Riboflavin and amotosalen photochemical treatments of platelet concentrates reduce thrombus formation kineticsin vitro

Universal irradiation of platelets: Does irradiation affect the quality, effectiveness, and safety of platelets for transfusion?

We aimed to identify any detrimental effects on platelet quality and clinical effectiveness, of irradiated platelets compared to non-irradiated platelets for transfusion. The review was conducted in accordance with PRISMA guidelines. The protocol was prospectively registered on PROSPERO [CRD42023441930]. Our search identified 3002 references, of which we included 44 studies. Forty-one were in vitro only studies, two studies were in healthy volunteers, and one study reported clinical outcomes in thrombocytopenic patients. X-ray was used exclusively in three studies, and alongside gamma irradiation in one study. Two studies did not report the source of irradiation. The remaining 38 studies used gamma irradiation only. We assessed risk of bias (ROB) for studies reporting clinical and in vivo outcomes using ROB 2.0 (3 studies). We adapted a ROB tool designed for animal studies to assess ROB for the studies reporting in vitro outcomes (43 studies). We assessed the certainty of the evidence for the eight outcomes deemed most important to assess platelet quality and clinical effectiveness (where day 0 is the day of the blood draw). Overall, gamma irradiation has little to no effect on most markers of platelet quality and effectiveness. Where there is evidence of detriment from irradiation, differences are small in vitro, and are unlikely to affect clinical outcomes following transfusion. However, the evidence base is limited. Only half the studies could be included in any analysis. There is very limited evidence for x-ray as a source of irradiation and, given the potential benefits of using x-ray over gamma irradiation (ease of use and safety requirements), we would welcome further research comparing x-ray to gamma, and x-ray to a non-irradiated control.

Single step method for high yield human platelet lysate production

BACKGROUND

We aimed to develop a single step method for the production of human platelet lysate (hPL). The method must result in high hPL yields, be closed system and avoid heparin use.

STUDY DESIGN AND METHODS

The method aimed at using glass beads and calcium. An optimal concentration of calcium and glass beads was determined by serial dilution. This was translated to a novel method and compared to known methods: freeze-thawing and high calcium. Quality outcome measures were transmittance, fibrinogen and growth factor content, and cell doubling time.

RESULTS

An optimal concentration of 5 mM Ca²⁺ and 0.2 g/ml glass beads resulted in hPL with yields of 92% ± 1% (n = 50) independent of source material (apheresis or buffy coat-derived). The transmittance was highest (56% ± 9%) compared to known methods (<39%). The fibrinogen concentration (7.0 ± 1.1 μg/ml) was well below the threshold, avoiding the need for heparin. Growth factor content was similar across hPL production methods. The cell doubling time of adipose derived stem cells was 25 ± 1 h and not different across methods. Batch consistency was determined across six batches of hPL (each n = 25 constituting concentrates) and was <11% for all parameters including cell doubling time. Calcium precipitation formed after 4 days of culturing stem cells in media with hPL prepared by the high (15 mM) Ca²⁺ method, but not with hPL prepared by glass bead method.

DISCUSSION

The novel method transforms platelet concentrates to hPL with little hands-on time. The method results in high yield, is closed system, without heparin and non-inferior to published methods.

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.

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.

Irradiation of platelets in Transfusion Medicine: risk and benefit judgments

Irradiation of platelet products is generally used to prevent transfusion-associated graft-versus-host disease (TA-GvHD) as well as transfusion-transmitted infections. As an essential prerequisite, gamma-irradiation of blood products prior to transfusion is required in patients who may develop TA-GVHD. Most studies suggest that gamma irradiation has no significant effect on the quality of platelet products; however, more recent studies have shown that the oxidative effects of gamma irradiation can lead to the induction of platelet storage lesion (PSL) and to some extent reduce the efficiency of transfused platelets. As the second widely used irradiation technique, UV-illumination was primarily introduced to reduce the growth of infectious agents during platelet storage, with the advantage that this method can also prevent TA-GvHD. However, the induction of oxidative conditions and platelet pre-activation that lead to PSL is more pronounced after UV-based methods of pathogen reduction. Since these lesions are large enough to clearly affect the post-transfusion platelet recovery and survival, more studies are needed to improve the safety and effectiveness of pathogen reduction technologies (PRTs). Therefore, pointing to other benefits of PRTs, such as preventing TA-GvHD or prolonging the shelf life of products by eliminating the possibility of pathogen growth during storage, does not yet seem to justify their widespread use due to above-mentioned effects. Even for gamma-irradiated platelets, some researchers have suggested that due to decreased 1-hour post-transfusion increments and increased risk of platelet refractoriness, their use should be limited to the patients who may develop TA-GVHD. It is noteworthy that due to the effect of X-rays in preventing TA-GvHD, some recent studies are underway to examine its effects on the quality and effectiveness of platelet products and determine whether X-rays can be used as a more appropriate and cost-effective alternative to gamma radiation. The review presented here provides a detailed description about irradiation-based technologies for platelet products, including their applications, mechanistic features, advantages, and disadvantages.

