Platelet ADP response deteriorates in synthetic storage media

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

BACKGROUND

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSION

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

Dual preparation of plasma and platelet concentrates in platelet additive solution from platelet concentrates in plasma using a novel filtration system

BACKGROUND AND OBJECTIVES

Platelet concentrates suspended in a platelet additive solution (PAS-PC) are associated with a reduction in allergic response and are suitable for preparing pathogen-inactivated PC. We aimed to develop an efficient platform for the dual preparation of PAS-PC and platelet-poor plasma.

MATERIALS AND METHODS

PAS-PC was prepared in six steps by using a hollow-fibre system based on cross-flow filtration: priming, loading PC, loading PAS, collection of filtered liquid (flow-through) and collection of platelets by washing with PAS followed by washing with air. In this study, the efficacy of platelet and plasma protein recovery and characteristics of recovered PAS-PC and flow-through plasma were analysed in detail.

RESULTS

Recoveries of platelet in PAS-PC and plasma protein in the flow-through were 95.4% ± 3.7% and 61.6% ± 5.0%, respectively. The residual plasma protein in PAS-PC was 34.1% ± 2.8%. Although the expression level of CD62P, a platelet activation marker, in recovered platelets was approximately 1.2-fold of that in original platelets, swirling patterns were well retained, and aggregation in PAS-PC was not visible. Agonist-induced aggregabilities, platelet morphology and hypotonic shock recovery were conserved. The patterns of plasma protein and lipoprotein in the flow-through were comparable with those in the original PCs. The multimeric pattern analysis of VWF remained unaltered.

CONCLUSION

We propose a highly efficient preparation system that enables the simultaneous production of PAS-PC and platelet-poor plasma. It also achieves a high recovery of functionally well-retained platelets with very low activation.

Influence of long-term proteasome inhibition on platelet responsiveness mediated by bortezomib

INTRODUCTION

Although platelets contain a full proteasome system, its role in platelet function is not completely understood yet. Since the proteasome system may be involved in time-delayed processes, platelet responsiveness was investigated after long-term, bortezomib-mediated proteasome inhibition.

MATERIALS AND METHODS

Citrate-anticoagulated whole blood was stored with 5 nM and 1 μM bortezomib for 24 h. Consecutively, aggregation was measured by light transmission in platelet-rich-plasma (PRP). Flow cytometry was performed to determine phosphorylation levels of the vasodilator-stimulated phosphoprotein (VASP), fibrinogen binding, PAC1-antibody binding and purinergic receptor expression in PRP, P2Y12 activity or glycoprotein (GP) Ib and IIb expression in whole blood. P2Y1 and P2X1 activities were assessed by calcium flux-induced fluorescence in washed platelets. Using PRP, adherent platelets on fibrinogen-, collagen- and ristocetin-coated surfaces were visualized and quantified by immunostaining.

RESULTS

Under bortezomib, VASP phosphorylation was less inducible and nitric oxide-induced inhibition of fibrinogen binding was slightly reduced. Proteasome inhibition did not tamper adenosine diphosphate-mediated aggregation or purinergic receptor expression and activity. Induced expression of activated fibrinogen receptors and fibrinogen binding were not significantly influenced by incubation with bortezomib for 24 h. Aggregation values with threshold agonist concentrations were increased under bortezomib. Despite unchanged GPIb expression, bortezomib-treated platelets showed enhanced adhesion on coated surfaces.

CONCLUSIONS

In platelets incubated for 24 h, bortezomib mediates a slight attenuation of inhibitory signaling, associated with facilitated platelet aggregation using threshold agonist concentrations and enhanced adhesion on agonist-coated surfaces.

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.

Haemostatic function measured by thromboelastography and metabolic activity of platelets treated with riboflavin and UV light

BACKGROUND

Pathogen reduction technology (PRT) may damage platelet (PLT) components. To study this, metabolic activity and haemostatic function of buffy coat (BC) PLT concentrates, with or without riboflavin and UV light PRT treatment, were compared.

MATERIAL AND METHODS

Twenty-four BC PLT concentrates, leukoreduced and diluted in additive solution, were grouped into 12 type-matched pairs, which were pooled and divided into 12 non-PRT-treated BC PLT concentrates (control units) and 12 riboflavin and UV PRT-treated BC PLT concentrates (test units). Haemostatic function and metabolic parameters were monitored by thrombelastography at days 1, 3, 7 and 14 post collection in both PLT groups.

RESULTS

Loss of PLT discoid shape, glucose consumption, lactate production, and decrease in pH were greater in the PRT-treated PLTs than in control PLTs over time (p<0.001). PLT haemostatic function evaluated by clot strength was also significantly weaker in PRT-treated PLTs compared with the excellent clot quality of control PLTs at day 7 (maximum amplitude: 41.27 vs 64.27; p<0.001), and even at day 14 (21.16 vs 60.39; p<0.001) of storage.

DISCUSSION

Pathogen reduction technology treatment accelerates and increases platelet storage lesion, resulting in glucose depletion, lactate accumulation, PLT acidification, and discoid shape loss. The clots produced by control PLTs at day 14 were still remarkably strong, whereas at day 7 PRT-treated PLTs produced weaker clots compared to the control group. Clinical trials investigating the efficacy of PRT-treated PLTs transfused at the end of the storage period (day 7), when the in vitro clot strength is weaker, are needed.

