Towards increasing shelf life and haemostatic potency of stored platelet concentrates

Increased Responsiveness of Stored Platelets after Short-Term Refrigeration

Introduction

Refrigeration of platelets is considered to provide advantages in therapy of acute hemorrhage due to increased platelet responsiveness. The alleviation of inhibitory signaling caused by cold temperature (CT) has been identified as an important mechanism contributing to enhanced platelet reactivity, detectable in freshly prepared platelets within 1 h of cold storage. The aim of this study was to confirm the effects of short-term refrigeration in platelets from apheresis-derived platelet concentrates (APC).

Methods

APC were stored under standardized conditions for 1 day or for 2 days at room temperature and then refrigerated for 1 h, followed by sampling of platelets for analysis. Platelet reactivity was measured by aggregation studies using threshold concentrations of different agonists and by detection of fibrinogen binding using flow cytometry. The exploration of inhibitory signaling comprised the detection of VASP phosphorylation using flow cytometry or Western blot and the measurement of cyclic nucleotide levels.

Results

Aggregation responses induced with ADP, collagen, or thrombin receptor-activating peptide-6 (TRAP-6) were increased in APC after cold storage for 1 h, associated with elevated TRAP-6-induced fibrinogen binding. VASP phosphorylation levels were decreased after cold exposition, detectable in 1-day- and 2-day-stored APC with flow cytometry, and in 2-day-stored APC with Western blot technique. Induced cGMP levels were lower after storage at CT in APC on day 1 and on day 2, whereas cAMP levels were reduced on 2-day-stored APC.

Conclusion

Short-term refrigeration for 1 h is sufficient to induce an attenuation of inhibitory signaling, accompanied with increased aggregation responses in APC stored for up to 2 days. The "on demand" refrigeration of PC may be a reasonable approach for the preparation of platelets with enhanced responsiveness to treat patients with hemorrhage more effectively, which should be further addressed in consecutive studies.

Effects of transfusing older red blood cells and platelets on obstetric patient outcomes: A retrospective cohort study

OBJECTIVE

To investigate associations between transfusion of blood products close to the end of shelf-life and clinical outcomes in obstetric inpatients.

METHODS

Mortality and morbidity were compared in patients transfused exclusively with red blood cells (RBC) stored for less than 21 days (fresh) versus RBC stored for 35 days or longer (old), and platelets (PLT) stored for 3 days or fewer (fresh) versus 4 days or longer (old) in Queensland, Australia from 2007 to 2013. Multivariable models were used to examine associations between these groups of blood products and clinical end points.

RESULTS

There were 3371 patients who received RBC and 280 patients who received PLT of the eligible storage durations. Patients transfused with old RBC received fewer transfusions (2.7 ± 1.8 vs. 2.3 ± 1.0 units; P < 0.001). However, a higher rate of single-unit transfusions was also seen in those patients who exclusively received old RBC (252 [9.3%] vs. 92 [13.7%]; P = 0.003). Comparison of fresh vs. old blood products revealed no differences in the quantities of transfused RBC (9.5 ± 5.9 vs. 9.1 ± 5.2 units; P = 0.680) or PLT (1.5 ± 0.8 vs. 1.4 ± 1.1 units; P = 0.301) as well as the length of hospital stay for RBC (3 [2-5] vs. 3 [2-5] days; P = 0.124) or PLT (5 [4-8] vs. 6 [4-9] days; P = 0.120).

CONCLUSION

Transfusing exclusively older RBC or PLT was not associated with increased morbidity or mortality.

Quantitative increases of extracellular vesicles in prolonged cold storage of platelets increases the potential to enhance fibrin clot formation

BACKGROUND

Platelet derived extracellular vesicles (EVs) display a pro-coagulant phenotype and are generated throughout platelet concentrate (PC) storage. Cold storage (CS) of PCs is thought to provide a superior haemostatic advantage over room temperature (RT) storage and could prolong the storage time. However, the effect of storage conditions on EV generation and PC function is unknown. We investigated EV production under CS and RT conditions and assessed whether these EVs exhibited a more pro-coagulant phenotype in model experiments.

