In vitroassessment of buffy-coat derived platelet components suspended in SSP+ treated with the INTERCEPT Blood system

Biochemical and functional characteristics of stored (double-dose) buffy-coat platelet concentrates treated with amotosalen and a prototype UVA light-emitting diode illuminator

BACKGROUND

Pathogen reduction of platelet concentrates (PCs) using amotosalen and broad-spectrum UVA illumination contributes to the safety of platelet transfusion by reducing the risk of transfusion-transmitted infections. We evaluated the in vitro quality of stored buffy-coat (BC) PCs treated with amotosalen and a prototype light-emitting diode (LED) illuminator.

METHODS

Double-dose BC-PCs collected into PAS-III/plasma or SSP+ /plasma (55/45%) were treated with amotosalen in combination with either conventional UVA lamps (INT100 Illuminator 320-400 nm) or LED illuminators at 350 nm. Platelet quality and function were evaluated over 7 days.

RESULTS

Platelet counts were conserved during storage in all groups, as was platelet swirling without appearance of macroscopic aggregates. Integrin αIIbβ3 and glycoprotein (GP) VI expression remained stable, whereas GPIbα and GPV declined similarly in all groups. UV lamp- and LED-treated PCs displayed similar glucose consumption, lactate generation, and pH variation. Comparable spontaneous and residual P-selectin and phosphatidylserine exposure, activated αIIbβ3 exposure, mitochondrial membrane potential, lactate dehydrogenase release, and adhesive properties under flow conditions were observed during storage. The use of SSP+ /plasma compared with PAS-III/plasma better preserved most of these parameters, especially during late storage, irrespective of the type of illuminator.

CONCLUSION

Replacing the UVA lamp for photochemical treatment by LED illuminators had no impact on platelet metabolism, spontaneous activation, apoptosis or viability, or on the in vitro function of BC-PCs stored for 7 days in SSP+ or PAS-III/plasma. These findings support improved procedures for the pathogen reduction and storage of PCs, to ensure transfusion safety and retention of platelet functional properties.

Pathogen Reduction Technologies and Their Impact on Metabolic and Functional Properties of Treated Platelet Concentrates: A Systematic Review

Pathogen reduction technologies (PRTs) such as Mirasol and Intercept were developed to eliminate transfusion-transmitted infections. The impact of PRTs on platelet function during the storage period, their effect on platelet storage lesions, and the optimal storage duration following PRTs have not been clearly defined. The aim of this study was to systematically review the existing literature and investigate the impact of PRTs on functional alterations of PRT-treated platelets during the storage period. The authors identified 68 studies suitable to be included in this review. Despite the high heterogeneity in the literature, the results of the published studies indicate that PRTs may increase platelet metabolic activity, accelerate cell apoptosis, and enhance platelet activation, which can subsequently lead to a late exhaustion of activation potential and reduced aggregation response. However, these effects have a minor impact on platelet function during the early storage period and become more prominent beyond the fifth day of the storage period. Large in vivo trials are required to evaluate the effectiveness of PRT-treated platelets during the storage period and investigate whether their storage can be safely extended to more than 5 days, and up to the traditional 7-day storage period.

Protein Concentrations in Stored Pooled Platelet Concentrates Treated with Pathogen Inactivation by Amotosalen Plus Ultraviolet a Illumination

Platelet granules contain a diverse group of proteins. Upon activation and during storage, platelets release a number of proteins into the circulation or supernatant of stored platelet concentrate (PC). The aim of this work was to investigate the effect of pathogen inactivation (PI) on a selection of proteins released in stored platelets. Materials and Methods: PCs in platelet additive solution (PAS) were produced from whole blood donations using the buffy coat (BC) method. PCs in the treatment arm were pathogen inactivated with amotosalen and UVA, while PCs in the second arm were used as an untreated platelet control. Concentrations of 36 proteins were monitored in the PCs during storage. Results: The majority of proteins increased in concentration over the storage period. In addition, 10 of the 29 proteins that showed change had significantly different concentrations between the PI treatment and the control at one or more timepoints. A subset of six proteins displayed a PI-related drop in concentration. Conclusions: PI has limited effect on protein concentration stored PC supernatant. The protein’s changes related to PI treatment with elevated concentration implicate accelerated Platelet storage lesion (PSL); in contrast, there are potential novel benefits to PI related decrease in protein concentration that need further investigation.

