Lentiviral gene therapy reverts GPIX expression and phenotype in Bernard-Soulier syndrome type C

Bernard-Soulier syndrome (BSS) is a rare congenital disease characterized by macrothrombocytopenia and frequent bleeding. It is caused by pathogenic variants in three genes (GP1BA, GP1BB, or GP9) that encode for the GPIbα, GPIbβ, and GPIX subunits of the GPIb-V-IX complex, the main platelet surface receptor for von Willebrand factor, being essential for platelet adhesion and aggregation. According to the affected gene, we distinguish BSS type A1 (GP1BA), type B (GP1BB), or type C (GP9). Pathogenic variants in these genes cause absent, incomplete, or dysfunctional GPIb-V-IX receptor and, consequently, a hemorrhagic phenotype. Using gene-editing tools, we generated knockout (KO) human cellular models that helped us to better understand GPIb-V-IX complex assembly. Furthermore, we developed novel lentiviral vectors capable of correcting GPIX expression, localization, and functionality in human GP9-KO megakaryoblastic cell lines. Generated GP9-KO induced pluripotent stem cells produced platelets that recapitulated the BSS phenotype: absence of GPIX on the membrane surface and large size. Importantly, gene therapy tools reverted both characteristics. Finally, hematopoietic stem cells from two unrelated BSS type C patients were transduced with the gene therapy vectors and differentiated to produce GPIX-expressing megakaryocytes and platelets with a reduced size. These results demonstrate the potential of lentiviral-based gene therapy to rescue BSS type C.

Full-length antithrombin frameshift variant with aberrant C-terminus causes endoplasmic reticulum retention with a dominant-negative effect

Antithrombin, a major endogenous anticoagulant, is a serine protease inhibitor (serpin). We characterized the biological and clinical impact of variants involving C-terminal antithrombin. We performed comprehensive molecular, cellular, and clinical characterization of patients with C-terminal antithrombin variants from a cohort of 444 unrelated individuals with confirmed antithrombin deficiency. We identified 17 patients carrying 12 C-terminal variants, 5 of whom had the p.Arg445Serfs*17 deletion. Five missense variants caused qualitative deficiency, and 7, including 4 insertion-deletion variants, induced severe quantitative deficiency, particularly p.Arg445Serfs*17 (antithrombin <40%). This +1 frameshift variant had a molecular size similar to that of WT antithrombin but possessed a different C-terminus. Morphologic and cotransfection experiments showed that recombinant p.Arg445Serfs*17 was retained at the endoplasmic reticulum and had a dominant-negative effect on WT antithrombin. Characterization of different 1+ frameshift, aberrant C-terminal variants revealed that protein secretion was determined by frameshift site. The introduction of Pro441 in the aberrant C-terminus, shared by 5 efficiently secreted variants, partially rescued p.Arg445Serfs*17 secretion. C-terminal antithrombin mutants have notable heterogeneity, related to variant type and localization. Aberrant C-terminal variants caused by 1+ frameshift, with similar size as WT antithrombin, may be secreted or not, depending on frameshift site. The severe clinical phenotypes of these genetic changes are consistent with their dominant-negative effects.

Elucidating the Mechanism of Action of the Attributed Immunomodulatory Role of Eltrombopag in Primary Immune Thrombocytopenia: An In Silico Approach

Eltrombopag is a thrombopoietin receptor (MPL) agonist approved for the treatment of primary immune thrombocytopenia (ITP). Recent evidence shows that some patients may sustain platelet counts following eltrombopag discontinuation. The systemic immunomodulatory response that resolves ITP in some patients could result from an increase in platelet mass, caused either by the direct action of eltrombopag on megakaryocytes through MPL stimulation, or potential MPL-independent actions on other cell types. To uncover the possible mechanisms of action of eltrombopag, in silico analyses were performed, including a systems biology-based approach, a therapeutic performance mapping system, and structural analyses. Through manual curation of the available bibliography, 56 key proteins were identified and integrated into the ITP interactome analysis. Mathematical models (94.92% mean accuracy) were obtained to elucidate potential MPL-dependent pathways in non-megakaryocytic cell subtypes. In addition to the effects on megakaryocytes and platelet numbers, the results were consistent with MPL-mediated effects on other cells, which could involve interferon-gamma, transforming growth factor-beta, peroxisome proliferator-activated receptor-gamma, and forkhead box protein P3 pathways. Structural analyses indicated that effects on three apoptosis-related proteins (BCL2L1, BCL2, BAX) from the Bcl-2 family may be off-target effects of eltrombopag. In conclusion, this study proposes new hypotheses regarding the immunomodulatory functions of eltrombopag in patients with ITP.

