Quantitation of coated platelet potential during collection, storage, and transfusion of apheresis platelets

BACKGROUND: Coated platelets (PLTs), a subpopulation of PLTs observed upon dual agonist stimulation with collagen and thrombin, are known to retain several procoagulant α‐granule proteins on their surface. By formation of a highly active membrane‐bound prothrombinase complex, these PLTs represent an important step in the coagulation cascade as a consequence of their ability to generate thrombin at the site of vascular injury. Various clinical observations suggest that higher levels of coated PLTs are associated with thrombosis while a deficiency of coated PLTs results in a bleeding diathesis. Current quality control guidelines for in vitro PLT storage measure PLT viability but no routine evaluation of the hemostatic function of stored PLTs and particularly no estimation of coated PLT potential is performed. Our primary objective was to evaluate if the process of apheresis and storage of PLT units alters the levels of coated PLTs. In addition, we sought to determine how transfusion of stored PLTs into patients with thrombocytopenia affects the patient's coated PLT levels. STUDY DESIGN AND METHODS: Coated PLT levels were analyzed in 13 voluntary PLT donors before donation, in the fresh apheresis product (Trima, CaridianBCT) and in the stored apheresis product just before transfusion. In addition, 10 patients with thrombocytopenia were analyzed for coated PLTs before and after transfusion of a stored PLT product. RESULTS: Coated PLT levels were significantly decreased after the process of apheresis (17% relative decline; p < 0.01) and with prolonged storage (1 to 5 days; 53% relative decline; p < 0.001). Transfusion of stored PLT units did not result in significant increment of coated PLT levels in patients with thrombocytopenia as expected considering the low level of coated PLTs in stored PLT units. Furthermore, there was no suggestion of regeneration of coated PLT potential upon reinfusion. CONCLUSIONS: Isolation and storage of apheresis PLTs by standard blood bank procedures results in a significant decline in coated PLT potential. Reinfusion of stored apheresis PLTs into patients with thrombocytopenia resulted in a predictable change in coated PLT potential with no suggestion of regeneration of lost coated PLT potential.     

Evaluation of the automated collection and extended storage of apheresis platelets in additive solution

BACKGROUND: Collecting apheresis platelets (PLTs) into additive solution has many potential benefits. The new Trima software (Version 6.0, CaridianBCT) allows automated addition of PLT additive solution (PAS) after collection, compared to Trima Version 5.1, which only collects PLTs into plasma. The aim of this study was to compare PLT quality during extended storage, after collection with the different Trima systems. STUDY DESIGN AND METHODS: Apheresis PLTs were collected using both Trima Accel apheresis systems. The test PLT units (n = 12) were collected using the new Trima Version 6.0 into PLT AS (PAS‐IIIM), while the control units (n = 8) were collected into autologous plasma using Trima Version 5.1. All units were stored for 9 days, and in vitro cell quality variables were evaluated during this time. RESULTS: PLTs collected in PAS‐IIIM maintained a stable pH between 7.2 and 7.4, whereas plasma‐stored apheresis units exhibited significantly increased acidity during storage, due to lactate accumulation and bicarbonate exhaustion. Plasma‐stored PLTs also demonstrated a more rapid consumption of glucose. However, there was little difference in PLT activation or cytokine secretion between PAS‐IIIM and control PLTs. CONCLUSION: These data indicate that apheresis PLT concentrates collected in PAS‐IIIM, using Trima Version 6.0 software, maintained acceptable PLT metabolic and cellular characteristics until Day 9 of storage.     