In Vitro Comparative Study of Platelets Treated with Two Pathogen-Inactivation Methods to Extend Shelf Life to 7 Days

Background and Objectives: Since 2015, platelet products have been pathogen-inactivated (PI) at the Luxemburgish Red Cross (LRC) using Riboflavin and UV light (RF-PI). As the LRC should respond to hospital needs at any time, platelet production exceeds the demand, generating a discard rate of 18%. To reduce this, we consider the extension of storage time from 5 to 7 days. This study’s objective was to evaluate the in vitro 7-day platelet-storage quality, comparing two PI technologies, RF-PI and amotosalen/UVA light (AM-PI), for platelet pools from whole-blood donations (PPCs) and apheresis platelets collected from single apheresis donation (APCs). Materials and Methods: For each product type, 6 double-platelet concentrates were prepared and divided into 2 units; one was treated with RF-PI and the other by AM-PI. In vitro platelet-quality parameters were tested pre- and post-PI, at days 5 and 7. Results: Treatment and storage lesions were observed in PPCs and APCs with both PI methods. We found a higher rate of lactate increase and glucose depletion, suggesting a stronger stimulation of the glycolytic pathway, a higher Annexin V binding, and a loss of swirling in the RF-PI-treated units from day 5. The platelet loss was significantly higher in the AM-PI compared with the RF-PI units. Conclusions: Results suggest that RF-PI treatment has a higher deleterious impact on in vitro platelet quality compared to AM-PI, but we observed higher loss of platelets with AM-PI due to the post-illumination amotosalen adsorption step. If 7-day storage is needed, it can only be achieved with AM-PI, based on our quality criteria.

Impact of different pathogen reduction technologies on the biochemistry, function, and clinical effectiveness of platelet concentrates: An updated view during a pandemic

Standard platelet concentrates (PCs) stored at 22°C have a limited shelf life of 5 days. Because of the storage temperature, bacterial contamination of PCs can result in life‐threatening infections in transfused patients. The potential of blood components to cause infections through contaminating pathogens or transmitting blood‐borne diseases has always been a concern. The current safety practice to prevent pathogen transmission through blood transfusion starts with a stringent screening of donors and regulated testing of blood samples to ensure that known infections cannot reach transfusion products. Pathogen reduction technologies (PRTs), initially implemented to ensure the safety of plasma products, have been adapted to treat platelet products. In addition to reducing bacterial contamination, PRT applied to PCs can extend their shelf life up to 7 days, alleviating the impact of their shortage, while providing an additional safety layer against emerging blood‐borne infectious diseases. While a deleterious action of PRTs in quantitative and qualitative aspects of plasma is accepted, the impact of PRTs on the quality, function, and clinical efficacy of PCs has been under constant examination. The potential of PRTs to prevent the possibility of new emerging diseases to reach cellular blood components has been considered more hypothetical than real. In 2019, a coronavirus‐related disease (COVID‐19) became a pandemic. This episode should help when reconsidering the possibility of future blood transmissible threats. The following text intends to evaluate the impact of different PRTs on the quality, function, and clinical effectiveness of platelets within the perspective of a developing pandemic.

Comparison of the platelet activation status of single-donor platelets obtained with two different cell separator technologies

BACKGROUND

The microparticle content (MP%) of apheresis platelets-a marker of platelet activation-is influenced by donor factors and by external stressors during collection and storage. This study assessed the impact of apheresis technology and other factors on the activation status (MP%) of single-donor apheresis platelets.

STUDY DESIGN AND METHODS

Data from six US hospitals that screened platelets by measuring MP% through dynamic light scattering (ThromboLUX) were retrospectively analyzed. Relative risks (RRs) were derived from univariate and multivariable regression models, with activation rate (MP% ≥15% for plasma-stored platelets; ≥10% for platelet additive solution [PAS]-stored platelets) and MP% as outcomes. Apheresis platform (Trima Accel vs Amicus), storage medium (plasma vs PAS), pathogen reduction, storage time, and testing location were used as predictors.

RESULTS

Data were obtained from 7511 platelet units collected using Trima (from 16 suppliers, all stored in plasma, 20.0% were pathogen-reduced) and 2456 collected using Amicus (from four different collection facilities of one supplier, 65.0% plasma-stored, 35.0% PAS-stored, none pathogen-reduced). Overall, 30.0% of Trima platelets were activated compared to 45.6% of Amicus platelets (P < .0001). Multivariable analysis identified apheresis platform as significantly associated with platelet activation, with a lower activation rate for Trima than Amicus (RR: 0.641, 95% confidence interval [CI]: 0.578; 0.711, P < .0001) and a 6.901% (95% CI: 5.926; 7.876, P < .0001) absolute reduction in MP%, when adjusting for the other variables.

