Platelet function in ischemic heart disease.

Blood platelets (PLTs) play a key role in atherothrombosis due to their ability of thrombus formation after rupture of an atherosclerotic plaque. Numerous clinical trials have established the efficacy of PLT function blockade in the prevention of acute coronary syndromes. Meanwhile, nearly all patients undergoing cardiopulmonary bypass grafting present with anti-PLT therapy. PLTs interact also with endothelial cells, leukocytes, and smooth muscle cells and are involved in vascular inflammation. This may result in an excessive fibroproliferative response after vessel dilatation. Furthermore, many PLT blockers are associated with response variability up to nonresponsiveness leading to increased reintervention and transfusion rates both identified as independent risk factors for an adverse clinical outcome after coronary interventions. Summarizing the role of PLTs for normal hemostasis and the pathophysiology of atherothrombosis, this review describes the current status of anti-PLT therapy and highlights some new anti-PLT drugs in the prevention of serious cardiovascular events.

Antiplatelet therapy in the prevention of coronary syndromes: mode of action, benefits, drawbacks.

Blood platelets play a key role in normal hemostasis but also in atherothrombosis due to their ability of thrombus formation at site of a ruptured atherosclerotic plaque. Platelets are also involved in vascular inflammation due to interactions with endothelial cells, leukocytes, and smooth muscle cells that may result in an excessive fibroproliferative response after vessel dilatation. This review article describes both, the current status of standard anti-platelet drug therapy using acetylsalicylic acid, adenosine diphosphate or glycoprotein IIb-IIIa receptor antagonists in the prevention of cardiovascular events as well as drawbacks like non-responsiveness or increased bleeding rates leading to enhanced reintervention and transfusion rates, both responsible for adverse clinical outcomes after coronary interventions.

Cell quality of apheresis-derived platelets treated with riboflavin-ultraviolet light after resuspension in platelet additive solution.

BACKGROUND: Previously, we evaluated the Mirasol pathogen reduction technology (PRT) system on platelet (PLT) function before resuspension. We now evaluated this system in the presence of PLT additive solution (PAS). STUDY DESIGN AND METHODS: Double-dose PLTs (n = 15) were generated using a commercially available apheresis system (Trima, Version 5.2, CaridianBCT) allowing for the resuspension in SSP+ (MacoPharma) immediately after collection. Paired units (n = 30) were PRT treated (M) or remained untreated (C) and analyzed for metabolism (pH, pO(2) , glucose, lactate, adenosine triphosphate [ATP]), swirl, hypotonic shock response (HSR), turbidometric aggregation, CD62P expression, annexin A5 and lactate dehydrogenase (LDH) release, mitochondrial enzymatic reduction activity (MTS), transmembrane mitochondrial potential (Δψ), and surface coverage (SC) during shear-induced adhesion throughout 8 days of storage. RESULTS: As seen previously, PRT treatment of PLT units, containing a mean of 3.9 × 10(11) ± 0.3 × 10(11) PLTs in 397 ± 10 mL with a 32% to 34% plasma carryover, was associated with significantly (p < 0.001) increased cell activation, acidity, and glycolytic flux. PRT treatment appeared to up regulate both oxidative pathway and adhesional properties as evidenced by significantly higher MTS reduction, oxygen consumption, and shear-induced SC on Day 1 (p ≤ 0.016). While no significant differences were found for LDH release and ATP content (except for Day 8), M units were significantly inferior (p ≤ 0.021) for aggregation (TRAP-6); for Δψ and annexin A5 release (by Day 5); and for swirl, HSR, and MTS reduction (by Day 7). CONCLUSION: PRT treatment in the presence of PAS was comparable to PRT treatment before resuspension preserving ATP content and mitochondrial function.

Platelet derived cytokine accumulation in platelet concentrates treated for pathogen reduction.

