Platelet concentrates prepared and stored under currently optimal conditions: minor impact on platelet adhesive and cohesive functions after storage

Collagen-dependent platelet dysfunction and its relevance to either mitochondrial ROS or cytosolic superoxide generation: a question about the quality and functional competence of long-stored platelets

Background

Upon vascular damage, the exposed subendothelial matrix recruits circulating platelets to site of injury while inducing their firm adhesion mainly via GPVI-collagen interaction. GPVI also supports aggregatory and pro-coagulant functions in arterial shear rate even on the matrix other than collagen. Reactive oxygen species (ROS) modulate these stages of thrombosis; however augmented oxidant stress also disturbs platelet functions. Stored-dependent platelet lesion is associated with the increasing levels of ROS. Whether ROS accumulation is also relevant to collagen-dependent platelet dysfunction is the main interest of this study.

Methods

Fresh PRP-PCs (platelet concentrates) were either stimulated with potent ROS-inducers PMA and CCCP or stored for 5 days. Intra-platelet superoxide (O₂ ^--) or mitochondrial-ROS and GPVI expression were detected by flowcytometery. GPVI shedding, platelet aggregation and spreading/adhesion to collagen were analyzed by western blot, aggregometry and fluorescence-microscopy, respectively.

Results

Mitochondrial-ROS levels in 5 days-stored PCs were comparable to those induced by mitochondrial uncoupler, CCCP while O₂ ^-- generations were higher than those achieved by PMA. Shedding levels in 5 days-stored PCs were higher than those induced by these potent stimuli. GPVI expressions were reduced comparably in CCCP treated and 5 days-stored PCs. Platelet adhesion was also diminished during storage while demonstrating significant reverse correlation with GPVI shedding. However, only firm adhesion (indicated by platelets spreading or adhesion surface area) was relevant to GPVI expression. Platelet adhesion and aggregation also showed reverse correlations with both O2^-- and mitochondrial-ROS formations; nonetheless mitochondrial-ROS was only relevant to firm adhesion.

Conclusion

As a sensitive indicator of platelet activation, GPVI shedding was correlated with either simple adhesion or spreading to collagen, while GPVI expression was only relevant to platelet spreading. Thereby, if the aim of GPVI evaluation is to examine platelet firm adhesion, expression seems to be a more specific choice. Furthermore, the comparable levels of ROS generation in 5 days-stored PCs and CCCP treated platelets, indicated that these products are significantly affected by oxidative stress. Reverse correlation of accumulating ROS with collagen-dependent platelet dysfunction is also a striking sign of an oxidant-induced lesion that may raise serious question about the post-transfusion quality and competence of longer-stored platelet products.

Autologous blood preparations rich in platelets, fibrin and growth factors

OBJECTIVES

Bone regeneration is often needed prior to dental implant treatment due to the lack of adequate quantity and quality after infectious diseases. The greatest regenerative power was obtained with autologous tissue, primarily the bone alive, taken from the same site or adjacent sites, up to the use centrifugation of blood with the selection of the parts with the greatest potential regenerative. In fact, various techniques and technologies were chronologically successive to cope with an ever better preparation of these concentrates of blood. Our aim is to review these advances and discuss the ways in which platelet concentrates may provide such unexpected beneficial therapeutic effects.

METHODS

The research has been carried out in the MEDLINE and Cochrane Central Register of Controlled Trials database by choosing keywords as "platelet rich plasma", "platelet rich fibrin", "platelet growth factors", and "bone regeneration" and "dentistry".

RESULTS

Autologous platelet rich plasma is a safe and low cost procedure to deliver growth factors for bone and soft tissue healing.

CONCLUSION

The great heterogeneity of clinical outcomes can be explained by the different PRP products with qualitative and quantitative difference among substance.

Determining the Effect of Preparation and Storage: An Effort to Streamline Platelet Components as a Source of Growth Factors for Clinical Application

BACKGROUND

In the present study, different methods for preparation of platelet-rich plasma (PRP) are investigated in order to standardize the component in terms of growth factor content. The effects of concentration technique and storage duration are also analyzed.

METHODS

PRP was collected from 40 donors by plateletpheresis as well as by the buffy coat and tube method. Concentration of growth factors was performed using double freeze thaw- and CaCl2-induced degranulation techniques. Growth factor estimation was performed using ELISA.