UV light-emitting diode (UV-LED) at 265 nm as a potential light source for disinfecting human platelet concentrates

The risk of sepsis through bacterial transmission is one of the most serious problems in platelet transfusion. In processing platelet concentrates (PCs), several methods have been put into practice to minimize the risk of bacterial transmission, such as stringent monitoring by cultivation assays and inactivation treatment by photoirradiation with or without chemical agents. As another potential option, we applied a light-emitting diode (LED) with a peak emission wavelength of 265 nm, which has been shown to be effective for water, to disinfect PCs. In a bench-scale UV-LED exposure setup, a 10-min irradiation, corresponding to an average fluence of 9.2 mJ/cm2, resulted in >2.0 log, 1.0 log, and 0.6 log inactivation (mean, n = 6) of Escherichia coli, Staphylococcus aureus, and Bacillus cereus, respectively, in non-diluted plasma PCs. After a 30-min exposure, platelet counts decreased slightly (18 ± 7%: mean ± SD, n = 7); however, platelet surface expressions of CD42b, CD61, CD62P, and PAC-1 binding did not change significantly (P>0.005), and agonist-induced aggregation and adhesion/aggregation under flow conditions were well maintained. Our findings indicated that the 265 nm UV-LED has high potential as a novel disinfection method to ensure the microbial safety of platelet transfusion.

Pathogen reduction of whole blood: Supplementing fibrinogen partly corrects clot formation in a massive transfusion model

BACKGROUND

The use of whole blood (WB) to treat trauma patients is becoming more common. Similar to the treatment of individual components, pathogen inactivation (PI) technologies are available to treat WB. The impact of PI on WB function is not well understood. This study investigated the impact of PI of WB with riboflavin/ultraviolet (UV) light on its hemostatic function by modeling transfusion scenarios for trauma patients and assessing transfusion efficacy by rotational thromboelastometry (ROTEM). As fibrinogen is affected by PI of WB, the effect of fibrinogen supplementation commonly used in trauma patients was also analyzed in this model.

STUDY DESIGN AND METHODS

Trauma transfusion scenarios were simulated by mixing untreated WB or WB treated with the Mirasol PI technology (riboflavin/UV) in different ratios with hemodiluted blood, and the thromboelasticity was monitored by ROTEM. The impact of supplementation with the fibrinogen concentrate RiaSTAP was investigated in this model.

RESULTS

Pathogen-inactivated WB (PI-WB) showed decreased activity in the hemostatic profile compared to the untreated control. Hemodiluted blood at a hematocrit (hct) of 20%, which was reconstituted with PI-WB or untreated WB, exhibited increased alpha values, maximum clot firmness, and clot formation time. Simulating transfusion scenarios by blood replacement with PI-WB resulted in a significant difference in ROTEM parameters between reconstituted PI-treated and -untreated WB (p ≥ .05). The effect of PI treatment waned when PI-WB was enriched with fibrinogen.

CONCLUSION

ROTEM investigations suggest that PI treatment has a negative impact on WB clot formation unless fibrinogen supplementation is used.

Cryopreservation of platelets treated with riboflavin and UV light and stored at -80°C for 1 year

BACKGROUND

The combination of pathogen reduction technologies (PRTs) and cryopreservation can contribute to building a safe and durable platelet (PLT) inventory. Information about cryopreserved riboflavin and UV light-treated PLTs is scarce.