MATERIALS AND METHODS

Buffy-coat-derived PCs in a platelet additive solution (PAS) to plasma ratio of approximately 65:35 were stored at RT (22 ± 2°C) or CS (4 ± 2°C) for a prolonged storage duration of 20 days. Impedance aggregometry assessed platelet function. EVs were isolated throughout storage and quantified using nanoparticle tracking analysis. EVs were applied to a coagulation assay to assess the impact on fibrin clot formation and lysis.

RESULTS

CS produced significantly larger EVs from day 4 onwards. EV concentration was significantly increased in CS compared to RT from day 15. EVs, regardless of storage, significantly reduced time to clot formation and maximum optical density measured compared to the no EV control. Clot formation was proportionate to the number of EV applied but was not statistically different across storage conditions when corrected for EV number.

CONCLUSION

EVs in CS and RT units showed similar clot formation capacity. However, the higher number of larger EVs generated in CS compared to RT suggests PC units derived from CS conditions may overall exhibit a haemostatically superior capacity compared to RT storage.

Topical Synthetic Platelets Loaded With Gentamicin Decrease Bacteria in Deep Partial-Thickness Burns

INTRODUCTION

Prolonged inflammation and infection in burns may cause inadequate healing. Platelet granules contain anti-inflammatory mediators that impact wound healing. Synthetic platelets (SPs) avoid portability and storage difficulties of natural platelets and can be loaded with bioactive agents. We evaluated wound healing outcomes in deep partial-thickness (DPT) burns treated topically with SP loaded with antibiotics.

MATERIALS AND METHODS

Thirty DPT burns were created on the dorsum of two Red Duroc hybrid pigs. Six wounds were randomized into five groups: SP alone, SP loaded with gentamicin vesicles, SP with gentamicin mixture, vehicle control (saline), or dry gauze. Wounds were assessed from postburn days 3-90. Primary outcome was re-epithelialization percentage at postburn day 28. Secondary outcomes included wound contraction percentage, superficial blood flow relative to normal skin controls, and bacterial load score.

RESULTS

Results showed that re-epithelialization with the standard of care (SOC) was 98%, SP alone measured 100%, SP loaded with gentamicin vesicles was 100%, and SP with gentamicin mixture was 100%. Wound contraction was 5.7% in the SOC and was ∼10% in both the SP loaded with gentamicin vesicles and SP with gentamicin mixture groups. Superficial blood flow in the SOC was 102.5%, SP alone was 170%, the SP loaded was 155%, and gentamicin mixture 162.5%. Bacterial load score in the SOC was 2.2/5.0 and was significantly less at 0.8/5.0 in SP loaded with gentamicin vesicles (P > 0.05). SP and gentamicin mixture scored 2.7 and 2.3/5.0.

CONCLUSIONS

Topical SP treatment did not significantly improve outcomes. However, SP loaded with gentamicin-infused vesicles decreased bacterial load.

Platelets from 13-lined ground squirrels are resistant to cold storage lesions

During torpor in a 13-lined ground squirrel heart rate and blood flow decrease, increasing the risk of blood clot formation. In response, cells involved in clotting called platelets are sequestered in the liver, stored in the cold for months, and released back into circulation upon arousal. This is in contrast to non-hibernating mammals, including humans, in which chilled platelets undergo cold storage lesions and phagocytosis, leading to rapid clearance from circulation post-transfusion. Because of this, human platelets must be stored at room temperature, limiting their shelf life to 7 days due to the increased risk of microbial contamination at warmer temperatures. Human and ground squirrel platelets were stored at room temperature or 4 °C before being analyzed for cold storage lesions. Human platelets stored at 4 °C displayed progressive increases in phosphatidylserine surface exposure and caspase activation, while ground squirrel platelets showed minimal change. Following cold storage, sialic acid residues on human platelets were cleaved, leading to increased phagocytosis of human platelets by HepG2 cells. Ground squirrel platelets stored in the cold showed no changes in desialylation and phagocytosis, with Taxol-treated ground squirrel platelets showing the lowest phagocytosis rates between both species and all treatments. These results suggest that ground squirrel platelets may be resistant to cold storage lesions seen in human platelets. Although these experiments were done in vitro, they suggest a mechanism by which ground squirrel platelets are adapted to be stored during hibernation and remain functional following arousal. Other hibernating species may employ similar adaptations to retain functional platelets following torpor.