Platelet Biochemistry and Morphology after Cryopreservation

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

Platelet in vitro assays: their correspondence with their in vivo hemostatic potential

Developments during the past few years have resulted in multiple kinds of platelet products for transfusion. This involves different collection methods, containers, preservative solutions, modifications of storage temperatures and durations, and additional treatments such as pathogen reduction. Much experience has been obtained testing these processes in vitro to seek indications of in vivo effectiveness. Availability of an in vitro method that correlated with in vivo effectiveness would be extremely valuable for these different kinds of platelet products and as more innovation in platelet preparation occurs in the future. This report reviews the methods for in vitro platelet testing with a view to their in vivo implications and whether such testing could be helpful in projecting the clinical effectiveness of different platelet products.

Generation of procoagulant collagen- and thrombin-activated platelets in platelet concentrates derived from buffy coat: the role of processing, pathogen inactivation, and storage

BACKGROUND

Collagen- and thrombin-activated (COAT) platelets (PLTs), generated by dual-agonist stimulation with collagen and thrombin (THR), enhance THR generation at the site of vessel wall injury. There is evidence that higher amounts of procoagulant COAT PLTs are associated with stroke, while a decreased ability to generate them is associated with bleeding diathesis. Our aim was to study PLT functions, particularly the ability to generate COAT PLTs, in PLT concentrates (PCs) from buffy coat. Thus, we investigated the effect of processing, pathogen inactivation treatment (amotosalen-UVA), and PC storage.

STUDY DESIGN AND METHODS

Two PCs from five donors each were pooled and split in two bags; one of them was pathogen inactivated and the other one was left untreated (n = 5). Flow cytometric analyses were performed immediately after PC preparation (Day 1) and thereafter on Days 2, 5, 7, and 9 in treated and untreated PCs to measure the reactivity of PLTs (CD62P and PAC-1), the content and secretion of dense granule after stimulation with different agonists, and the percentage of COAT PLTs after dual stimulation with convulxin (agonist of the collagen receptor GPVI) and THR.

RESULTS

Preparation of PCs resulted in a significant decrease of COAT PLTs and in an impaired response to adenosine 5'-diphosphate sodium (ADP). Storage further decreased ADP response. Minor differences were observed between untreated or amotosalen-UVA-treated PCs.

CONCLUSION

Preparation of PCs from buffy coats decreased the ability to generate COAT PLTs and impaired PLT response to ADP.

Comparison of platelet function tests for the in vitro quality assessment of platelet concentrates produced under real-life conditions

Platelet quality in different platelet concentrates (PCs) has been the subject of several studies. Nonetheless, there is a lack of robust data on the correlation and agreement among platelet function tests as a prerequisite for the association of PC functionality in vitro with platelet function in vivo post PC transfusion. The purpose of our study was to correlate a larger panel of platelet function assays in PCs and to assess whether the methods agree sufficiently and can be used interchangeably. Twelve apheresis platelet concentrates in plasma (APC), 16 pooled platelet concentrates in plasma (PPC), and 12 PPC in T-sol (PPCA) were examined on days 1 and 4 after production. PCs were tested for platelet count, light transmission aggregation (LTA) induced by ADP, collagen, or TRAP; platelet ATP release induced by collagen; and spontaneous and ADP and TRAP-induced increase in CD62P and PAC1 expression measured by flow cytometry. All tests were performed in undiluted platelet-rich plasma, recalcified and mixed with an inhibitor of factor Xa and thrombin. Most platelet function parameters correlated significantly with each other, but agreement among methods was insufficient. A proper inverse correlation was observed between ADP-induced LTA and spontaneous platelet activation assessed by CD62P expression (r = -0.61, p < 0.0001). Spontaneous CD62P correlated also significantly with spontaneous PAC1 (r = 0.69, p < 0.0001) and inversely with TRAP-induced CD62P expression (r = -0.86, p < 0.0001). We found significant correlations among all flow cytometric assays measuring platelet CD62P and PAC1 expression induced by ADP or TRAP. Subsequent Bland Altman analysis revealed insufficient agreement between methods. With one exception (collagen-induced LTA compared with TRAP-induced LTA, percentage error = 16%) the limits of agreement expressed as percentage error exceeded the chosen acceptable difference of 30%. In APC, platelet count was 41% and 44% higher, respectively, than in PPC and PPCA (p < 0.0001). Spontaneous CD62P and PAC1 expression were significantly greater, and ADP-induced aggregation and agonist-induced increase in CD62P and PAC1 were significantly lower in PPCA compared to APC and PPC on day 4 of storage. ADP and TRAP-induced CD62P and PAC1 activatability fell significantly during storage between day 1 and day 4 in APC and PPCA, but not in PPC. In conclusion, different platelet function tests capture different aspects of platelet function and do not correlate and agree sufficiently to be used interchangeably.

Maximising platelet availability by delaying cold storage

BACKGROUND AND OBJECTIVES

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSION

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

Implementation of buffy-coat-derived pooled platelet concentrates for internal quality control of light transmission aggregometry: a proof of concept study

Essentials In platelet function testing, standardized internal controls (IQC) are not commercially provided. Platelet function testing was performed daily on aliquoted pooled platelet concentrates. Pooled platelet concentrates showed stability for control purposes from Monday to Friday. Pooled platelet concentrates provide the necessary steadiness to serve as IQC material.