STUDY DESIGN AND METHODS

Twenty-four buffy coat (BC) PLT concentrates were grouped into 12 type-matched pairs, pooled, and divided into 12 non-PRT-treated control units and 12 riboflavin and UV light PRT-treated test units. Both were cryopreserved with 5% DMSO and stored at -80°C for 1 year. The cryopreservation method used was designed to avoid the formation of aggregates. PLT variables (PLT recovery, swirling, pH, MPV, and LDH) and hemostatic function measured by thromboelastography (TEG) were analyzed before cryopreservation (day 1) and post-cryopreservation at day 14 and months 3, 6, and 12 of storage at -80°C. The analyses were carried out within 1-h post-thaw.

RESULTS

No aggregates were found in either PLT group at any time. Swirling was observed in both groups. MPV increased and mean pH values decreased over time (p < .001), but the mean pH value was never below 6.4 in either group after 12 months of storage at -80°C. PLT recovery was good and clotting time became significantly shorter over the storage period in both groups (p < .001).

CONCLUSION

Our cryopreservation and thawing method prevented aggregate formation in cryopreserved riboflavin-UV-light-treated PLTs, which exhibited good recovery, swirling, pH > 6.4, and procoagulant potential, as evidenced by a reduced clotting time after 12 months of storage at -80°C. The clinical relevance of these findings should be further investigated in clinical trials.

The effect of gamma irradiation on platelet redox state during storage

BACKGROUND

As a method with insignificant adverse effects on in vitro quality of platelet concentrates (PCs), gamma irradiation is applied to abrogate the risk of transfusion-associated graft-vs-host disease in vulnerable recipients. However, there is some evidence of lower posttransfusion responses and proteomic alterations in gamma-irradiated platelets (PLTs), which raises some questions about their quality, safety, and efficacy. Since reactive oxygen species (ROS) are considered as markers of PLT storage lesion (PSL), the study presented here investigated oxidant state in gamma-irradiated PCs.

STUDY DESIGN AND METHODS

PLT-rich plasma PC was split into two bags, one kept as control while other was subjected to gamma irradiation. Within 7 days of storage, the levels of intra-PLT superoxide, H₂ O₂ , mitochondrial ROS, P-selectin expression, and phosphatidylserine (PS) exposure were detected by flow cytometry while intracellular reduced glutathione (GSH), glucose concentration, and lactate dehydrogenase (LDH) activity were measured by enzymocolorimetric method.

RESULTS

GSH decreased, while ROS generation and LDH activity increased, during storage. Gamma irradiation significantly attenuated GSH whereas increased ROS generation in earlier and later stages of storage associated with either P-selectin or PS exposure increments.

CONCLUSION

Gamma irradiation can significantly increase cytosolic ROS generation in two distinct phases, one upon irradiation and another later in longer-stored PCs. While earlier ROS influx seems to be governed by direct effect of irradiation, the second phase of oxidant stress is presumably due to the storage-dependent PLT activation. Intriguingly, these observations were also in line with early P-selectin increments and increased PS exposure in longer-stored PLTs. Given the mutual link between ROS generation and PLT activation, further investigation is required to explore the effect of gamma irradiation on the induction of PSL.

In vitro thrombus formation and in vivo hemostasis mediated by platelets irradiated with bactericidal ultraviolet C from xenon flash under flow conditions

BACKGROUND

We previously reported a flow path-ultraviolet C (UVC) irradiation system for platelet concentrates (PCs) with platelet additive solution (PAS) to minimize contamination by bacteria. Here, we investigated functionalities of irradiated platelets (PLTs) in in vitro thrombus formation and in vivo hemostasis.

STUDY DESIGN AND METHODS

PAS-PCs were irradiated with flash UVC using the flow path system. Their variables (PLT count, mean platelet volume, pH, glucose, lactate, glycoprotein [GP] Ib, and activated integrin αIIbβ3) were evaluated. Static adhesion to collagen or fibrinogen was analyzed using fluorescent microscopy. Thrombus formation under flow conditions was assessed using a collagen-coated bead column. Adenosine diphosphate (ADP)-induced Akt phosphorylation was determined by western blot. In vivo hemostasis and circulatory survival of PLTs were assessed with a rabbit bleeding model.

