Platelet Additive Solutions: A Review of the Latest Developments and Their Clinical Implications

The 2024 international survey of platelet products and practice

BACKGROUND

Previously, two international surveys have addressed the wider application of platelet collection by apheresis technology and practical issues of platelet transfusion.

STUDY DESIGN AND METHODS

A questionnaire was sent to persons with leadership roles related to blood banking and transfusion medicine in their countries/areas/centers, to document the implementation of modern technologies for platelet manufacturing, preservation, and transfusion risk reduction.

RESULTS

Responses to the questionnaire finally came from 52 contributors in 40 countries/areas. Adult platelet doses ranged between 2.0×1011 and 3.0×1011 (median 2.5×1011). In approximately 10 % of centers, apheresis platelets comprised more than 90 % of the platelet inventory. More than 70 % of centers adopted universal or near universal leukocyte-reduction by filtration, apheresis, or both. Almost 20 % of centers irradiated all platelet products. Cold-stored platelets were rarely reported; only 3 centers produce such components for 1 % to 5 % of their supply. The use of platelet additive solution was reported by 18 responders (45 %), mainly in Europe, USA, and Australasia. Bacterial detection systems were reported by 18 responders from around the globe. One fatality was reported after transfusion of a platelet product contaminated with Bacillus cereus, whereas no sequelae were observed after transfusion of >350 platelet products contaminated by Cutibacteriae. Pathogen-reduction/pathogen-inactivation technology has been adopted in 15 centers, with little or no extended expiration period. Export of platelets across national borders was extremely rare.

CONCLUSION

With this addition to the literature on platelet transfusion, considerable heterogeneity in collection, processing, and transfusion can be seen across the globe, through which readers may adopt, and adapt, best practices for their unique local circumstances.

Platelet Additive Solutions and Pathogen Reduction Impact on Transfusion Safety, Patient Management and Platelet Supply

Since 1998, leuko-reduction is used in France for all platelet concentrates (PCs), apheresis-derived (APCs) and pooled whole blood-derived buffy-coats (BCPCs). Platelet additive solutions (PAS), introduced in 2005, accounted for over 80% of the platelet supply from 2011 to 2017. The Intercept pathogen reduction technology (PR), started in a pilot study in 2007, was generalized in 2018. Between 2007 and 2021, the use of BCPCs increased steadily from 23% to 70% of the supply. Objectives: to analyze the impact of these modifications on adverse transfusion reactions (ATRs), patient management and blood transfusion organization. Results: The overall incidence of ATRs /105 PCs is significantly lower with PAS- and PR-PCs as compared to PCs in plasma (PL), with the decreasing hierarchy PL > PAS > PR. PAS- and PR-PCs lead to significantly lower incidences of allergy and alloimmunization to RBC antigens (RC-AI) ATRs. The incidence of bacteria transmission (TTBI) is significantly reduced by 95% with PR-PCs. APC-related ATR incidence is significantly higher than BCPC for allergy (+233%), TTBI (+100%), APTR (+75%), Major-ABO-II (+65%), HLA/HPA-AI (+38%), FNHTR (+22%), and life-threatening ATRs (+106%). A single diagnosis is significantly less associated with APCs: RC-AI (-47%). The generalization of PR-PCs, which exhibit a lower platelet content than PAS- and PL-PCs, is associated with a significant 9% decrease in the ATR incidence per PC, a 13% increase in the number of PCs transfused per patient, and a nonsignificant 3% increase in the ATR incidence per patient. The outdated PCs percentage declined significantly from 3.7% to 1.7%.

Biotinylation of human platelets is compatible with pathogen inactivation treatment and cold storage for clinical studies

BACKGROUND

Production of platelet concentrates (PCs) involves several steps that significantly affect platelet behavior. To gain a deeper understanding of how storage conditions impact donor platelet recirculation and functionality post-transfusion, ex vivo platelet labeling is a feasible approach. However, before pursuing clinical investigations of platelet recirculation and function in humans, we aimed to determine the effects of pathogen inactivation technology (PIT) and storage conditions (4°C vs. room temperature [RT]) on phenotype and function of biotinylated platelets compared to conventional PIT PCs for transfusion.

METHODS

Nine PCs were prepared in 61% additive solution from 45 buffy coats (five buffy coats each). A pool-and-split of three units was used to prepare three equivalent PCs: two labeled with biotin and stored at RT or 4°C, and one without labeling and stored at RT. All PCs were then treated by PIT (amotosalen/UVA) and stored for 14 days. Labeling efficiency, platelet concentration, metabolic parameters, aggregation response (ADP, collagen, co-aggregation with epinephrine), and platelet phenotype (CD42b, CD62-P, phosphatidylserine) at the basal stage and upon stimulation (ADP or TRAP-6) were performed.

RESULTS

Labeling efficiency of PIT and 4°C PCs was stable over 14 days of storage. Differences in platelet function and phenotype were mainly due to the storage temperature and not the biotinylation process. Phenotypes at baseline or after stimulation were equivalent in biotin-positive and biotin-negative platelets.

CONCLUSION

Biotin-labeled platelets can effectively enable investigation of the effects of PIT and storage temperature for clinical studies. This method shows great potential for improving platelet transfusion knowledge.

Platelet Additive Solutions SSP+ and T-PAS+ Are Interchangeable for Platelet Concentrate Storage despite Differences in Composition and Plasticizer

Introduction

Platelet additive solutions support ex vivo storage of platelet concentrates used for transfusion. The composition of platelet additive solutions within one generation (i.e., PAS-E) is similar but not identical. Additionally, the platelet additive solution storage bag may contain different plasticizers. This study compares the effect of two PAS-E solutions (SSP+ vs. T-PAS+, stored in a DEHP-containing and DEHP-free bag, respectively) to investigate if both additive solutions are interchangeable for platelet concentrate storage.

Methods

Platelet concentrates stored in plasma supplemented with SSP+ or T-PAS+ were compared by using a pool-and-split design. Platelet metabolism was investigated using a blood gas analyzer. The degree of platelet storage lesion was determined by flow cytometry to measure granule release and phosphatidylserine scrambling.

Results

The quality of platelet concentrates stored in either SSP+ or T-PAS+ is acceptable as pH decreased only slightly as a function of time. PH remained above 7.2 on exiration day +1 (day 6), which is far above the minimal criterion of 6.4. Platelet storage lesion was comparable between the two study groups with only limited α-granule release and phosphatidylserine surface expression in both groups after storage for 5 days, p = 0.547 and p = 0.825, respectively.

Conclusion

This study supports a safe switch between SSP+ and T-PAS+ storage solutions for platelet concentrates despite slight differences in storage solution composition and DEHP content.