RESULTS

The levels of growth factors were highest in PRP from buffy coat, moderately lower in plasma gained by plateletpheresis and lowest in that obtained by the tube method. Mean levels of platelet-derived growth factors (PDGF) AB and BB are significantly higher when CaCl2 was used for concentrating the growth factors. The mean levels of transforming growth factor β1 and insulin-like growth factor I were higher when applying the double freeze thaw technique. There was a substantial decline in the levels of growth factors during storage.

CONCLUSION

The buffy coat method is suitable as preparation method for PRP in most settings. The double freeze thaw technique is better suited as concentration technique as it causes lysis of both platelets and white blood cells for releasing growth factors and is easier to perform. Growth factors are not stable in plasma, thus PRP should be frozen immediately after preparation.

The effect of 24 h resting of old PCs at 22-24°С in permeable bags on in vitro platelet parameters

BACKGROUND

During transporting periods, platelet (PLT) concentrates (PCs) usually undergo a long period without agitation. Whether this interruption, improves quality and viability, or has deleterious effect at 72 h stored PCs, is here investigated. The aim of our study is to investigate effect of metabolic resting (24 h interruption of agitation) versus continue agitation of 72 h-stored PCs (old), prior to transfusion in the blood bank of Tehran.

STUDY DESIGN AND METHODS

PCs were prepared using the platelet-rich plasma (PRP) method and stored in the permeable bags in the shaker/incubator, for 72 h at 20-24°C. Then by simply stopping the agitator, PCs remained at stationary condition without agitation for 24 h (WA24h) before sampling. In vitro measurements of PLT quality were carried out just after the termination of interruption period, and the results were compared with continuously agitated platelet within the same day (designated as control group, CA). In vitro variables which are measured were pH, Platelet count, swirling, Ristocetin-induced aggregation (GPIb-related function), LDH, PF4 release and P-selectin expression (activation marker).

RESULTS

Compared with control group, the mean platelets PF4 release and P-selectin expression showed no significant differences (p=0.101, p=0.739 respectively). The mean level of pH was not significant (p=0.156); WA24h (7.12±0.14) and CA (7.17±0.11). Also Ristocetin-induced aggregation study showed significant differences (p=0.0281) between CA (76.6±3.2) and WA24h (62.69±21.43). Other in vitro variables between CA and WA groups including swirling, Platelet count and LDH showed no significant differences after 72 h of storage.

CONCLUSIONS

We observed that 24 h resting of old PCs (WA24h) at 22-24°С in permeable bags preserved pH, swirling, LDH, Ristocetin-induced aggregation and platelet's activation as good as control group after 72 h of storage.

Platelet transfusion - the art and science of compromise

SUMMARY

Many modern therapies depend on platelet (PLT) transfusion support. PLTs have a 4- to 7-day shelf life and are frequently in short supply. In order to optimize the inventory PLTs are often transfused to adults without regard for ABO compatibility. Hemolytic reactions are infrequent despite the presence of 'high titer' anti-A and anti-B antibodies in some of the units. Despite the low risk for hemolysis, some centers provide only ABO identical PLTs to their recipients; this practice might have other beneficial outcomes that remain to be proven. Strategies to mitigate the risk of hemolysis and the clinical and laboratory outcomes following ABO-matched and mismatched transfusions will be discussed. Although the PLTs themselves do not carry the D antigen, a small number of RBCs are also transfused with every PLT dose. The quantity of RBCs varies by the type of PLT preparation, and even a small quantity of D+ RBCs can alloimmunize a susceptible D- host. Thus PLT units are labeled as D+/-, and most transfusion services try to prevent the transfusion of D+ PLTs to D- females of childbearing age. A similar policy for patients with hematological diseases is controversial, and the elements and mechanisms of anti-D alloimmunization will be discussed.