CONCLUSION

Trima-collected platelets were significantly less likely to be activated than Amicus-collected platelets, irrespective of the storage medium, the use of pathogen reduction, storage time, and testing site.

Quality control in veterinary blood banks: evaluation of canine platelet concentrates stored for five days

Background

Platelets undergo structural, biochemical and functional alterations when stored, and platelet storage lesions reduce platelet function and half-life after transfusion. The objective of this study was to evaluate stored canine platelet concentrates with platelet aggregation, flow cytometry and biochemistry assays. Twenty-two bags of canine platelet concentrates were obtained by the platelet-rich plasma method and were assessed on days 1, 3 and 5 after collection. Parameters such as platelet counts, residual leukocytes, platelet swirling, glucose, lactate, pH, CD62P expression (platelet activation), JC-1 (mitochondrial function) and annexin V (apoptosis and cell death) were assessed.

Results

Over the five days of storage there was a significant decrease in glucose, HCO₃, pCO₂, ATP, pH, swirling and mitochondrial function, associated with a significant increase in lactate levels and pO₂. At the end of storage pH was 5.9 ± 0.6 and lactate levels were 2.8 ± 1.2 mmol/L. Results of the quality parameters evaluated were similar to those reported in human platelets studies. The deleterious effects of storage were more pronounced in bags with higher platelet counts (> 7.49 × 10¹⁰/unit), suggesting that canine platelet concentrates should not contain an excessive number of platelets.

Conclusions

Quality parameters of canine platelets under standard storage conditions were similar to those observed in human platelets. Our results have potential to be used for the routine evaluation and quality control in veterinary blood banks.

Metabolomics study of platelet concentrates photochemically treated with amotosalen and UVA light for pathogen inactivation

BACKGROUND

The risk of bacterial contamination and the deterioration of platelet (PLT) quality limit the shelf-life of platelet concentrates (PCs). The INTERCEPT pathogen inactivation system reduces the risk of pathogen transmission by inhibiting nucleic acid replication using a combination of a photo-reactive compound and UVA illumination. The goal of this study was to investigate the effects the INTERCEPT system has on the PLT metabolome and metabolic activity.

STUDY DESIGN AND METHODS

Paired units of buffy coat-derived PCs were generated using a pool and split strategy (n = 8). The paired PCs were either treated with the INTERCEPT system or left untreated. Samples were collected on Days 1, 2, 4, and 7 of storage. Ultra-performance chromatography coupled with time-of-flight mass spectrometry was used to analyze the extra- and intracellular metabolomes. Constraint-based metabolic modeling was then used to predict the metabolic activity of the stored PLTs.

RESULTS

A relatively large number of metabolites in the extracellular environment were depleted during the processing steps of the INTERCEPT system, in particular, metabolites with hydrophobic functional groups, including acylcarnitines and lysophosphatidylcholines. In the intracellular environment, alterations in glucose and glycerophospholipid metabolism and decreased levels of 2-hydroxyglutarate were observed following the INTERCEPT treatment. Untargeted metabolomics analysis revealed residual amotosalen dimers present in the treated PCs. Systems-level analysis of PLT metabolism indicated that the INTERCEPT system does not have a significant impact on the PLT energy metabolism and nutrient utilization.

CONCLUSIONS

The INTERCEPT system significantly alters the metabolome of the stored PCs without significantly influencing PLT energy metabolism.

The impact of bilirubin ditaurate on platelet quality during storage

Bilirubin ditaurate (BRT), a conjugated bilirubin analogue, has demonstrated anti-platelet characteristics following acute ex vivo exposure. Scavenging of mitochondrial superoxide and attenuation of granule exocytosis suggested a potential benefit for including BRT for storage. With no reports of cytotoxicity following acute exposure, the impact of 35µM BRT on platelet function was investigated, in clinically suppled units, for up to seven days. Exposure to 35µM BRT significantly reduced mitochondrial membrane potential and increased glucose consumption until exhaustion after 72 hours. Platelet aggregation and activation was significantly impaired by BRT. Mitochondrial superoxide production and phosphatidylserine expression were significantly elevated following glucose exhaustion, with decreased viability observed from day five onwards. Lactate accumulation and loss of bicarbonate, support a metabolic disturbance, leading to a decline of quality following BRT inclusion. Although acute ex vivo BRT exposure reported potentially beneficial effects, translation from acute to chronic exposure failed to combat declining platelet function during storage. BRT exposure resulted in perturbations of platelet quality, with the utility of BRT during storage therefore limited. However, these are the first data of prolonged platelet exposure to analogues of conjugated bilirubin and may improve our understanding of platelet function in the context of conjugated hyperbilirubinemia.