Assessment of the soluble proteins HMGB1, CD40L and CD62P during various platelet preparation processes and the storage of platelet concentrates: The BEST collaborative study

BACKGROUND

Structural and biochemical changes in stored platelets are influenced by collection and processing methods. This international study investigates the effects of platelet (PLT) processing and storage conditions on HMGB1, sCD40L, and sCD62P protein levels in platelet concentrate supernatants (PCs).

STUDY DESIGN/METHODS

PC supernatants (n = 3748) were collected by each international centre using identical centrifugation methods (n = 9) and tested centrally using the ELISA/Luminex platform. Apheresis versus the buffy coat (BC-PC) method, plasma storage versus PAS and RT storage versus cold (4°C) were investigated. We focused on PC preparation collecting samples during early (RT: day 1-3; cold: day 1-5) and late (RT: day 4-7; cold: day 7-10) storage time points.

RESULTS

HMGB1, sCD40L, and sCD62P concentrations were similar during early storage periods, regardless of storage solution (BC-PC plasma and BC-PC PAS-E) or temperature. During storage and without PAS, sCD40L and CD62P in BC-PC supernatants increased significantly (+33% and +41%, respectively) depending on storage temperature (22 vs. 4°C). However, without PAS-E, levels decreased significantly (-31% and -20%, respectively), depending on storage temperature (22 vs. 4°C). Contrastingly, the processing method appeared to have greater impact on HMGB1 release versus storage duration. These data highlight increases in these parameters during storage and differences between preparation methods and storage temperatures.

CONCLUSIONS

The HMGB1 release mechanism/intracellular pathways appear to differ from sCD62P and sCD40L. The extent to which these differences affect patient outcomes, particularly post-transfusion platelet increment and adverse events, warrants further investigation in clinical trials with various therapeutic indications.

Platelet-mimicking procoagulant nanoparticles augment hemostasis in animal models of bleeding

Treatment of bleeding disorders using transfusion of donor-derived platelets faces logistical challenges due to their limited availability, high risk of contamination, and short (5 to 7 days) shelf life. These challenges could be potentially addressed by designing platelet mimetics that emulate the adhesion, aggregation, and procoagulant functions of platelets. To this end, we created liposome-based platelet-mimicking procoagulant nanoparticles (PPNs) that can expose the phospholipid phosphatidylserine on their surface in response to plasmin. First, we tested PPNs in vitro using human plasma and demonstrated plasmin-triggered exposure of phosphatidylserine and the resultant assembly of coagulation factors on the PPN surface. We also showed that this phosphatidylserine exposed on the PPN surface could restore and enhance thrombin generation and fibrin formation in human plasma depleted of platelets. In human plasma and whole blood in vitro, PPNs improved fibrin stability and clot robustness in a fibrinolytic environment. We then tested PPNs in vivo in a mouse model of thrombocytopenia where treatment with PPNs reduced blood loss in a manner comparable to treatment with syngeneic platelets. Furthermore, in rat and mouse models of traumatic hemorrhage, treatment with PPNs substantially reduced bleeding and improved survival. No sign of systemic or off-target thrombotic risks was observed in the animal studies. These findings demonstrate the potential of PPNs as a platelet surrogate that should be further investigated for the management of bleeding.

Bioinspired artificial platelets: past, present and future

Platelets are anucleate blood cells produced from megakaryocytes predominantly in the bone marrow and released into blood circulation at a healthy count of 150,000-400,00 per μL and circulation lifespan of 7-9 days. Platelets are the first responders at the site of vascular injury and bleeding, and participate in clot formation via injury site-specific primary mechanisms of adhesion, activation and aggregation to form a platelet plug, as well as secondary mechanisms of augmenting coagulation via thrombin amplification and fibrin generation. Platelets also secrete various granule contents that enhance these mechanisms for clot growth and stability. The resultant clot seals the injury site to stanch bleeding, a process termed as hemostasis. Due to this critical role, a reduction in platelet count or dysregulation in platelet function is associated with bleeding risks and hemorrhagic complications. These scenarios are often treated by prophylactic or emergency transfusion of platelets. However, platelet transfusions face significant challenges due to limited donor availability, difficult portability and storage, high bacterial contamination risks, and very short shelf life (~5-7 days). These are currently being addressed by a robust volume of research involving reduced temperature storage and pathogen reduction processes on donor platelets to improve shelf-life and reduce contamination, as well as bioreactor-based approaches to generate donor-independent platelets from stem cells in vitro. In parallel, a complementary research field has emerged that involves the design of artificial platelets utilizing biosynthetic particle constructs that functionally emulate various hemostatic mechanisms of platelets. Here, we provide a comprehensive review of the history and the current state-of-the-art artificial platelet approaches, along with discussing the translational opportunities and challenges.