Genetic engineering of transfusable platelets with mRNA-lipid nanoparticles is compatible with blood banking practices

ABSTRACT

Platelets contribute to a variety of physiological processes, including inflammation, sepsis, and cancer. However, because of their primary role in hemostasis, platelet transfusions are largely restricted to managing thrombocytopenia and bleeding. One way to expand the utility of platelet transfusions would be to genetically engineer donor platelets with new or enhanced functions. We have previously shown that lipid nanoparticles containing mRNA (mRNA-LNP) can be used to genetically modify authentic platelets in a nonclinical crystalloid solution. Currently, platelets collected for transfusion are stored in plasma or in plasma supplemented with platelet additive solution (PAS) at supraphysiological concentrations at room temperature, or at 4°C if intended for use in acute hemorrhage. Here, we describe a new plasma-optimized mRNA-LNP for transfecting platelets directly in plasma and plasma supplemented with PAS that is scalable to physiological and supraphysiological platelet concentrations. Transfecting platelets in clinical solutions with mRNA-LNP does not affect aspects of in vitro physiology, and transfected platelets are storable. The compatibility of this transfection system with current clinical practices could enable future mRNA-LNP-based platelet products and cell therapies.

Oxidative modulations in platelets stored in SSP+, PAS-G and Tyrode's buffer: a comparative analysis

BACKGROUND

Platelet additive solutions (PASs) improve the efficacy of stored platelets. Oxidative stress causes storage lesions and platelet functions deteriorate. Studies assessing the influence of oxidative stress on platelets stored in PASs are limited. This study compares variations in platelets in different storage solutions (SSP+, PAS-G and Tyrode's buffer).

METHODS

Platelets isolated from the blood of Wistar rats were resuspended in SSP+, PAS-G and Tyrode's buffer and stored for seven days at 22 °C. The markers of platelet metabolism, function, oxidative stress, antioxidant status and viability were analyzed on Days 1, 3, 5 and 7 of storage.

MAIN RESULTS

SSP+ is associated with platelet function, viability and antioxidant defenses (SOD, CAT and GSH); it decreased primary lipid peroxidation products and maintained the susceptible protein groups in reduced state. Platelet function, antioxidant defenses such as SOD and GSH improved, and lipids and thiols were protected from oxidation in PAS-G. SOD and GSH increased, and lipids and thiols were preserved in Tyrode's buffer.

CONCLUSION

SSP+ and PAS-G are more effective in maintaining platelet efficacy till Day 7 compared to Tyrode's buffer. Thus, PAS-G and SSP+ are better than Tyrode's buffer in terms of platelet responses to oxidative stress during storage. This is the first comparative account on the influence of PASs (SSP+, PAS-G and Tyrode's buffer) on platelets in altering oxidative stress. It provides a comprehensive view of the differential responses of platelets in PASs.

Developments in Transfusion Medicine: Pulmonary Transfusion Reactions and Novel Blood Cell Labeling Techniques

Staying updated on advancements in transfusion medicine is crucial, especially in critical care and perioperative setting, where timely and accurate transfusions can be lifesaving therapeutic interventions. This narrative review explores the landscape of transfusion-related adverse events, focusing on pulmonary transfusion reactions such as transfusion-associated circulatory overload (TACO) and transfusion-related acute lung injury (TRALI). TACO and TRALI are the leading causes of transfusion-related morbidity and mortality; however, specific treatments are lacking. Understanding the current incidence, diagnostic criteria, pathogenesis, treatment, and prevention strategies can equip clinicians to help reduce the incidence of these life-threatening complications. The review discusses emerging pathogenic mechanisms, including the possible role of inflammation in TACO and the mechanisms of reverse TRALI and therapeutic targets for TACO and TRALI, emphasizing the need for further research to uncover preventive and treatment modalities. Despite advancements, significant gaps remain in our understanding of what occurs during transfusions, highlighting the necessity for improved monitoring methods. To address this, the review also presents novel blood cell labeling techniques in transfusion medicine used for improving monitoring, quality assessment, and as a consequence, potentially reducing transfusion-related complications. This article aims to provide an update for anesthesiologists, critical care specialists, and transfusion medicine professionals regarding recent advancements and developments in the field of transfusion medicine.

Impact of production methods and storage conditions on extracellular vesicles in packed red blood cells and platelet concentrates

The use of blood and blood products can be life-saving, but there are also certain risks associated with their administration and use. Packed red blood cells (pRBCs) and platelet concentrates are the most commonly used blood products in transfusion medicine to treat anemia or acute and chronic bleeding disorders, respectively. During the production and storage of blood products, red blood cells and platelets release extracellular vesicles (EVs) as a result of the storage lesion, which may affect product quality. EVs are subcellular structures enclosed by a lipid bilayer and originate from the endosomal system or from the plasma membrane. They play a pivotal role in intercellular communication and are emerging as important regulators of inflammation and coagulation. Their cargo and their functional characteristics depend on the cell type from which they originate, as well as on their microenvironment, influencing their capacity to promote coagulation and inflammatory responses. Hence, the potential involvement of EVs in transfusion-related adverse events is increasingly recognized and studied. Here, we review the knowledge regarding the effect of production and storage conditions of pRBCs and platelet concentrates on the release of EVs. In this context, the mode of processing and anticoagulation, the influence of additive solutions and leukoreduction, as well as the storage duration will be addressed, and we discuss potential implications of EVs for the clinical outcome of transfusion.

The platelet storage lesion, what are we working for?

BACKGROUND

Platelet concentrate (PC) transfusions are crucial in prevention and treatment of bleeding in infection, surgery, leukemia, and thrombocytopenia patients. Although the technology for platelet preparation and storage has evolved over the decades, there are still challenges in the demand for platelets in blood banks because the platelet shelf life is limited to 5 days due to bacterial contamination and platelet storage lesions (PSLs) at 20-24°C under constant horizontal agitation. In addition, the relations between some adverse effects of platelet transfusions and PSLs have also been considered. Therefore, understanding the mechanisms of PSLs is conducive to obtaining high quality platelets and facilitating safe and effective platelet transfusions.

OBJECTIVE

This review summarizes developments in mechanistic research of PSLs and their relationship with clinical practice, providing insights for future research.

METHODS

Authors conducted a search on PubMed and Web of Science using the professional terms "PSL" and "platelet transfusion." The obtained literature was then roughly categorized based on their research content. Similar studies were grouped into the same sections, and further searches were conducted based on the keywords of each section.

RESULTS

Different studies have explored PSLs from various perspectives, including changes in platelet morphology, surface molecules, biological response modifiers (BMRs), metabolism, and proteins and RNA, in an attempt to monitor PSLs and identify intervention targets that could alleviate PSLs. Moreover, novel platelet storage conditions, including platelet additive solutions (PAS) and reconsidered cold storage methods, are explored. There are two approaches to obtaining high-quality platelets. One approach simulates the in vivo environment to maintain platelet activity, while the other keeps platelets at a low activity level in vitro under low temperatures.

CONCLUSION

Understanding PSLs helps us identify good intervention targets and assess the therapeutic effects of different PSLs stages for different patients.

What's in Your Transfusion? A Bedside Guide to Blood Products and Their Preparation

An understanding of the contents of blood products and how they are modified before transfusion will help any physician. This article will review five basic blood products and the five most common product modifications.