RESULTS

All variables, except for GPIb expression, were slightly, but significantly, impaired after flash UVC irradiation throughout the 6-day storage period. No difference was observed in static adhesion to either collagen or fibrinogen between irradiated and nonirradiated PAS-PCs. In vitro thrombus formation of flash UVC-irradiated PAS-PCs was significantly greater than that of nonirradiated PAS-PCs. ADP-induced Akt phosphorylation was enhanced in irradiated PAS-PCs. In vivo hemostatic efficacy was comparable between the groups on Day 1. The efficacy declined in nonirradiated PAS-PCs on Day 5, while it was retained in flash UVC-irradiated PAS-PCs. Circulatory survival of PLTs was lower in irradiated PAS-PCs.

CONCLUSIONS

PAS-PCs irradiated with UVC from xenon flash have favorable properties to achieve hemostasis compared with nonirradiated PAS-PCs.

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.

Impact of cold storage on platelets treated with Intercept pathogen inactivation

BACKGROUND

Pathogen inactivation and cold or cryopreservation of platelets (PLTs) both significantly affect PLT function. It is not known how PLTs function when both are combined.

STUDY DESIGN AND METHODS

Standard PLT concentrates (PCs) were compared to pathogen‐inactivated PCs treated with amotosalen photochemical treatment (AS‐PCT) when stored at room (RT, 22°C), cold (4°C, n = 6), or cryopreservation (−80°C, n = 8) temperatures. The impact of alternative storage methods on both arms was studied in flow cytometry, light transmittance aggregometry, and hemostasis in collagen‐coated microfluidic flow chambers.

RESULTS

Platelet aggregation of cold‐stored AS‐PCT PLTs was 44% ± 11% compared to 57% ± 14% for cold‐stored standard PLTs and 58% ± 21% for RT‐stored AS‐PCT PLTs. Integrin activation of cold‐stored AS‐PCT PLTs was 53% ± 9% compared to 77% ± 6% for cold‐stored standard PLTs and 69% ± 13% for RT‐stored AS‐PCT PLTs. Coagulation of cold‐stored AS‐PCT PLTs started faster under flow (836 ± 140 sec) compared to cold‐stored standard PLTs (960 ± 192 sec) and RT‐stored AS‐PCT PLTs (1134 ± 220 sec). Fibrin formation rate under flow was also highest for cold‐stored AS‐PCT PLTs. This was in line with thrombin generation in static conditions because cold‐stored AS‐PCT PLTs generated 297 ± 47 nmol/L thrombin compared to 159 ± 33 nmol/L for cold‐stored standard PLTs and 83 ± 25 nmol/L for RT‐stored AS‐PCT PLTs. So despite decreased PLT activation and aggregation, cold storage of AS‐PCT PLTs promoted coagulation. PLT aggregation of cryopreserved AS‐PCT PLTs (23% ± 10%) was not significantly different from cryopreserved standard PLTs (25% ± 8%).

CONCLUSION

This study shows that cold storage of AS‐PCT PLTs further affects PLT activation and aggregation but promotes (pro)coagulation. Increased procoagulation was not observed after cryopreservation.

A comparison of haematopoietic stem cells from umbilical cord blood and peripheral blood for platelet production in a microfluidic device

BACKGROUND AND OBJECTIVES

Several sources of haematopoietic stem cells have been used for static culture of megakaryocytes to produce platelets in vitro. This study compares and characterizes platelets produced in shear flow using precursor cells from either umbilical (UCB) or adult peripheral blood (PB).

MATERIALS AND METHODS

The efficiency of platelet production of the cultured cells was studied after perfusion in custom-built von Willebrand factor-coated microfluidic flow chambers. Platelet receptor expression and morphology were investigated by flow cytometry and microscopy, respectively.

RESULTS

Proliferation of stem cells isolated out of UCB was significantly higher (P < 0·0001) compared to PB. Differentiation of these cells towards megakaryocytes was significantly lower from PB compared to UCB where the fraction of CD42b/CD41 double positive events was 44 ± 9% versus 76 ± 11%, respectively (P < 0·0001). However, in vitro platelet production under hydrodynamic conditions was more efficient with 7·4 platelet-like particles per input cell from PB compared to 4·2 from UCB (P = 0·02). The percentage of events positive for CD42b, CD41 and CD61 was comparable between both stem cell sources. The mean number of receptors per platelet from UCB and PB was similar to that on blood bank platelets with on average 28 000 CD42b, 57 000 CD61 and 5500 CD49b receptors. Microscopy revealed platelets appearing similar to blood bank platelets in morphology, size and actin cytoskeleton, alongside smaller fragments and source megakaryocytes.