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.

Frozen and cold-stored platelets: reconsidered platelet products

Platelet transfusion, both prophylactic and therapeutic, is a key element in modern medicine. Currently, the standard platelet product for clinical use is platelet concentrates at room temperature (20-24°C) under gentle agitation. As this temperature favors bacterial growth, storage is limited to 5-7 days, which result in high wastage rate, and complicates inventory and product availability at remote areas. Frozen and/or cold storage would ameliorate those disadvantages by reducing the risk of bacterial contamination and by extending the product shelf-life to weeks or even years. Consequently, the usefulness in transfusion medicine of platelet cryopreservation and refrigeration, two old and scarcely used platelet storage approaches, is reemerging. Indeed, there have been substantial recent research efforts to characterize both cold and cryopreserved platelets. Most recent studies indicate that cryopreserved and cold platelets display a pro-coagulant profile that may produce the rapid hemostatic response which is needed in bleeding patients. Thus, it seems appropriate that blood banks and blood transfusion centers explore the possibility of split platelet inventories consisting of platelets stored at room temperature and cryopreserved and cold-stored platelets.

Process analysis of pluripotent stem cell differentiation to megakaryocytes to make platelets applying European GMP

Quality, traceability and reproducibility are crucial factors in the reliable manufacture of cellular therapeutics, as part of the overall framework of Good Manufacturing Practice (GMP). As more and more cellular therapeutics progress towards the clinic and research protocols are adapted to comply with GMP standards, guidelines for safe and efficient adaptation have become increasingly relevant. In this paper, we describe the process analysis of megakaryocyte manufacture from induced pluripotent stem cells with a view to manufacturing in vitro platelets to European GMP for transfusion. This process analysis has allowed us an overview of the entire manufacturing process, enabling us to pinpoint the cause and severity of critical risks. Risk mitigations were then proposed for each risk, designed to be GMP compliant. These mitigations will be key in advancing this iPS-derived therapy towards the clinic and have broad applicability to other iPS-derived cellular therapeutics, many of which are currently advancing towards GMP-compliance. Taking these factors into account during protocol design could potentially save time and money, expediting the advent of safe, novel therapeutics from stem cells.

Generation and manipulation of human iPSC-derived platelets

The discovery of iPSCs has led to the ex vivo production of differentiated cells for regenerative medicine. In the case of transfusion products, the derivation of platelets from iPSCs is expected to complement our current blood-donor supplied transfusion system through donor-independent production with complete pathogen-free assurance. This derivation can also overcome alloimmune platelet transfusion refractoriness by resulting in autologous, HLA-homologous or HLA-deficient products. Several developments were necessary to produce a massive number of platelets required for a single transfusion. First, expandable megakaryocytes were established from iPSCs through transgene expression. Second, a turbulent-type bioreactor with improved platelet yield and quality was developed. Third, novel drugs that enabled efficient feeder cell-free conditions were developed. Fourth, the platelet-containing suspension was purified and resuspended in an appropriate buffer. Finally, the platelet product needed to be assured for competency and safety including non-tumorigenicity through in vitro and in vivo preclinical tests. Based on these advancements, a clinical trial has started. The generation of human iPSC-derived platelets could evolve transfusion medicine to the next stage and assure a ubiquitous, safe supply of platelet products. Further, considering the feasibility of gene manipulations in iPSCs, other platelet products may bring forth novel therapeutic measures.

The Impact of Cold Storage on Adenosine Diphosphate-Mediated Platelet Responsiveness

Introduction  Cold storage of platelets is considered to contribute to lower risk of bacterial growth and to more efficient hemostatic capacity. For the optimization of storage strategies, it is required to further elucidate the influence of refrigeration on platelet integrity. This study focused on adenosine diphosphate (ADP)-related platelet responsiveness.