Platelet-derived extracellular vesicles play an important role in platelet transfusion therapy

Extracellular vesicles (EVs) contain the characteristics of their cell of origin and mediate cell-to-cell communication. Platelet-derived extracellular vesicles (PEVs) not only have procoagulant activity but also contain platelet-derived inflammatory factors (CD40L and mtDNA) that mediate inflammatory responses. Studies have shown that platelets are activated during storage to produce large amounts of PEVs, which may have implications for platelet transfusion therapy. Compared to platelets, PEVs have a longer storage time and greater procoagulant activity, making them an ideal alternative to platelets. This review describes the reasons and mechanisms by which PEVs may have a role in blood transfusion therapy.

Expanding applications of allogeneic platelets, platelet lysates, and platelet extracellular vesicles in cell therapy, regenerative medicine, and targeted drug delivery

Platelets are small anucleated blood cells primarily known for their vital hemostatic role. Allogeneic platelet concentrates (PCs) collected from healthy donors are an essential cellular product transfused by hospitals to control or prevent bleeding in patients affected by thrombocytopenia or platelet dysfunctions. Platelets fulfill additional essential functions in innate and adaptive immunity and inflammation, as well as in wound-healing and tissue-repair mechanisms. Platelets contain mitochondria, lysosomes, dense granules, and alpha-granules, which collectively are a remarkable reservoir of multiple trophic factors, enzymes, and signaling molecules. In addition, platelets are prone to release in the blood circulation a unique set of extracellular vesicles (p-EVs), which carry a rich biomolecular cargo influential in cell-cell communications. The exceptional functional roles played by platelets and p-EVs explain the recent interest in exploring the use of allogeneic PCs as source material to develop new biotherapies that could address needs in cell therapy, regenerative medicine, and targeted drug delivery. Pooled human platelet lysates (HPLs) can be produced from allogeneic PCs that have reached their expiration date and are no longer suitable for transfusion but remain valuable source materials for other applications. These HPLs can substitute for fetal bovine serum as a clinical grade xeno-free supplement of growth media used in the in vitro expansion of human cells for transplantation purposes. The use of expired allogeneic platelet concentrates has opened the way for small-pool or large-pool allogeneic HPLs and HPL-derived p-EVs as biotherapy for ocular surface disorders, wound care and, potentially, neurodegenerative diseases, osteoarthritis, and others. Additionally, allogeneic platelets are now seen as a readily available source of cells and EVs that can be exploited for targeted drug delivery vehicles. This article aims to offer an in-depth update on emerging translational applications of allogeneic platelet biotherapies while also highlighting their advantages and limitations as a clinical modality in regenerative medicine and cell therapies.

Cost Effectiveness of Different Platelet Preparation, Storage, Selection and Dosing Methods in Platelet Transfusion: A Systematic Review

BACKGROUND AND OBJECTIVE

Evidence-based guidelines on platelet transfusion therapy assist clinicians to optimize patient care, but currently do not take into account costs associated with different methods used during the preparation, storage, selection and dosing of platelets for transfusion. This systematic review aimed to summarize the available literature regarding the cost effectiveness (CE) of these methods.

METHODS

Eight databases and registries, as well as 58 grey literature sources, were searched up to 29 October 2021 for full economic evaluations comparing the CE of methods for preparation, storage, selection and dosing of allogeneic platelets intended for transfusion in adults. Incremental CE ratios, expressed as standardized cost (in 2022 EUR) per quality-adjusted life-year (QALY) or per health outcome, were synthesized narratively. Studies were critically appraised using the Philips checklist.

RESULTS

Fifteen full economic evaluations were identified. Eight investigated the costs and health consequences (transfusion-related events, bacterial and viral infections or illnesses) of pathogen reduction. The estimated incremental cost per QALY varied widely from EUR 259,614 to EUR 36,688,323. For other methods, such as pathogen testing/culturing, use of apheresis instead of whole blood-derived platelets, and storage in platelet additive solution, evidence was sparse. Overall, the quality and applicability of the included studies was limited.

CONCLUSIONS

Our findings are of interest to decision makers who consider implementing pathogen reduction. For other preparation, storage, selection and dosing methods in platelet transfusion, CE remains unclear due to insufficient and outdated evaluations. Future high-quality research is needed to expand the evidence base and increase our confidence in the findings.

Platelet Additive Solutions as an Alternative Storage Medium of Apheresis Platelets to Reduce ABO Antibody Titer for ABO-Incompatibility Platelet Transfusion

Introduction Platelet additive solutions (PASs) are nutrient media commonly used to replace and reduce the need for storage plasma. They are an alternative medium to maintain high-quality platelets lasting longer on the shelf for about seven days. Platelets with high titer of ABO antibody can pose a hemolytic transfusion reaction (HTR) risk if units are given across the ABO barrier. The risk of complication is greater when group O platelet is released to non-group O patients. The PAS has been known as a safe medium, where the titer of ABO antibodies is expected to be diluted. In this study, we compared the anti-A and anti-B antibody titers of apheresis platelets in PAS and non-PAS (plasma) as the suspending media. Methods A total of 20 apheresis platelet donors were selected, with seven from blood group A, eight from blood group B, and five from blood group O. The platelets were collected using an Amicus cell separator. They were suspended in PAS and plasma before being stored at a temperature range of 22-24º C. Anti-A (blood group B and O) and Anti-B (blood group A and O) antibody titers were measured and compared between the two suspending media. Wilcoxon signed-rank test is used for statistical analysis, and a p-value <0.05 is considered significant. Results The median titer of the anti-A antibody of apheresis platelets showed a significant difference between suspended in PAS (2.50) and plasma (4.00), p=0.002. Similar findings were also seen with the median titer of the anti-B antibody of apheresis platelet, in which it showed a significant difference between suspended in PAS (2.00) and plasma (4.00), p=0.004. It was observed that there was a significant reduction in both anti-A and anti-B antibody titers in the PAS as compared to the plasma group. Conclusion The decrease in ABO antibody titer in apheresis platelets stored with PAS can be beneficial for patients. This reduces the risk of HTRs if ABO-incompatible platelet units need to be issued. Thus, using PAS as a storage medium significantly improves platelet inventory management without compromising patient safety.

Update on transfusion-related acute lung injury: an overview of its pathogenesis and management

Transfusion-related acute lung injury (TRALI) is a severe adverse event and a leading cause of transfusion-associated death. Its poor associated prognosis is due, in large part, to the current dearth of effective therapeutic strategies. Hence, an urgent need exists for effective management strategies for the prevention and treatment of associated lung edema. Recently, various preclinical and clinical studies have advanced the current knowledge regarding TRALI pathogenesis. In fact, the application of this knowledge to patient management has successfully decreased TRALI-associated morbidity. This article reviews the most relevant data and recent progress related to TRALI pathogenesis. Based on the existing two-hit theory, a novel three-step pathogenesis model composed of a priming step, pulmonary reaction, and effector phase is postulated to explain the process of TRALI. TRALI pathogenesis stage-specific management strategies based on clinical studies and preclinical models are summarized with an explication of their models of prevention and experimental drugs. The primary aim of this review is to provide useful insights regarding the underlying pathogenesis of TRALI to inform the development of preventive or therapeutic alternatives.

