The quality of platelets after storage for 7 days

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.

Evaluation of the procoagulant properties of a newly developed platelet modified lysate product

BACKGROUND

Platelet transfusion is associated with logistical problems with the national storage guidelines of platelets. This results in decreased function in vivo as a result of the platelet storage lesion, and complications such as allergic or hemolytic reactions and thrombosis. We evaluated a new, freshly prepared platelet modified lysate (PML) product designed to be more procoagulant than fresh and stored platelets.

METHODS

Fresh platelets were concentrated, sonicated, and centrifuged to produce PML. Samples of both washed and unwashed PML were evaluated for particle size, concentration, and activity, and then tested for clot kinetics and thrombin generation. PML samples were also stored at various temperatures for durations up to 6 months and evaluated for clot kinetics and thrombin generation throughout.

RESULTS

PML showed significantly higher concentration of platelet microparticles, increased procoagulant properties, and increased thrombin generation as compared to fresh and stored platelets. In addition, PML maintained its clot kinetics over a 6-month storage period with variable storage conditions.

CONCLUSIONS

The newly proposed PML product is more procoagulant, stable, and has additional potential applications than currently available platelet products. Further studies will be performed to assess its functions in vivo and to assess thrombotic potential.

Reactive Oxygen Species Generated by CD45-Cells Distinct from Leukocyte Population in Platelet Concentrates Is Correlated with the Expression and Release of Platelet Activation Markers during Storage

Background

Platelet stimulation with agonists is accompanied by the generation of reactive oxygen species (ROS) which promotes further platelet activation and aggregation. Considering different cell populations in platelet concentrates (PCs), this study investigates the correlation of ROS generation with the expression and release of platelet activation markers during storage.

Methods

Samples obtained from 6 PCs were subjected to flow cytometry and ELISA to evaluate the expression and shedding of platelet P-selectin or CD40L during storage. Intracellular ROS were detected in either CD45- or CD45+ population by flow cytometry using dihydrorhodamine 123, while ROS production was analyzed in both P-selectin+ or P-selectin- and CD40L+ or CD40L- populations. To further evaluate the correlation between ROS generation and release function, TRAP-stimulated platelets were also subjected to flow cytometry analysis.

Results

ROS detected in the CD45-population (leukocyte-free platelets) was significantly increased by fMLP and PMA. P-selectin- or CD40L- platelet did not show significant amount of ROS. Total ROS generation was significantly increased during platelet storage (day 0 vs. day 5; p = 0.0002) while this increasing pattern was directly correlated with the expression of P-selectin (r = 0.72; p = 0.0001) and CD40L (r = 0.69; p = 0.0001). ROS generations were significantly correlated with ectodomain shedding of these pro-inflammatory molecules.

Conclusion

Our data confirmed increasing levels of intracellular ROS generation in both platelets (CD45-) and platelet-leukocyte aggregates (CD45+) during PC storage. The amount of detected ROS is directly correlated with platelet activation and release in each population while platelet-leukocyte aggregates generate higher levels of ROS than single platelets.

Big data modeling to predict platelet usage and minimize wastage in a tertiary care system

In modern hospital systems where complicated, severely ill patient populations are the norm, there is currently no reliable way to forecast the use of perishable medical resources to enable a smart and economic way to deliver optimal patient care. We here demonstrate a statistical model using hospital patient data to quantitatively forecast, days in advance, the need for platelet transfusions. This approach can be leveraged to significantly decrease platelet wastage, and, if adopted nationwide, would save approximately 80 million dollars per year. We believe our approach can be generalized to all other aspects of patient care involving timely delivery of perishable medical resources.

Maintaining a robust blood product supply is an essential requirement to guarantee optimal patient care in modern health care systems. However, daily blood product use is difficult to anticipate. Platelet products are the most variable in daily usage, have short shelf lives, and are also the most expensive to produce, test, and store. Due to the combination of absolute need, uncertain daily demand, and short shelf life, platelet products are frequently wasted due to expiration. Our aim is to build and validate a statistical model to forecast future platelet demand and thereby reduce wastage. We have investigated platelet usage patterns at our institution, and specifically interrogated the relationship between platelet usage and aggregated hospital-wide patient data over a recent consecutive 29-mo period. Using a convex statistical formulation, we have found that platelet usage is highly dependent on weekday/weekend pattern, number of patients with various abnormal complete blood count measurements, and location-specific hospital census data. We incorporated these relationships in a mathematical model to guide collection and ordering strategy. This model minimizes waste due to expiration while avoiding shortages; the number of remaining platelet units at the end of any day stays above 10 in our model during the same period. Compared with historical expiration rates during the same period, our model reduces the expiration rate from 10.5 to 3.2%. Extrapolating our results to the ∼2 million units of platelets transfused annually within the United States, if implemented successfully, our model can potentially save ∼80 million dollars in health care costs.

Duration of platelet storage and outcomes of critically ill patients

BACKGROUND

The storage duration of platelet (PLT) units is limited to 5 to 7 days. This study investigates whether PLT storage duration is associated with patient outcomes in critically ill patients.

STUDY DESIGN AND METHODS

This study was a retrospective analysis of critically ill patients admitted to the intensive care unit (ICU) of two hospitals in Australia who received one or more PLT transfusions from 2008 to 2014. Storage duration was approached in several different ways. Outcome variables were hospital mortality and ICU-acquired infection. Associations between PLT storage duration and outcomes were evaluated using multiple logistic regression and also by Cox regression.

RESULTS

Among 2250 patients who received one or more PLT transfusions while in the ICU, the storage duration of PLTs was available for 64% of patients (1430). In-hospital mortality was 22.1% and ICU infection rate 7.2%. When comparing patients who received PLTs of a maximum storage duration of not more than 3, 4, or 5 days, there were no significant differences in baseline characteristics. After confounders were adjusted for, the storage duration of PLTs was not independently associated with mortality (4 days vs. ≤3 days, odds ratio [OR] 0.88, 95% confidence interval [CI] 0.59-1.30; 5 days vs. ≤3 days, OR 0.97, 95% CI 0.68-1.37) or infection (4 days vs. ≤3 days, OR 0.71, 95% CI 0.39-1.29; 5 days vs. ≤3 days, OR 1.11, 95% CI 0.67-1.83). Similar results were obtained regardless of how storage duration of PLTs was approached.