SUMMARY

Background Standardized commercially available control material for internal quality control (IQC) of light transmission aggregometry (LTA) is still lacking. Moreover, the availability of normal blood donors to provide fresh platelets is difficult in small laboratories, where 'volunteers' may be in short supply. Objectives To evaluate the implementation of buffy-coat-derived pooled platelet concentrates (PCs) for IQC material for LTA. Methods We used buffy-coat-derived pooled PCs from the blood bank as IQC material for LTA. On each weekend one PC was prepared (> 200 mL) and aliquoted from the original storage bag on a daily basis in four baby bags (40-50 mL), which were delivered from Monday to Friday to our laboratory. The IQC measurements of at least 85 work-weeks (from Monday to Friday) were evaluated with this new IQC material. LTA was performed on a four-channel Chronolog 700 Aggregometer (Chronolog Corporation, Havertown, PA, USA) (agonists: collagen, adenosine diphosphate [ADP], arachidonic acid [AA] and thrombin receptor activator peptide-6 [TRAP-6]). Results The medians of platelet aggregation from IQC measurements with collagen, ADP and AA from Monday to Friday were 68.0-59.5, 3.0-2.0 and 51.0-50.0%, respectively, and the mean of platelet aggregation with TRAP-6 was 71.2-66.4%. Conclusions Buffy-coat-derived pooled PCs serve as a reliable and robust IQC material for LTA measurements and would be beneficial for the whole laboratory procedure and employees' safety.

Monitoring storage induced changes in the platelet proteome employing label free quantitative mass spectrometry

Shelf life of platelet concentrates is limited to 5-7 days due to loss of platelet function during storage, commonly referred to as the platelet storage lesion (PSL). To get more insight into the development of the PSL, we used label free quantitative mass spectrometry to identify changes in the platelet proteome during storage. In total 2501 proteins were accurately quantified in 3 biological replicates on at least 1 of the 7 different time-points analyzed. Significant changes in levels of 21 proteins were observed over time. Gene ontology enrichment analysis of these proteins revealed that the majority of this set was involved in platelet degranulation, secretion and regulated exocytosis. Twelve of these proteins have been shown to reside in α-granules. Upon prolonged storage (13-16 days) elevated levels of α-2-macroglobulin, glycogenin and Ig μ chain C region were identified. Taken together this study identifies novel markers for monitoring of the PSL that may potentially also be used for the detection of "young" and "old" platelets in the circulation.

Impedance aggregometric analysis of platelet function of apheresis platelet concentrates as a function of storage time

Multiple electrode (impedance) aggregometry (MEA) allows reliable monitoring of platelet function in whole blood. The aims of the present study were to implement MEA for analyzing aggregation in platelet concentrates and to correlate results with storage time and blood gas analysis (BGA). We investigated the influence of platelet counts, calcium concentrations and agonists on platelet aggregation. Samples of apheresis concentrates up to an age of 12 days were investigated by MEA and BGA. For ASPI- and TRAPtest MEA was reproducible for a platelet count of 400 per 10^-9L and a calcium concentration of 5 mmol L^-1. Platelets at the age of 2-4 days yielded steady aggregation. Platelet concentrates exceeding the storage time for transfusion showed steady aggregation up to 10 days, but a significant decline on day 12. Weak correlation was found regarding pCO₂ and MEA as well as regarding glucose concentration and MEA. Our results indicate that MEA is applicable for evaluation of aggregation in stored apheresis concentrates. Prolonged storage seems not to be prejudicial regarding platelet aggregation. Platelet concentrates showed acceptable BGA throughout storage time. Further studies are required to evaluate the application of MEA for quality controls in platelet concentrates.

Evaluation of the role of the GPIb-IX-V receptor complex in development of the platelet storage lesion

BACKGROUND AND OBJECTIVES

In mice, loss of sialic acid resulting in shedding of glycoprotein (GP) Ibα and GPV has been linked to platelet survival. The aim of this study was to determine whether loss of sialic acid and the GPIb-IX-V complex contributes to development of the platelet storage lesion (PSL) in human platelet concentrates (PCs).

MATERIALS AND METHODS

PCs (stored in plasma (with or without Mirasol treatment); PAS-C or PAS-E) were stored at room temperature. Flow cytometry was used to monitor membrane expression of the GPIb-IX-V complex, CD62P, surface glycans and PS exposure. The functionality of stored platelets was determined employing aggregometry and ristocetin-induced VWF binding.

RESULTS

Storage time of PCs in blood banks is limited to 7 days. During this time period, a minor but gradually increasing subpopulation of GPIbα-negative platelets was observed. Also, ristocetin-induced VWF binding was impaired in a small population of platelets. Mean surface expression of GPIbα and GPV remained stable until day 9, whereas CD62P expression increased; also a rapid decrease in ADP-induced aggregation was observed for PAS-C, PAS-E and Mirasol-treated PCs. Upon prolonged storage (>9 days), a slow decline in surface expression of GPIbα and GPV was observed; no major changes were observed in surface sialylation with the exception of Mirasol-treated platelets.

CONCLUSION

In a small population of stored platelets, changes in GPIbα occur from day 2 onwards. Loss of sialic acid and subsequent shedding of GPIbα and GPV is not an early event during the development of the PSL.

Role of Purinergic Receptor Expression and Function for Reduced Responsiveness to Adenosine Diphosphate in Washed Human Platelets

Background

Washing of platelets is an important procedure commonly used for experimental studies, e.g. in cardiovascular research. As a known phenomenon, responsiveness to adenosine diphosphate (ADP) is reduced in washed platelets, although underlying molecular mechanisms—potentially interfering with experimental results—have not been thoroughly studied.