Protocols for the Isolation of Platelets for Research and Contrast to Production of Platelet Concentrates for Transfusion

Platelets are specialized cellular elements of blood and play a central role in maintaining normal hemostasis, wound healing, and host defense but also are implicated in pathologic processes of thrombosis, inflammation, and tumor progression and dissemination. Transfusion of platelet concentrates is an important treatment for thrombocytopenia (low platelet count) due to disease or significant blood loss, with the goal being to prevent bleeding or to arrest active bleeding. In blood circulation, platelets are in a resting state; however, when triggered by a stimulus, such as blood vessel injury, become activated (also termed procoagulant). Platelet activation is the basis of their biological function to arrest active bleeding, comprising a complex interplay of morphological phenotype/shape change, adhesion, expression of signaling molecules, and release of bioactive factors, including extracellular vesicles/microparticles. Advances in high-throughput mRNA and protein profiling techniques have brought new understanding of platelet biological functions, including identification of novel platelet proteins and secreted molecules, analysis of functional changes between normal and pathologic states, and determining the effects of processing and storage on platelet concentrates for transfusion. However, because platelets are very easily activated, it is important to understand the different in vitro methods for platelet isolation commonly used and how they differ from the perspective for use as research samples in clinical chemistry. Two simple methods are described here for the preparation of research-scale platelet samples from human whole blood, and detailed notes are provided about the methods used for the preparation of platelet concentrates for transfusion.

Platelet transfusion in adults: An update

Many patients worldwide receive platelet components (PCs) through the transfusion of diverse types of blood components. PC transfusions are essential for the treatment of central thrombocytopenia of diverse causes, and such treatment is beneficial in patients at risk of severe bleeding. PC transfusions account for almost 10% of all the blood components supplied by blood services, but they are associated with about 3.25 times as many severe reactions (attributable to transfusion) than red blood cell transfusions after stringent in-process leukoreduction to less than 10⁶ residual cells per blood component. PCs are not homogeneous, due to the considerable differences between donors. Furthermore, the modes of PC collection and preparation, the safety precautions taken to limit either the most common (allergic-type reactions and febrile non-hemolytic reactions) or the most severe (bacterial contamination, pulmonary lesions) adverse reactions, and storage and conservation methods can all result in so-called PC "storage lesions". Some storage lesions affect PC quality, with implications for patient outcome. Good transfusion practices should result in higher levels of platelet recovery and efficacy, and lower complication rates. These practices include a matching of tissue ABH antigens whenever possible, and of platelet HLA (and, to a lesser extent, HPA) antigens in immunization situations. This review provides an overview of all the available information relating to platelet transfusion, from donor and donation to bedside transfusion, and considers the impact of the measures applied to increase transfusion efficacy while improving safety and preventing transfusion inefficacy and refractoriness. It also considers alternatives to platelet component (PC) transfusion.

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 components and bacterial contamination: hospital perspective 2022

Bacterial contamination of platelet units has been one of the most common transfusion-transmitted infections. Approximately 4 to 7 fatalities are being reported to the US Food and Drug Administration (FDA) annually, which cites bacterially contaminated platelet units as the cause. Over the past 3 decades, different mitigation strategies have been introduced to minimize the risk of morbidity and mortality related to contaminated platelet units. The process of platelet collection and manufacturing as well as storage at 20°C to 24°C contributes to higher prevalence of contaminated units. The risk of transfusing bacterially contaminated platelets can be lowered using different types of interventions. Prevention of bacterial contamination can be done by strict adherence to techniques that minimize contamination during unit collection. The detection of bacteria in platelet products can be improved with a combination of rapid testing and bacterial cultures that involve large volume and delayed sampling. Finally, pathogen reduction can inactivate bacteria or other pathogens present in the unit. This article describes different strategies that blood centers and transfusion services have undertaken since October 2021 to meet FDA guidance requirements. Market forces as well as feasibility of different FDA-proposed approaches have limited the number of practical solutions to just a few. In addition, the blood product availability required hospitals to adopt more progressive strategies to provide patients with needed platelet products.

Two novel platelet biotinylation methods and their impact on stored platelet concentrates in a blood bank environment

BACKGROUND

Storage of platelet concentrates (PCs) has an impact on platelet quality and possibly affects their functions after transfusion. The influence of processing and storage conditions of PCs on their in vivo function upon transfusion is unknown. One option for investigating this question is to implement an ex vivo labeling of human platelets, to analyze them after transfusion into heathy volunteers and/or patients. In this study, we developed two labeling methods employing biotin.

METHODS

Two methods of biotinylation were compared to a control (standard PC). The "Bio-Wash" process used washing steps to label all platelets within the PC; for the other method, "Bio-Direct," one fifth of the PC were directly labeled without washing steps. The control and the two biotinylated PCs were analyzed over 7 days of storage. Labeling efficiency, platelet counts, phenotypes, and functions, along with time and costs, were evaluated to select the best process.

RESULTS

Both methods achieved a stable labeling through the storage, with similar platelet counts and metabolism in comparison to control PCs. Bio-Wash showed higher activation phenotype and lower aggregation response in comparison to the Bio-Direct method. The Bio-Direct was performed within 1.5 h versus 3 h for the Bio-Wash. However, the Bio-Direct required 12 mg of biotin instead of 8 mg for the other process.

CONCLUSION

We set up two methods of biotinylation that can be easily implemented in a blood bank environment. The Bio-Direct process was preferred to the Bio-Wash because of its similarity, from a functional and phenotypic point of view, with standard PCs.

DAMPS and complement activation in platelet concentrates that induce adverse reactions in patients

BACKGROUND

Patients with severe thrombocytopenia due to bone marrow failure and after chemotherapy are still treated with platelet transfusions. Platelet concentrates (PC) are associated with a high incidence of adverse reactions (AR). Platelet-derived damage-associated molecular patterns (DAMPS) and complement were proposed to play a role in the pathology of AR.

STUDY DESIGN AND METHODS

Single donor apheresis platelet concentrates (SDA PCs) were produced in a regional setting of the French Blood Establishment. After transfusion samples were collected from PC and possible AR in patients were recorded. Platelet activation markers, High mobility group box 1 (HMGB1) and complement activation products (CAP) were measured. The correlation between platelet activation, and HMGB1 and complement activation was analyzed.

RESULTS

A total of 56 PC were included in the study. 30 PC induced no AR, and 26 induced AR (Febrile non-hemolytic transfusion reaction n = 16; Atypical Allergic Transfusion Reactions n = 11; hemodynamic instability n = 5) in the patients. The levels of P-selectin, sCD40L, HMGB1, C3b/c, and C4b/c were all significantly increased in PC that induced AR following transfusion in patients. Additionally, HMGB1, C3b/c, and C4b/c were positively correlated with P-selectin and sCD40L.