Effect of storage on levels of nitric oxide metabolites in platelet preparations

BACKGROUND: Nitric oxide (NO), a potent signaling molecule, is known to inhibit platelet (PLT) function in vivo. We investigated how the levels of NO and its metabolites change during routine PLT storage. We also tested whether the material of PLT storage containers affects nitrite content since many plastic materials are known to contain and release nitrite. STUDY DESIGN AND METHODS: For nitrite and nitrate measurement, leukoreduced apheresis PLTs and concurrent plasma (CP) were collected from healthy donors using a cell separator. Sixty‐milliliter aliquots of PLT or CP were stored in CLX or PL120 Teflon containers at 20 to 24°C with agitation and daily samples were processed to yield PLT pellet and supernatant. In a separate experiment, PLTs were stored in PL120 Teflon to measure NO generation using electron paramagnetic resonance (EPR). RESULTS: Nitrite level increased markedly in both PLT supernatant and CP stored in CLX containers at a rate of 58 and 31 nmol/L/day, respectively. However, there was a decrease in nitrite level in PLTs stored in PL120 Teflon containers. Nitrite was found to leach from CLX containers and this appears to compensate for nitrite consumption in these preparations. Nitrate level did not significantly change during storage. CONCLUSION: PLTs stored at 20 to 24°C maintain measurable levels of nitrite and nitrate. The nitrite decline in nonleachable Teflon containers in contrast to increases in CLX containers that leach nitrite suggests that it is consumed by PLTs, residual white blood cells, or red blood cells. These results suggest NO‐related metabolic changes occur in PLT units during storage.     

Decreased responsiveness and development of activation markers of PLTs stored in plasma

BACKGROUND: Circulating PLTs have a low activation state and high responsiveness, which ensures adequate hemostatic activity at sites of vessel wall damage. PLTs collected for transfusion purposes preferably have retained these properties to restore impaired hemostasis with thrombocytopenia. STUDY DESIGN AND METHODS: We determined activation properties and coagulant activity of PLT-plasma preparations that were pooled or collected from single donors via apheresis. RESULTS: In comparison to freshly isolated PLTs, both apheresis and pooled PLTs exhibited slow exposure of CD62 upon storage, followed by surface appearance of procoagulant phosphatidylserine (PS) but not activated integrin alpha IIb beta 3. During storage, thrombin- and ADP-induced Ca2+ signal generation consistently decreased in apheresis and pooled PLTs, which was accompanied by lower agonist-induced CD62 exposure and alpha IIb beta 3 activation. In flowing whole blood, stored apheresis PLTs showed lower collagen-induced Ca2+ responses and strikingly diminished participation in thrombus formation. Both apheresis and pooled PLT-plasma concentrates exhibited high tissue factor-triggered thrombin generation, which was insensitive to PLT inhibition and attributable to PS-exposing microparticles. CONCLUSION: PLTs stored in plasma develop surface activation markers but, simultaneously, show markedly decreased responsiveness toward physiologic agonists. The plasma contains high coagulant activity, which is no longer PLT (activation)-dependent.     

Extended storage of platelet‐rich plasma–prepared platelet concentrates in plasma or Plasmalyte

BACKGROUND: Using bacterial detection or pathogen reduction, extended platelet (PLT) storage may be licensed if PLT viability is maintained. The Food and Drug Administration (FDA)'s poststorage PLT acceptance guidelines are that autologous stored PLT recoveries and survivals should be 66 and 58% or greater, respectively, of each donor's fresh PLT data. STUDY DESIGN AND METHODS: Nonleukoreduced PLT concentrates were prepared from whole blood donations. Autologous PLT concentrates from 62 subjects were stored in 100% plasma (n = 44) or 20% plasma/80% Plasmalyte (n = 18), an acetate‐based, non–glucose‐containing crystalloid solution previously used for PLT storage. Fresh PLTs were obtained on the day the donor's stored PLTs were to be transfused. The fresh and stored PLTs were alternately radiolabeled with either ⁵¹chromium or ¹¹¹indium, and in vitro measurements were performed on the stored PLTs. RESULTS: The FDA's PLT recovery criteria were met for 7 days of plasma storage, but PLT survivals maintained viability for only 6 days. Plasmalyte‐stored PLTs did not meet either acceptance criteria after 6 days of storage. After 7 days of storage, PLT recoveries averaged 43 ± 4 and 30 ± 4% and survivals 4.1 ± 0.4 and 2.0 ± 0.2 days for plasma‐ and Plasmalyte‐stored PLTs, respectively (p = 0.03 for recoveries and p < 0.001 for survivals). Poststorage PLT recoveries correlated with the commonly used in vitro PLT quality measurements of hypotonic shock response and annexin V binding, while survivals correlated with extent of shape change, morphology score, and pH. CONCLUSION: There is a progressive decrease in recoveries and survivals of plasma‐stored PLTs over time. PLT viability is better maintained in plasma than Plasmalyte.     