CONCLUSIONS

In this large observational study in a heterogeneous ICU population, storage duration of PLTs was not associated with an increased risk of mortality or infection.

Responsiveness of platelets during storage studied with flow cytometry--formation of platelet subpopulations and LAMP-1 as new markers for the platelet storage lesion

BACKGROUND AND OBJECTIVES

Storage lesions may prevent transfused platelets to respond to agonists and arrest bleeding. The aim of this study was to evaluate and quantify the capacity of platelet activation during storage using flow cytometry and new markers of platelet activation.

MATERIALS AND METHODS

Activation responses of platelets prepared by apheresis were measured on days 1, 5, 7 and 12. In addition, comparisons were made for platelet concentrates stored until swirling was affected. Lysosome-associated membrane protein-1 (LAMP-1), P-selectin and phosphatidylserine (PS) exposure were assessed by flow cytometry on platelets in different subpopulations in resting state or following stimulation with platelet agonists (cross-linked collagen-related peptide (CRP-XL), PAR1- and PAR4-activating peptides).

RESULTS

The ability to form subpopulations upon activation was significantly decreased already at day 5 for some agonist combinations. The agonist-induced exposure of PS and LAMP-1 also gradually decreased with time. Spontaneous exposure of P-selectin and PS increased with time, while spontaneous LAMP-1 exposure was unchanged. In addition, agonist-induced LAMP-1 expression clearly discriminated platelet concentrates with reduced swirling from those with retained swirling. This suggests that LAMP-1 could be a good marker to capture changes in activation capacity in stored platelets.

CONCLUSION

The platelet activation potential seen as LAMP-1 exposure and fragmentation into platelet subpopulations is potential sensitive markers for the platelet storage lesion.

Translational approaches to functional platelet production ex vivo

Platelets, which are released by megakaryocytes, play key roles in haemostasis, angiogenesis, immunity, tissue regeneration and wound healing. The scarcity of clinical cures for life threatening platelet diseases is in a large part due to limited insight into the mechanisms that control the developmental process of megakaryocytes and the mechanisms that govern the production of platelets within the bone marrow. To overcome these limitations, functional human tissue models have been developed and studied to extrapolate ex vivo outcomes for new insight on bone marrow functions in vivo. There are many challenges that these models must overcome, from faithfully mimicking the physiological composition and functions of bone marrow, to the collection of the platelets generated and validation of their viability and function for human use. The overall goal is to identify innovative instruments to study mechanisms of platelet release, diseases related to platelet production and new therapeutic targets starting from human progenitor cells.

A randomized noninferiority crossover trial of corrected count increments and bleeding in thrombocytopenic hematology patients receiving 2- to 5- versus 6- or 7-day-stored platelets

BACKGROUND

Bacterial screening offers the possibility of extending platelet (PLT) storage to Day 7. We conducted a noninferiority, crossover trial comparing PLTs stored for 6 or 7 days versus 2 to 5 days.

STUDY DESIGN AND METHODS

Stable hematology patients were allocated to receive blocks of 2- to 5- and 6- or 7-day PLTs in random order. The primary outcome was the proportion of successful transfusions during the first block, defined as a corrected count increment (CCI) of more than 4.5 at 8 to 24 hours posttransfusion.

RESULTS

Of 122 patients with an evaluable first block, 87 (71%) and 84 (69%) had successful transfusions after 2- to 5- and 6- or 7-day PLTs of mean (SD) ages of 3.8 (1.0) and 6.4 (0.5) days, respectively. Six- or 7-day PLTs were declared noninferior to 2- to 5-day PLTs since the upper confidence interval (CI) limit was less than the predefined noninferiority margin of 10% (95% CI, -14.0% to 9.1%; p = 0.766). Logistic regression analysis gave an adjusted odds ratio of 0.86 (95% CI, 0.47-1.58; p = 0.625). Mean (SD) 8- to 24-hour CCIs were 9.4 (7.9) and 7.7 (7.1) after transfusion with 2- to 5- or 6- or 7-day PLTs (95% CI, -3.31 to 0.03; p = 0.054). The proportions of days with bleeding scores of WHO Grade 2 or higher were 13% (38/297 days) and 11% (32/296 days; 95% CI, -3.2 to 7.2; p = 0.454). Median interval to next PLT transfusion (2 days) was unaffected (95% CI, -10.5 to 5.4; p = 0.531).

CONCLUSION

In hematology patients, there was no evidence that 6- or 7-day PLTs were inferior to 2- to 5-day PLTs, as measured by proportion of patients with successful transfusions, bleeding events, or interval to next transfusion.

Comparative Analysis of Various Aspects of Plateletpheresis on the Fenwal Amicus and Fresenius COM.TEC Cell Separator Instruments

OBJECTIVE

To compare the Fenwal Amicus and the Fresenius COM.TEC apheresis instruments regarding donor peripheral blood parameters, operational variables of the instruments, and quality control parameters of the product obtained.

METHODS

We performed 100 platelet collections from 100 voluntary donors using the 2 studied devices. We measured platelet count using an automated analyzer and analyzed the activation statuses using a flow cytometer.

RESULTS

The median time needed to perform the procedures was significantly longer with the COM.TEC. However, the product we obtained using the Amicus instrument showed higher degrees of platelet-activation. All products we obtained with both instruments had white blood cell counts of less than 5 × 10(6) per bag. We observed no statistical difference regarding collection efficiency and collection rates between the devices.

CONCLUSION

Both instruments collected platelets efficiently, with minimal donor discomfort. Compared with the COM.TEC instrument, the Amicus reached the platelet target yield more quickly; however, it displayed an increase in platelet activation.