CONCLUSION

In this study, we observed an association between HMGB1 and CAP and the incidence of AR. Furthermore, we demonstrated that both HMGB1 and complement activation were correlated to platelet activation.

In vitro evaluation of platelet extracellular vesicles (PEVs) for corneal endothelial regeneration

Corneal endothelial cells (CECs) slowly decrease in number with increasing age, which is a clinical issue as these cells have very limited regenerative ability. Therapeutic platelet biomaterials are increasingly used in regenerative medicine and cell therapy because of their safety, cost-effective manufacture, and global availability from collected platelet concentrates (PCs). Platelet extracellular vesicles (PEVs) are a complex mixture of potent bioactive vesicles rich in molecules believed to be instrumental in tissue repair and regeneration. In this study we investigated the feasibility of using a PEVs preparation as an innovative regenerative biotherapy for corneal endothelial dysfunction. The PEVs were isolated from clinical-grade human PC supernatants by 20,000 × g ultracentrifugation and resuspension. PEVs exhibited a regular, fairly rounded shape, with an average size of <200 nm and were present at a concentration of approximately 10¹¹ /mL. PEVs expressed cluster of differentiation 41 (CD41) and CD61, characteristic platelets membrane markers, and CD9 and CD63. ELISA and LC-MS/MS proteomic analyses revealed that the PEVs contained mixtures of growth factors and multiple other trophic factors, as well as proteins related to extracellular exosomes with functional activities associated with cell cadherin and adherens pathways. CECs treated with PEVs showed increased viability, an enhanced wound-healing rate, stronger proliferation markers, and an improved adhesion rate. PEVs did not exert cellular toxicity as evidenced by the maintenance of cellular morphology and preservation of corneal endothelial proteins. These findings clearly support further investigations of PEV biomaterials in animal models for translation as a new CEC regeneration biotherapy.

Cold-stored platelet function is not significantly altered by agitation or manual mixing

BACKGROUND

Cold storage of platelets (CS-PLT), results in better maintained hemostatic function compared to room-temperature stored platelets (RT-PLT), leading to increased interest and use of CS-PLT for actively bleeding patients. However, questions remain on best storage practices for CS-PLT, as agitation of CS-PLT is optional per the United States Food and Drug Administration. CS-PLT storage and handling protocols needed to be determined prior to upcoming clinical trials, and blood banking standard operating procedures need to be updated accordingly for the release of units due to potentially modified aggregate morphology without agitation.

STUDY DESIGN AND METHODS

We visually assessed aggregate formation, then measured surface receptor expression (GPVI, CD42b (GPIbα), CD49 (GPIa/ITGA2), CD41/61 (ITGA2B/ITGB3; GPIIB/GPIIIA; PACI), CD62P, CD63, HLAI), thrombin generation, aggregation (collagen, adenosine diphosphate [ADP], and epinephrine activation), and viscoelastic function (ExTEM, FibTEM) in CS-PLT (Trima collection, 100% plasma) stored for 21 days either with or without agitation (Phase 1, n = 10 donor-paired units) and then without agitation with or without daily manual mixing to minimize aggregate formation and reduce potential effects of sedimentation (Phase 2, n = 10 donor-paired units).

RESULTS

Agitation resulted in macroaggregate formation, whereas no agitation caused film-like sediment. We found no substantial differences in CS-PLT function between storage conditions, as surface receptor expression, thrombin generation, aggregation, and clot formation were relatively similar between intra-Phase storage conditions.

DISCUSSION

Storage duration and not condition impacted phenotype and function. CS-PLT can be stored with or without agitation, and with or without daily mixing and standard metrics of hemostatic function will not be significantly altered.

Platelet additive solution suspended apheresis platelets in a tertiary care hospital: A step toward universal single donor platelets

BACKGROUND

Transfusion of ABO-compatible single donor platelets (SDP) is preferable for better outcomes over group switchover SDP. The use of SDP containing ABO-incompatible plasma is associated with a risk of allergic and acute hemolytic transfusion reactions. Moreover, high titer O group donors SDP impose a further threat to patient safety. Platelet additive solution (PAS) is used worldwide for the storage of platelets which reduces plasma volume available in SDP. SSP + (Macopharma) is one such PAS which can provide improved availability, logistical management, decrease wastage, and improvement in patient safety. The aim of this study was to assess the feasibility of using PAS to obtain low titer SDP units which can be utilized across a larger patient population and to study quality control parameters of these units.

MATERIALS AND METHODS

The study was performed in the department of Transfusion Medicine from June 2017 to January 2018 after clearance from the Institutional Review Board. The study design comprised two cohorts (A and B). In cohort A, the temporal trend of in-vitro changes in the quality parameters was tested and analyzed for PAS modified and unmodified products on days 1, 5 and 7. In cohort B, the original plasma from the SDP donors of all blood group donors except the AB group was tested for antibody titers before (prepreparation) and after modification (postpreparation) by PAS.

RESULTS

In cohort A, in the control group, there was a significant change in the mean platelet volume, potassium, and bicarbonate levels from day 1 to day 7, whereas no significant change in the biochemical parameters was noted in the study group where PAS was used. In cohort B, on comparing the anti-A and anti-B, before and after modification of SDP with PAS, there was a significant reduction in the median titers across all the groups studied.

CONCLUSION

PAS added SDP is an efficient strategy to reduce the ABO-antibody levels significantly. PAS added SDP also helps in the better inventory management of available groups.

CPT2 K79 Acetylation Regulates Platelet Lifespan

CPT2 K79 acetylation caused by NAD⁺ exhaustion and Sirt3 dysfunction resulted in LCAC accumulation and platelet damage.

Blocking acylcarnitine generation with AMPK or CPT1 inhibitors, Sirt3 agonists, and antioxidants retarded platelet storage lesion.

The short life span of platelets is a major challenge to platelet transfusion services because of the lack of effective intervention. Here, we found that the accumulation of long-chain acylcarnitines (LCACs) is responsible for mitochondrial damage and platelet storage lesion. Further studies showed that the blockade of fatty acid oxidation and the activation of AMP-activated protein kinase (AMPK)/acetyl-CoA carboxylase/carnitine palmitoyltransferase 1 (CPT1) pathways that promote fatty acid metabolism are important reasons for the accumulation of LCACs. The excessive accumulation of LCACs can cause mitochondrial damage and a short life span of stored platelets. The mechanism study elucidated that NAD⁺ exhaustion and the subsequent decrease in sirtuin 3 (Sirt3) activity caused an increase in the level of CPT2 K79 acetylation, which is the primary cause of the blockade of fatty acid oxidation and the accumulation of LCACs. Blocking LCAC generation with the inhibitors of AMPK or CPT1, the agonists of Sirt3, and antioxidants tremendously retarded platelet storage lesion in vitro and prolonged the survival of stored platelets in vivo posttransfusion with single or combined use. In summary, we discovered that CPT2 acetylation attenuates fatty acid oxidation and exacerbates platelet storage lesion and may serve as a new target for improving platelet storage quality.