Viability and function of 8-day-stored apheresis platelets

BACKGROUND: Methods of bacterial detection and pathogen inactivation of platelets (PLTs) may allow extended storage of PLTs as long as PLT quality is maintained. STUDY DESIGN AND METHODS: Twenty normal volunteers had their PLTs collected with an apheresis machine (Haemonetics Corp.). A variety of in vitro PLT function and metabolic assays were performed both on Day 0 and after 8 days of storage. On Day 8, a small blood sample was drawn from each donor to obtain fresh PLTs. The fresh and stored autologous PLTs were labeled with either (51)Cr or (111)In, and the radiolabeled PLTs were transfused. Posttransfusion serial blood samples were drawn to determine the relative posttransfusion recoveries and survivals of the fresh versus the stored PLTs. RESULTS: Although the in vitro assays showed some differences between the two trial sites, the results were generally within the ranges expected for fresh and stored PLTs. Overall, PLT recoveries averaged 66 +/- 16 percent versus 53 +/- 20 percent and survivals averaged 8.5 +/- 1.6 days versus 5.6 +/- 1.6 days, respectively, for fresh compared to 8-day-stored PLTs. There were no significant differences in the in vivo PLT data between the trial sites or based on the radiolabel used for the measurements. CONCLUSION: After 8 days of storage, the in vivo posttransfusion recovery and survival of autologous Haemonetics apheresis PLTs meet the proposed standards for poststorage PLT quality.     

Storing apheresis platelets without agitation with simulated shipping conditions during two separate periods: immediately after collection and subsequently between Day 2 and Day 3

BACKGROUND: Apheresis platelet (PLT) units are not routinely agitated during transit. Our study compared the in vitro properties of apheresis PLT units that were stored with continuous agitation (CA) and without continuous agitation (WCA) during two separate periods, immediately after collection and between Day 2 and Day 3 of storage. STUDY DESIGN AND METHODS: Two identical apheresis PLTs units were prepared from collections with Amicus (n = 11, Fenwal, Inc.) and Trima (n = 10, CaridianBCT) cell separators. One apheresis PLT unit was continuously agitated, starting routinely within 30 minutes of collection, and an identical apheresis PLT unit was held without agitation initially for 7 to 8 hours and subsequently for 24 hours between Day 2 and Day 3 of storage. The apheresis PLT units were maintained WCA at 20 to 24°C in a shipping box. In vitro PLT properties were evaluated on Day 1 (day after collection), after 5 and 7 days of storage. RESULTS: With both Amicus and Trima apheresis PLT units, the mean PLT content and concentration of CA and WCA were comparable and essentially constant throughout storage. Mean pH levels (±1 SD) after 5 days for Amicus apheresis PLT units were 6.97 ± 0.20 (WCA) and 7.13 ± 0.16 (p < 0.001, CA) and for Trima apheresis PLT units 6.97 ± 0.21 (WCA) and 7.22 ± 0.17 (p < 0.001, CA). In vitro variables, including percentage of disc PLTs, extent of shape change, and hypotonic stress levels, after 5 days of storage, showed mean differences between WCA and CA that were less than 15%. CONCLUSION: The in vitro results show that apheresis PLT units can be stored without agitation for 7 to 8 hours immediately after collection and also subsequently during storage for 24 hours with minimal influence on in vitro PLT properties compared to continuously agitated PLTs.     