BACKGROUND: Pathogen reduction technologies (PRTs) prevent replication and proliferation of pathogens in platelet (PLT) concentrates (PCs) by modifying nucleic acids. Due to increased cell activation, PRT may also lead to increased cytokine release from α granules and promote adverse transfusion reactions in the recipient. DESIGN: Fifteen double-dose leukoreduced apheresis PCs were collected on the Trima Accel platform (vs. 5.2.) allowing for the resuspension in PLT additive solution (PAS) immediately after collection. After a 2-h resting period (1st hour without, 2nd hour with agitation), splitting was performed: one unit remained untreated to serve as control (C), while the other was riboflavin-UVB treated using the Mirasol-PRT system according to the manufacturer's instructions (M). During 8 days of storage, PCs were analyzed for contaminating white and red blood cells, bacterial growth, PLT activation, LDH and cytokine release (MIP-1 α, RANTES, PF4, and TGF-ß-1). Results obtained were opposed to a former study, where triple-dose PCs underwent Mirasol-PRT prior to resuspension or the INTERCEPT BLOOD SYSTEM (psoralen-UVA) or remained untreated. RESULTS: Despite similar LDH release, PRT treatment was associated with significantly higher (p<0.05) cell activation but only slightly higher cytokine accumulation during storage. Differences became significant only for PF4 and RANTES at day 8 of storage. On the other hand, in the investigation on triple-dose PCs (yielding higher cytokine levels), TGF beta-1 and RANTES remained significantly (p<0.05) lower after PRT treatment compared to untreated units. CONCLUSION: Factors, such as collection modality, onset of resuspension and additional amounts of magnesium/potassium in the PAS used may be of equal or even greater impact for cytokine accumulation in stored PCs than PRT treatment.

In-vitro assessment of platelet function.

Platelets (PLTs), play a key role in hemostasis, clot stability and retraction as well as in vascular repair and anti-microbial host defense. Upon vessel wall damage, PLTs undergo a highly regulated set including adhesion, spreading, aggregation, release reactions as well as exposure of procoagulant surfaces to rapidly form a hemostatic plug that occludes the site of damage. When PLT function is impaired, the bleeding risk increases, but (hyperreactive) PLTs are also involved in many pathophysiological events like thrombosis, vessel constriction, atherogenesis, tumor growth and metastasis, inflammation including atherosclerosis and the subsequent formation of arterial thrombi resulting in stroke and myocardial infarction. While hereditary PLT function disorders are very rare, acquired PLT function abnormalities occur in the course of many diseases and can be associated with many drugs, i.e., non-steroidal anti-inflammatorics, antibiotics or heparin. Therefore, apart from disease diagnosis, severity, and prognosis, assessment of PLT function also serves for identifying the efficacy of anti-PLT therapy and PLT hyperfunction as a possible predictor for thromboembolic events. Since PLTs undergo a lot of measurable changes during storage ex-vivo, one effort of transfusion medicine is the quality monitoring of PLT concentrates (PCs), but also the detection of donors with PLT dysfunction and the determination of patients in which PLT transfusions are effective. The majority of PLT tests focus only on PLT functions involved directly in hemostasis including adhesion/aggregation, coagulation, and clot retraction. Traditional tests, almost complex, time-consuming, and poorly specified, are meanwhile enriched by more user friendly and easy-to-use point-of-care tests on fully automated instruments within whole blood without the requirement of sample processing. These tests help identifying surgical patients at increased risk of post-operative bleeding or with resistance to anti-PLT therapy, therefore at increased risk of thromboembolism. However, up to now, no study shows real outcome benefits by including these tests into the disease management. To date, no function test is suitable to address all distinct steps of PLT activation or reliably predict PLT behavior in vivo following transfusion.

Annexin V Release and Transmembrane Mitochondrial Potential during Storage of Apheresis-Derived Platelets Treated for Pathogen Reduction.