The Missing Pieces to the Cold-Stored Platelet Puzzle

Cold-stored platelets are making a comeback. They were abandoned in the late 1960s in favor of room-temperature stored platelets due to the need for longer post-transfusion platelet recoverability and survivability in patients with chronic thrombocytopenia. However, the current needs for platelet transfusions are rapidly changing. Today, more platelets are given to patients who are actively bleeding, such as ones receiving cardiac surgeries. It has been established that cold-stored platelets are more hemostatically effective, have reduced bacterial growth, and have longer potential shelf lives. These compelling characteristics led to the recent interest in bringing back cold-stored platelets to the blood systems. However, before reinstating cold-stored platelets in the clinics again, a thorough investigation of in vitro storage characteristics and in vivo transfusion effects is required. This review aims to provide an update on the recent research efforts into the storage characteristics and functions of cold-stored platelets using modern investigative tools. We will also discuss efforts made to improve cold-stored platelets to be a better and safer product. Finally, we will finish off with discussing the relevance of in vitro data to in vivo transfusion results and provide insights and directions for future investigations of cold-stored platelets.

Comparison of Quality and Efficacy of Apheresis Platelets Stored in Platelet Additive Solution Vis a Vis Plasma

PAS, by replacing part of the plasma in the platelet storage bag, reduces post transfusion allergic reactions and DHTR in the recipient. In this study we compared quality and efficacy of PAS and usual plasma stored platelets. Platelet concentration, content, MPV, pH, swirling, LDH and glucose concentration were tested in SDPs after preparation and on the day of transfusion; and compared between control (plasma-stored SDP) and study (PAS-stored SDP) groups. CCI was compared between the two groups. Transfusion reactions were also noted. In both groups quality parameters were similar except glucose [significantly decreased (p < 0.001) in plasma] and LDH [increased significantly (p: -0.005) in PAS]. CCI was similar in both groups. Transfusion reaction rate were 0.012% and 0.049% in both groups respectively. Quality and post-transfusion efficacy in both groups were similar. PAS stored platelets may be transfused in multi-transfused patients with allergic manifestations and in minor ABO incompatible transfusions.

The Effect of a Single Freeze-Thaw Cycle on Matrix Metalloproteinases in Different Human Platelet-Rich Plasma Formulations

Storing platelet-rich plasma (PRP) for future use is a compelling approach, presuming the retention of biological properties is maintained. However, certain factors in PRP preparations have deleterious effects for the treatment of certain musculoskeletal conditions. The purpose of this study was to measure and compare matrix metalloproteinase protein (MMP) concentrations between fresh and freeze-thawed leukocyte-rich PRP (LR-PRP) inactivated (LR-I) and activated (LR-A) preparations, and leukocyte-poor PRP (LP-PRP) inactivated (LP-I) and activated (LP-A) preparations. A volume of 60 mL of whole blood was drawn from 19 healthy donors. LP-I and LR-I samples were processed using a manual extraction and centrifugation methodology. LP-A and LR-A products were activated with 10% CaCl2 and recombinant thrombin. Blood fractions were either immediately assayed and analyzed or stored at -80 °C for 24, 72 and 160 h. Multiplex immunoassay was used to measure MMP-1, MMP-2, MMP-3, MMP-9, MMP-10, and MMP-12. MMP-1 concentrations increased in LR-A (p < 0.05) and MMP-9 significantly increased in LR-I (p < 0.05), while MMP-2 significantly decreased in LR-I (p < 0.05) and MMP-3 concentrations significantly decreased in LR-A (p < 0.05). MMP-12 concentrations also significantly decreased in LR-I (p < 0.05) from baseline concentrations. There were no significant differences between LP-A and LP-I preparations and MMP concentrations. MMP-10 concentrations in all PRP samples compared to each freezing time point were also not significantly different. MMPs regulate components of the extracellular matrix (ECM) in the remodeling phase of musculoskeletal injury. In this study, we observed a significant increase and decrease in MMP concentrations in response to a single freeze-thaw cycle in inactivated PRP and activated PRP preparations. This evidence contributes to the growing body of literature on the optimization of PRP preparation and storage strategies prior to delivery. Our findings suggest that specific PRP preparations after a single freeze-thaw may be more advantageous for certain musculoskeletal applications based on the presence of MMP concentrations.

Transfusion-Associated Circulatory Overload and Transfusion-Related Acute Lung Injury

OBJECTIVES

To review the new current diagnostic criteria of transfusion-associated circulatory overload (TACO) and transfusion-related acute lung injury (TRALI) from the literature while highlighting distinguishing features. We provide comprehensive understanding of the importance of hemovigilance and its role in appropriately identifying and reporting these potentially fatal transfusion reactions.

METHODS

A review of the English language literature was performed to analyze TACO and TRALI while providing further understanding of the rationale behind the historical underrecognition and underreporting.

RESULTS

Our review demonstrates the new 2018 and 2019 case definitions for TACO and TRALI, respectively. With more comprehensive diagnostic strategies, adverse transfusion events can be better recognized from mimicking events and underlying disease. In addition, there are mitigation strategies in place to help prevent complications of blood product transfusion, with emphasis on the prevention of TACO and TRALI.

CONCLUSIONS

TACO and TRALI are potentially fatal adverse complications of blood transfusion. Both have been historically underrecognized and underreported due to poor defining criteria and overlapping symptomatology. Developing a thorough clinical understanding between these two entities can improve hemovigilance reporting and can contribute to risk factor identification and preventative measures.

Current challenges in platelet transfusion

The supply of platelets for transfusion is a logistical challenge due to the physiology of platelets and current measures of transfusion performance dictating storage at 22°C and a short product shelf-life (<7 days). Demand for platelets has increased in recent years and changes in the demographics of the population may enhance this further. Many studies have been conducted to understand what the optimal dose and trigger for transfusion should be, mainly in hematology patients who are the largest cohort that receive platelets, mostly to prevent bleeding. Emerging data suggests that for bleeding patients, where immediate hemostasis is a key consideration, the current standard product may not be optimal. Alternative platelet preparation methods/storage options that may improve the hemostatic properties of platelets are under active development. In parallel with research into alternative platelet products that might enhance hemostasis, better measures for assessing bleeding risk and platelet efficacy are needed.

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.

Preventing adverse reactions in pediatric transfusions using washed platelet concentrate

Blood transfusion is an important form of supportive care in children; however, transfusion-associated adverse reactions (TARs) are a problem. As with adults, allergic transfusion reactions (ATRs) and febrile non-hemolytic transfusion reactions (FNHTRs) are major TARs, and the frequency of ATRs caused by platelet concentrate (PC) tends to be particularly high. The plasma component of the blood product is thought to be a major factor in the onset of TARs such as ATR and FNHTR. By contrast, in children, age, underlying disease, and number of blood transfusions may be relevant patient-related factors. Although acetaminophen or diphenhydramine may be used prophylactically to prevent TARs, there is no clear evidence of their effectiveness. Volume-reduced PC is used to prevent TARs; however, it may be difficult to maintain the quality of platelets. Plasma-replaced PC stored with platelet additive solution raises the concern that TARs cannot be completely prevented by residual plasma. Washed PC removes most of the plasma, so it can effectively prevent ATR and FNHTR. The recent development of platelet additive solution [M-sol, bicarbonate Ringer's solution supplemented with acid-citrate-dextrose formula A (BRS-A)] in Japan has enabled the maintenance of the quality of platelets for long periods. The clinical use of washed PC in Japan has therefore progressed. Washed PC with M-sol or BRS-A for pediatric patients can effectively prevent TARs without diminishing the transfusion effect. The supply of washed PC has begun from the Japanese Red Cross Society, and it has become possible to use washed PC at all medical institutions in Japan.