Romiplostim in adults with newly diagnosed or persistent immune thrombocytopenia

Introduction: Three distinct phases are recognized in immune thrombocytopenia (ITP): newly diagnosed (≤3 months after diagnosis), persistent (>3-12 months after diagnosis), and chronic (>12 months). Several international guidelines/expert recommendations have been released in the past 2 years regarding the treatment of newly diagnosed/persistent ITP. Areas covered: Across the guidelines/expert recommendations, thrombopoietin receptor agonists (TPO-RAs), including romiplostim (the focus of this review), are recommended in newly diagnosed or persistent ITP for patients who fail to respond to corticosteroids or intravenous immunoglobulin (or where these are contraindicated). To identify data relating to romiplostim in adults with newly diagnosed or persistent ITP, we conducted a search of PubMed (with no time limit applied) and abstracts from 2019 EHA/ASH meetings using the term 'romiplostim.' Expert opinion: The findings from nine clinical trials, six real-world studies and ten case reports provide insight into the early use of romiplostim, which could help to reduce exposure to the adverse effects associated with prolonged corticosteroid use, as well as reduce the risk of severe bleeding. Additionally, given the durable responses observed in patients with newly diagnosed/persistent ITP, as well as the potential for treatment-free responses following discontinuation, romiplostim might help to avoid the need for subsequent treatment.

Platelet activation and neutrophil extracellular trap (NET) formation in immune thrombocytopenia: is there an association?

No biological predictors for the increased risk of thrombosis in patients with immune thrombocytopenia (ITP) have been identified. The aim of the study was to investigate platelet and neutrophil activation as well neutrophil extracellular trap (NET) formation in 63 ITP patients and 30 healthy volunteers. Platelet and neutrophil activation was assessed during steady state using flow cytometry analysis, and NETs were evaluated by quantitation of cell free DNA (cfDNA), and citrullinated histone-3-DNA (CitH3-DNA). Patient platelets and neutrophils showed increased CD62 and CD11b expression compared to controls (p = .038, and p = .022, respectively). In patients, platelet activation inversely correlated with platelet count and platelet size (p < .001), and positively correlated with neutrophil degranulation (p = .024). More NET formation, both CitH3-DNA (p = .025) and cfDNA(p < .001), were present in ITP patients compared to controls. CitH3-DNA inversely correlated with CD62 expression on platelets (p = .042), but higher levels of cfDNA were observed in individuals with classical cardiovascular risk factors for thrombosis, and in those with a previous history of thrombotic events. In this disease, the increased platelet activation and plasma NET levels seem to be separable processes that associate (either positively or inversely in the case of CitH3-DNA or platelet degranulation, respectively) to platelet mass.

Deciphering predictive factors for choice of thrombopoietin receptor agonist, treatment free responses, and thrombotic events in immune thrombocytopenia

Very few data exist on when a particular thrombopoietin-receptor agonist (TPO-RA) is favored in clinical practice for the treatment of patients with immune thrombocytopenia (ITP), about novel risk factors for vascular events (VE) with these drugs, nor about predictive factors for therapy free responses (TFR). We conducted an observational, retrospective, long-term follow-up multicenter study from November 2016 to January 2018 of 121 adult ITP patients initiating TPO-RA between January 2012 to December 2014. Data reflected that a platelet count ≤25 × 10⁹/l at the time when the TPO-RA was initiated was associated with a 2.8 higher probability of receiving romiplostim vs. eltrombopag (P = 0.010). VE on TPO-RA was related to previous neoplasia in patients over 65 years (50% vs. 2.2%, P < 0.001), and to previous splenectomy in younger patients (100% vs. 33%, P = 0.001). Receiving romiplostim as first TPO-RA with no subsequent TPO-RA switching was associated with a 50% likelihood of TFR after 2.9 years of therapy (3.3 years in chronic ITP patients). These real-world data help deciphering some areas of uncertainty, and offer insight into some of the most relevant challenges of ITP which may help clinicians make appropriate treatment decisions in the management of adult ITP patients with TPO-RA.