Objectives

Since ADP mediates its effects via three purinergic receptors P2Y1, P2X1 and P2Y12, their surface expression and function were investigated in washed platelets and, for comparison, in platelet-rich-plasma (PRP) at different time points for up to 2 hours after preparation.

Results

In contrast to PRP, flow cytometric analysis of surface expression in washed platelets revealed an increase of all receptors during the first 60 minutes after preparation followed by a significant reduction, which points to an initial preactivation of platelets and consecutive degeneration. The activity of the P2X1 receptor (measured by selectively induced calcium flux) was substantially maintained in both PRP and washed platelets. P2Y12 function (determined by flow cytometry as platelet reactivity index) was partially reduced after platelet washing compared to PRP, but remained stable in course of ongoing storage. However, the function of the P2Y1 receptor (measured by selectively induced calcium flux) continuously declined after preparation of washed platelets.

Conclusion

In conclusion, decreasing ADP responsiveness in washed platelets is particularly caused by impaired activity of the P2Y1 receptor associated with disturbed calcium regulation, which has to be considered in the design of experimental studies addressing ADP mediated platelet function.

Riboflavin and UV light treatment of platelets: a protective effect of platelet additive solution?

BACKGROUND

Pathogen reduction technologies (PRTs) increase the safety of the blood supply, but are also associated with cell damage. Our aim was to investigate the effect of Mirasol PRT on platelet (PLT) concentrates stored in plasma and whether the use of a PLT additive solution (PAS) is able to improve in vitro quality.

STUDY DESIGN AND METHODS

Twenty-two buffy coats (BCs) were pooled and split into two equal parts. To one half, 2 units of plasma were added, and to the other, 2 units of SSP+ PAS were added. Each part was equally split in half again (to resemble pooling five BCs) and PLT concentrates were prepared. One plasma PLT concentrate was Mirasol treated, and the other served as control; similarly, one SSP+ PLT concentrate was Mirasol treated, and the other not. PLT concentrates were stored for 8 days (n = 12).

RESULTS

Mirasol PRT led to elevated lactate production in PLT concentrates in plasma, giving lower pH values throughout storage. The use of SSP+ mostly abrogated this effect, and Mirasol-treated PLT concentrates in SSP+ had only slightly higher lactate production rates and annexin A5 binding as control PLT concentrates in plasma. However, irrespective whether plasma or SSP+ was used, Mirasol PRT led to higher CD62P expression and lower hypotonic shock response (HSR) scores.

CONCLUSION

Mirasol treatment leads to higher PLT activation and lower HSR scores both when stored in plasma or SSP+. However, if Mirasol-treated PLTs are stored in SSP+, lactate metabolism and annexin A5 binding are lower, showing that PAS can partly mitigate the effect of PRT. The clinical relevance of this finding needs to be demonstrated.

Effects of pathogen reduction systems on platelet microRNAs, mRNAs, activation, and function

Pathogen reduction (PR) systems for platelets, based on chemically induced cross-linking and inactivation of nucleic acids, potentially prevent transfusion transmission of infectious agents, but can increase clinically significant bleeding in some clinical studies. Here, we documented the effects of PR systems on microRNA and mRNA levels of platelets stored in the blood bank, and assessed their impact on platelet activation and function. Unlike platelets subjected to gamma irradiation or stored in additive solution, platelets treated with Intercept (amotosalen + ultraviolet-A [UVA] light) exhibited significantly reduced levels of 6 of the 11 microRNAs, and 2 of the 3 anti-apoptotic mRNAs (Bcl-xl and Clusterin) that we monitored, compared with platelets stored in plasma. Mirasol (riboflavin + UVB light) treatment of platelets did not produce these effects. PR neither affected platelet microRNA synthesis or function nor induced cross-linking of microRNA-sized endogenous platelet RNA species. However, the reduction in the platelet microRNA levels induced by Intercept correlated with the platelet activation (p < 0.05) and an impaired platelet aggregation response to ADP (p < 0.05). These results suggest that Intercept treatment may induce platelet activation, resulting in the release of microRNAs and mRNAs from platelets. The clinical implications of this reduction in platelet nucleic acids secondary to Intercept remain to be established.

The effects of pneumatic tube transport on fresh and stored platelets in additive solution

BACKGROUND

Limited scientific work has been conducted on potential in vitro effects of transport on pneumatic tube systems on blood components, in particular platelets.

MATERIALS AND METHODS

To evaluate the possible effects of the Swisslog TranspoNet system on the cellular, metabolic, phenotypic and secreting properties of fresh and stored platelets, we set up a four-arm paired study comparing transported and non-transported platelets. Platelets were aliquoted, prepared with the OrbiSac system and suspended in 70% SSP+ (n=8). All in vitro parameters were monitored over a 7-day storage period.

RESULTS

Throughout storage, no differences were observed in glucose consumption, lactate production, pH, pCO2, ATP, hypotonic shock response reactivity, CD62P, PAC-1, platelet endothelial cell adhesion molecule-1 or CD42b. The release of sCD40L increased (p<0.01) in all units but without any significant differences between groups.

CONCLUSION

The storage stability of all platelets conveyed by the Swisslog TranspoNet system was not impaired throughout 7 days of storage. The Swisslog TranspoNet system does not, therefore, seem to be a risk for increased metabolic activity, activation or release reactions from the platelets. This lack of effect of the pneumatic tube transport system did not seem to be affected by the age of the platelets or repeated transport.