Redistribution and hemostatic action of recombinant activated factor VII associated with platelets

Clinical evidence accumulated from hemophilic patients during prophylaxis with recombinant activated factor VII (rFVIIa) suggests that the duration of the hemostatic action of rFVIIa exceeds its predicted plasma half-life. Mechanisms involved in this outcome have not been elucidated. We have investigated in vitro the redistribution of rFVIIa in platelets from healthy donors, patients with FVII deficiency, and one patient with Bernard-Soulier syndrome. Platelet-rich plasma was exposed to rFVIIa (3 to 60 μg/mL). Flow cytometry, immunocytochemistry, and coagulation tests were applied to detect and quantify rFVIIa. The hemostatic effect of rFVIIa associated to platelets was evaluated using perfusion models. Our studies revealed a dose-dependent association of rFVIIa to the platelet cytoplasm with redistribution into the open canalicular system, and α granules. Mechanisms implicated in the internalization are multiple, involve GPIb and GPIV, and require phospholipids and cytoskeletal assembly. After platelet activation with thrombin, platelets exposed rFVIIa on their membrane. Perfusion studies revealed that the presence of 30% of platelets containing FVIIa improved platelet aggregate formation and enhanced fibrin generation (P < 0.01 versus control). Our results indicate that, at therapeutic concentrations, rFVIIa can be internalized into platelets, where it is protected from physiological clearance mechanisms and can still promote hemostatic activity. Redistribution of rFVIIa into platelets may explain the prolonged prophylactic effectiveness of rFVIIa in hemophilia.

Inhibition of tyrosine kinase activity prevents the adhesive and cohesive properties of platelets and the expression of procoagulant activity in response to collagen

INTRODUCTION

Platelet activation leads to signal transduction mechanisms, in which phosphotyrosine proteins play a relevant role.

MATERIAL AND METHODS

Platelet suspensions were independently activated by collagen and thrombin in the absence and in the presence of two tyrosine kinase inhibitors, tyrphostin 47 and genistein. Samples were processed to visualize morphological changes by electron microscopy, to evaluate changes in cytoskeletal assembly, to analyze modifications in the expression of activation dependent antigens, and the procoagulant activity at the surface level by flow cytometry. Additional experiments applying flow conditions were performed to assess the effect of inhibiting tyrosine phosphorylation on primary platelet adhesion and fibrin formation.

RESULTS

Inhibition of tyrosine phosphorylation blocked shape change and cytoskeletal assembly induced by collagen, and inhibited, though partially, those effects due to thrombin. Both activating agents induced the expression of the intraplatelet antigens CD62P and CD63 at the surface, although only collagen promoted expression of anionic phospholipids. Both tyrphostin 47 and genistein prevented those effects. The extent of platelet adhesion on both collagen-coated and subendothelial surfaces was significantly diminished by the presence of the tyrosine kinase inhibitors assayed. Fibrin formation was also significantly reduced.

CONCLUSIONS

Platelet shape change and secretion during platelet activation depends on tyrosine phosphorylation. In addition, primary adhesion of platelets induces signaling through tyrosine kinases to achieve full spreading, and results in the exposure of a procoagulant surface on platelets.

Stability of soluble adhesion molecules, selectins, and C-reactive protein at various temperatures: implications for epidemiological and large-scale clinical studies

BACKGROUND

We assessed the impact of sample storage conditions on soluble vascular cell adhesion molecules (sVCAM), soluble intracellular adhesion molecules (sICAM-1), soluble (s)E-selectin, C-reactive protein (CRP), and sP-selectin.

METHODS

Markers were measured by ELISA in venous blood from 10 healthy volunteers on aliquots stored as plasma or whole blood at 4, 21, or 30 degrees C for 1-5 days and after 1-5 freeze-thaw cycles. We compared results on these samples to results for samples processed immediately and stored at -80 degrees C. Statistical models assessed time-related effects and effects of postprocessing conditions.

RESULTS

Using an upper limit of 10% variation from baseline with P >0.05, we found that stability duration in plasma was 5 days for sVCAM-1 and sICAM-1 and at least 2 days for sE-selectin at 4, 21, and 30 degrees C and 5 days for CRP at 4 and 21 degrees C and 1 day at 30 degrees C. Stability duration in whole blood was 5 days for sVCAM-1 and sICAM-1 and at least 2 days for sE-selectin at 4, 21, and 30 degrees C and 5 days for CRP at 4 and 21 degrees C and 2 days at 30 degrees C. sP-selectin was not stable in plasma or whole blood. sICAM-1, sVCAM-1, CRP, and sE-selectin were stable after 5 freeze-thaw cycles.

CONCLUSIONS

sVCAM-1, sICAM-1, and CRP are stable in plasma or whole blood at 4 and 21 degrees C for at least 3 days and sE-selectin for 2 days. sP-selectin is not stable and therefore requires immediate assay.