Pathogen inactivation with amotosalen plus UVA illumination minimally impacts microRNA expression in platelets during storage under standard blood banking conditions

BACKGROUND

To reduce the risk of transfusion transmission infection, nucleic acid targeted methods have been developed to inactivate pathogens in PCs. miRNAs have been shown to play an important role in platelet function, and changes in the abundance of specific miRNAs during storage have been observed, as have perturbation effects related to pathogen inactivation (PI) methods. The aim of this work was to investigate the effects of PI on selected miRNAs during storage.

STUDY DESIGN AND METHODS

Using a pool and split strategy, 3 identical buffy coat PC units were generated from a pool of 24 whole blood donors. Each unit received a different treatment: 1) Untreated platelet control in platelet additive solution (C-PAS); 2) Amotosalen-UVA-treated platelets in PAS (PI-PAS); and 3) untreated platelets in donor plasma (U-PL). PCs were stored for 7 days under standard blood banking conditions. Standard platelet quality control (QC) parameters and 25 selected miRNAs were analyzed.

RESULTS

During the 7-day storage period, differences were found in several QC parameters relating to PI treatment and storage in plasma, but overall the three treatments were comparable. Out of 25 miRNA tested changes in regulation of 5 miRNA in PI-PAS and 3 miRNA U-PL where detected compared to C-PAS. A statistically significant difference was observed in down regulations miR-96-5p on Days 2 and 4, 61.9% and 61.8%, respectively, in the PI-PAS treatment.

CONCLUSION

Amotosalen-UVA treatment does not significantly alter the miRNA profile of platelet concentrates generated and stored using standard blood banking conditions.

Haemostatic responsiveness and release of biological response modifiers following cryopreservation of platelets treated with amotosalen and ultraviolet A light

BACKGROUND

Due to the risk of replication of contaminating pathogens, platelets have a limited storage time of 5 days, which can be prolonged to 7 days by the use of pathogen inactivation technologies. Cryopreservation (CP) may be an alternative to permit longer storage periods and increased availability. However, the preparation of platelets can result in secretion of biological response modifiers (BRM), which can cause adverse transfusion reactions in the recipient. We investigated the impact of CP on platelet function and release of BRM in untreated (conventional) and pathogen-inactivated (PI) platelet concentrates.

MATERIALS AND METHODS

Twelve buffy coat-derived platelet units were treated with amotosalen and ultraviolet A light to inactivate pathogens. Twelve untreated units were used as controls. The 24 units were cryopreserved and in vitro variables were analysed before and after CP. The in vitro variables investigated included platelet surface receptors and activation markers by flow cytometry, and coagulation time by viscoelastography. A panel of BRM, including cytokines, was investigated.

RESULTS

CP of both conventional and PI platelets resulted in a significant increase of BRM with similar increases of most of the BRM after CP of conventional and PI platelet concentrates. The increase in some of the BRM correlated significantly with shortened coagulation time, increased P-selectin expression, reduced mitochondrial transmembrane potential, and reduced capacity to respond to stimulation with ADP and collagen.

DISCUSSION

Cryopreservation of both conventional and PI platelets results in secretion of BRM. The increase in some of the BRM correlated with changes in platelet function variables and suggests that BRM release is affected, in part, in a similar way by CP as are changes in platelet function variables. PI with amotosalen and ultraviolet A light in combination with CP did not affect the release of immunomodulatory factors more than CP alone did.

Cryopreservation of UVC pathogen-inactivated platelets

BACKGROUND

Extending the platelet (PLT) shelf life and enhancing product safety may be achieved by combining cryopreservation and pathogen inactivation (PI). Although studied individually, limited investigations into combining these treatments has been performed. The aim of this study was to investigate the effect of PI treating PLTs before cryopreservation on in vitro PLT quality and function.

STUDY DESIGN AND METHODS

ABO-matched buffy coat-derived PLTs in PLT additive solution (SSP+; Macopharma) were pooled and split to form matched pairs (n = 8). One unit remained untreated and the other was treated with the THERAFLEX UV-Platelets System (UVC; Macopharma). For cryopreservation, 5% to 6% dimethyl sulfoxide was added to the PLTs, and they were frozen at -80°C. After being thawed, untreated cryopreserved PLTs (CPPs) and UVC-treated CPPs (UVC-CPPs) were resuspended in plasma. In vitro quality was assessed immediately after thawing and after 24 hours of room temperature storage.