CONCLUSION

This characterization study suggests that platelets produced in vitro under flow either from UCB or from PB share receptor expression and morphology with donor platelets stored in the blood bank.

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.

Comparison of three commercially available buffy coat pooling sets for the preparation of platelet concentrates

BACKGROUND

A disposable set for platelet concentrate (PC) preparation by the buffy coat method allows pooling of buffy coats, centrifugation and cell separation with in-line leucocyte filtration. This study compares three commercially available pooling sets in combination with INTERCEPT pathogen inactivation (PI).

MATERIALS AND METHODS

Sets for pooling of buffy coats were from Fresenius Kabi (FRE), Macopharma (MAC) and Terumo BCT (TER). Platelet yield, recovery and concentration were compared before and after PI (n = 20). Platelet quality was assessed by annexin V binding, P-selectin expression and PAC1 binding.

RESULTS

The TER pooling set had the highest platelet yield (5·39 ± 0·44 × 1011 ) compared with MAC (4·53 ± 0·77) and FRE (4·56 ± 0·51) prior to PI. This was the result of a significantly higher platelet concentration in the TER storage bag (1·41 ± 0·12 × 106 /μL) compared with MAC (1·18 ± 0·19) and FRE (1·28 ± 0·15). However, the TER platelet content decreased by 15·6% after PI, yielding 4·55 ± 0·47 × 1011 platelets compared with smaller reductions at 9·5% for MAC (4·10 ± 0·69) and 4·4% for FRE (4·36 ± 0·52). None of the individual PC contained >106 leucocytes. The pH in TER PC was lower compared with MAC and FRE caused by a higher lactic acid production rate. Consequently, PAC1 binding after TRAP activation was lowest for TER PC on day 6. P-selectin and annexin V were not different between suppliers.

CONCLUSION

This study demonstrates the added value of evaluating the entire component production process when introducing a new consumable. This study helped to inform a decision on what pooling set is ideally suited for routine implementation taking into account PI.

High platelet content can increase storage lesion rates following Intercept pathogen inactivation primarily in platelet concentrates prepared by apheresis

BACKGROUND

Pathogen inactivation methods for platelet concentrates are increasingly being used in blood banks worldwide. In vitro studies have demonstrated its effects on storage lesion, but little routine quality control data on blood banking outcomes have been reported.

MATERIALS AND METHODS

Swirling of distributed products was monitored before and after implementation of Intercept pathogen inactivation. Metabolic parameters pH, glucose and lactic acid were determined in a random cohort of expired pathogen-inactivated products. Storage lesion indicators in apheresis concentrates with premature low swirling were compared to concentrates with normal swirling.

RESULTS

During validation for implementing Intercept pathogen inactivation, pH and glucose levels decreased faster in apheresis platelet concentrates with high platelet content than with low platelet content or than in pathogen-inactivated pooled buffy coat-derived products. In routine products, glucose exhaustion was more often found in apheresis compared to buffy coat-derived platelet concentrates despite 3-7% more plasma carryover in the former. Annual incidence of premature low swirling increased significantly by 50% following implementation of pathogen inactivation implementation for apheresis but not for pooled buffy coat platelet concentrates. In addition, apheresis concentrates with premature low swirling had a significantly higher median platelet count (5·0 × 10¹¹ ) than unaffected products (3·5 × 10¹¹ ).

CONCLUSION

The risk of increased storage lesion rates following Intercept pathogen inactivation is higher for apheresis than for buffy coat-derived platelet concentrates, especially when platelet contents are higher than 5·0 × 10¹¹ .