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

BACKGROUND

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

STUDY DESIGN AND METHODS

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

RESULTS

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

CONCLUSION

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

Measures of Thrombosis and Fibrinolysis

Our recent understanding of acute coronary syndrome as an atherothrombotic process has led to research efforts in the development of markers of thrombosis and fibrinolysis for risk prediction in cardiovascular heart disease. Although American Heart Association/American College of Cardiology guidelines recommend fibrinogen as a category I risk factor and also suggest factor VII, plasminogen activator inhibitor-1, tissue-type plasminogen activator, and von Willebrand factor as other potentially clinically useful markers, these tests have not come into routine clinical use. Their development as predictors of risk may be hampered by inconsistent laboratory methodology, which causes difficulty in comparing result interpretation with published trial studies. This article presents the history of development for these tests, proper laboratory handling, the best trial data that present evidence of their accuracy, and current guidelines for clinical use.

Effects of a new pathogen-reduction technology (Mirasol PRT) on functional aspects of platelet concentrates

BACKGROUND

Several strategies are being developed to reduce the risk of pathogen transmission associated with platelet (PLT) transfusion.

STUDY DESIGN AND METHODS

The impact of a new technology for pathogen reduction based on riboflavin plus illumination (Mirasol PRT, Navigant Biotechnologies, Inc.) at 6.2 and 12.3 J per mL on functional and biochemical characteristics of PLTs was evaluated. PLT concentrates (PCs) obtained by apheresis were treated with Mirasol PRT and stored at 22 degrees C. Modifications in major PLT glycoproteins (GPIbalpha, GPIV, and GPIIb-IIIa), adhesive ligands (von Willebrand factor [VWF], fibrinogen [Fg], and fibronectin), activation antigens (P-selectin and LIMP), and apoptotic markers (annexin V binding and factor [F]Va) were analyzed by flow cytometry. Adhesive and cohesive PLT functions were evaluated with well-established perfusion models. Studies were performed on the preparation day (Day 0) and during PCs storage (Days 3 and 5).

RESULTS

Levels of glycoproteins remained stable during storage in PCs treated with 6.2 J per mL pathogen reduction technology (PRT) and similar to those observed in nontreated PCs. When 12.3 J per mL PRT was applied, however, levels of GPIbalpha moderately decreased on Days 3 and 5. VWF, Fg, and FVa were not modified in their expression levels, either by treatment or by storage period. Fibronectin appeared more elevated in all PRT samples. A progressive increase in P-selectin and LIMP expression and in annexin V binding was observed during storage of PRT-treated PCs. Functional studies indicated that 6.2 J per mL Mirasol PRT-treated PLTs preserved adhesive and cohesive functions to levels compatible with those observed in the respective control PCs.

CONCLUSION

PLT function was well preserved in PCs treated with 6.2 J per mL Mirasol PRT and stored for 5 days.

Effect of platelet-rich plasma with autogenous bone graft for maxillary sinus augmentation in a rabbit model

PURPOSE

To evaluate the effect of platelet-rich plasma (PRP) on autogenous bone graft remodeling during sinus augmentation in a rabbit model.

MATERIALS

Twelve New Zealand White rabbits were divided randomly into 3 groups based on their time of sacrifice (2, 4, and 8 weeks). All animals underwent a general anesthetic and harvesting of an autogenous bone graft from the right iliac crest with subsequent bilateral maxillary sinus augmentation. PRP was prepared via standard approved technique by acquiring 21 cc of autogenous blood and performing differential centrifugation to obtain PRP. One cc of PRP was produced that was mixed with bovine topical thrombin and calcium chloride. The left maxillary sinus received only autogenous bone, while the right maxillary sinus received a mixture of PRP mixed with autogenous bone, thus each animal acted as its own control. Equal volumes of bone were inserted in each maxillary sinus. Animals were sacrificed at 2, 4, and 8 weeks and all specimens were harvested for peripheral quantitative computed tomography (pQ-CT), static, and dynamic and histomorphometric analysis.

RESULTS

Student t tests were performed comparing bone density via pQ-CT analysis, histomorphometric parameters of total bone area, and bone apposition rate. PRP had no statistically significant effect on bone graft healing in maxillary sinus augmentation when compared using standard pQ-CT, static, and dynamic histologic criteria.