Review of in vivo studies of dimethyl sulfoxide cryopreserved platelets

A literature review was conducted to assess the efficacy and safety of dimethyl sulfoxide (DMSO) cryopreserved platelets for potential military use. In vivo DMSO cryopreserved platelet studies published between 1972 and June of 2013 were reviewed. Assessed were the methods of cryopreservation, posttransfusion platelet responses, prevention or control of bleeding, and adverse events. Using the Department of Defense's preferred 6% DMSO cryopreservation method with centrifugation to remove the DMSO plasma before freezing at -65°C and no postthaw wash, mean radiolabeled platelet recoveries in 32 normal subjects were 33% ± 10% (52% ± 12% of the same subject's fresh platelet recoveries), and survivals were 7.5 ± 1.2 days (89% ± 15% of fresh platelet survivals). Using a variety of methods to freeze autologous platelets from 178 normal subjects, mean radiolabeled platelet recoveries were consistently 39% ± 9%, and survivals, 7.4 ± 1.4 days. More than 3000 cryopreserved platelet transfusions were given to 1334 patients. There were 19 hematology/oncology patient studies, and, in 9, mean 1-hour corrected count increments were 11 100 ± 3600 (range, 5700-15 800) after cryopreserved autologous platelet transfusions. In 5 studies, bleeding times improved after transfusion; in 3, there was either no improvement or a variable response. In 4 studies, there was immediate cessation of bleeding after transfusion; in 3 studies, patients being supported only with cryopreserved platelets had no bleeding. In 1 cardiopulmonary bypass study, cryopreserved platelets resulted in significantly less bleeding vs standard platelets. In 3 trauma studies, cryopreserved platelets were hemostatically effective. No significant adverse events were reported in any study. In summary, cryopreserved platelets have platelet recoveries that are about half of fresh platelets, but survivals are only minimally reduced. The platelets appear hemostatically effective and have no significant adverse events.

Platelet storage media

Present platelet storage media often designated platelet additive solutions (PAS) basically contain acetate, citrate and phosphate and recently also potassium and magnesium. However, there seems to be an increasing interest in developing PASs that can be used also after further reduction of residual plasma content below 15-20% plasma. Inclusion of glucose but also calcium and bicarbonate in such solutions have been suggested to improve platelet (PLT) storage, especially when plasma content is reduced to very low levels. Results from a limited number of studies using novel PAS alternatives have been presented during the last years, such as InterSol-G, PAS-5, M-sol, PAS-G and SAS. Most of them are experimental solutions. The combined results presented in those studies suggest that presence of glucose may be necessary during PLT storage, primarily to maintain ATP at acceptable levels. At plasma inclusion below 15-20%, the content of glucose will generally be too low to support PLT metabolism for more than a few days making glucose addition in PAS necessary. Significant effects associated with presence of calcium was observed in PLTs stored in PAS with 5% inclusion but not with 20-35% plasma inclusion, suggesting that the content of plasma could be of importance. Bicarbonate only seems to be of importance for pH regulation, primarily when plasma inclusion is reduced to about 5%. Reduction in rate of glycolysis was observed in some PAS alternatives containing potassium and magnesium but not in others. Differences in pH or in concentrations of the various compounds included in PAS may be possible explanations. Additionally, novel PAS containing glucose, calcium and bicarbonate does not seem to be associated with improved in vitro results as compared to SSP+ or CompoSol when PLTs are stored with 35% plasma inclusion. The results would then also suggest that excess of glucose in novel PAS environment may not be associated with additional positive effects on PLT metabolism. This review is based on the few publications on novel PAS available, and additional studies would be needed in the future.

Extended storage of buffy coat platelet concentrates in plasma or a platelet additive solution

BACKGROUND

Platelet (PLT) concentrates (PCs) prepared from whole blood in the United States are made using the PLT-rich plasma method. The PCs must be made within 8 hours of blood collection and stored for only 5 days. In Europe and Canada, PCs are made using the buffy coat (BC) method from whole blood held overnight at 22 °C and storage times may be up to 7 days. Our studies were designed to determine how long BC PLTs can be stored in plasma or Plasmalyte while meeting the FDA's poststorage viability criteria.

STUDY DESIGN AND METHODS

Normal subjects donated whole blood that was stored at 22 °C for 22 ± 2 hours before preparation of BC PLTs. PLTs were stored for 5 to 8 days in either plasma or Plasmalyte concentrations of 65 or 80%. Radiolabeled autologous stored versus fresh PLT recoveries and survivals were assessed as well as poststorage in vitro assays.

RESULTS

BC PLTs stored in either plasma or 65% Plasmalyte met FDA poststorage PLT recovery criteria for 7 days but survivals for only 6 days, while storage in 80% Plasmalyte gave very poor results. Both stored PLT recoveries and survivals correlated with the same donor's fresh results, but the correlation was much stronger between recoveries than survivals. In vitro measures of extent of shape change, morphology score, and pH best predicted poststorage PLT recoveries, while annexin V binding best predicted PLT survivals.

CONCLUSION

BC PLTs stored in either plasma or 65% Plasmalyte meet FDA's poststorage viability criteria for 6 days.

Immune-reactive soluble OX40 ligand, soluble CD40 ligand, and interleukin-27 are simultaneously oversecreted in platelet components associated with acute transfusion reactions

BACKGROUND

Leukoreduction of labile blood components dramatically decreases the frequency of minor, intermediate, and severe adverse events (AEs), referred to as acute transfusion reactions (ATRs), especially after transfusion of platelet components (PCs). The pathophysiology of AEs may result from accumulation of soluble, secreted, platelet (PLT) factors with proinflammatory functions stored in PCs. Thus, several cosynergizing factors associated with PLT accumulation in PCs may contribute to clinically reported ATRs with inflammatory symptoms.

STUDY DESIGN AND METHODS

We screened for 65 PLT-associated secretory products in PCs that caused ATRs and identified PLT molecules associated with ATRs and inflammation. A functional in vitro study using PC supernatants assayed on reporting immune cells was performed to indicate relevance.

RESULTS

Among 10,600 apheresis PCs, 30 caused inflammatory ATRs and contained significantly elevated levels of soluble CD40 ligand (sCD40L), interleukin (IL)-27, and soluble OX40 ligand (sOX40L). Normal PLTs secreted IL-27 and sOX40L at bioactive concentrations upon thrombin stimulation and were up regulated in association with ATRs, similar to sCD40L. Other secreted products were identified but not investigated further as their positivity was not consistent.