BACKGROUND: In vitro function of stored platelet (PLT) con-centrates was analyzed after applying two different techniques of pathogen reduction technology (PRT) treatment, which could increase cellular injury during processing and storage. METHODS: Nine triple-dose PLT apheresis donations were split into 27 single units designated to riboflavin-UVB (M) or psoralen-UVA (I) treatment or remained untreated (C). Throughout 8 days of storage, samples were analyzed for annexin V release, the mitochondrial transmembrane potential (Deltapsi) and some classical markers of PLT quality (pH, LDH release, hypotonic shock response (HSR)). RESULTS: PLT count and LDH release of all units maintained initial ranges. All units exhibited a decrease in pH and HSR and an increase in annexin V release and Deltapsi disruption. Notably, throughout the entire storage period, annexin V release re-mained lowest in M units. Throughout 7 days of storage, M units remained comparable to C units (p > 0.05), whereas inferior values were observed with I units. Here, differences to C units reached significance by day 1 (pH: p < 0.0001), day 5 (annexin V release: p < 0.014), and day 7 (HSR, Deltapsi: p

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 (Deltapsi; JC-1 assay), and metabolism based on pH, pO(2), glucose, lactate, and ATP content. RESULTS: During storage, Deltapsi 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 (Deltapsi) 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.

Platelet function assessed by shear-induced deposition of split triple-dose apheresis concentrates treated with pathogen reduction technologies.

BACKGROUND: Pathogen inactivation/reduction technology (PRT) may alter quality of stored platelet (PLT) concentrates (PCs). Therefore, PLT adhesion and aggregation should be studied before transfusion of PRT-treated PLTs. STUDY DESIGN AND METHODS: A three-arm in vitro study on triple-dose apheresis PCs (n = 9) was conducted. Split single units were designated to PRT treatment with either a riboflavin (M)- or a psoralen (I)-based technique and compared to untreated controls (C). Samples were taken on Days 0, 1, 5, 7, and 8 to assess PLT function via a cone and plate(let) analyzer, flow cytometric P-selectin expression, and turbidometric aggregation response to thrombin receptor-activating peptide 6 (TRAP-6). RESULTS: P-selectin expression increased and TRAP-6-inducible expression decreased steadily in all units until reaching a plateau on Day 5 of storage. PRT-treated units demonstrated significant (p < or = 0.008) differences to C units due to a more pronounced upregulation in P-selectin expression after PRT treatment. The same was true for TRAP-6 after Day 5 of storage. C units were significantly superior over PRT-treated units (p < or = 0.002), among which M yielded higher values than I (p < or = 0.008). Although M demonstrated increased shear-induced PLT deposition that remained stable during storage (p = 0.082), surface coverage significantly declined in C (p = 0.047) and especially in I (p = 0.003), but differences between M, C, and I did not reach significance. All units exhibited a slight increase in aggregate size that remained comparable throughout storage (p > or = 0.141). CONCLUSIONS: Irrespective of storage-related changes in PLT activation and turbidometric aggregation response, riboflavin-based PRT seemed to benefit shear-induced PLT adhesion. The impact of this finding for PLT function and thrombogenesis in vivo must await clinical evaluation.

Cell integrity and mitochondrial function after Mirasol-PRT treatment for pathogen reduction of apheresis-derived platelets: Results of a three-arm in vitro study.

