groups was <1x106. The mean platelet recovery rate in the plasma-diluted group (88.1±9.5%) was higher than that in the 0.9% NaCl-diluted group (63±10%). These results were compatible with the European Directorate for the Quality of Medicines quality criteria. Expectedly, there was no aggregation response to platelet aggregation test. The mean thrombin generation potential of post-thaw APCs was higher in the plasma-diluted group (2411 nmol/L per minute) when compared to both the 0.9% NaCl-diluted group (1913 nmol/L per minute) and the before-freezing period (1681 nmol/L per minute). The flow-cytometric analysis results for the viability of APCs after cryopreservation were 94.9% and 96.6% in the plasma and 0.9% NaCl groups, respectively.

Conclusion:

Cryopreservation of platelets with 6% DMSO and storage at -80 °C increases their shelf life from 7 days to 2 years. Besides the increase in hemostatic functions of platelets, the cryopreservation process also does not affect their viability rates.

Cryopreservation of red blood cells

Cryopreservation of red blood cell concentrates (RBCs) is an important method for maintaining an inventory of rare RBC units and managing special transfusion circumstances. The permeating additive glycerol is used as a cryoprotectant to protect RBCs against freezing damage. The use of thawed RBCs was hampered a 24-h outdating period due to potential bacterial contamination when a functionally open system was used for addition and removal of the glycerol. With the introduction of a functionally closed system for the glycerolization and deglycerolization of RBC units, extended post-thaw storage became possible. Here, we describe the cryopreservation of red blood cells according to the high-glycerol method, using a functionally closed processing system.

Utilization and quality of cryopreserved red blood cells in transfusion medicine

Cryopreserved (frozen) red blood cells have been used in transfusion medicine since the Vietnam war. The main method to freeze the red blood cells is by usage of glycerol. Although the usage of cryopreserved red blood cells was promising due to the prolonged storage time and the limited cellular deterioration at subzero temperatures, its usage have been hampered due to the more complex and labour intensive procedure and the limited shelf life of thawed products. Since the FDA approval of a closed (de) glycerolization procedure in 2002, allowing a prolonged postthaw storage of red blood cells up to 21 days at 2-6°C, cryopreserved red blood cells have become a more utilized blood product. Currently, cryopreserved red blood cells are mainly used in military operations and to stock red blood cells with rare phenotypes. Yet, cryopreserved red blood cells could also be useful to replenish temporary blood shortages, to prolong storage time before autologous transfusion and for IgA-deficient patients. This review describes the main methods to cryopreserve red blood cells, explores the quality of this blood product and highlights clinical settings in which cryopreserved red blood cells are or could be utilized.