CONCLUSIONS

This study demonstrates the putative participation of PLT-derived sOX40L, IL-27, and sCD40L, which accumulate in PC supernatants, with inflammatory-type ATRs. Further studies are required to determine the clinical significance of these findings to forecast preventive measures whenever possible.

An inhibition of p38 mitogen activated protein kinase delays the platelet storage lesion

BACKGROUND AND OBJECTIVES

Platelets during storage undergo diverse alterations collectively known as the platelet storage lesion, including metabolic, morphological, functional and structural changes. Some changes correlate with activation of p38 mitogen activated protein kinase (p38 MAPK). Another MAPK, extracellular signal-related kinase (ERK), is involved in PLT activation. The aim of this study was to compare the properties of platelets stored in plasma in the presence or absence of p38 and ERK MAPK inhibitors.

MATERIALS AND METHODS

A single Trima apheresis platelet unit (n = 12) was aliquoted into five CLX storage bags. Two aliquots were continuously agitated with or without MAPK inhibitors. Two aliquots were subjected to 48 hours of interruption of agitation with or without MAPK inhibitors. One aliquot contained the same amount of solvent vehicle used to deliver the inhibitor. Platelets were stored at 20-24°C for 7 days and sampled on Days 1, 4, and 7 for 18 in vitro parameters.

RESULTS

Inhibition of p38 MAPK by VX-702 leads to better maintenance of all platelet in vitro storage parameters including platelet mitochondrial function. Accelerated by interruption of agitation, the platelet storage lesion of units stored with VX-702 was diminished to that of platelets stored with continuous agitation. Inhibition of ERK MAPK did not ameliorate decrements in any in vitro platelet properties.

CONCLUSION

Signaling through p38 MAPK, but not ERK, is associated with platelet deterioration during storage.

Platelet aggregation and quality control of platelet concentrates produced in the Amazon Blood Bank

Background

The study of platelet aggregation is essential to assess in vitro platelet function by different platelet activation pathways.

Objective

To assess aggregation and biochemical parameters of random platelet concentrates produced at the Fundação HEMOAM using the quality control tests defined by law.

Methods

Whole blood samples from 80 donors and the respective platelet concentrate units were tested. Platelet concentrates were tested (platelet count, aggregation and pH) on days 1, 3 and 5 of storage. Additionally a leukocyte count was done only on day 1 and microbiological tests on day 5 of storage. Collagen and adenosine diphosphate were used as inducing agonists for platelet aggregation testing.

Results

Donor whole blood had normal aggregation (aggregation with adenosine diphosphate = 67% and with collagen = 78%). The median aggregation in platelet concentrates with adenosine diphosphate was low throughout storage (18% on day 1, 7% on day 3 and 6% on day 5) and the median aggregation with collagen was normal only on day 1 and low thereafter (54.4% on day 1, 20.5% on day 3 and 9% on day 5).

Conclusion

Although the results were within the norms required by law, platelet concentrates had low aggregation rates. We suggest the inclusion of a functional assessment test for the quality control of platelet concentrates for a more effective response to platelet replacement therapy.

Extended storage of autologous apheresis platelets in plasma

BACKGROUND AND OBJECTIVES

The purpose of our studies was to determine the effects of extended platelet storage on poststorage platelet viability.

MATERIALS AND METHODS

Normal subjects were recruited to donate platelets using two different apheresis systems: either the COBE Spectra (n = 58) or the Haemonetics MCS+ (n = 84). Platelet recovery and survival data from the two systems were compared with each other and with in vitro measurements of the stored platelets.

RESULTS

There were no significant differences in either platelet recoveries or survivals between the two machines between 1 and 8 days of storage. Combining the data from both machines, platelet recoveries decreased by 2.6% and survivals by 0.3 days/storage day. In vitro assays did not predict either platelet recoveries or survivals during storage for 5-8 days. After 9 days of storage, pHs were unacceptable (≤ 6.1), suggesting that 8 days will be the longest possible storage time.

CONCLUSIONS

These data suggest that, if stored platelet bacterial contamination issues are resolved, significant extension of platelet storage times is possible.

Results of an educational program to promote the use of pooled instead of single-donor platelet transfusions

Transfusion of platelets is commonly indicated in the inpatient oncology setting. These platelets are obtained either through apheresis from a single donor or pooled from the whole blood of several donors. The amount of transfused platelets, infection risk, incidence of alloimmunization, and increases in posttransfusion platelet count are similar for these two platelet products. Although single-donor platelets are preferred over pooled platelets in some instances, single-donor platelets are often given regularly, despite a higher cost and more limited donor supply. Oncology fellows at Baylor University Medical Center at Dallas initiated an education campaign regarding the indications for pooled and single-donor platelet transfusions. The quality improvement campaign included seminars led by oncology fellows for nursing personnel and resident housestaff on the two oncology floors, as well as electronic correspondence to attending physicians. The number of pooled and single-donor platelet transfusions on the two floors was recorded for the 3 months after the education campaign (July-September 2011) and compared with the corresponding data from the previous year. Over the 3-month study period after the education campaign, the average percentage of pooled platelets transfused increased to 34.1% from 13.1% for the prior year. Given this increase, the estimated cost benefit over the 3-month study period was $45,000.

Comparison of cytokine levels and metabolic parameters of stored platelet concentrates of the Fundação Hemominas, Belo Horizonte, Brazil

Background

Prolonged storage of platelets could improve availability and logistical management and decrease wastage. Immunobiochemical methods can be used to guarantee the quality of platelets after prolonged storage.

Objective

The aim of this study was to compare storage-related changes in buffy coat-derived platelet concentrations versus platelet-rich plasmal.

Methods

Units of whole blood were drawn using a quadruple-bag blood container system. Platelet-rich plasma and buffy coat prepared from whole blood following standard methods were stored for 9 days. During this period test samples were aseptically collected for analysis on Days 1, 2, 3, 5, 7 and 9.