BACKGROUND: Mirasol pathogen reduction technology (PRT) treatment uses riboflavin (vitamin B(2)) in combination with ultraviolet light (UV) to inactivate pathogens in platelet concentrates (PCs). This treatment has been reported to increase glycolytic flux, which could result from damage to mitochondria and/or increased ATP demand. DESIGN: Triple-dose PCs were collected by the Trima Accel device. Immediately after splitting, single units were designated to Mirasol-PRT treatment (M), gamma irradiation (X) or remained untreated (C). Platelet (PLT) mitochondrial transmembrane potential (Deltapsi) was evaluated (JC-1 assay) as well as mitochondrial enzymatic activity (MTS assay). LDH release, p selectin expression, glucose/oxygen consumption and lactate production rates were quantified and compared among study groups during 7days of storage. RESULTS: Immediately after PRT treatment, no significant changes were found in JC-1 signal, MTS activity, and LDH release indicating that PRT treatment did not alter functional/structural cell or mitochondrial integrity as evidenced by LDH release comparable to untreated study groups. In parallel to significantly higher p selectin expression, treated PLTs exhibited significantly accelerated oxygen and glucose consumption rates associated with increased acidity due to higher lactate production rates throughout storage. Despite larger cell populations with depolarized Deltapsi particularly at days 5 and 7, mitochondrial reduction activity of M units as measured by the MTS assay was maintained and appeared to be up-regulated relative to untreated and irradiated controls. CONCLUSION: Mirasol-PRT treated PLTs increased both glycolytic flux as well as respiratory/enzymatic mitochondrial activity. An increased demand for ATP due to increased alpha granule degranulation may be the driving force for these observations.

Evaluation of White Blood Cell- and Platelet-Derived Cytokine Accumulation in MIRASOL-PRT-Treated Platelets.

BACKGROUND: Soluble mediators in platelet concentrates (PCs) released from contaminating white blood cells (WBCs) and platelets (PLTs) themselves are supposed to promote allergic and non-hemolytic febrile transfusion reactions in the recipient. Pathogen reduction technologies (PRTs) prevent replication and proliferation of pathogens as well as of WBCs, and may reduce cytokine accumulation in PCs during storage and prevent adverse events after PLT transfusion. On the other hand, such treatments may also lead to increased cytokine production by stimulation of WBCs or PLTs due to the photochemical or photodynamical process itself. MATERIAL AND METHODS: 12 triple-dose PLT apheresis collections were leukoreduced by the process-controlled leukoreduction system of the Trima Accel machine and split into 3 units undergoing Mirasol-PRT treatment (M) or gamma irradiation (X) or remaining untreated (C). During storage for up to 7 days, PLT activation, WBC-derived Th-1/2, and inflammatory as well as PLT-derived cytokines were measured by cytometric bead array and enzymelinked immunosorbent assay, respectively. RESULTS: Independent of treatment, all PLT products exhibited low levels of WBC-associated cytokines near or below assay detection limits. WBC-associated cytokines were not elevated by Mirasol-PRT treatment. PLT-derived cytokines were detected at higher levels and increased significantly during storage in all units. Most likely due to higher PLT activation, M units showed significantly higher levels of PLT-derived cytokines compared to untreated and gamma-irradiated units on day 5 of storage. CONCLUSION: In all PCs, PLTs themselves were the main source of cytokine release. Mirasol-PRT treatment was associated with a significantly increased PLT activation and accumulation of PLT-derived cytokines during storage, without affecting WBC-derived cytokines relative to controls.

Effects of Mirasol PRT treatment on storage lesion development in plasma-stored apheresis-derived platelets compared to untreated and irradiated units.