The role of bicarbonate in platelet additive solution for apheresis platelet concentrates stored with low residual plasma

BACKGROUND: Complex platelet additive solutions (PASs) are required to store platelet (PLT) concentrates with plasma levels below 30%. Previously, apheresis PLTs stored with 5% plasma in acetate‐ and bicarbonate‐containing PAS maintained stable pH and bicarbonate levels during 7‐day storage. Due to this observation, the necessity of added bicarbonate in PAS was investigated and whether the concurrent increase in PAS pH after bicarbonate addition had any effect on PLT storage. STUDY DESIGN AND METHODS: Apheresis PLTs were stored in 5% plasma‐95% high‐ or low‐pH PAS, with or without bicarbonate (n = 10 per arm). Bicarbonate PAS PLTs were paired and nonbicarbonate PAS PLTs were paired (split from same double‐dose collection). PLTs were evaluated for in vitro variables on Days 1 and 7 and up to Day 14 if the Day 7 pH was higher than 6.2. RESULTS: PLT pH was maintained above 7.3 to Day 14 in bicarbonate PAS PLTs while pH failures below 6.2 were observed in 4 of 10 and 2 of 10 units on Day 7 in low‐ and high‐pH nonbicarbonate PAS arms, respectively. Day 7 in vitro variables in nonbicarbonate PAS PLTs with pH values of higher than 6.2 were comparable to Day 7 variables in bicarbonate PAS PLTs. The pH of bicarbonate PAS did have a small effect on pH and bicarbonate levels in PLT units, but did not have an effect on functional variables and metabolism. CONCLUSION: Bicarbonate was not required to maintain in vitro PLT function in 5% plasma‐95% PAS, but was required as a pH buffer and increased PAS pH did not significantly contribute to this effect.     

Evaluation of platelet mitochondria integrity after treatment with Mirasol pathogen reduction technology

BACKGROUND: Previous studies showed that Mirasol (Navigant Biotechnologies, Inc.) pathogen reduction technology (PRT) treatment resulted in an increase in platelet (PLT) glucose consumption and lactate production rates and decrease in pH in media during PLT storage. Increased glycolytic flux could result from damage to mitochondria and/or increased ATP consumption. STUDY DESIGN AND METHODS: PLT concentrates were collected by standard automated blood component collection system (Trima, Gambro BCT) procedure on Day 0 and treated with Mirasol PRT treatment on Day 1. PLT mitochondrial transmembrane potential was evaluated by staining PLTs with JC-1 followed by flow cytometry analysis. Mitochondrial enzymatic activity was measured by the MTT assay. ATP content and pH were also quantified. The values for these measurements were compared among control, untreated, and pathogen reduction technology (PRT)-treated PLTs during PLT storage for up to 7 days. RESULTS: No significant changes were found in pH, JC-1 signal, MTT activity, and ATP content of the PLTs immediately after PRT treatment. The treated PLTs exhibited a moderate but significantly accelerated decrease in pH and lower ATP content after 7-day storage when compared to control PLTs. Neither the JC-1 assay nor the MTT assay, however, showed a significant difference between control and treated PLTs during PLT storage. CONCLUSIONS: There is no evidence from these studies that Mirasol PRT treatment alters PLT mitochondrial structural and functional integrity immediately after treatment and during PLT storage. An increased demand for ATP may be the driving force for observed increases in both the glycolytic flux and the oxidative metabolism observed in treated PLTs.     

In vitro quality of single-donor platelets treated with riboflavin and ultraviolet light and stored in platelet storage medium for up to 8 days

BACKGROUND: The Mirasol pathogen reduction technology system is known to increase the activation and metabolic rate of platelets (PLTs). Storage of Mirasol PLTs in PLT storage medium (PSM) has the potential to slow this accelerated PLT storage lesion. We investigated the quality of Mirasol‐treated PLTs stored in either 50% SSP+ or 50% Composol for 8 days. STUDY DESIGN AND METHODS: Single‐donor double hyperconcentrates were divided between control and Mirasol‐treated arms and after treatment were suspended in approximately 50% (vol/vol) SSP+ (n = 8) or Composol (n = 7). In vitro markers of PLT activation and/or apoptosis were measured over an 8‐day storage period. RESULTS: Mirasol treatment resulted in increased spontaneous PLT activation and glycolysis and these effects were worsened when PLTs were treated below a certain volume (150 mL). At higher treatment volumes there were no significant differences between treated units stored in either Composol or SSP+. When low‐volume units were stored in Composol the median pH fell below 6.4 on Day 5 and bicarbonate was undetectable, whereas in SSP+ the median pH value was greater than 6.9 and bicarbonate remained at detectable levels, despite other markers of in vitro function being similar to those of Composol. CONCLUSION: Mirasol treatment of PLTs followed by storage in PSM results in increased PLT activation and metabolism to a level similar to that reported for PLTs treated and stored in plasma. Units treated at a low volume (<150 mL) showed poor in vitro quality.     