Amotosalen/ultraviolet A pathogen inactivation technology reduces platelet activatability, induces apoptosis and accelerates clearance

Amotosalen and ultraviolet A (UVA) photochemical-based pathogen reduction using the Intercept™ Blood System (IBS) is an effective and established technology for platelet and plasma components, which is adopted in more than 40 countries worldwide. Several reports point towards a reduced platelet function after Amotosalen/UVA exposure. The study herein was undertaken to identify the mechanisms responsible for the early impairment of platelet function by the IBS. Twenty-five platelet apheresis units were collected from healthy volunteers following standard procedures and split into 2 components, 1 untreated and the other treated with Amotosalen/UVA. Platelet impedance aggregation in response to collagen and thrombin was reduced by 80% and 60%, respectively, in IBS-treated units at day 1 of storage. Glycoprotein Ib (GpIb) levels were significantly lower in IBS samples and soluble glycocalicin correspondingly augmented; furthermore, GpIbα was significantly more desialylated as shown by Erythrina Cristagalli Lectin (ECL) binding. The pro-apoptotic Bak protein was significantly increased, as well as the MAPK p38 phosphorylation and caspase-3 cleavage. Stored IBS-treated platelets injected into immune-deficient nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mice showed a faster clearance. We conclude that the IBS induces platelet p38 activation, GpIb shedding and platelet apoptosis through a caspase-dependent mechanism, thus reducing platelet function and survival. These mechanisms are of relevance in transfusion medicine, where the IBS increases patient safety at the expense of platelet function and survival.

Psoralen and Ultraviolet A Light Treatment Directly Affects Phosphatidylinositol 3-Kinase Signal Transduction by Altering Plasma Membrane Packing

Psoralen and ultraviolet A light (PUVA) are used to kill pathogens in blood products and as a treatment of aberrant cell proliferation in dermatitis, cutaneous T-cell lymphoma, and graft-versus-host disease. DNA damage is well described, but the direct effects of PUVA on cell signal transduction are poorly understood. Because platelets are anucleate and contain archetypal signal transduction machinery, they are ideally suited to address this. Lipidomics on platelet membrane extracts showed that psoralen forms adducts with unsaturated carbon bonds of fatty acyls in all major phospholipid classes after PUVA. Such adducts increased lipid packing as measured by a blue shift of an environment-sensitive fluorescent probe in model liposomes. Furthermore, the interaction of these liposomes with lipid order-sensitive proteins like amphipathic lipid-packing sensor and α-synuclein was inhibited by PUVA. In platelets, PUVA caused poor membrane binding of Akt and Bruton's tyrosine kinase effectors following activation of the collagen glycoprotein VI and thrombin protease-activated receptor (PAR) 1. This resulted in defective Akt phosphorylation despite unaltered phosphatidylinositol 3,4,5-trisphosphate levels. Downstream integrin activation was furthermore affected similarly by PUVA following PAR1 (effective half-maximal concentration (EC₅₀), 8.4 ± 1.1 versus 4.3 ± 1.1 μm) and glycoprotein VI (EC₅₀, 1.61 ± 0.85 versus 0.26 ± 0.21 μg/ml) but not PAR4 (EC₅₀, 50 ± 1 versus 58 ± 1 μm) signal transduction. Our findings were confirmed in T-cells from graft-versus-host disease patients treated with extracorporeal photopheresis, a form of systemic PUVA. In conclusion, PUVA increases the order of lipid phases by covalent modification of phospholipids, thereby inhibiting membrane recruitment of effector kinases.

Current Status of Platelet Transfusion in Pediatric Patients

Outside the neonatal period, most platelets that are transfused to pediatric patients are given to those who are thrombocytopenic secondary to malignancy and associated therapy and/or hematopoietic progenitor cell transplant, or to those with significant bleeding associated with surgery, especially cardiac surgery. Indications for platelet transfusion, doses, and other practices for children largely mimic adult platelet transfusion protocols because there are few pediatric-specific studies in this area. Pediatric platelet transfusion practices would benefit from focused pediatric research. The appropriate indications and doses for platelet transfusions in oncology, hematopoietic progenitor cell transplant, and cardiac surgery patients need to be determined.

Reduction of bacteria and human immunodeficiency virus Type 1 infectivity of platelet suspension in plasma using xenon flash-pulse light in a bench-scale trial

BACKGROUND

Current pathogen reduction systems for platelet concentrates (PCs) require addition of chemical compounds and/or reduction of plasma content in PCs. We have investigated a new method using xenon (Xe) flash-pulse light without additional compounds or plasma replacement.