RESULTS

UVC-CPPs had lower in vitro recovery compared to CPPs. By flow cytometry, PLTs demonstrated a similar abundance of GPIX (CD42a), GPIIb (CD41a), and GPIbα (CD42b-HIP1), while the activation of GPIIb/IIIa (PAC-1) was increased in UVC-CPPs compared to CPPs. UVC-CPPs demonstrated greater phosphatidylserine exposure (annexin V) and microparticle shedding but similar P-selectin (CD62P) abundance compared to CPPs. UVC-CPPs displayed similar functionality to CPPs when assessed using aggregometry, thromboelastography, and thrombin generation.

CONCLUSIONS

This study demonstrates the feasibility of cryopreserving UVC-PI-treated PLT products. UVC-PI treatment may increase the susceptibility of PLTs to damage caused during cryopreservation, but this is more pronounced during postthaw storage at room temperature.

The role of pathogen-reduced platelet transfusions on HLA alloimmunization in hemato-oncological patients

BACKGROUND

Platelet transfusions can induce alloimmunization against HLA antigens. The use of pathogen-reduced platelet concentrates (PCs) was suggested to reduce HLA alloimmunization and concomitant transfusion refractoriness.

METHODS

This study investigated HLA alloimmunization in available samples from 448 hemato-oncological patients who were randomized for the Pathogen Reduction Evaluation and Predictive Analytical Rating Score (PREPAReS) trial to receive either untreated or pathogen-reduced PCs (Mirasol, Terumo BCT Inc.). Anti-HLA Class I and II antibodies were determined before the first platelet transfusion and weekly thereafter using multiplex assay with standard cutoffs to detect low- as well as high-level antibodies.

RESULTS

When using the lower cutoff, in patients who were antibody negative at enrollment, 5.4% (n = 12) developed anti-HLA Class I antibodies after receiving untreated PCs, while this was significantly higher in patients receiving pathogen-reduced PCs, 12.8% (n = 29; p = 0.009, intention-to-treat [ITT] analysis). A similar but nonsignificant trend was observed in the per-protocol (PP) analysis (5.4% vs. 10.1%; p = 0.15). HLA class II antibody formation was similar between both types of PCs in the ITT analysis, while the PP analysis showed a trend toward lower immunization after receiving pathogen-reduced PCs. Multivariate analysis identified receiving pathogen-reduced platelets as an independent risk factor for HLA Class I alloimmunization (ITT: odds ratio [95% confidence interval] = 3.02 [1.42-6.51], PP: odds ratio [95% confidence interval] = 2.77 [1.00-5.40]), without affecting HLA Class II alloimmunization. When using the high cutoff value, the difference in HLA Class I alloimmunization between study arms remained significant in the ITT analysis and again was not significant in the PP analysis.

CONCLUSION

Our data clearly indicate that Mirasol pathogen inactivation does not prevent HLA Class I or II alloimmunization after platelet transfusions.

Influence of platelet preparation techniques on in vitro storage quality after psoralen-based photochemical treatment using new processing sets for triple-dose units

BACKGROUND

The INTERCEPT Blood System (IBS) for platelets (PLTs) uses a combination of psoralen and ultraviolet-A light to inactivate pathogens that may contaminate PLT concentrates (PCs). However, no data are available on the quality of IBS-treated PLTs from different apheresis and buffy-coat PC preparation platforms using the new triple storage (TS) set.

STUDY DESIGN AND METHODS

The objective of this study was to evaluate the TS set on three different preparation platforms compared with the large-volume (LV) set, as control. PLT in vitro metabolic and activation parameters were studied over 7 days.

RESULTS

Several statistical differences are observed between the two sets, particularly for pH, oxygen pressure (pO₂ ), carbonic gaz pressure (pCO₂ ), and bicarbonate. The three different preparation techniques influence PLT parameters, and the difference is statistically significant for all the studied parameters, except for pCO₂ . The TS set has the advantage of shorter compound adsorption device time, higher PLT recoveries, and less PLT activation.

CONCLUSION

Results from the measured metabolic parameters and PLT variables obtained from PCs treated by LV and TS sets indicated good PLT function preservation up to 7 days of storage. The in vitro assessment results demonstrated acceptable PLT function for transfusion.