Materials and Methods  Platelets were prepared from apheresis-derived platelet concentrates or from peripheral whole blood, stored either at room temperature or at 4°C. ADP-induced aggregation was tested with light transmission. Activation markers, purinergic receptor expression, and P2Y12 receptor function were determined by flow cytometry. P2Y1 and P2X1 function was assessed by fluorescence assays, cyclic nucleotide concentrations by immunoassays, and vasodilator-stimulated phosphoprotein (VASP)-phosphorylation levels by Western blot analysis.

Results  In contrast to room temperature, ADP-induced aggregation was maintained under cold storage for 6 days, associated with elevated activation markers like fibrinogen binding or CD62P expression. Purinergic receptor expression was not essentially different, whereas P2Y1 function deteriorated rapidly at cold storage, but not P2Y12 activity. Inhibitory pathways of cold-stored platelets were characterized by reduced responses to nitric oxide and prostaglandin E1. Refrigeration of citrated whole blood also led to the attenuation of induced inhibition of platelet aggregation, detectable within 24 hours.

Conclusion  ADP responsiveness is preserved under cold storage for 6 days due to stable P2Y12 activity and concomitant disintegration of inhibitory pathways enabling a higher reactivity of stored platelets. The ideal storage time at cold temperature for the highest hemostatic effect of platelets should be evaluated in further studies.

Treatment of platelet concentrates with the L-carnitine modulates platelets oxidative stress and platelet apoptosis due to mitochondrial reactive oxygen species reduction and reducing cytochrome C release during storage

Platelet concentrate (PC) transfusion is administrated to reduce the hemostatic complications in patients with thrombocytopenia. Strength platelet against oxidative stress conditions lead to decrease in platelet storage lesion (PSL). This study was aimed to evaluate L-carnitine (LC) effects on platelet oxidative stress and platelet apoptosis during storage time. PC bags were randomly selected and each bag was divided into two equal parts. L-carnitine was added to test groups. Normal saline was added to control groups. Platelets count, mean platelet volume (MPV), pH, Platelet aggregation, nitric oxide metabolism (nitric/nitrate), total antioxidant capacity (TAC), malondealdehyde concentration (MDA), lactate dehydrogenase (LDH) enzyme activity, mitochondrial reactive oxygen species (ROS) and cytochrome C releasing were assayed by standard methods in 1, 3, 5 and 7 days of platelet storage. LDH enzyme activity was increased during storage but it had lower level in L-carnitine-treated platelets. LC treatment led to reduction in MDA concentration (3.35 ± 0.98 vs 5.3 ± 1.32, p = 0.003 and 6.52 ± 1.88 vs 5.67 ± 1.25, p = 0.005 for day 5 and day 7 respectively). Increased level of TAC was detected in LC-treated platelets in comparison to control (0.29 ± 0.06 vs 0.21 ± 0.05, p = 0.008 and 0.22 ± 0.03 vs 0.16 ± 0.03, p = 0.003 for day 5 and day 7 respectively). Interestingly, mitochondrial ROS and cytochrome C releasing was significantly lower in LC-treated versus control group during platelet storage. L-carnitine not only decreases mitochondrial ROS but also reduces cytochrome C releasing in PCs during storage. It might be considered as safe additive to decrease PSL in the future.

Multifaceted role of glycosylation in transfusion medicine, platelets, and red blood cells

Glycosylation is highly prevalent, and also one of the most complex and varied posttranslational modifications. This large glycan diversity results in a wide range of biological functions. Functional diversity includes protein degradation, protein clearance, cell trafficking, cell signaling, host-pathogen interactions, and immune defense, including both innate and acquired immunity. Glycan-based ABO(H) antigens are critical in providing compatible products in the setting of transfusion and organ transplantation. However, evidence also suggests that ABO expression may influence cardiovascular disease, thrombosis, and hemostasis disorders, including alterations in platelet function and von Willebrand factor blood levels. Glycans also regulate immune and hemostasis function beyond ABO(H) antigens. Mutations in glycogenes (PIGA, COSMC) lead to serious blood disorders, including Tn syndrome associated with hyperagglutination, hemolysis, and thrombocytopenia. Alterations in genes responsible for sialic acids (Sia) synthesis (GNE) and UDP-galactose (GALE) and lactosamine (LacNAc) (B4GALT1) profoundly affect circulating platelet counts. Desialylation (removal of Sia) is affected by human and pathogenic neuraminidases. This review addresses the role of glycans in transfusion medicine, hemostasis and thrombosis, and red blood cell and platelet survival.