BACKGROUND: The aim of this study was to examine the effects of a new riboflavin-based pathogen reduction technology (PRT), the Mirasol PRT process (Navigant Biotechnologies) on platelet (PLT) storage lesion development. STUDY DESIGN AND METHODS: A three-arm in vitro study was conducted comparing cell quality of apheresis PLTs (n = 12 each) treated with Mirasol PRT (M) to untreated (C) and gamma-irradiated units (X) collected from the same donors and stored for up to 7 days under equal conditions. RESULTS: PLT count, lactate dehydrogenase, and K+ release of M units were not significantly different from C units, indicating retention of cell integrity during storage. The immediate effect (Day 1) of PRT treatment was a significant decrease in hypotonic shock response (M, 80.6 +/- 7.8% vs. 89.2 +/- 8.3%) and aggregation (M, 85.7 +/- 15.2%/min vs. 111.8 +/- 31.5%/min) as well as a significant acceleration of mitochondrial membrane depolarization (M, 1.43 +/- 0.44% vs. 0.91 +/- 0.27%) and P-selectin expression (M, 38.4 +/- 13.8% vs. 15.8 +/- 7.7%) resulting in lower swirl scores on Day 5 (1.5 +/- 0.7 vs. 2.7 +/- 0.4). Significantly higher glucose consumption (60 +/- 13 nmol/10(12) cells/hr vs. 31 +/- 9 nmol/10(12) cells/hr) and lactate production rates (82 +/- 17 nmol/10(12) cells/hr vs. 40 +/- 8 nmol/10(12) cells/hr) caused higher acidity in treated units (pH on Day 5, 6.97 +/- 0.15 vs. 7.42 +/- 0.10). After PRT treatment, oxidative metabolism was still active and, from calculation of oxygen consumption (1.09 +/- 0.23 nmol/min/10(9) PLTs), appeared to be up regulated relative to controls (0.76 +/- 0.27 nmol/min/10(9) PLTs). CONCLUSION: Although storage variables clearly showed the effects of PRT treatment, apheresis PLTs treated with Mirasol PRT retained cell quality during 5 days of storage without loss of mitochondria-based oxidative respiration.

Evaluation of Four Bedside Test Systems for Card Performance, Handling and Safety.

SUMMARY: OBJECTIVE: Pretransfusion ABO compatibility testing is a simple and required precaution against ABO-incompatible transfusion, which is one of the greatest threats in transfusion medicine. While distinct agglutination is most important for correct test interpretation, protection against infectious diseases and ease of handling are crucial for accurate test performance. Therefore, the aim of this study was to evaluate differences in test card design, handling, and user safety. DESIGN: Four different bedside test cards with pre-applied antibodies were evaluated by 100 medical students using packed red blood cells of different ABO blood groups. Criteria of evaluation were: agglutination, labelling, handling, and safety regarding possible user injuries. Criteria were rated subjectively according to German school notes ranging from 1 = very good to 6 = very bad/insufficient. RESULTS: Overall, all cards received very good/good marks. The ABO blood group was identified correctly in all cases. Three cards (no. 1, no. 3, no. 4) received statistically significant (p < 0.008) prominence (mean values shown) concerning clearness of agglutination (1.7-1.9 vs. 2.4 for no. 2). Systems with dried antibodies (no. 2, no. 4) outmatched the other systems with respect to overall test system performance (2.0 vs. 2.8-2.9), labelling (1.5 vs. 2.2-2.4), handling (1.9-2.0 vs. 2.5), and user safety (2.5 vs. 3.4). Analysis of card self-explanation revealed no remarkable differences. CONCLUSION: Despite good performance of all card systems tested, the best results when including all criteria evaluated were obtained with card no. 4 (particularly concerning clear agglutination), followed by cards no. 2, no. 1, and no. 3.

In vitro quality of red blood cells (RBCs) collected by multicomponent apheresis compared to manually collected RBCs during 49 days of storage.