A rest period before agitation may improve some in vitro apheresis platelet parameters during storage

BACKGROUND: Whole blood‐derived platelets (PLTs) prepared by the PLT‐rich plasma method are subjected to a recommended 1‐hour rest period after the second centrifugation to avoid excessive PLT activation. Different apheresis PLT preparation methods demonstrate different levels of PLT activation and ability to form macroscopic aggregates immediately after collection. PLT collections are lost on Day 1 of storage if aggregates are not dispersed. It is possible that a rest period may help to disperse PLT aggregates. It is not established whether apheresis PLTs require a rest period before agitation and what the length of this period should be. STUDY DESIGN AND METHODS: Apheresis PLTs (Amicus, Fenwal, Inc.) were divided into five identical aliquots. One aliquot was placed on the flatbed agitator immediately after division. The other aliquots were subjected to agitation after 1, 2, 4, and 6 hours of rest. Samples were taken on Days 1, 5, and 7 for standard PLT assays. RESULTS: No differences during 7‐day storage were observed in PLT content, mean PLT volume, pH levels, bicarbonate, glucose, lactate, oxygen and carbon dioxide levels, hypotonic shock response, aggregation, and activation markers in PLT aliquots subjected to different rest periods or without a rest period. In contrast, values of extent of shape change, percentage of discoid PLTs, and expression of GP1b‐α were greater in aliquots subjected to different periods of rest compared to those of PLTs without a rest period. CONCLUSION: A rest period from 1 to 6 hours may improve some but not all in vitro PLT storage parameters.     

Maintenance of storage properties of pediatric aliquots of apheresis platelets in fluoroethylene propylene containers

BACKGROUND: Platelet (PLT) aliquots for pediatric use have been shown to retain in vitro properties when stored in gas‐impermeable syringes for up to 6 hours. As an alternative, PLT aliquots can be stored for longer periods in containers used for storage of whole blood–derived PLTs. These containers are not available separate from whole blood collection sets and PLT volumes less than 35 mL either have not been evaluated or may be unsuitable for PLT storage. Gas‐permeable fluoroethylene propylene (FEP) containers have been used in the storage of cell therapy preparations and are available in multiple sizes as single containers but have not been evaluated for PLT storage. STUDY DESIGN AND METHODS: A single apheresis unit was divided on Day 3 into small aliquots with volume ranging from 20 to 60 mL, transferred using a sterile connection device, and stored for an additional 2 days either in CLX (control) or in FEP containers. PLT storage properties of PLTs stored in FEP containers were compared to those stored in CLX containers. Standard PLT in vitro assays were performed (n = 6). RESULTS: PLT storage properties were either similar to those of CLX containers or differed by less than 20% excepting carbon dioxide levels, which varied less than 60%. CONCLUSION: Pediatric PLT aliquots of 20, 30, and 60 mL transferred on Day 3 into FEP cell culture containers adequately maintain PLT properties for an additional 2 days of storage.     