CONCLUSION

This study fails to find a direct stimulatory effect of PRP on healing of autogenous bone grafts using pQ-CT, static, and dynamic histomorphometric analyses.

Transplantation of marrow-derived mesenchymal stem cells and platelet-rich plasma during distraction osteogenesis--a preliminary result of three cases

Clinical results of distraction osteogenesis with transplantation of marrow-derived mesenchymal stem cells (MSCs) and platelet-rich plasma (PRP) were reviewed in three femora and two tibiae of the two patients with achondroplasia and one patient with congenital pseudarthrosis of the tibia. MSCs derived from the iliac crest were cultured with osteogenic supplements and differentiated into osteoblast-like cells. PRP, which is known to contain several growth factors and coagulate immediately by a minute introduction of thrombin and calcium, was prepared just before transplantation. Culture-expanded osteoblast-like cells and autologous PRP were injected into the distracted callus with the thrombin-calcium mixture so that the PRP gel might develop within the injected site. Transplantation of MSCs and PRP was done at the lengthening and consolidation period in each patient. The target lengths were obtained in every leg without major complications and the average healing index was 23.0 days/cm (18.8-26.9 days/cm). Although these results are still preliminary, transplantation of osteoblast-like cells and PRP, which seemed to be a safe and minimally invasive cell therapy, could shorten the treatment period by acceleration of bone regeneration during distraction osteogenesis.

Aggregates of endothelial microparticles and platelets circulate in peripheral blood. Variations during stable coronary disease and acute myocardial infarction

INTRODUCTION

Activated endothelial cells on the surface of atherosclerotic plaques can shed membrane microparticles (MPs) with procoagulant potential. We have investigated whether circulating endothelial MPs could bind platelets, form aggregates, and be involved in thrombus formation during acute myocardial infarction (AMI).

PATIENTS/METHODS AND RESULTS

We first assessed the in vitro formation of aggregates comprising endothelial MPs and platelets by incubating supernatants of activated endothelial cells in culture with freshly isolated platelets. Endothelial MP-platelets (EMP-P) aggregates were characterized by flow cytometry using antibodies to specific markers of endothelial cells and of platelets. Identical EMP-P aggregates were detected in vivo in the peripheral blood of healthy individuals, of patients with stable coronary disease (SCD), and of patients with AMI. The levels of EMP-P aggregates were significantly higher in patients with SCD than in controls (16.7+/-1.8/microl versus 7.1+/-0.3/microl, P<0.0002). In contrast, the levels of EMP-P aggregates in the first hours of AMI were significantly lower than in controls and in SCD, both before primary angioplasty (2.5+/-0.7/microl) and 2 h after reperfusion (1.7+/-0.3 microl) (P<0.0001 versus healthy controls and versus SCD). However, 48 h after the onset of AMI, the levels of EMP-P aggregates (14.7+/-1.8/microl) had returned to values close to those observed in SCD.

CONCLUSIONS

Endothelial MPs can bind to platelets and form aggregates. The enumeration of those aggregates in peripheral blood shows significant differences between the various groups of patients tested. This new test can help in the evaluation of the level of endothelial cell activation and the damages created by chronic atherosclerosis.

Nitric oxide infusion alleviates cellular activation during preparation, leukofiltration and storage of platelets

Nitric oxide (NO) is a reversible inhibitor of platelet activation that generates S-nitrosylated compounds in plasma. Since platelets are activated during processing to platelet concentrates and storage, NO is anticipated to dampen the rate of lesion development. Platelet-rich plasma (PRP) was separated into aliquots that were unfiltered, filtered to remove leukocytes, or treated with NO or nitrite before filtration. Platelets were resuspended and stored up to four days at 22 degrees C. Samples removed were measured for S-nitrosylation of plasma, P-Selectin release, complement activation, and cGMP levels. Direct infusion of a NO solution (authentic NO) to PRP before filtration decreased adherence of platelets and improved yields. An infusion rate resulting in 1/1000 dilution of a saturated NO solution was optimal. C3a formation and soluble P-Selectin released from NO-treated-filtered platelets were about half that in unfiltered and filtered controls after four days (p<0.05 by Student-Newman-Keuls method after ANOVA for repeated measures). Plasma isolated from NO-treated PRP combined with untreated platelets protected the latter to a similar extent. Increases in S-nitrosylated compounds in PRPs were correlated with NO effects on platelet recovery and storage. Sodium nitrite failed to inhibit platelet activation and cyclic GMP levels were significantly increased in NO-treated cells. Results indicate that NO inhibited platelet activation associated with processing and storage and suggest that slow release of NO from S-nitrosylated plasma components afforded long-term protection. The infusion of authentic NO into PRPs is potentially an efficacious method for generating anti-platelet compounds to inhibit storage lesions.