Effects and Side Effects of Platelet Transfusion

Aside from their canonical role in hemostasis, it is increasingly recognized that platelets have inflammatory functions and can regulate both adaptive and innate immune responses. The main topic this review aims to cover is the proinflammatory effects and side effects of platelet transfusion. Platelets prepared for transfusion are subject to stress injury upon collection, preparation, and storage. With these types of stress, they undergo morphologic, metabolic, and functional modulations which are likely to induce platelet activation and the release of biological response modifiers (BRMs). As a consequence, platelet concentrates (PCs) accumulate BRMs during processing and storage, and these BRMs are ultimately transfused alongside platelets. It has been shown that BRMs present in PCs can induce immune responses and posttransfusion reactions in the transfusion recipient. Several recent reports within the transfusion literature have investigated the concept of platelets as immune cells. Nevertheless, current and future investigations will face the challenge of encompassing the immunological role of platelets in the scope of transfusion.

Human platelets labeled at two discrete biotin densities are functional in vitro and are detected in vivo in the murine circulation: A promising approach to monitor platelet survival in vivo in clinical research

BACKGROUND

The production of platelet concentrates (PCs) is evolving, and their survival capacity needs in vivo evaluation. This requires that the transfused platelets (PLTs) be distinguished from those of the recipient. Labeling at various biotin (Bio) densities allows one to concurrently trace multiple PLT populations, as reported for red blood cells.

STUDY DESIGN AND METHODS

A method is described to label human PLTs at two densities of Bio for future clinical trials. Injectable-grade PLTs were prepared in a sterile environment, using injectable-grade buffers and good manufacturing practices (GMP)-grade Sulfo-NHS-Biotin. Sulfo-NHS-Biotin concentrations were chosen to maintain PLT integrity and avoid potential alloimmunization while enabling the detection of circulating BioPLTs. The impact of biotinylation on human PLT recirculation was evaluated in vivo in a severe immunodeficient mouse model using ex vivo flow cytometry.

RESULTS

BioPLTs labeled with 1.2 or 10 μg/ml Sulfo-NHS-Biotin displayed normal ultrastructure and retained aggregation and secretion capacity and normal expression of the main surface glycoproteins. The procedure avoided detrimental PLT activation or apoptosis signals. Transfused human BioPLT populations could be distinguished from one another and from unlabeled circulating mouse PLTs, and their survival was comparable to that of unlabeled human PLTs in the mouse model.

CONCLUSIONS

Provided low Sulfo-NHS-Biotin concentrations (<10 μg/ml) are used, injectable-grade BioPLTs comply with safety regulations, conserve PLT integrity, and permit accurate in vivo detection. This alternative to radioisotopes, which allows one to follow different PLT populations in the same recipient, should be valuable when assessing new PC preparations and monitoring PLT survival in clinical research.

Antioxidant prevents clearance of hemostatically competent platelets after long-term cold storage

BACKGROUND

Cold storage of platelets (PLTs) has the potential advantage of prolonging storage time while reducing posttransfusion infection given the decreased likelihood of bacterial outgrowth during storage and possibly beneficial effects in treating bleeding patients. However, cold storage reduces PLT survival through the induction of complex storage lesions, which are more accentuated when storage is prolonged.

STUDY DESIGN AND METHODS

Whole blood-derived PLT-rich plasma concentrates from seven PLT pools (n = 5 donors per pool). PLT additive solution was added (67%/33% plasma) and the product was split into 50-mL bags. Split units were stored in the presence or absence of 1 mM of N-acetylcysteine (NAC) under agitation for up to 14 days at room temperature or in the cold and were analyzed for PLT activation, fibrinogen-dependent spreading, microparticle formation, mitochondrial respiratory activity, reactive oxygen species (ROS) generation, as well as in vivo survival and bleeding time correction in immunodeficient mice.

RESULTS

Cold storage of PLTs for 7 days or longer induces significant PLT activation, cytoskeletal damage, impaired fibrinogen spreading, enhances mitochondrial metabolic decoupling and ROS generation, and increases macrophage-dependent phagocytosis and macrophage-independent clearance. Addition of NAC prevents PLT clearance and allows a correction of the prolonged bleeding time in thrombocytopenic, aspirin-treated, immunodeficient mice.

CONCLUSIONS

Long-term cold storage induces mitochondrial uncoupling and increased proton leak and ROS generation. The resulting ROS is a crucial contributor to the increased macrophage-dependent and -independent clearance of functional PLTs and can be prevented by the antioxidant NAC in a magnesium-containing additive solution.

Analysis of the mechanism of damage produced by thiazole orange photoinactivation in apheresis platelets

BACKGROUND

Pathogen Reduction Technologies (PRTs) are broad spectrum nucleic acid replication-blocking antimicrobial treatments designed to mitigate risk of infection from blood product transfusions. Thiazole Orange (TO), a photosensitizing nucleic acid dye, was previously shown to photoinactivate several types of bacterial and viral pathogens in RBC suspensions without adverse effects on function. In this report we extended TO treatment to platelet concentrates (PCs) to see whether it is compatible with in vitro platelet functions also, and thus, could serve as a candidate technology for further evaluation.

MATERIAL AND METHODS

PCs were treated with TO, and an effective treatment dose for inactivation of Staphylococci was identified. Platelet function and physiology were then evaluated by various assays in vitro.

RESULTS

Phototreatment of PCs yielded significant reduction (≥4-log) in Staphylococci at TO concentrations ≥20 μM. However, treatment with TO reduced aggregation response to collagen over time, and platelets became unresponsive by 24 hours post-treatment (from >80% at 1 h to 0% at 24 h). TO treatment also significantly increased CD62P expression (<1% CD62P+ for untreated and >50% for TO treated at 1 h) and induced apoptosis in platelets (<1% Annexin V+ for untreated and >50% for TO treated at 1 h) and damaged mitochondrial DNA. A mitochondria-targeted antioxidant and reactive oxygen species (ROS) scavenger Mito-Tempo mitigated these adverse effects.

DISCUSSION

The results demonstrate that TO compromises mitochondria and perturbs internal signaling that activates platelets and triggers apoptosis. This study illustrates that protecting platelet mitochondria and its functions should be a fundamental consideration in selecting a PRT for transfusion units containing platelets, such as PCs.