Two novel variants of the ABCG5 gene cause xanthelasmas and macrothrombocytopenia: a brief review of hematologic abnormalities of sitosterolemia

Essentials Diagnosis of sitosterolemia, a rare recessive or syndromic disorder, is usually delayed. Peripheral blood smear is extremely useful for establishing the suspicion of sitosterolemia. High-throughput sequencing technology enables the molecular diagnosis of inherited thrombocytopenias. Accurate characterization of sitosterolemia helps us determine appropriate management.

SUMMARY

Background Sitosterolemia (STSL) is a recessive inherited disorder caused by pathogenic variants in the ABCG5 and ABCG8 genes. Increased levels of plasma plant sterols (PSs) usually result in xanthomas and premature coronary atherosclerosis, although hematologic abnormalities may occasionally be present. This clinical picture is unfamiliar to many physicians, and patients may be at high risk of misdiagnosis. Objectives To report two novel ABCG5 variants causing STSL in a Spanish patient, and review the clinical and mutational landscape of STSL. Patient/Methods A 46-year-old female was referred to us with lifelong macrothrombocytopenia. She showed familial hypercholesterolemia-related xanthomas. Molecular analysis was performed with high-throughput sequencing. Plasma PS levels were evaluated with gas-liquid chromatography. The STSL landscape was reviewed with respect to specific online databases and all reports published since 1974. Results A blood smear revealed giant platelets and stomatocytes. Novel compound heterozygous variants were detected in exons 7 (c.914C>G) and 13 (c.1890delT) of ABCG5. The patient showed an increased plasma level of sitosterol. These findings support the diagnosis of STSL. In our review, we identified only 25 unrelated STLS patients who presented with hematologic abnormalities including macrothrombocytopenia. It remains unknown why only some patients develop hematologic abnormalities. Conclusions This is the first Spanish STSL patient to be reported and molecularly characterized. The early diagnosis of STLS is strongly supported by the presence of stomatocytes in blood smears. The definitive diagnosis of STSL by measurement of serum PS levels and molecular analyses prompted the use of ezetimibe therapy.

An atypical IgM class platelet cold agglutinin induces GPVI-dependent aggregation of human platelets

Platelet cold agglutinins (PCA) cause pseudothrombocytopenia, spurious thrombocytopenia due to ex vivo platelet clumping, complicating clinical diagnosis, but mechanisms and consequences of PCA are not well defined. Here, we characterised an atypical immunoglobulin (Ig)M PCA in a 37-year-old woman with lifelong bleeding and chronic moderate thrombocytopenia, that induces activation and aggregation of autologous or allogeneic platelets via interaction with platelet glycoprotein (GP)VI. Patient temperature-dependent pseudothrombocytopenia was EDTA-independent, but was prevented by integrin αIIbβ3 blockade. Unstimulated patient platelets revealed elevated levels of bound IgM, increased expression of activation markers (P-selectin and CD63), low GPVI levels and abnormally high thromboxane (TX)A2 production. Patient serum induced temperature- and αIIbβ3-dependent decrease of platelet count in allogeneic donor citrated platelet-rich plasma (PRP), but not in PRP from Glanzmann's thrombasthenia or afibrinogenaemia patients. In allogeneic platelets, patient plasma induced shape change, P-selectin and CD63 expression, (14)C-serotonin release, and TXA2 production. Activation was not inhibited by aspirin, cangrelor or blocking anti-Fc receptor (FcγRIIA) antibody, but was abrogated by inhibitors of Src and Syk, and by a soluble GPVI-Fc fusion protein. GPVI-deficient platelets were not activated by patient plasma. These data provide the first evidence for an IgM PCA causing platelet activation/aggregation via GPVI. The PCA activity persisted over a five-year follow-up period, supporting a causative role in patient chronic thrombocytopenia and bleeding.