Biomolecular Consequences of Platelet Pathogen Inactivation Methods

Pathogen inactivation (PI) for platelet concentrates (PC) is a fairly recent development in transfusion medicine that is intended to decrease infectious disease transmission from the donor to the receiving patient. Effective inactivation of viruses, bacteria and eukaryotic parasites adds a layer of safety, protecting the blood supply against customary and emerging pathogens. Three PI methods have been described for platelets. These are based on photochemical damage of nucleic acids which prevents replication of most infectious pathogens and contaminating donor leukocytes. Because platelets do not replicate, the collateral damage to platelet function is considered low to non-existing. This is disputable however because photochemistry is not specific for nucleic acids and significantly affects platelet biomolecules as well. The impact of these biomolecular changes on platelet function and hemostasis is not well understood, but is increasingly being studied. The results of these studies can help explain current and future clinical observations with PI platelets, including the impact on transfusion yield and bleeding. This review summarizes the biomolecular effects of PI treatment on platelets. We conclude that despite a comparable principle of photochemical inactivation, all three methods affect platelets in different ways. This knowledge can help blood banks and transfusion specialists to guide their choice when considering the implementation or clinical use of PI treated platelets.

Storage-Induced Platelet Apoptosis Is a Potential Risk Factor for Alloimmunization Upon Platelet Transfusion

Platelet transfusion can elicit alloimmune responses leading to alloantibody formation against donor-specific polymorphic residues, ultimately resulting in platelet transfusion refractoriness. Universal leukoreduction significantly reduced the frequency of alloimmunization after platelet transfusion, thereby showing the importance of white blood cells (WBCs) in inducing this alloresponse. It is, however, unknown if the residual risk for alloimmunization is caused by WBCs remaining after leukoreduction or if alloimmunization can be induced by platelets themselves. This study investigated the capacity of platelets to induce alloimmunization and identified potential product-related risk factors for alloimmunization. First, internalization of allogeneic platelets by dendritic cells (DCs) was demonstrated by confocal microscopy. Second, after internalization, presentation of platelet-derived peptides was shown by mass spectrometry analysis of human leukocytes antigen (HLA)-DR eluted peptides. Third, platelet-loaded DCs induced platelet-specific CD4 T cell responses. Altogether, this indicates a platelet-specific ability to induce alloimmunization. Therefore, factors enhancing platelet internalization may be identified as risk factor for alloimmunization by platelet concentrates. To investigate if storage of platelets is such a risk factor, internalization of stored platelets was compared with fresh platelets and showed enhanced internalization of stored platelets. Storage-induced apoptosis and accompanied phosphatidylserine exposure seemed to be instrumental for this. Indeed, DCs pre-incubated with apoptotic platelets induced the strongest IFN-γ production by CD4 T cells compared with pre-incubation with untreated or activated platelets. In conclusion, this study shows the capacity of platelets to induce platelet-specific alloimmune responses. Furthermore, storage-induced apoptosis of platelets is identified as potential risk factor for alloimmunization after platelet transfusions.

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

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

Double Dose Plateletpheresis: A Savior to Shrinking Donor Pool and Platelet Inventory Management

The double dose plateletpheresis (DDP) is considered to be a cost effective way of preparing platelets, owing to the low incidence of infectious complications and by also minimizing allogeneic donor exposure to the patients. We aimed at collecting DDP at our center and study its effect on donor hematological parameters, evaluate the product quality and the adverse donor reactions thereafter. Double Dose Platelet was collected from 160 eligible apheresis donors on Amicus cell separator (Fenwal, Inc. Three Corporate Drive Lake Zurich, IL, USA). The donor hematological parameters, product yield, adverse effects on the donors, collection efficiency (CE) and collection rate of the machine were noted. A total of 160 DDPs were collected. The total blood volume processed to achieve the yield of 6.0 × 1011 was 3673.5 ± 276.56 mL. The average yield achieved was 6.14 ± 0.26 × 1011. The average run time was 68.05 ± 6.25 min. Total ACD used was 408.33 ± 33.81 mL. We observed significant relation of pre-donation donor platelet count and platelet yield (p < 0.001). The CE was 78.09 ± 5.15%. There was a significant drop in the post DDP platelet count (p < 0.01) causing no adverse effect. Fourteen donors (8.75%) experienced mild citrate related adverse events. DDP does not lead to major adverse effects and post DDP hematological parameters are also within the acceptable range. It also helps to maintain apheresis platelet inventory, reduce donor exposure, reduce donor requirement and reduce the cost of the product.