Results

The highest CD42b expression was greater than 95%. The percentage of CD62p was significantly lower than the CD42b expression. The pH remained fairly stable during storage. Measurement of pO₂ and pCO₂ showed that oxygen levels were significantly higher than carbon dioxide levels. There were no significant differences in bicarbonate levels, glucose consumption and lactate production between the groups. The swirling effect with platelet-rich plasma samples decreased after 5 days of storage and after 7 days of storage for buffy coat samples. There was a significant twenty-fold increase in the mean IL-1β after 5 days of storage for both groups. Slight increases in IL-6 and IL-8 levels were seen at 5 days.

Conclusion

The quality of platelet concentrates remained acceptable during 7 days of storage in respect to the swirling effect, pH and platelet activation. There were no significant differences between buffy coat-derived platelets and platelet-rich plasma in this study.

Optimization of platelet concentrate quality: application of proteomic technologies to donor management

Quality management of blood products is essential for blood banking. It is influenced by both processing and donor characteristics and assured by monitoring routine in vitro parameters to defined product specifications. However, these measures correlate poorly with the in vivo behavior of transfused platelets and cannot be used to select optimal donors. Since radiolabeled platelet recovery and survival studies are expensive and time consuming, there is an ongoing search for simpler measures that predict platelet transfusion outcomes. We performed a pilot study using semi-qualitative proteomics to assess changes in the platelet protein profile of donors with either acceptable or unacceptable in vivo radiolabeled autologous platelet recovery and survival measurements. Proteins changing during a 9-day storage period included cytoskeletal elements talin, vinculin and moesin as well as signal transduction proteins 14-3-3, RhoGDI and Rap1. Two of nine donations exhibited a decrease in these proteins and poor in vivo platelet recovery and survival whereas the remaining donors showed acceptable platelet recovery and survival and expected protein profiles. Analyses revealed a significant correlation between protein levels of Rap1 and RhoGDI during storage and platelet recovery and survival. This study provides for the first time preliminary data showing evidence of the utility of protein profiling to predict platelet transfusion quality. This article is part of a Special Issue entitled: Integrated omics.

Proteomic analysis of plasma derived from platelet buffy coats during storage at room temperature. An application of ProteoMiner™ technology

The present study was aimed at revealing new insights into the analysis of storage-related processes occurring in the supernatants of platelet concentrates (PCs) derived from pooled buffy coats suspended in whole plasma. To reduce the dynamic range of plasma protein concentrations and access low-abundance proteins, we made use of a solid-phase combinatorial peptide ligand library, known under the trade name of ProteoMiner™. Afterwards, two-dimensional electrophoresis (2-DE) was coupled with mass spectrometry (MS) to reveal changes in proteomic profiles. Several storage-induced protein alterations were identified including changes to major plasma proteins. In particular, a precursor of the secretory form of clusterin was shown to accumulate during storage of PC supernatants, together with platelet-derived tropomyosin, suggesting a progressive loss of platelet integrity. Platelet-released proteins following activation have also been detected (alpha-1-B-glycoprotein, kininogen-1, and serpin proteinase inhibitor 8). Moreover, specific protein fragments (vitronectin, plakoglobin, hornerin, and apolipoprotein A-IV) were found to be modulated upon storage, possibly indicating a time-dependent buffy-coat PC deterioration. Globally, our findings provided the disclosure of unique proteins in PC supernatants with respect to previous studies conducted in similar experimental conditions, suggesting ProteoMiner enrichment technology to be a possible complementary tool in the identification of diagnostically relevant proteins as age/quality biomarkers of therapeutic products.

Effects of storage duration and volume on the quality of leukoreduced apheresis-derived platelets: implications for pediatric transfusion medicine

BACKGROUND

Platelet (PLT) storage adversely affects PLT structure and function in vitro and is associated with decreased PLT recovery and function in vivo. In pediatric transfusion medicine, it is not uncommon for small residual volumes to remain in parent units after aliquot preparation of leukoreduced apheresis-derived PLTs (LR-ADP). However, limited data exist regarding the impact of storage on residual small-volume LR-ADP.

STUDY DESIGN AND METHODS

Standard metabolic testing was performed on residual volumes of LR-ADP after aliquot removal and PLT aggregometry using a dual agonist of ADP and collagen was performed on stored, small-volume aliquots (10-80mL) created from an in vitro model of PLT storage.

RESULTS

Seventy-seven LR-ADP underwent metabolic (n=67) or metabolic and aggregation (n=10) studies. All products maintained a pH value of more than 6.89 throughout storage. Lactate and pCO(2) increased proportionally with longer storage time. Regardless of acceptable metabolism during storage, aggregation in 10- to 20-mL aliquots was impaired by Day 4 and aliquots less than 40 mL demonstrated the most dramatic decrease in aggregation from baseline.

CONCLUSIONS

Despite maintenance of acceptable metabolic conditions, residual volumes of LR-ADP develop impaired aggregation in vitro that may adversely affect PLT survival and function in vivo. At volumes below 40mL, LR-ADP revealed reduced aggregation. As a result, it is recommended to monitor and record volumes of LR-ADP used for pediatric transfusion. Moreover, once LR-ADP attain a volume of 50mL or less on Day 4 or Day 5 of storage, consider discarding these products until their in vivo efficacy can be studied.

Extended storage of platelet-rich plasma-prepared platelet concentrates in plasma or Plasmalyte

BACKGROUND

Using bacterial detection or pathogen reduction, extended platelet (PLT) storage may be licensed if PLT viability is maintained. The Food and Drug Administration (FDA)'s poststorage PLT acceptance guidelines are that autologous stored PLT recoveries and survivals should be 66 and 58% or greater, respectively, of each donor's fresh PLT data.

STUDY DESIGN AND METHODS

Nonleukoreduced PLT concentrates were prepared from whole blood donations. Autologous PLT concentrates from 62 subjects were stored in 100% plasma (n=44) or 20% plasma/80% Plasmalyte (n=18), an acetate-based, non-glucose-containing crystalloid solution previously used for PLT storage. Fresh PLTs were obtained on the day the donor's stored PLTs were to be transfused. The fresh and stored PLTs were alternately radiolabeled with either (51) chromium or (111) indium, and in vitro measurements were performed on the stored PLTs.