Temperature cycling improves in vivo recovery of cold‐stored human platelets in a mouse model of transfusion

BACKGROUND: Platelet (PLT) storage at room temperature (RT) is limited to 5 days to prevent growth of bacteria, if present, to high levels. Storage in cold temperatures would reduce bacterial proliferation, but cold‐exposed PLTs are rapidly cleared from circulation by the hepatic Ashwell‐Morell (AM) receptor, which recognizes PLT surface carbohydrates terminated by β‐galactose. We cycled storage temperature between 4 and 37°C to preserve PLT function and reduce bacterial growth. STUDY DESIGN AND METHODS: Temperature‐cycled (TC) human PLTs were stored at 4°C for 12 hours and then incubated at 37°C for 30 minutes before returning back to cold storage. PLTs stored at RT or at 4°C (COLD) or TC for 2, 5, and 7 days were infused into SCID mice and the in vivo recovery was determined at 5, 20, and 60 minutes after transfusion. RESULTS: PLTs stored for 2 days in COLD had significantly lower in vivo recoveries than RT PLTs. TC PLTs had improved recoveries over COLD and comparable to RT PLTs. After 5‐ and 7‐day storage, TC PLTs had better recoveries than RT and COLD PLTs. PLT surface β‐galactose was increased significantly for both COLD and TC PLTs compared to RT. Blocking of the AM receptor by asialofetuin increased COLD but not TC PLT recovery. CONCLUSION: TC cold storage may be an effective method to store PLTs without loss of in vivo recovery. The increased β‐galactose exposure in TC PLTs suggests that mechanisms in addition to AM receptors may mediate clearance of cold‐stored PLTs.     

In vitro and in vivo quality of leukoreduced apheresis platelets stored in a new platelet additive solution

BACKGROUND: Platelets (PLTs) stored in additive solutions (PASs) may reduce the risk of several plasma‐associated adverse transfusion reactions such as allergic reactions and potentially transfusion‐associated lung injury. The objective of this study was to determine the in vitro characteristics and the in vivo radiolabeled recovery and survival of apheresis PLTs (APs) stored in a new PAS and compare the latter to Food and Drug Administration (FDA) criteria. STUDY DESIGN AND METHODS: Hyperconcentrated APs were collected from healthy subjects in a paired crossover study comparing PAS (35% plasma) and 100% plasma‐stored APs (Part 1) up to 7 days and, in Part 2, to determine the in vivo recovery and survival of PAS stored AP at 5 days compared to fresh PLT controls. In vitro and in vivo assays were performed following standard methods. RESULTS: Sixty‐six and 25 evaluable subjects successfully completed Parts 1 and 2, respectively. pH for PAS AP was maintained above 6.6 for 5 days of storage. P‐selectin values were consistent with published values for commonly transfused PLT products. The PAS in vivo PLT recovery (54.3 ± 8.1%) was 86.7% of the fresh control, and survival (6.4 ± 1.3 days) was 78.0% of the fresh control, both meeting the FDA performance criteria. CONCLUSION: APs stored in PAS with 35% plasma carryover maintained pH over 5 days of storage and met current FDA criteria for radiolabeled recovery and survival. The use of PAS for storage of single‐donor PLTs in clinical practice represents an acceptable transfusion product that reduces the volume of plasma associated with PLT transfusion.     

Cell viability during platelet storage in correlation to cellular metabolism after different pathogen reduction technologies

BACKGROUND: The objective of this study was to evaluate if pathogen reduction technologies (PRTs) affect platelet (PLT) viability by alteration of PLT metabolism during storage.
STUDY DESIGN AND METHODS: Twenty-seven split triple-dose apheresis PLTs were PRT treated using ultraviolet light with either riboflavin-UVB (M) or psoralen-UVA (I) or remained untreated (C). Samples were taken on Days 0, 1, 5, 7, and 8 and analyzed for annexin V release (enzyme-linked immunosorbent assay), mitochondrial enzymatic activity (MTS assay), transmembrane mitochondrial potential (Δψ; JC-1 assay), and metabolism based on pH, pO₂, glucose, lactate, and ATP content.
RESULTS: During storage, Δψ and MTS reduction activity decreased, while annexin V release and acidity increased in all units, more pronounced, however, after PRT treatment, which led to higher lactate accumulation due to acceleration in glycolytic flux. No significant differences were found between C and M, whereas I was significantly different by Day 1 (pH value), Day 5 (annexin V release), and Day 7 (Δψ) of storage. Intracellular ATP content remained similar between C and M but was significantly lower in end-stored I units. Cell viability markers of I units were highly correlated with the oxidative pathway, which appeared impaired in I but up regulated in M units.
CONCLUSION: PRT treatment using M increased both anoxidative glycolytic flux and oxidative phosphorylation. The I-based technique was associated with an impaired mitochondria-based respiration. During terminal storage, this resulted in significantly lower maintenance of ATP and cell viability. The impact of these findings for storage prolongation or clinical use must await further evaluation.     