In vitro properties of concentrated canine platelets stored in two additive solutions: a comparative study

BACKGROUND

Platelet transfusion therapy poses many challenges in veterinary clinical practice. Lack of readily available blood donors, short shelf-life, and inability to administer a sufficient number of platelets to meet a dog's transfusion need are the major difficulties encountered. Platelet additive solutions are already in use at American and European human blood banks, showing to be a realistic alternative. This study compares the in vitro platelet function in plasma, Composol, or SSP+ during storage for 13 days. Platelet rich plasma-platelet concentrate with 35% plasma and 65% platelet additive solutions (Composol or SSP+) and a control group (100% plasma) were prepared. Swirling, platelet count, blood gases, metabolic variables, platelet activation markers, and apoptosis markers were analyzed on days 1, 5, 9 and 13.

RESULTS

Swirling was well preserved and pH was acceptable (> 6.2) during storage for all platelet additive solutions units until day 9. SSP + units showed more stable pH and metabolic variables until day 13. Platelets in plasma showed higher glucose consumption than in Composol or in SSP+. The platelet additive solutions units showed better platelet metabolism maintenance, reduced glucose consumption and lactate production. The apoptotic markers were still low for 9 days in platelet concentrates with platelet additive solutions, suggesting the possibility to extend the shelf life with the use of SSP+ or Composol.

CONCLUSIONS

Our findings suggest that the uses of Composol and SSP+ in canine platelet concentrates are potential alternatives in veterinary blood banks.

Pathogen reduction technologies: The pros and cons for platelet transfusion

The transfusion of platelets is essential for diverse pathological conditions associated with thrombocytopenia or platelet disorders. To maintain optimal platelet quality and functions, platelets are stored as platelet concentrates (PCs) at room temperature under continuous agitation-conditions that are permissive for microbial proliferation. In order to reduce these contaminants, pathogen reduction technologies (PRTs) were developed by the pharmaceutical industry and subsequently implemented by blood banks. PRTs rely on chemically induced cross-linking and inactivation of nucleic acids. These technologies were initially introduced for the treatment of plasma and, more recently, for PCs given the absence of a nucleus in platelets. Several studies verified the effectiveness of PRTs to inactivate a broad array of bacteria, viruses, and parasites. However, the safety of PRT-treated platelets has been questioned in other studies, which focused on the impact of PRTs on platelet quality and functions. In this article, we review the literature regarding PRTs, and present the advantages and disadvantages related to their application in platelet transfusion medicine.

The role of microRNAs in platelet biology during storage

Platelet storage lesions seriously affect the quality of stored platelets, even causing them to be ineffective in vivo after transfusion. Past research have been focused on what mechanism(s) cause the formation of storage lesions. One proposed mechanism is microRNAs (miRNAs)-based molecular regulation of the platelet mRNAs that are relevant to the storage lesion. Platelets continue to translate proteins from mRNA while in a storage environment. A strong correlation exists between the platelet transcriptome and its subsequent proteomic profile, which supports de novo platelet translational capabilities. Thus, miRNA may play a crucial role in platelet biology during storage conditions. Importantly, this suggests the exciting possibility of post-transcriptional regulation of gene expression in platelets that are in storage. Given this, the differential profiling of miRNAs could be a useful tool in identifying changes to ex vivo stored platelets. Any identified miRNAs could then be considered as potential markers to assess the viability of platelet concentrates. The present review summarizes the current experimental and clinical evidence that clarifies the role miRNAs play during platelet ex vivo storage.

Peculiarities of studying the effects of pathogen reduction technologies on platelets

The transfusion of platelet concentrates (PCs) is mainly used for treatment of thrombocytopenic, trauma or surgery patients. The integrity and safety of these platelet preparations, however, is compromised by the presence of pathogens, such as viruses, bacteria and parasites. The transfer of allogeneic donor leukocytes contaminating PCs can also potentially cause adverse reactions in recipients. These considerations prompted the development and implementation of pathogen reduction technologies (PRT), which are based on chemically induced cross-linking and inactivation of nucleic acids. While the incumbent PRT may provide some protection against transfusion-transmitted infections, they are ineffective against infectious prions and may not inactivate other emerging pathogens. In addition, the safety of PRT concerning platelet viability and function has been questioned in several reports. Recent studies suggest that PRT, such as Intercept, may adversely affect the messenger RNA (mRNA) and microRNA content of platelets, as well as their functional integrity, which may compromise the clinical benefits of PRT. Here, we will discuss about the peculiarities of studying the effects of PRT on platelets, which will need to be taken into account in future studies aimed to characterize further, and polish, the rugged side of this otherwise useful and potentially important approach in transfusion medicine.

In vitro Quality of Platelets with Low Plasma Carryover Treated with Ultraviolet C Light for Pathogen Inactivation

BACKGROUND

The THERAFLEX UV-Platelets system uses shortwave ultraviolet C light (UVC, 254 nm) to inactivate pathogens in platelet components. Plasma carryover influences pathogen inactivation and platelet quality following treatment. The plasma carryover in the standard platelets produced by our institution are below the intended specification (<30%).