RESULTS

The FDA's PLT recovery criteria were met for 7 days of plasma storage, but PLT survivals maintained viability for only 6 days. Plasmalyte-stored PLTs did not meet either acceptance criteria after 6 days of storage. After 7 days of storage, PLT recoveries averaged 43±4 and 30±4% and survivals 4.1±0.4 and 2.0±0.2 days for plasma- and Plasmalyte-stored PLTs, respectively (p=0.03 for recoveries and p<0.001 for survivals). Poststorage PLT recoveries correlated with the commonly used in vitro PLT quality measurements of hypotonic shock response and annexin V binding, while survivals correlated with extent of shape change, morphology score, and pH.

CONCLUSION

There is a progressive decrease in recoveries and survivals of plasma-stored PLTs over time. PLT viability is better maintained in plasma than Plasmalyte.

Hemostatic function of buffy coat platelets in additive solution treated with pathogen reduction technology

BACKGROUND

Pathogen reduction technologies (PRTs) may influence the hemostatic potential of stored platelet (PLT) concentrates. To investigate this, buffy coat PLTs (BCPs) stored in PLT additive solution (SSP+) with or without Mirasol PRT treatment (CaridianBCT Biotechnologies) were compared by functional hemostatic assays.

STUDY DESIGN AND METHODS

We performed in vitro comparison of PRT (PRT-BCP) and control pooled-and-split BCPs (CON-BCP) after 2, 3, 6, 7, and 8 days' storage. Hemostatic function was evaluated with thrombelastography (TEG) and impedance aggregometry (Multiplate), the latter also in a sample matrix (Day 2) with or without addition of red blood cells (RBCs), control plasma, and/or PRT-treated plasma.

RESULTS

PRT treatment of 8-day-stored BCPs influenced clot formation (TEG) minimally, with reductions in maximum clot strength (maximum amplitude, p = 0.014) but unchanged initial fibrin formation (R), clot growth rate (α), and fibrinolysis resistance. In the absence of RBCs and plasma, PRT impaired aggregation (Multiplate) in stored BCPs, with reduced aggregation against thrombin receptor activating peptide-6 (p < 0.001), collagen (p = 0.014), adenosine 5'-diphosphate (p = 0.007), and arachidonic acid (p = 0.070). Addition of RBCs and PRT-treated or untreated plasma to PRT-BCP and CON-BCP, respectively, enhanced aggregation in both groups.

CONCLUSIONS

Mirasol PRT treatment of BCPs had a minimal influence on clot formation, whereas aggregation in the absence of RBCs and plasma was significantly reduced. Addition of RBCs and plasma increased agonist-induced responses resulting in comparable aggregation between PRT-BCP and CON-BCP. The clinical relevance for PLT function in vivo of these findings will be investigated in a clinical trial.

Proteomics meets blood banking: identification of protein targets for the improvement of platelet quality

Proteomics has brought new perspectives to the fields of hematology and transfusion medicine in the last decade. The steady improvement of proteomic technology is propelling novel discoveries of molecular mechanisms by studying protein expression, post-translational modifications and protein interactions. This review article focuses on the application of proteomics to the identification of molecular mechanisms leading to the deterioration of blood platelets during storage - a critical aspect in the provision of platelet transfusion products. Several proteomic approaches have been employed to analyse changes in the platelet protein profile during storage and the obtained data now need to be translated into platelet biochemistry in order to connect the results to platelet function. Targeted biochemical applications then allow the identification of points for intervention in signal transduction pathways. Once validated and placed in a transfusion context, these data will provide further understanding of the underlying molecular mechanisms leading to platelet storage lesion. Future aspects of proteomics in blood banking will aim to make use of protein markers identified for platelet storage lesion development to monitor proteome changes when alterations such as the use of additive solutions or pathogen reduction strategies are put in place in order to improve platelet quality for patients.

The platelet storage lesion

The continuous increase in the demand for platelet transfusion has necessitated the need to establish standards for determining the quality of platelets during storage. Bacterial contamination of platelet products and deleterious changes in structure and function referred to as the platelet storage lesion (PSL), have restricted the platelet shelf life to 5 days. The PSL and platelet health variables have been well studied and documented. The precise correlation between in vitro assays and in vivo platelet recovery and survival is yet to be established. This review presents an overview of the current understanding of PSL and the novel approaches being developed to negate the storage lesion.

Differential activation and inhibition of human platelet thrombin receptors by structurally distinct α-, β- and γ-thrombin

The development of drugs to neutralize the action of thrombin has to date focused on the alpha form of the protease. It is generally agreed that inactive prothrombin is proteolytically converted to active alpha-thrombin which may be further hydrolyzed to beta- and gamma-thrombin. While all three forms of the enzyme retain catalytic activities, only alpha-thrombin is presumed to be physiologically important. The beta- and gamma-thrombin are presumed to be degradation products of no physiological significance. Our demonstration that beta- and gamma-thrombin selectively activate PAR-4 in this and a previous report (J. Biol. Chem. 276, 21173-21183, 2001) necessitates a reevaluation of how we view their physiological roles and how we approach the pharmacological regulation of their actions. Beta-thrombin, like gamma-thrombin, at nM levels selectively activates PAR-4. This was demonstrated by full retention of aggregatory activity with platelets whose PAR-1 and GP Ib receptors were inactivated. Furthermore, the beta-thrombin response was abrogated by desensitizing platelets with suboptimal levels of the thrombin receptor activating peptide for PAR-4 (TRAP-4). For beta-thrombin and gamma-thrombin to have a physiological role, it is necessary to show they can be generated under physiological conditions. We demonstrate, for the first time, that alpha-thrombin is hydrolyzed in less than 1 min by activated factor X at physiological pH, in vitro. This implies that alpha-thrombin may be rapidly converted to beta-thrombin and/or gamma-thrombin in vivo in the proper microenvironment. The differential activation of the three platelet thrombin receptors by alpha-, beta- and gamma-thrombin implies selective structural variations between these thrombin species. Structural differences are likely to account for the marked differential responses observed with the antithrombotic, hirudin, which inhibits alpha-thrombin , is a slightly weaker inhibitor of beta-thrombin and a very weak inhibitor of gamma-thrombin -induced platelet aggregations. The converse order of inhibition is observed with the physiological protease inhibitor, alpha(1)-antitrypsin. Finally, a non-traditional inhibitor, histone-1, selectively inhibits only beta- and gamma-thrombin , primarily at the receptor level of PAR-4 rather than on the thrombin molecule. Trypsin, like beta- and gamma-thrombin , activates PAR-4 and is also inactive with TRAP-4 desensitized platelets. Therefore, it was reasoned that trypsin would be more structurally similar to gamma-thrombin than to alpha-thrombin. The analysis of the crystalline structures of alpha-, gamma-thrombin and trypsin from the databases confirm that this is the case. These findings should help to elucidate structure-function relationships of the different thrombins and may aid in the development of new anti-thrombotic drugs.