Effect of holding buffy coats 4 or 18 hours before preparing pooled filtered PLT concentrates in plasma

BACKGROUND

Filtered PLT concentrates (PCs) were prepared in plasma pooling three (for children) or six buffy coats (BCs; for adults) after holding them a maximum of 4 hours (blood bags collected in the afternoon) or 18 hours (blood bags collected in the morning).

STUDY DESIGN AND METHODS

With flow cytometry, PCs prepared after holding BCs 4 or 18 hours were compared. BCs removed from whole-blood donations in quadruple bag packs ("top-top") were held 4 or 18 hours before pooling them with a sterile connecting device. After the BCs were centrifuged, the supernatant was transferred through a BC filter (Autostop, Pall Medical) to a CLX bag. Samples for analysis were collected from the whole-blood bag, BCs, and PCs immediately after preparation and after 1, 3, 5, and 7 days of storage on a flat-bed agitator at 22 +/- 2 degrees C. The main PLT membrane glycoproteins (GPs, IIb-IIIa, IV, and Ibalpha), some of their ligands (fibrinogen, fibronectin, and VWF), activation-dependent antigens (CD62P and CD63), and procoagulant activity markers (annexin V and bound coagulation FV-Va) have been studied.

RESULTS

In the 12 PCs (six pools of 3 units each group) studied, a minor increase in activation markers during preparation was observed. During the storage, a significant increase in the expression of GPIIb-IIIa, CD62P, CD63, annexin V, and FVa was measured. After 5 days of storage, only the percentage of PLTs with bound fibrinogen was significantly greater in PCs prepared after holding BCs for 4 hours.

CONCLUSION

In PCs prepared after holding BCs 4 or 18 hours before pooling and filtering, only a minor significant difference in the percentage of PLTs with bound fibrinogen was found after 5 days of storage. This difference is probably of little, if any, transfusional significance.

Blood component fractionation: manual versus automatic procedures

Over the last few years, quality system requirements have been introduced for blood components. The necessary compliance with standard productions will have a considerable impact on Blood Banks. The introduction of automated methods is the most satisfactory means to meet these requirements for blood component preparation. A new device has been developed to automate the fractionation of blood into components. We evaluated the efficacy of this instrument as compared to manual methods. A total of 218 units of blood have been collected, into several different commercial blood bag systems (77 into standard quadruple bag systems, 141 into bag systems with integrated in line filters), and used to evaluate the universality of the instrument. Whole blood units were processed using the Top/Top system and the Compomat G4 (Fresenius HemoCare). A separate program protocol was developed for each kind of bag. Use of the Compomat G4 resulted in a statistically significant (p<0.001) increase of the hemoglobin in filtered red cell concentrates (RCC) in comparison with the manual procedure, and a similar trend, even not statistically significant, has been observed for filtered RCC. Regardless of bag systems, we were able to observe a statistically significant increase of platelets in the platelet concentrates (PCs), when comparing automatic versus manual procedure. The automated procedure has been shown to be fast, and easy for the operators. This device reliably produces acceptable blood components, and has been shown adaptable to use with different blood bag systems.

Absence of anti-D alloimmunization in hematologic patients after D-incompatible platelet transfusions

BACKGROUND

Rh antigens are not present on the platelet surface. However, platelet concentrates may contain enough RBCs to elicit an anti-D response. Thus, D status must be considered in platelet transfusion. In immunosuppressed patients, frequencies of D alloimmunization of up to 19 percent have been previously reported.

STUDY DESIGN AND METHODS

Here a prospective study is reported in which 22 D- patients with hematologic disease received D+ platelet transfusions. Platelet concentrates were prepared from whole-blood donations according to the buffy coat method and were pooled before administration. The antibody screen test to detect anti-D was performed by LISS- IAT using the gel test.