Cold-Stored Platelets: Review of Studies in Humans

Although numerous reviews and editorials have been published about the biologic features of platelets exposed to cold temperature and their in vitro function, none has focused on the data from studies after transfusion in healthy human participants and patients. This may, in part, be due to the paucity of well-controlled in vivo investigations of cold-stored platelets. Although numerous studies are looking into the recovery and survival of cold-stored platelets (ie, the percentage of infused platelets maintained in circulation over time), very few assess in vivo platelet function. Another caveat is that most studies were performed in the 1960s and 1970s, at a time when platelet collection and storage were different compared to today. Despite these limitations, we believe the transfusion community can take valuable information from these studies. This review is limited to data on cold-stored platelets in plasma or additive solution and does not include data on whole blood or resuspended whole blood from components because the hemostatic properties of whole blood are likely very different (the interested reader is referred to the review article focused on the hemostatic properties of platelets stored in whole blood by van der Meer et al in this special edition of Transfusion Medicine Reviews). In this review, we report that room temperature storage consistently results in a longer in vivo platelet circulation time at the expense of bacterial growth and shorter storage duration, resulting in expiration, wastage, and regional and national shortages. Cold storage of platelets universally results in moderately reduced recovery and markedly reduced survival. We found inconsistent data about the efficacy of cold-stored platelets likely due to study design differences. The analysis of the available data suggests that there is a short-lasting hemostatic effect of cold-stored platelets. Storage time or choice of anticoagulant did not have a clear effect on platelet efficacy after cold storage. In summary, more data and clinical trials are needed to better understand the effect of cold-stored platelets after transfusion into humans.

What about Platelet Function in Platelet Concentrates?

The characterization of platelet concentrates (PCs) in transfusion medicine has been performed with different analytical methods and platelet lesions (from biochemistry to cell biology) have been documented. In routine quality assessment and validation of manufacturing processes of PCs for transfusion purposes, only basic parameters are monitored and the platelet functions are not included. However, PCs undergo several manipulations during the processing and the basic parameters do not provide sensitive analyses to properly picture out the impact of the blood component preparation and storage on platelets. To improve the transfusion supply chain and the platelet functionalities, additional parameters should be used. The present short review will focus on the different techniques to monitor ex vivo platelet lesions from phenotype characterization to advanced omic analyses. Then, the opportunities to use these methods in quality control, process validation, development, and research will be discussed. Functional markers should be considered because they would be an advantage for the future developments in transfusion medicine.

Platelet storage and functional integrity

Platelet transfusion is a topic of common interest for many specialists involved in patient care, from laboratory staff to clinical physicians. Various aspects make this type of transfusion different from those of other blood components. In this review, the challenges in platelet transfusion practice that are relevant for laboratory colleagues will be discussed, highlighting how the biochemical and structural characteristics of these blood elements directly affect their function and consequently the clinical outcome. More than 1,300 platelet concentrates are transfused in Germany every day, and several types are offered by their respective manufacturers. We describe the technological advances in platelet concentrate production, with a focus on how the storage conditions of platelets can be improved. Laboratory quality assessment procedures for a safe transfusion are discussed in detail. For this purpose, we will refer to the Hemotherapy Directives (Richtlinie Hämotherapie) of the German Medical Association.

Protective effect of L-carnitine on platelet apoptosis during storage of platelet concentrate

BACKGROUND

Platelet apoptosis is considered as one of the important factors involved in platelet storage lesion (PSL) and affect the quality of platelets during storage. The beneficial effect of L-carnitine (LC) on platelet apoptosis during platelet concentrates (PCs) storage has not been fully investigated. The aim of this study was to evaluate the effects of LC on platelets of PC regarding their apoptosis markers during storage.

METHODS

Ten PCs from healthy donors were investigated in this study. PCs were prepared by platelet rich plasma (PRP) method and stored at 22±2°C with gentle agitation during storage. The effects of LC (15mM) on the platelet apoptosis were assessed by analyzing different indicative presence or absence of LC. Sampling was performed to evaluate apoptosis markers during platelet storage.

RESULTS

The results indicated significantly higher mitochondrial membrane potential for LC-treated platelets than the untreated on the days 2 and 5 of storage (P_day2=0.001, P_day5=0.001). Phosphatidylserine (PS) exposure significantly increased on the untreated compared with LC-treated platelets on the second and third days of storage (P_day2=0.014, P_day3=0.012). Also, active caspase 3 was lower in the LC- treated platelets than the control group on the day 5 of storage (P_day5=0.004). Cytosolic cytochrome C was so significantly lower in LC-treated compared to the untreated platelets during storage time (P_day2=0.002, P_day3=0.001, Pday5=0.001).

CONCLUSION

The results of this study indicate that the use of LC as an additive solution in platelets may be useful to reduce PSL by decreasing platelet apoptosis via mitochondrial pathway and increase platelet quality during storage.

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.

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.

Towards the understanding of the UV light, riboflavin and additive solution contributions to the in vitro lesions observed in Mirasol®-treated platelets

OBJECTIVES

Pathogen reduction technologies are implemented to increase the safety of blood products. We previously showed that the UVB alone significantly contributes to the storage lesions observed in platelets treated with riboflavin/UVB using a home-made illuminator. The present study aims at confirming these observations using the commercial Mirasol® technology.

METHODS

A three-arm study (untreated, UV-, Mirasol®-treated platelets) was conducted to investigate the platelet storage lesions throughout storage (n=4). A two-arm study was then designed to compare Intersol and T-PAS+ additive solutions (n=3). Phenotype and functional platelet characteristics were assessed using flow cytometry, aggregometry, antioxidant assays and metabolic parameters.

RESULTS

Mirasol®-treated platelets exhibit enhanced storage lesions compared to controls (increase of activation markers and glycolysis rate, lower hypotonic shock and double-agonist activation responses, and decrease of total antioxidant capacity). Here, we also confirmed that the UV radiation alone is causing platelet lesions. Riboflavin tends to have an intracellular protective role while it decreases the extracellular antioxidant defenses. Furthermore, benefits of platelet additive solutions containing potassium and magnesium were confirmed as it reduces the extent of storage lesions.

CONCLUSIONS

The photosensitizer, UV illumination and composition of the platelet additive solutions are key parameters influencing the platelet storage lesion. The clinical relevance of these findings is not fully understood and recent published clinical studies could not show increase in bleeding in patients receiving Mirasol-treated platelets. New developments in storage solutions might help to improve storage conditions of PRT-treated platelets and should be prioritised as research subject in the future.

New Approaches and Trials in Pediatric Transfusion Medicine

Blood transfusions are frequently lifesaving, but there is growing awareness of their associated infectious and noninfectious adverse events. Patient blood management advocates for judicious use of transfusions and considerations of alternatives to correct anemia or achieve hemostasis. Several transfusion practices, either already implemented or under investigation, aim to further improve the safety of transfusions. An enduring challenge in pediatric and neonatal transfusion practice is that studies typically focus on adults, and findings are extrapolated to younger patients. This article aims to summarize some of the newer developments in transfusion medicine with a focus on the neonatal and pediatric population.