STUDY DESIGN AND METHODS

An aliquot of apheresis platelets (PLTs) in plasma inoculated with bacteria or human immunodeficiency virus Type 1 (HIV-1) was irradiated with Xe flash-pulse light (Xe flash phototreatment). Bacterial growth was monitored up to 6 days of storage, whereas HIV-1 infectivity was assayed just after treatment. Pairs of Xe flash-phototreated and untreated PCs were examined for PLT lesion during the storage period.

RESULTS

Under the current conditions, a low titer (1.8 colony-forming units [CFUs]/mL) of Staphylococcus aureus did not proliferate during the 6-day storage period, but grew in some cases at high-titer (24.0 CFUs/mL) inoculation. HIV-1 infectivity was reduced by 1.8 log. PLT recovery of the treated PCs was lower than untreated ones. An increase of mean PLT volume and glucose consumption, together with a decrease of hypotonic shock response and pH, were enhanced by the treatment. CD62P- and PAC-1-positive PLTs increased after the treatment, indicating the induction of PLT activation. Among biologic response modifiers, soluble CD40 ligand was significantly increased in the treated PCs on Day 6.

CONCLUSIONS

Xe flash phototreatment could prevent bacterial proliferation and reduce HIV-1 infectivity in 100% plasma PCs without any additional compounds, but enhanced PLT storage lesions. Further improvement is required to increase the potency of pathogen inactivation with reducing PLT damage.

Microfluidic Flow Chambers Using Reconstituted Blood to Model Hemostasis and Platelet Transfusion In Vitro

Blood platelets prepared for transfusion gradually lose hemostatic function during storage. Platelet function can be investigated using a variety of (indirect) in vitro experiments, but none of these is as comprehensive as microfluidic flow chambers. In this protocol, the reconstitution of thrombocytopenic fresh blood with stored blood bank platelets is used to simulate platelet transfusion. Next, the reconstituted sample is perfused in microfluidic flow chambers which mimic hemostasis on exposed subendothelial matrix proteins. Effects of blood donation, transport, component separation, storage and pathogen inactivation can be measured in paired experimental designs. This allows reliable comparison of the impact every manipulation in blood component preparation has on hemostasis. Our results demonstrate the impact of temperature cycling, shear rates, platelet concentration and storage duration on platelet function. In conclusion, this protocol analyzes the function of blood bank platelets and this ultimately aids in optimization of the processing chain including phlebotomy, transport, component preparation, storage and transfusion.

The contribution of von Willebrand factor-GPIbα interactions to persistent aggregate formation in apheresis platelet concentrates

BACKGROUND AND OBJECTIVES

Apheresis platelet concentrates sometimes contain persistent aggregates (PA). Because apheresis involves extracorporeal circulation, we hypothesized that interactions between GPIbα and von Willebrand factor (VWF) underlie their origin.

MATERIALS AND METHODS

Platelets in donations with PA were compared to aggregate-free (AF) controls. Flow cytometry was used to determine platelet bound VWF. Degranulation was measured using P-selectin expression in flow cytometry and cytokine release using immunosorbent assays. Platelet adhesion to VWF was assessed in hydrodynamic flow and real-time video microscopy.

RESULTS

Platelets in PA concentrates had significantly more (P = 0·009, n ≥ 8) bound VWF compared to AF platelets, but differences in VWF concentration, VWF collagen binding, activated VWF or GPIbα expression were not found. Degranulation was higher (P = 0·030, n = 7) in PA than AF concentrates on day 1 of storage, but adhesion to immobilized VWF under hydrodynamic flow conditions was normal at that moment. On day 6, however, significantly less VWF adhesion (P = 0·009, n ≥ 6) was found for PA platelets compared to AF, indicating accelerated storage lesion in PA products. In a model that mimicks PA formation by chemically induced binding of VWF to platelets, we found that degranulation, phosphatidylserine expression and metabolism did not differ with paired controls at any time during subsequent storage.

CONCLUSION

Accelerated storage lesion is found in concentrates with PA, but this cannot be explained solely by increased platelet bound VWF following apheresis. Therefore, additional stressors are probably responsible for the increases observed in platelet degranulation and storage lesion in products with PA.