Platelet storage lesion: a new understanding from a proteomic perspective

Platelet storage and availability for the purposes of transfusion are currently restricted by a markedly short shelf life of 5 to 7 days owing to an increased risk of bacterial growth and storage-related deterioration called the platelet storage lesion. Because most bacteria grow to confluence within 5 days during storage at room temperature, there is little increased risk of bacterial overgrowth with testing in place, and the only remaining issue is the quality of platelets during the extended storage. Although the manifestations of the storage lesion have been well studied using a variety of in vitro measures, the precise biochemical pathways involved in the initiation and progression of this process have yet to be identified. Proteomics has emerged as a powerful tool to identify and monitor changes during platelet storage and, in combination with biochemical and physiologic studies, facilitates the development of a sophisticated mechanistic view. In this review, we summarize recent experimental work that has led to a detailed overview of protein changes linked to platelet functions and signaling pathways, providing potential targets for inhibitors to ameliorate the storage lesion.

Measurement of phosphatidylserine exposure during storage of platelet concentrates using the novel probe lactadherin: a comparison study with annexin V

BACKGROUND

Annexin V binding to platelets (PLTs) is considered the gold standard for monitoring phosphatidylserine (PS) exposure. However, recent comparison of annexin V with the new calcium-independent PS probe lactadherin revealed that annexin V requires a certain threshold of PS exposure (2%-8%) for binding to occur. The aim of this study was to compare annexin V and lactadherin labeling of PLTs in PLT concentrates (PCs).

STUDY DESIGN AND METHODS

Optimal labeling conditions for lactadherin and annexin V were established and then compared in either resting or calcium ionophore (CI)-activated PLTs from normal whole blood. Furthermore, 40 PCs (20 apheresis-derived and 20 pooled buffy coat-derived) were stored under standard blood bank conditions and PLT activation was monitored by measuring PS exposure with annexin V and lactadherin along with CD42b, CD61, and CD62P by flow cytometry on Days 1, 3, 5, and 7.

RESULTS

Lactadherin reported a higher exposure of PS than did annexin V in normal PLTs at submaximal doses of CI. PLTs from both types of concentrate, as expected, demonstrated evidence of increased activation during storage using annexin V, lactadherin, CD42b, or CD62P. However, a significantly higher percentage of PS-positive PLTs was found with lactadherin than annexin V.

CONCLUSION

PS exposure on the surface of stored PLTs has been previously underestimated due to the wide use of annexin V. Lactadherin provides a truer reflection of the degree of PS exposure and offers a new calcium-independent approach to studying PLT activation and/or apoptosis.

[Platelet-leukocyte aggregates as a marker for platelet activation in platelet concentrates]

OBJECTIVES

Several in vitro laboratory tests to assess the quality control of platelet concentrates (PC) are available. Some of them have a good correlation with the platelet recovery index. To assess the quality control of standard PC prepared in our blood bank, we measured the blood gas and the degree of platelet activation.

MATERIALS AND METHODS

SPC were prepared by the PRP method. Fifty-five SPC (45 SPC at day one of storage and 20 SPC at day five of storage) were analysed. Blood gas (pH, PO(2), PCO(2) and bicarbonate concentration) in the SPC were measured by blood gas automate. Platelet activation profile were determined by measuring the percentage of platelet expressing the CD62p (% CD62) and the percentage of platelet-leukocyte aggregate (% PLA).

RESULTS

The pH values of all studied SPC were comprised between 7.0 and 7.6. SPC at day 1 of storage have a significantly higher pH than those at day 5 of storage (7.5+/-0.05 versus 7.3+/-0.14; p<0.001). The % CD62p were higher in SPC at day five compared to the SCP at day one without reaching a statistical significance (28.4+/-15% versus 24.3+/-9.7%, p=0.052). The percentage of PLA were higher in SPC at day one compared to SCP at day five although this difference is not statistically significant (22.2+/-7.5% versus 17.9+/-8.0%; p=0.23).

CONCLUSION

Preparation and storage procedure adopted in our centre did not significantly affect the quality SPC. Our study is the first to assess the PLA in PC. Studies assessing the PLA are warranted to appreciate the clinical impact of this parameter.

Clinica use of platelet additive solutions

Randomised clinical trial (RCT) to study the clinical efficacy and safety of new platelet products using platelet additive solutions are scarce. In this paper a number of recent RCT's is discussed. It can be the start of a development where new transfusion products enter a RCT before the product is applied in clinical practice.

Impairment of the hemostatic potential of platelets during storage as evaluated by flow cytometry, thrombin generation, and thrombelastography under conditions promoting formation of coated platelets

BACKGROUND

The increasing demand for platelet (PLT) transfusions has focused attention on appropriate use. Coated PLTs are a subpopulation of highly procoagulant PLTs formed by simultaneous stimulation by the agonist's collagen and thrombin hypothesized to drive clot formation at the site of vascular injury. Prolonged storage of PLTs may reduce their ability to support optimal hemostasis upon transfusion.

STUDY DESIGN AND METHODS

PLT concentrates (PCs) stored for 1, 4, 6, and 8 days were costimulated with thrombin and the collagen glycoprotein VI (GPVI) receptor agonist convulxin, and their ability to form coated PLTs was determined by flow cytometry. Further, a plasma-based thrombin generation assay and thrombelastography were used to evaluate the aged PCs' capacity to support thrombin generation and clot formation, respectively. The stored PCs were additionally tested by standard quality control methods.