Preserved functional and biochemical characteristics of platelet components prepared with amotosalen and ultraviolet A for pathogen inactivation

BACKGROUND

Platelet concentrate (PC) functionality decreases during storage. This is referred to as the storage lesion. Pathogen inactivation may accelerate or induce lesions, potentially accounting for reduced viability. Our aim was to characterize functional and biochemical properties of platelets (PLTs) from photochemically treated buffy-coat PCs (PCT-PCs) compared to those from conventional PCs.

STUDY DESIGN AND METHODS

Four PCT-PCs and four conventional PCs were stored for 6.5 days and PLT function and proteomic profiles were examined at various time points during storage. To evaluate their intrinsic properties, samples of stored PLTs were taken, washed, and suspended in Tyrode's buffer before testing.

RESULTS

PLT counts and morphology were conserved although a slight increase in the PLT volume was observed after PCT. Glycoprotein (GP) IIbIIIa, IaIIa, and VI expression remained stable while GPIbα declined similarly in both types of PCs. A steep decrease (50%) in GPV occurred on Day 1.5 in PCT-PCs and Day 2.5 in control PCs. For both PCT- and control PCs, P-selectin expression and activated GPIIbIIIa remained low during storage. PCT- and control PCs were fully responsive to aggregation agonists up to Day 4.5 and exhibited similar perfusion functionality. Mitochondrial membrane potential and annexin A5 binding of PCT-PCs and control PCs were comparable. Two-dimensional differential in-gel electrophoresis and mass spectrometry profiles for 1882 protein spots revealed only three proteins selectively changed in PCT-PCs compared to control-PCs.

CONCLUSION

Washed treated and untreated PCs have similar functional, morphologic, and proteomic characteristics provided that PLTs are suspended in an appropriate medium during testing.

Mean platelet volume as a diagnostic marker for cardiovascular disease: drawbacks of preanalytical conditions and measuring techniques

After the first description of platelets more than a century ago, the knowledge about their origin and function grew continuously. The development of the impedance method as a completely automated assay allowed integrating mean platelet volume (MPV) measurement as a routine parameter of the complete blood count. This enabled us to focus more on the association of platelet function and size. Since then, many authors described MPV as a marker of platelet reactivity and risk factor for cardiovascular diseases. Hence, the preanalytical variability of this parameter is known from its introduction as standard laboratory value. Unfortunately no preanalytical standards have been implemented. This review shows the high variability in the literature with MPV as a risk factor for cardiovascular disease. After a brief description of the biology of platelets, we provide an in-depth survey of the measurement methods and their drawbacks. Finally, we propose a possible approach to standardization.

Evaluation of platelet function during extended storage in additive solution, prepared in a new container that allows manual buffy-coat platelet pooling and leucoreduction in the same system

BACKGROUND

A novel and practical storage container designed for manual buffy-coat pooling and leucodepletion was evaluated to assess its filtration performance and to analyse the quality of stored leucoreduced buffy-coat-derived platelet pools.

MATERIALS AND METHODS

To analyse the grifols leucored transfer PL system, blood was collected from random donors into standard triple bag systems, and fractionated using standard procedures to obtain buffy-coats. Ten leucodepleted platelet pools were prepared each from five units of buffy-coats in additive solution. Concentrates were stored for 10 days at 22 °C on an end-over-end agitator. On days 0, 5, 7, and 10 of storage, samples were tested using standard in vitro platelet parameters.

RESULTS

The use of this novel system for volume reduction and leucodepletion of buffy-coats resuspended in additive solution led to platelet pools that met the European requirements. pH was maintained well, declining from an initial value of 7.11±0.04 to 6.88±0.08 after 10 days. Parameters of cell lysis, response to a hypotonic stimulus and aggregation induced by agonists (arachidonic acid, ristocetin, collagen or thrombin receptor activating peptide) were also well-preserved. During storage, the quality profile of the platelet pools remained very similar to that previously reported in platelet concentrates in terms of metabolism, platelet activation (CD62, CD63, sCD62), expression of glycoproteins Ib and IIb/IIIa, capacity of glycoprotein IIb/IIIa to become activated upon ADP stimulation, and release of biological response modifiers (sCD40L and RANTES).

DISCUSSION

This new system allows the preparation of leucodepleted buffy-coat platelet pools in additive solution with good preservation of platelet function. The logistics of the procedure are relatively simple and it results in good-quality components, which may reduce costs and ease the process of buffy-coat pooling and leucocyte reduction in transfusion services.

In vitro effects on platelets irradiated with short-wave ultraviolet light without any additional photoactive reagent using the THERAFLEX UV-Platelets method

BACKGROUND

A novel short-wave ultraviolet light (UVC) pathogen reduction technology (THERAFLEX UV-Platelets; MacoPharma, Mouvaux, France) without the need of any additional photoactive reagent has recently been evaluated for various bacteria and virus infectivity assays. The use of UVC alone has on the one hand been shown to reduce pathogens but may, on the other hand, have some impact on the platelet (PLT) quality. The purpose of this study was to determine the potential effects on PLT quality of pathogen inactivation treatment using the novel UVC method for PLT concentrates.

STUDY DESIGN AND METHODS

Buffy-coat-derived PLTs suspended in SSP+ were irradiated with UVC light in plastic bags (MacoPharma) made of ethyl vinyl acetate, considered to be highly permeable to UVC light. The UVC-treated (test, n=8) as well as the untreated (reference, n=8) PLT units were stored in PLT storage bags composed of n-butyryl, tri n-hexyl citrate-plasticized polyvinyl chloride (MacoPharma) on a flat bed agitator for in vitro testing during 7 days of storage.