BACKGROUND: New technologic developments enable automated collection and preparation of red blood cells (RBCs). This study's aim was to evaluate quality of apheresis-derived RBCs (ARBCs) collected as single units along with platelets (RBC-Ps) or double units (2-RBCs) with four different apheresis systems. STUDY DESIGN AND METHODS: Sixty-six donors with similar baseline variables underwent RBC apheresis collection with various machines (Amicus [15 RBC-Ps] and Alyx [15 2-RBCs], Baxter; the Trima Accel [9 RBC-Ps, 8 2-RBCs], Gambro, and the MCS+[9 RBC-Ps, 10 2-RBCs], Haemonetics Corp.). In vitro properties were analyzed during 49 days of storage and compared to manual RBCs (MRBCs, n = 14). RESULTS: All units but one, Alyx, demonstrated white blood cell counts of less than 1 x 10(6). ARBCs showed lower variability in volume compared to MRBCs. All units met international requirements (European, AABB) for hematocrit (50%-70%), hemoglobin (>40 g/unit), and RBC mass (>or=153 mL). pH values remained similar between study groups without reaching critical limits in any unit. MRBCs had slight advantages for hemolysis at the end of storage and were significantly superior in energy maintenance as indicated by less ATP degradation and potassium leak most likely due to more pronounced anoxidative glycolysis particularly during the first half of storage. Owing to more declining oxidative glucose metabolism, ARBCs demonstrated higher methemoglobin formation and subsequent oxygen release until the end of storage. CONCLUSION: ARBCs exhibited better predictability in volume and absolute RBC mass than MRBCs and demonstrated sufficient in vitro quality throughout storage, even though lower ATP preservation and higher methemoglobin formation were observed compared to MRBCs probably due to differences in glucose metabolism.

Prospective evaluation of double RBC collection using three different apheresis systems.

BACKGROUND: Automated component collection systems offer the possibility of increasing blood supply and improving transfusion safety. DESIGN: 30 blood donors were randomly assigned to double RBC collection with either the Baxter Alyx (AX), the Haemonetics MCS Plus (MCS+), or the Gambro Trima Accel (TA). Procedures were prospectively evaluated focussing on yield, time, efficiency, citrate donor load, and in vitro quality. RESULTS: All units showed sufficient in vitro quality throughout 42 days of storage and complied with international requirements. Donor reactions were limited to mild citrate reactions. AX was the fastest and most efficient system* * (* *p approximately 0.001) attaining the highest yield* * from similar amounts of whole blood. The drawbacks were a higher RBC loss* (*p < 0.05) and accelerated citrate infusion* *. Due to lower collection rates* * * (* * *p < 0.001), MCS+ was slower than TA* * * but compensated with lower citrate load * * *. CONCLUSION: Double RBC apheresis was performed safely and efficiently with all three instruments. AX had advantages for most parameters evaluated.

Pathophysiology, epidemiology, diagnosis and treatment of heparin-induced thrombocytopenia (HIT).

Due to the widespread use of unfractionated (UFH) and low molecular weight heparins (LWH) for prophylaxis and treatment of thrombosis, heparin-induced thrombocytopenia is considered to be the most frequent (and potentially the most devastating) drug-induced thrombocytopenia. Induced by an immune response, excessive activation of platelets and endothelium cells causes massive thrombin generation and, as a result, life-threatening venous and arterial thrombotic vessel occlusion. The rate of mortality and amputation in HIT II is estimated to be 30% and 20%, respectively. The clinical course of HIT II depends highly on early therapeutic intervention consisting of immediate interruption of heparin application and, most important, of compatible thrombin inhibition. All measures implying a potentially procoagulant risk such as begin of oral anticoagulation or platelet substitution may result in disastrous side effects.

Epidemiology, etiology and diagnosis of venous thrombosis.

Venous thromboembolism (VTE) is one of the most frequent multifactorial diseases. It manifests clinically by deep vein thrombosis (DVT) and pulmonary embolism (PE) leading to death in about 6%. It is important to emphasize, that 50% of the patients do not present any symptoms. The prevalence is influenced by age and ethnics. Both, hereditary (Factor V Leiden, G20210A prothrombin gene mutation, deficiencies of protein C, S or antithrombin) and acquired risk factors (estrogen replacement, cancer, cardiovascular disease, surgery, trauma, immobility, use of central venous catheters, autoimmune disease such as anti-phospholipid syndrome) contribute to VTE. The risk increases dramatically by the addition of hyperhomocysteinemia or the combination of several risk factors. Since VTE is a dynamic process able to manifest clinically or to resolve completely, the identification of persons at increased risk is mainly important for early diagnosis and treatment. The diagnostic strategy including clinical scores and laboratory tests (D-dimer measurement) as initial steps to confirm the suspicion of VTE may exclude patients who do not need further, sometimes invasive imaging tests (venography, compression ultrasonography combined or not combined with colour Doppler imaging, magnetic resonance imaging). Laboratory tests for suspected inherited thrombophilia should be performed six months after clinical presentation.