RESULTS

PLT quality as measured by standard analyses was acceptable according to current practice. The hemostatic potential, however, was impaired with increasing storage time. The formation of coated PLTs decreased significantly from approximately 85 to 55 percent with increasing storage time (p<0.05). The velocity of clot formation was significantly increased from Day 4 (p<0.05). The velocity of thrombin generation and resistance against fibrinolysis were significantly reduced on Day 8 compared to Day 1 of storage (p<0.05).

CONCLUSION

Data in the present study suggest that storage significantly reduced the stored PLTs' ability to respond to conditions expected to exist at the site of vascular injury and that storage-induced reduction in PLT activation sensitivity correlated with a loss of hemostatic potential.

New Strategies for the Optimal Use of Platelet Transfusions

Patients with severe thrombocytopenia are presumed to be at increased risk for bleeding, and consequently it has been standard practice for the past four decades to give allogeneic platelet transfusions to severely thrombocytopenic patients as supportive care. Platelet transfusions may be given either prophylactically to reduce the risk of bleeding, in the absence of clinical hemorrhage (prophylactic transfusions), or to control active bleeding when present (therapeutic transfusions). While no one would argue with the need for platelet transfusions in the face of severe bleeding, important questions remain about what constitutes clinically significant bleeding and whether a strategy of prophylactic platelet transfusions is effective in reducing the risk of bleeding in clinically stable patients. It is now uncommon for patients undergoing intensive chemotherapy or bone marrow transplantation to die of hemorrhage, but it is open to debate as to what degree platelet transfusions have been responsible for this change in outcome, given the many other advances in other aspects of supportive care.

If a prophylactic strategy is followed, the optimal transfusion trigger or quantity of platelets to be transfused prophylactically per transfusion episode needs to be addressed in adequately powered clinical trials, but these remain highly controversial issues. This is because, until recently, there have been few high-quality, prospective, randomized clinical trial (RCT) data for evaluating the relative effects of different platelet transfusion regimens or platelet doses on clinical outcomes. Moreover, most of these RCTs have not used bleeding as the primary outcome measure. Two such studies on platelet dose have now been undertaken, the PLADO (Prophylactic PLAtelet DOse) and the SToP (Strategies for the Transfusion of Platelets) trials. Data from these RCTs are not contained in this overview, as these data have not yet been completely analyzed or submitted for peer review publication.

In addition to the above, several recent observational studies have raised the possibility that there is not a clear association between the occurrence of a major clinical bleeding episode and the platelet count in thrombocytopenic patients. Such findings have led to the questioning of the efficacy of prophylactic platelet transfusions in all clinically stable patients, and whether a policy of therapeutic transfusions used only when patients have clinical bleeding might be as effective and safe for selected patients. At least two RCTs evaluating the relative value of prophylactic versus therapeutic platelet transfusions have been initiated in thrombocytopenic patients with hematological malignancies. One such study, known as the TOPPS (Trial of Prophylactic Platelets Study) study, is currently underway in the U.K.

Translation of glycoprotein IIIa in stored blood platelets

BACKGROUND

Platelet (PLT) products have a short shelf life (5 days) owing in part to the deterioration of the quality of PLTs stored at 22 degrees C. This creates significant inventory challenges, and blood banks may suffer shortages and high wastage as a result. The precise biochemical pathways involved in the PLT storage lesion are unknown and must be understood before storage time can be extended.

STUDY DESIGN AND METHODS

Informed by previous proteomics analysis, specific PLT glycoprotein (GP) concentration and surface expression were examined by Western blot and flow cytometry. mRNA concentration was determined by Northern blot and real-time polymerase chain reaction. Protein synthesis was confirmed by [(35)S]methionine labeling.

RESULTS

Western blots of GPIIIa revealed a twofold increase in concentration on Day 7 of storage and a fourfold increase on Day 10. By flow cytometry, surface expression of the GPIIb/IIIa increased by 13.4 percent on Day 7 and 41.9 percent on Day 10. Full-length GPIIIa mRNA was present throughout this storage period and was shown to have a half-life of approximately 2.9 days. Translation of GPIIb and IIIa during storage was confirmed by [(35)S]methionine labeling.

CONCLUSION

This article confirms that PLTs are capable of synthesizing biologically relevant proteins ex vivo throughout a 10-day storage period with particularly long-lived mRNA and provides a framework through which the biochemical mechanisms involved in the translational regulation of proteins thought to be involved in the initiation or exacerbation of the PLT storage lesion can be investigated.

In vitro and in vivo effects of potassium and magnesium on storage up to 7 days of apheresis platelet concentrates in platelet additive solution

BACKGROUND AND OBJECTIVE

Prolonged storage of platelets up to 7 days provides improved availability, logistical management and decreased wastage. Beside methods of bacterial detection, addition of magnesium and potassium to the platelet storage solution (SSP+) may further improve the quality of platelets with extended storage.

MATERIALS AND METHODS

Apheresis platelets from 10 donors were divided and stored in two different platelet additive solutions (PAS) (Intersol and SSP+) for a paired comparison. A variety of in vitro platelet function and metabolic assays were performed both on day 1 and after 7 days of storage. For in vivo study, platelets were labelled with either (111)Indium or (51)Chromium after 7 days of storage and were injected into the corresponding donor. Serial blood samples were drawn for recovery and survival measurements.

RESULTS

In vitro parameters for SSP+ showed significantly reduced glycolysis (lower glucose consumption and decreased production of lactate), a higher hypotonic shock response (HSR) and the extent of shape change reactivity and a lower degree of platelet activation by means of RANTES (regulated on activation, normal, T cell-expressed, and secreted), CD62p and CD63 expression. Platelet recovery on day 7 was higher for Intersol as compared to SSP+, 65 +/- 11 vs. 53 +/- 13% (P = 0.023), and survival showed no difference 4.2 +/- 1.9 vs. 3.6 +/- 1.4 days.

CONCLUSION

In vitro characteristics of platelets stored in PAS with addition of potassium and magnesium indicated higher quality, but this could not be verified by the in vivo parameters by means of recovery and survival.