METHODS

A pool and split study was carried out comparing untreated and UVC-treated platelets with <30% plasma carryover (n = 10 pairs). This data was compared to components that met specifications (>30% plasma). The platelets were tested over storage for in vitro quality.

RESULTS

Platelet metabolism was accelerated following UVC treatment, as demonstrated by increased glucose consumption and lactate production. UVC treatment caused increased externalization of phosphatidylserine on platelets and microparticles, activation of the GPIIb/IIIa receptor (PAC-1 binding), and reduced hypotonic shock response. Platelet function, as measured with thrombelastogram, was not affected by UVC treatment. Components with <30% plasma were similar to those meeting specification with the exception of enhanced glycolytic metabolism.

CONCLUSION

This in vitro analysis demonstrates that treatment of platelets with <30% plasma carryover with the THERAFLEX UV-Platelets system affects some aspects of platelet metabolism and activation, although in vitro platelet function was not negatively impacted. This study also provides evidence that the treatment specifications of plasma carryover could be extended to below 30%.

Treatment of Platelet Concentrates with the Mirasol Pathogen Inactivation System Modulates Platelet Oxidative Stress and NF-κB Activation

BACKGROUND

Pathogen inactivation (PI) technologies for platelets aim to improve transfusion safety by preventing the replication of contaminating pathogens. However, as a consequence of treatment, aspects of the platelet storage lesion are amplified. Mirasol treatment also affects platelet signal transduction and apoptotic protein expression. The aim of this study was to examine the effect of Mirasol treatment on the generation of reactive oxygen species (ROS) and subsequent oxidative stress.

METHODS

Pooled platelet concentrates were prepared in platelet-additive solution (70% SSP+ / 30% plasma). ABO-matched platelets were pooled and split, and treated with the Mirasol system (TerumoBCT) or left untreated as a control. Platelet samples were tested on day 1, 5, and 7 post-collection.

RESULTS

Mirasol-treated platelets had increased formation of ROS by day 5 of storage. Oxidative damage, in the form of protein carbonylation, was higher in Mirasol-treated platelets, whilst no effect on nitrotyrosine formation or lipid peroxidation was detected. The NF-κB signaling pathway was also activated in Mirasol-treated platelets, with increased expression and phosphorylation of NF-κB p65 and IκBα.

CONCLUSION

These data demonstrate that Mirasol-treated platelets produce more ROS and display protein alterations consistent with oxidative damage.

In vitro evaluation of pathogen-inactivated buffy coat-derived platelet concentrates during storage: psoralen-based photochemical treatment step-by-step

BACKGROUND

The Intercept Blood SystemTM (Cerus) is used to inactivate pathogens in platelet concentrates (PC). The aim of this study was to elucidate the extent to which the Intercept treatment modifies the functional properties of platelets.

MATERIAL AND METHODS

A two-arm study was conducted initially to compare buffy coat-derived pathogen-inactivated PC to untreated PC (n=5) throughout storage. A four-arm study was then designed to evaluate the contribution of the compound adsorbing device (CAD) and ultraviolet (UV) illumination to the changes observed upon Intercept treatment. Intercept-treated PC, CAD-incubated PC, and UV-illuminated PC were compared to untreated PC (n=5). Functional characteristics were assessed using flow cytometry, hypotonic shock response (HSR), aggregation, adhesion assays and flow cytometry for the detection of CD62P, CD42b, GPIIb-IIIa, phosphatidylserine exposure and JC-1 aggregates.

RESULTS

Compared to fresh platelets, end-of-storage platelets exhibited greater passive activation, disruption of the mitochondrial transmembrane potential (Δψm), and phosphatidylserine exposure accompanied by a decreased capacity to respond to agonist-induced aggregation, lower HSR, and CD42b expression. The Intercept treatment resulted in significantly lower HSR and CD42b expression compared to controls on day 7, with no significant changes in CD62P, Δψm, or phosphatidylserine exposure. GPIIbIIIa expression was significantly increased in Intercept-treated platelets throughout the storage period. The agonist-induced aggregation response was highly dependent on the type and concentration of agonist used, indicating a minor effect of the Intercept treatment. The CAD and UV steps alone had a negligible effect on platelet aggregation.

DISCUSSION

The Intercept treatment moderately affects platelet function in vitro. CAD and UV illumination alone make negligible contributions to the changes in aggregation observed in Intercept-treated PC.

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.