Functional characteristics of buffy-coat PLTs photochemically treated with amotosalen-HCl for pathogen inactivation.

BACKGROUND: One blood system for PLTs (INTERCEPT, Baxter Transfusion Therapies) is based on photochemical treatment (PCT) with small molecules that target cross-link nucleic acids (Helinx technology, Cerus Corp.) with amotosalen-HCl (S-59) and UVA light (320-400 nm) to inactivate pathogens and WBCs. STUDY DESIGN AND METHODS: A two-arm in vitro study was conducted to compare pooled buffy-coat-derived PLT concentrates (PCs) treated with the INTERCEPT blood system, resuspended in PLT additive solution (PAS) III (InterSol, Baxter Transfusion Therapies), and stored for up to 7 days (test units, n = 20) with unpaired, nontreated PCs, resuspended in PAS II (T-Sol, Baxter Transfusion Therapies), and prepared at the same center in the same manner (control units, n = 18). RESULTS: PLT dose (x 1011/unit +/- SD) on Day 1 immediately following PCT was 3.0 +/- 0.4 for test units and 3.2 +/- 0.4 for control units. After 7 days of storage, the pH of all test units was maintained above 6.8. No marked trend was observed in the hypotonic shock response (HSR). Values among study groups were similar at the end of observation period: 68 +/- 11 percent for control unites versus 67 +/- 8 percent for test units (p > 0.05). Aggregation response to ristocetin was slightly lower in test units: at Day 7, 65 +/- 10 percent versus 76 +/- 6 percent (p < 0.05). Significantly higher (p < 0.001) glucose consumption, lactate production, and CD62P expression were observed in test units. CONCLUSION: Compared to nontreated PLTs, the PCT process was associated with a variety of differences of in vitro analyses. Although significant, these changes were relatively small in most cases. Characteristics correlated with survival in vivo such as HSR and swirling were comparable between both study groups, indicating that the viability of the majority of cells appears to have persisted throughout 7 days of storage. The impact of this finding, however, remains to be investigated in clinical trials performed with 7-day stored PLTs.

Function, expression and localization of annexin A7 in platelets and red blood cells: insights derived from an annexin A7 mutant mouse.

BACKGROUND: Annexin A7 is a Ca2+- and phospholipid-binding protein expressed as a 47 and 51 kDa isoform, which is thought to be involved in membrane fusion processes. Recently the 47 kDa isoform has been identified in erythrocytes where it was proposed to be a key component in the process of the Ca2+-dependent vesicle release, a process with which red blood cells might protect themselves against an attack by for example complement components. RESULTS: The role of annexin A7 in red blood cells was addressed in erythrocytes from anxA7-/- mice. Interestingly, the Ca2+-mediated vesiculation process was not impaired. Also, the membrane organization appeared not to be disturbed as assessed using gradient fractionation studies. Instead, lack of annexin A7 led to an altered cell shape and increased osmotic resistance of red blood cells. Annexin A7 was also identified in platelets. In these cells its loss led to a slightly slower aggregation velocity which seems to be compensated by an increased number of platelets. The results appear to rule out an important role of annexin A7 in membrane fusion processes occurring in red blood cells. Instead the protein might be involved in the organization of the membrane cytoskeleton. Red blood cells may represent an appropriate model to study the role of annexin A7 in cellular processes. CONCLUSION: We have demonstrated the presence of both annexin A7 isoforms in red blood cells and the presence of the small isoform in platelets. In both cell types the loss of annexin A7 impairs cellular functions. The defects observed are however not compatible with a crucial role for annexin A7 in membrane fusion processes in these cell types.