RESULTS

Our series comprises 22 immunosuppressed D+ patients with a median age of 56 years (range, 23-79). The patients received 121 D-incompatible pooled platelet transfusions. The mean +/- SD of RBC content was 4.17 +/- 1.74 mL. None of the 22 patients developed detectable anti-D after a median follow-up of 8 weeks (range, 1-37).

CONCLUSION

The risk of D alloimmunization is low in patients with hematologic disease after D-incompatible platelet transfusions using platelet concentrates prepared by the buffy coat method.

Inhibition of cytoskeletal assembly by cytochalasin B prevents signaling through tyrosine phosphorylation and secretion triggered by collagen but not by thrombin

Activation of platelets leads to cytoskeletal assembly that is responsible for platelet motility and internal contraction. We have evaluated the involvement of the cytoskeleton in platelet activation by two strong agonists, collagen and thrombin. Activation was assessed by measuring changes in cytoskeletal assembly, externalization of activation-dependent markers and expression of procoagulant activity, and tyrosine phosphorylation of proteins, in both the absence and the presence of cytochalasin B. Activation of platelets with collagen and thrombin induced morphological changes and increased the expression of CD62P, CD63, glycoprotein IV, and binding of annexin V to platelets. Moreover, both activating agents induced actin polymerization, increased the association of other contractile proteins, and promoted tyrosine phosphorylation of multiple proteins, some of which were associated with the cytoskeleton. The presence of cytochalasin B blocked the previous events when collagen was used as the activating agent, although binding of annexin V still occurred. In contrast, platelet response to thrombin was not completely prevented by the presence of cytochalasin B. Thus, activation by collagen requires a functional cytoskeleton to trigger signaling through tyrosine phosphorylation and secretion. This is not the case for thrombin, which is capable of activating signaling mechanisms in the presence of strong inhibitors of cytoskeletal assembly. Moreover, the expression of a procoagulant surface in platelets still occurs even when platelet motility has been inhibited.

Platelet procoagulant activity induced in vivo by muromonab-CD3 infusion in uremic patients

BACKGROUND

Muromonab-CD3 is a murine monoclonal antibody (MoAb) that is used in the prophylaxis and treatment of acute graft rejection. Activation of coagulation and fibrinolysis following anti-CD3 administration have been reported in some patients to lead to irreversible intragraft thrombosis.

DESIGN AND METHODS

We have studied the effect of muromonab-CD3 infusion on platelets using flow cytometry in six patients who received three daily doses of muromonab-CD3 as prophylaxis of rejection before receiving a living donor renal transplant. Samples were collected before, 15 and 60 min after muromonab-CD3 infusion. Immunolabeling of platelets was performed in whole blood using dual-color analysis. The following conjugated MoAb were used: anti-CD41a, -CD36, -CD42b, -CD62P, -CD63, -factor V/Va and nonspecific Ig. Samples were analyzed with a FACScan flow cytometer (Becton Dickinson, Mountain View, CA, USA).

RESULTS

After muromonab-CD3 infusion, an increase in the binding of MoAb anti-factor V/Va to platelets was seen, which was only statistically significant (2.2% vs. 12.8%, P=.04) after 15 min of the second dose. No significant changes were seen in the other MoAbs studied. No thrombotic complications were observed after transplantation.

INTERPRETATION AND CONCLUSION

In uremic patients receiving muromonab-CD3 infusion as prophylaxis of graft rejection, an increase in the binding of anti-factor V/Va, denoting an increased exposure of anionic phospholipids in platelets, was seen. This increase in platelet procoagulant activity might contribute to the appearance of thromboses within renal graft seen in some patients who received muromonab-CD3.

Different preparation methods to obtain platelet components as a source of growth factors for local application

BACKGROUND

Autologous platelet components were recently used as part of tissue-engineering strategies in oral and maxillofacial surgery. Various preparation methods were investigated to define standardized blood bank components and to collect data on the growth factor content of human platelets before and after storage.

STUDY DESIGN AND METHODS

Apheresis platelets (AP), buffy coat-derived platelets (BCP), platelets prepared by tube method (TP), and highly concentrated samples prepared from AP and from BCP were evaluated for standard quality criteria of platelet components and for their concentration of transforming growth factor (TGF)-ss1, platelet-derived growth factor (PDGF)-AB, and PDGF-BB. AP were stored for 5 days. On Days 3 and 5, these components and freshly prepared, highly concentrated samples were evaluated for the same measures.