RESULTS

No significant difference in PLT counts and lactate dehydrogenase between the groups was detected. During storage, glucose decreased more and lactate increased more in the test units. Statistically significant differences were found for glucose (P<0·01) and lactate (P<0·05) on day 7. ATP levels were higher (P<0·01 from day 5) in the reference units. With exception of day 7 (P<0·01 reference vs. test), hypotonic shock response reactivity was not different between groups. Extent of shape change was lower (P<0·01), and CD62P (P<0·05 day 5) was higher in the test units. CD42b and CD41/61 showed similar trends throughout storage, without any significant difference between the units. pH was maintained at >6·8 (day 7) and swirling remained at the highest level (score = 2) for all units throughout storage.

CONCLUSION

Our results suggest that irradiation with UVC light has a slight impact on PLT in vitro quality and appears to be insignificant with regard to current in vitro standards.

Meta-analysis of the randomized controlled trials of the hemostatic efficacy and capacity of pathogen-reduced platelets

BACKGROUND

A recent independently funded randomized controlled trial (RCT; Br J Haematol 2010;150:209-17) questioned prevailing opinion concerning the hemostatic capacity of pathogen-reduced platelets (PLTs). Meta-analysis was used to calculate the effect of pathogen reduction (PR) of PLTs on hemostatic efficacy and capacity based on all available data and to investigate possible reasons for the variation in reported findings.

STUDY DESIGN AND METHODS

RCTs allocating patients to receive routine PLT transfusions with pathogen-reduced or untreated PLTs and reporting on at least one of six hemostasis endpoints were eligible for analysis. Five RCTs of hemato-oncology patients met eligibility criteria. Endpoints determined by similar criteria in all RCTs were integrated by fixed-effects methods. Endpoints determined by different criteria were integrated by random-effects methods.

RESULTS

Studies were statistically homogeneous in all analyses. Pathogen-reduced PLTs were associated with a significant (p < 0.05) reduction in 1- and 24-hour posttransfusion corrected count increments (summary mean difference, 3260; 95% confidence interval [CI], 2450-4791; and summary mean difference, 3315; 95% CI, 2027-4603) as well as a significant increase in all and in clinically significant bleeding complications (summary odds ratio [OR], 1.58; 95% CI, 1.11-2.26; and summary OR, 1.54; 95% CI, 1.11-2.13). The frequency of severe bleeding complications did not differ.

CONCLUSION

The results of the recent RCT are not inconsistent with those of the earlier studies. Introduction of PR technologies in their current stage of development would result in an increase in mild and moderate (albeit not severe) bleeding complications, which the transfusion-medicine community must explicitly tolerate to reap the benefits from PR.

Storage of buffy-coat-derived platelets in additive solution: in vitro effects on platelets of the air bubbles and foam included in the final unit

BACKGROUND

The air bubbles and foam that develop during the preparation of platelet units have traditionally been considered to interact with the platelets, causing activation and release reactions. However, there actually seems to be no data available concerning the platelet damage that may occur as a result of air bubbles and foam present in the final unit. In this in vitro study we, therefore, investigated the effects of not removing air bubbles/foam from final platelet units, by measuring in vitro parameters during a 7-day storage period.

DESIGN AND METHODS

Platelet samples (n=8) from eight pools of 12 buffy-coats were aliquoted and prepared with the OrbiSac system for storage with (test) or without (reference) air bubbles/foam included in the final units. The metabolic, cellular and activation parameters of all units, comprising approximately 30% plasma and 70% SSP+ platelet additive solution, were analysed during the 7-day storage period.

RESULTS

Differences in platelet counts and contents between the test and reference units were detected throughout storage (p<0.05 at day 5 and p<0.01 at day 7). Lactate dehydrogenase increased during storage in the test units and was significantly higher than in the reference units (p<0.01 from day 5). The hypotonic shock response was greater in the reference units (p<0.05 on day 2 and p<0.01 from day 5). The extent of shape changes was less in the test units (p<0.05 until day 5 and p<0.01 on day 7). CD62P was higher in the test units (p<0.05 on day 7). CD42b decreased in all units but was lower in the test units (p<0.01 on day 5). CD41, CD61 and PAC-1 showed no difference throughout storage between the units (p=NS). Aggregates were visible (day 7) and occurred in three of the test units. pH was maintained at >6.8 (day 7) and swirling remained at the highest level (score =2) for all units throughout storage.

CONCLUSIONS

This study shows that storage with air bubbles/foam causes considerable enhancement of disintegration of platelets. In addition, various in vitro parameters of the platelets remaining seem to be negatively affected. The results of this study suggest that platelets should be stored without air bubbles/foam, given that these cause increased disintegration of platelets.

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.

Hemostatic and signaling functions of transfused platelets

Metabolic studies have revealed a gradual impairment in platelet integrity during storage, a process termed the platelet storage lesion. Recent evidence shows that stored platelets also lose signaling responses to physiological agonists with impaired integrin activation, secretion, and aggregation of the cells. On the other hand, storage leads to a gain in platelet activation properties, such as release of microparticles and appearance of surface epitopes for their clearance by macrophages. New techniques for measuring flow-induced thrombus formation and platelet-dependent coagulation provide evidence that the hemostatic activity of platelets decreases during storage. Besides pharmacological inhibition, novel storage strategies, like metabolic suppression, should be considered to better preserve platelet functionality while limiting the expression of clearance markers. Understanding the changes that occur in association with the platelet storage lesion and the use of updated storage methods will help to generate platelets for transfusion with optimal hemostatic function and a long circulation time after transfusion.