Novel Mouse Model for Studying Hemostatic Function of Human Platelets

OBJECTIVE

Platelets are critical to the formation of a hemostatic plug and the pathogenesis of atherothrombosis. Preclinical animal models, especially the mouse, provide an important platform to assess the efficacy and safety of antiplatelet drugs. However, these studies are limited by inherent differences between human and mouse platelets and the species-selectivity of many drugs. To circumvent these limitations, we developed a new protocol for the adoptive transfer of human platelets into thrombocytopenic nonobese diabetic/severe combined immune deficiency mice, that is, a model where all endogenous platelets are replaced by human platelets in mice accepting xenogeneic tissues. Approach and Results: To demonstrate the power of this new model, we visualized and quantified hemostatic plug formation and stability by intravital spinning disk confocal microscopy following laser ablation injury to the saphenous vein. Integrin α_IIbβ₃-dependent hemostatic platelet plug formation was achieved within ≈30 seconds after laser ablation injury in humanized platelet mice. Pretreatment of mice with standard dual antiplatelet therapy (Aspirin+Ticagrelor) or PAR1 inhibitor, L-003959712 (an analog of vorapaxar), mildly prolonged the bleeding time and significantly reduced platelet adhesion to the site of injury. Consistent with findings from clinical trials, inhibition of PAR1 in combination with dual antiplatelet therapy markedly prolonged bleeding time in humanized platelet mice.

CONCLUSIONS

We propose that this novel mouse model will provide a robust platform to test and predict the safety and efficacy of experimental antiplatelet drugs and to characterize the hemostatic function of synthetic, stored and patient platelets.

A cross-sectional study of prevalence, distribution, cause, and impact of blood product recalls in the United States

Defective blood products that are recalled because of safety or potency deviations can trigger adverse health events and constrict the nation's blood supply chain. However, the underlying characteristics and impact of blood product recalls are not fully understood. In this study, we identified 4700 recall events, 7 reasons for recall, and 144 346 units affected by recalls. Using geospatial mapping of the newly defined county-level recall event density, we discovered hot spots with high prevalence and likelihood of blood product recall events. Distribution patterns and distribution distances of recalled blood products vary significantly between product types. Blood plasma is the most recalled product (87 980 units), and leukocyte-reduced products (34 230 units) are recalled in larger numbers than non-leukocyte-reduced products (8076 units). Donor-related reasons (92 382 units) and sterility deviations (22 408 units) are the major cause of blood product recalls. Monetary loss resulting from blood product recalls is estimated to be $17.9 million, and economic sensitivity tests show that donor-related reasons and sterility deviations contribute most to the overall monetary burden. A total of 2.8 million days was required to resolve recall events, and probabilistic survival time analysis shows that sterility deviations and contamination took longer to resolve because of their systemic effect on blood collection and processing. Our studies demonstrate that better donor screening procedures, rigorous sterility requirements, improved containment methods, and mitigation of recall events in high-prevalence regions will enable a more robust blood supply chain.

The effect of platelet storage temperature on haemostatic, immune, and endothelial function: potential for personalised medicine

Reports from both adult and paediatric populations indicate that approximately two-thirds of platelet transfusions are used prophylactically to prevent bleeding, while the remaining one-third are used therapeutically to manage active bleeding. These two indications, prophylactic and therapeutic, serve two very distinct purposes and therefore will have two different functional requirements. In addition, disease aetiology in a given patient may require platelets with different functional characteristics. These characteristics can be derived from the various manufacturing methods used in platelet product production, including collection methods, processing methods, and storage options. The iterative combinations of manufacturing methods can result in a number of unique platelet products with different efficacy and safety profiles, which could potentially be used to benefit patient populations by meeting diverse clinical needs. In particular, cold storage of platelet products causes many biochemical and functional changes, of which the most notable characterised to date include increased haemostatic activity and altered expression of molecules inherent to platelet:leucocyte interactions. The in vivo consequences, both short- and long-term, of these molecular and cellular cold-storage-induced changes have yet to be clearly defined. Elucidation of these mechanisms would potentially reveal unique biologies that could be harnessed to provide more targeted therapies. To this end, in this new era of personalised medicine, perhaps there is an opportunity to provide individual patients with platelet products that are tailored to their clinical condition and the specific indication for transfusion.

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.