RESULTS

Platelet concentration in TP was lower than that in the other groups (p<0.05). However, the concentrations of PDGF-AB, PDGF-BB, and TGF-ss1 were comparable in the three groups. TP showed higher spontaneous CD62 expression than did AP and BCP. The three preparation procedures resulted in significantly different WBC contamination, with the highest levels in TP. For the whole series of measurements, there was a strong correlation between growth factor levels and platelet concentration (p<0.05), which was due to the face that the growth factor content of concentrated platelet samples was tenfold that of AP, BCP, and TP. In TP, the WBC concentration was correlated with PDGF levels (p<0.05). After 5-day storage, the mean levels of PDGF-AB, PDGF-BB, and TGF-ss1 were 57.1, 43.0, and 72.0 percent of the initial values in AP. Overall, multiple regression analysis revealed the following factors influencing the measured growth factor concentrations: platelet concentration, baseline CD62 expression, lactate production, and WBC contamination.

CONCLUSION

Various methods enable the preparation of platelet components and of highly concentrated components for local use according to standard blood banking criteria. The obtained components differ, particularly in their WBC content and in vitro platelet activation. These findings are relevant for planning and evaluating further studies of locally usable autologous platelet components.

Platelet storage in PAS-2 or autologous plasma: impact on functional parameters

Currently, several platelet additive solutions for long-term platelet storage have been introduced. The aim of this study was to compare the deterioration of functional status of platelets stored for up to 5 days in autologous plasma (AP) only, with platelet stored in PAS-2, a salt solution containing acetate, citrate and sodium chloride. Change in platelet adhesion, aggregation and activation was measured by flow cytometric technique. In addition, beta-Thromboglobulin (beta-TG), lactate and glucose were determined. After 5 days of storage, the expression of P-Selectin was significantly higher, the production of lactate and the consumption of glucose were significantly lower, in platelets stored in PAS-2 than in autologous plasma. No significant differences were detected on day 5 between the two groups with regard to fibrinogen, von Willebrand factor binding capacity, or to beta-TG release. It can be concluded that neither storage medium was consistently better for the parameters tested. However, it must be emphasized that platelets stored in autologous plasma exhibited less lesion, in terms of P-Selectin expression compared with platelets stored in PAS-2.

Effects of the addition of second-messenger effectors to platelet concentrates separated from whole-blood donations and stored at 4 degrees C or -80 degrees C

BACKGROUND

Platelet concentrates (PCs) are currently stored at 22 degrees C under continuous agitation. Because of the potential risk of the overgrowth of bacteria in case of contamination, PC shelf life is limited to 5 days. A mixture of second-messenger effectors is being evaluated to determine if it has benefits for cold liquid storage and cryopreservation of platelets.

STUDY DESIGN AND METHODS

PCs separated from whole-blood donations by the buffy coat method were randomly assigned (n = 6 each) to be stored for 5 days at 22 degrees C under continuous agitation or at 4 degrees C after treatment with a platelet storage medium (ThromboSol, LifeCell Corp. ). PCs were also cryopreserved with 6-percent DMSO (final concentration) or with ThromboSol plus 2-percent DMSO (final concentration) (TC). After storage, platelets were analyzed by flow cytometry, transmission electron microscopy, and aggregation and perfusion techniques.

RESULTS

Cold liquid storage of ThromboSol-treated platelets resulted in a lower binding of coagulation factor Va on the platelet surface than on platelets stored at 22 degrees C. In transmission electron microscopy, a conversion to spherical morphology was seen in the case of cold liquid storage. No difference between ThromboSol-treated platelets stored at 4 degrees C and platelets stored at 22 degrees C was seen in perfusion studies. Cryopreservation in the presence of TC prevented the reduction in glycoprotein Ib and IV expression on platelet surface that is seen in 6-percent DMSO-cryopreserved platelets. Platelets cryopreserved in TC covered, by thrombus, a significantly greater percentage of the perfused surface after the freezing and thawing process.

CONCLUSION

ThromboSol-treated PCs separated from whole-blood donations by the buffy coat method, stored at 4 degrees C for 5 days, or cryopreserved in the presence of TC, maintained in vitro functional activity comparable to that achieved by current methods of storage, although discoid morphology was not preserved during cold liquid storage with ThromboSol.