In vitro function of buffy coat-derived platelet concentrates stored for 9 days in CompoSol, PASII or 100% plasma in three different storage bags

BACKGROUND AND OBJECTIVES

The aim of the study was to compare the in vitro quality of buffy coat-derived platelet concentrates (PC) during extended storage in plasma or additive solution in three different storage bags.

MATERIALS AND METHODS

A pooled and split design was chosen so that identical PCs were produced in either 100% plasma, 70% PASII : 30% plasma or 70% CompoSol : 30% plasma (n = 6 each). This was repeated for three different manufacturers' platelet storage bags (Fresenius, Baxter and Pall). PCs were sampled on days 1, 5, 7 and 9 of storage and tested in vitro using a variety of tests of platelet function. For each bag type, storage in PASII or Composol was compared with plasma (data taken across the entire storage period), and differences occurring with time were analysed for all storage media.

RESULTS

The pH of all PCs was > 6.8 at day 9 of storage. In vitro platelet function, as assessed by markers of platelet activation and metabolism, of PCs stored in CompoSol appeared to be similar to that of PCs stored in plasma over 9 days of storage. In contrast, PCs stored in PASII tended to have significantly higher levels of platelet activation (almost a twofold increase in % platelets positive for CD62P by day 5) and lower hypotonic shock response (approximately 40%, by day 7) compared to either PCs stored in 100% plasma or 70% CompoSol. The magnitude of the differences observed between platelet storage media appeared to be dependent on the type of platelet storage bag with the highest degree of platelet activation and lowest hypotonic shock response values being observed in Fresenius bags in combination with PASII.

CONCLUSIONS

The maintenance of platelet function in vitro during extended storage of PCs in platelet additive solutions is dependent on the combination of type of additive solution and type of platelet storage bag. For all bag types studied, storage in PASII resulted in poorer platelet function in vitro.

Evaluation of bacterial inactivation in prestorage pooled, leukoreduced, whole blood?derived platelet concentrates suspended in plasma prepared with photochemical treatment

BACKGROUND

Photochemical treatment (PCT) with amotosalen and ultraviolet light was developed to inactivate pathogens in platelet (PLT) components suspended in 35 percent plasma and 65 percent additive solution (AS). Because PLT additive solutions (ASs) are not used in the United States, this study evaluated the ability of the PCT process to inactivate low levels of bacteria in pooled whole blood-derived PLTs (RDP) suspended in 100 percent plasma.

STUDY DESIGN AND METHODS

Four replicate experiments were performed with two Gram-positive organisms, Staphylococcus epidermidis and Staphylococcus aureus, and two Gram-negative organisms, Klebsiella pneumoniae and Escherichia coli. For each experiment, 6 ABO-identical RDP units were pooled, leukoreduced before or after pooling, inoculated to approximately 1 to 10 colony-forming units per mL with plasma-resistant bacteria, and treated with the PCT process. Residual viable bacterial levels were measured before and after each step and 4 and 6 days after inoculation. For each bacterium studied, a fifth RDP pool was prepared and contaminated, but not treated. These units served as controls for bacterial growth.

RESULTS

Growth of S. epidermidis, S. aureus, and K. pneumoniae was eliminated in all four treated pools while growth continued in the control pools. There was no growth of E. coli in the treated pools and the control pool.

CONCLUSION

These pilot experiments demonstrate inactivation of bacteria in PLTs suspended in plasma, suggesting that the PCT process may address contamination in conventional RDPs. Additional experiments with a wider range of bacteria and evaluation of PLT function in 100 percent plasma will be needed before implementation.

In vitro evaluation of metabolic changes and residual platelet responsiveness in photochemical treated and gamma-irradiated single-donor platelet concentrates during long-term storage

BACKGROUND

Photochemical treatment (PCT) prevents replication of pathogens in platelet concentrates (PCs) by cross-linking nucleic acids and thus affects all cells containing DNA or RNA.

STUDY DESIGN AND METHODS

Fourteen double-dose single-donor PCs were divided into two study arms. The double-dose PCs were split in two identical units, PCT and conventional control PCs. Study Arm A consisted of seven PCT PCs with corresponding untreated controls, whereas Study Arm B consisted of seven PCT PCs with corresponding gamma-irradiated control. Metabolic changes and agonist-induced platelet (PLT) response were evaluated during storage for up to 12 days.

RESULTS

Higher rate of PLT destruction, illustrated by reduced PLT content, increased lactate dehydrogenase levels, and higher CD61+ microparticle formation rate, were observed after PCT. Generally PCT accelerated metabolic changes in PCs and reduced agonist-induced (collagen or thrombin receptor activator peptide [TRAP]) aggregation responses. Flow cytometric analysis of CD62P and CD42b (GPIbalpha) expression showed higher spontaneous PLT activation in PCT PCs from 5 days of storage. Correspondingly, a reduced capacity for up regulation of CD62P expression and down regulation of CD42b was observed in PCT PLTs after stimulation by the agonists ADP or TRAP.