A rest period does not affect in vitro storage properties in apheresis platelets collected from the buffy coat layer

BACKGROUND: A previous study demonstrated that several in vitro storage properties of apheresis platelets (PLTs) that are isolated by sedimentation against the collection container and subsequently resuspended can benefit from a rest period before continuous agitation. This study examines whether the in vitro storage properties of apheresis PLTs isolated by collection from the buffy coat layer benefit from a rest period before agitation. STUDY DESIGN AND METHODS: Freshly collected apheresis PLTs (Trima, GambroBCT) were divided into five 60‐mL aliquots. One aliquot was immediately placed on a flat‐bed agitator; the other aliquots were held on a laboratory bench for 1, 2, 4, and 6 hours before continuous agitation. Samples were obtained on Days 1, 5, and 7 for standard in vitro PLT assays. The experiment was repeated 12 times. RESULTS: For each sampling day, no significant differences were observed in aliquots held with or without a rest period for any of the following PLT properties: PLT content, mean PLT volume, pH, pCO₂, bicarbonate, glucose, lactate, hypotonic shock response, extent of shape change, aggregation, morphology, CD62P, CD63, and CD42b. Although regression analysis identified several in vitro properties whose mean levels appeared to improve with increasing length of the rest period, maximum differences in mean levels were small (<6%). CONCLUSION: The in vitro storage properties of Trima apheresis PLTs isolated from the buffy coat layer do not benefit from a rest period.     

In vitro properties of apheresis platelet during extended storage in plasma treated with anandamide

BackgroundIn China apheresis platelets (PLTs) are stored in plasma for only 5 days, resulting in PLT inventory pressures. Anandamide (ANA) was reported to be a potential agent to inhibit PLT apoptosis. The aim of this study was to evaluate the characteristics of extended storage PLTs in plasma treated with ANA in vitro.MethodsApheresis PLTs (n = 20) were prepared in plasma treated with ANA, and stored at 22 °C for up to 11 days. On day 1, 3, 5, 7, 9 and 11, PLTs were tested for PLT count, mean PLT volume (MPV), PLT distribution width (PDW), pH, pCO₂, pO₂, hypotonic shock response (HSR), phosphatidylserine (PS) exposure and soluble P-selectin content.ResultsPLTs stored in plasma with/without ANA didn't show significant differences during the first 5 days of storage. From the 7^th day on, PLTs stored in plasma with ANA displayed significantly lower PS expression, soluble P-selectin content and higher HSR scores than those stored in plasma without ANA (P <0.05), respectively.ConclusionThe extended storage of PLTs in plasma treated with 0.5 µmol/l ANA showed better characteristics of the PLTs, compared with the control group, which was suggested to potentially alleviate the PLT storage lesion.     