CONCLUSION

Generally reduced in vitro PLT quality was observed after PCT during storage for up to 12 days, with marked reduction from 5 days of storage. Compared to conventional PCs, reduced agonist-induced aggregation and glycoprotein expression were observed after PCT during storage, corresponding to significantly higher level of spontaneous PLT activation in PCT PCs. Clinical studies of efficacy and safety of PCT PCs stored for more than 5 days are recommended.

Leukoreduced buffy coat?derived platelet concentrates photochemically treated with amotosalen HCl and ultraviolet A light stored up to 7�days: assessment of hemostatic function under flow conditions

BACKGROUND

Amotosalen plus ultraviolet A light photochemical treatment (PCT) inactivates high titers of bacteria, and other pathogens, in platelet concentrates (PCs) potentially allowing the storage of platelets (PLTs) for up to 7 days. Adhesion and aggregation of PLTs to injured vascular surfaces are critical aspects of PLT hemostatic function.

STUDY DESIGN AND METHODS

Two ABO-identical leukoreduced buffy coat-derived PCs in additive solution were mixed and divided: one-half underwent PCT (PCT-PCs) and the other was kept as a control (C-PCs); both were stored under standard conditions. The total number of paired PCs studied was nine. Samples were taken on Day 1 (before PCT) and after 5 and 7 days of storage. The adhesion and aggregation capacities were evaluated under flow conditions in a ex vivo perfusion model.

RESULTS

Compared to control, PCT resulted in a decrease in PLT count of 6.5 percent (p = 0.004) and 10.2 percent (p = 0.008) after 5 and 7 days' storage, respectively (n = 9). PLT interaction with subendothelium was mainly in form of adhesion. The surface covered by PCT PLTs on Day 1 was 26.0 +/- 4.2 percent (mean +/- SEM). On Day 5, PCT-PCs showed a covered surface of 20.9 +/- 2.2 percent, and the C-PCs, 20.6 +/- 1.6 percent. After 7 days, PCT-PCs produced a nonsignificant higher PLT deposition compared to control (27.1 +/- 2.9% vs. 21.2 +/- 2.8%, p = 0.06).

CONCLUSION

PCT of PCs and storage up to 7 days was associated with a 10.2 percent decrease in PLT count due to processing losses compared to C-PC. PLT adhesive and aggregating capacities under flow conditions of PCT-PCs were similar to C-PCs and remained well preserved for up to 7 days of storage.

Novel methodology for assessment of prophylactic platelet transfusion therapy by measuring increased thrombus formation and thrombin generation

Currently, patients developing severe thrombocytopenia during chemotherapy treatment are prophylactically transfused with platelets. We developed two platelet function tests to report the improved haemostasis in the transfused patients, which were capable of detecting aberrant responsiveness of the platelets after transfusion. First, in a whole-blood flow test, platelet adhesion and thrombus formation were determined under high-shear flow conditions. Second, the procoagulant function of platelets was assayed in platelet-rich plasma by measurement of thrombin generation. Experimental conditions were established, where flow-induced adhesion and thrombin generation test parameters increased semi-linearly with the platelet concentration, and informed on the activation properties of platelets. The transfusion effects were evaluated for 38 thrombocytopenic patients, who were transfused with platelets stored in plasma or in synthetic medium (platelet additive solution II). In most but not all patients, transfusion resulted in increased adhesion and thrombus formation, as well as in improved platelet-dependent coagulation. Taken together, the increase in platelet count after transfusion explained 57% of the overall improvement in platelet function. In acute graft-versus-host disease, thrombus formation was normal, while platelet-dependent coagulation was higher than expected. We conclude that assessment of flow-induced adhesion and thrombin generation in acquired thrombocytopenia adequately determines the improved haemostatic activity by transfused platelets.

Calcium-sensitive mitochondrial membrane potential in human platelets and intrinsic signals of cell death

The mechanisms involved in storage-induced damage in platelets are not well understood, but membrane signalling via Ca2+ ion flux may affect mitochondrial H+ gradients and metabolism and the intrinsic pathways of cell death, platelet survival and function. In this study, the effects of blood bank storage conditions, including reduced plasma concentration and interrupted agitation, were evaluated in platelets from 136 healthy donors. Mitochondrial membrane potential (DeltaPsim), an indicator of intrinsic cell death, and its sensitivity to Ca2+ ionophore A23187, were monitored using JC-1 by flow cytometry and fluorescence microscopy. Platelet survival was examined using lactate dehydrogenase release, annexin V binding and caspase-3/7 activity. Decreased plasma concentration and interrupted agitation affected DeltaPsim and caspase-3/7. Over 7 days in 30% plasma DeltaPsim showed a significant reduction (86.3 +/- 1.1% platelets with polarised mitochondria day 1; 79.9 +/- 2.1% day 5; 75.1 +/- 3.8% day 7, P = 0.01 day 1 vs. day 7). Whilst DeltaPsim in agitated platelets in 100% plasma was unchanged up to day 7, interruption of agitation was associated with a 44% reduction in the proportion of platelets with polarised mitochondria after 5 days (56 +/- 11%). The Ca2+ sensitivity of DeltaPsim changed earlier: 5 microM A23187 caused a 20-30% change in the fraction of platelets with polarised mitochondria by day 5. Ca2+ sensitivity also increased during interrupted agitation and reduced plasma concentration. DeltaPsim also correlated with indicators of platelet death, caspase-3 activity and annexin V binding (correlation coefficients of 0.8). In conclusion, changes in Ca2+-sensitive DeltaPsim are involved in the initiation of storage-induced cell death signals that influence platelet count and function in vivo.