In vitro properties of platelets stored in three different additive solutions

BACKGROUND: New platelet (PLT) additive solutions (PASs) contain compounds that might improve the storage conditions for PLTs. This study compares the in vitro function, including hemostatic properties (clot formation and elasticity), of PLTs in T‐Sol, Composol, or SSP+ during storage for 5 days. STUDY DESIGN AND METHODS: Fifteen buffy coats were pooled and divided into three parts. PLT concentrates (PCs) with 30% plasma and 70% PAS (T‐Sol, Composol, or SSP+) were prepared (n = 10). Swirling, PLT count, blood gases, metabolic variables, PLT activation markers, and coagulation by free oscillation rheometry (FOR) were analyzed on Days 1 and 5. RESULTS: Swirling was well preserved and pH acceptable (6.4‐7.4) during storage for all PASs. Storage of PLTs in T‐Sol led to a decrease in PLT count whereas the number of PLTs was unchanged in Composol or SSP+ PCs. PLTs in T‐Sol showed higher glucose metabolism than PLTs in Composol or in SSP+. At the end of storage PLTs in T‐Sol had higher spontaneous activation and lower ability to respond to an agonist than PLTs in Composol or SSP+. PLTs in all the PASs had a similar ability to promote clot formation and clot elasticity. CONCLUSION: Storage of PLTs in Composol or in SSP+ improved the quality of PCs in terms of better maintained PLT count, lower glucose metabolism, lower spontaneous activation, and improved response to a PLT agonist compared to PLTs in T‐Sol. PLTs stored in the various PASs had similar hemostatic properties. These findings make Composol and SSP+ interesting alternatives as PASs.     

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

BACKGROUND: Platelet (PLT) storage adversely affects PLT structure and function in vitro and is associated with decreased PLT recovery and function in vivo. In pediatric transfusion medicine, it is not uncommon for small residual volumes to remain in parent units after aliquot preparation of leukoreduced apheresis‐derived PLTs (LR‐ADP). However, limited data exist regarding the impact of storage on residual small‐volume LR‐ADP. STUDY DESIGN AND METHODS: Standard metabolic testing was performed on residual volumes of LR‐ADP after aliquot removal and PLT aggregometry using a dual agonist of ADP and collagen was performed on stored, small‐volume aliquots (10‐80 mL) created from an in vitro model of PLT storage. RESULTS: Seventy‐seven LR‐ADP underwent metabolic (n = 67) or metabolic and aggregation (n = 10) studies. All products maintained a pH value of more than 6.89 throughout storage. Lactate and pCO₂ increased proportionally with longer storage time. Regardless of acceptable metabolism during storage, aggregation in 10‐ to 20‐mL aliquots was impaired by Day 4 and aliquots less than 40 mL demonstrated the most dramatic decrease in aggregation from baseline. CONCLUSIONS: Despite maintenance of acceptable metabolic conditions, residual volumes of LR‐ADP develop impaired aggregation in vitro that may adversely affect PLT survival and function in vivo. At volumes below 40 mL, LR‐ADP revealed reduced aggregation. As a result, it is recommended to monitor and record volumes of LR‐ADP used for pediatric transfusion. Moreover, once LR‐ADP attain a volume of 50 mL or less on Day 4 or Day 5 of storage, consider discarding these products until their in vivo efficacy can be studied.     

Apheresis donors and platelet function: inherent platelet responsiveness influences platelet quality

BACKGROUND: Process-induced platelet (PLT) activation occurs with all production methods, including apheresis. Recent studies have highlighted the range and consistence of interindividual variation in the PLT response, but little is known about the contribution of a donors' inherent PLT responsiveness to the activation state of the apheresis PLTs or the effect of frequent apheresis on donors' PLTs. STUDY DESIGN AND METHODS: The relationship between the donors' PLT response on the apheresis PLTs was studied in 47 individuals selected as having PLTs with inherently low, intermediate, or high responsiveness. Whole-blood flow cytometry was used to measure PLT activation (levels of bound fibrinogen) before donation and in the apheresis PLTs. The effects of regular apheresis on the activation status of donors' PLTs were studied by comparing the in vivo activation status of PLTs from apheresis (n = 349) and whole-blood donors (n = 157), before donation. The effect of apheresis per se on PLT activation was measured in 10 apheresis donors before and after donation. RESULTS: The level of PLT activation in the apheresis packs was generally higher than in the donor, and the most activated PLTs were from high-responder donors. There was no significant difference in PLT activation before donation between the apheresis and whole-blood donors (p = 0.697), and there was no consistent evidence of activation in the donors immediately after apheresis. CONCLUSION: The most activated apheresis PLTs were obtained from donors with more responsive PLTs. Regular apheresis, however, does not lead to PLT activation in the donors.