Generation of iPSCs from genetically corrected Brca2 hypomorphic cells: implications in cell reprogramming and stem cell therapy

Fanconi anemia (FA) is a complex genetic disease associated with a defective DNA repair pathway known as the FA pathway. In contrast to many other FA proteins, BRCA2 participates downstream in this pathway and has a critical role in homology-directed recombination (HDR). In our current studies, we have observed an extremely low reprogramming efficiency in cells with a hypomorphic mutation in Brca2 (Brca2(Δ) (27/) (Δ27)), that was associated with increased apoptosis and defective generation of nuclear RAD51 foci during the reprogramming process. Gene complementation facilitated the generation of Brca2(Δ) (27/) (Δ27) induced pluripotent stem cells (iPSCs) with a disease-free FA phenotype. Karyotype analyses and comparative genome hybridization arrays of complemented Brca2(Δ) (27/) (Δ27) iPSCs showed, however, the presence of different genetic alterations in these cells, most of which were not evident in their parental Brca2(Δ) (27/) (Δ27) mouse embryonic fibroblasts. Gene-corrected Brca2(Δ) (27/) (Δ27) iPSCs could be differentiated in vitro toward the hematopoietic lineage, although with a more limited efficacy than WT iPSCs or mouse embryonic stem cells, and did not engraft in irradiated Brca2(Δ) (27/) (Δ27) recipients. Our results are consistent with previous studies proposing that HDR is critical for cell reprogramming and demonstrate that reprogramming defects characteristic of Brca2 mutant cells can be efficiently overcome by gene complementation. Finally, based on analysis of the phenotype, genetic stability, and hematopoietic differentiation potential of gene-corrected Brca2(Δ) (27/) (Δ) (27) iPSCs, achievements and limitations in the application of current reprogramming approaches in hematopoietic stem cell therapy are also discussed.

Towards the targeted management of Chediak-Higashi syndrome

Chediak-Higashi syndrome (CHS) is a rare, autosomal recessive congenital immunodeficiency caused by mutations in CHS1, a gene encoding a putative lysosomal trafficking protein. In the majority of patients, this disorder is typically characterized by infantile-onset hemophagocytic lymphohistiocytosis (HLH), which is lethal unless allogeneic transplantation is performed. A small number of individuals have the attenuated form of the disease and do not benefit from transplant. Improved outcomes of transplantation have been reported when performed before the development of HLH, thus it is important to quickly differentiate patients that present with the childhood form of disease and to prematurely enroll them into a transplantation protocol. In addition, this would also preclude those that exhibit clinical phenotypes of adolescent and adult CHS from this treatment. Patients with an absence of cytotoxic T lymphocyte (CTL) function have a high risk for developing HLH, and could therefore benefit the most from early hematopoietic stem cell transplantation (HSCT). However, although normal CTL cytotoxicity or bi-allelic missense mutations do not exclude the occurrence of HLH in childhood, a more conservative approach is justified. This article summarizes recent advances in the clinical characterization of CHS patients, provides updates on promising new testing methods, and focuses on specific therapeutic approaches.

Hermansky-Pudlak syndrome. Overview of clinical and molecular features and case report of a new HPS-1 variant

Hermansky-Pudlak syndrome (HPS) is a rare, autosomal recessive disorder affecting lysosome-related organelles (LRO), including dense platelet granules. HPS causes oculocutaneous hypopigmentation, bleeding diathesis and granulomatous colitis or pulmonary fibrosis. To date, there is no curative treatment and the clinical management depends on the severity of symptoms. A prompt diagnosis of HPS patients could improve their quality of life and clinical management. However, the absence of a specific platelet function test, the wide molecular heterogeneity, and the lack of phenotype-genotype correlations hamper the rapid diagnosis. Nine subtypes of HPS have been identified as a result of mutations in nine genes that codify for proteins involved in formation and shuttle of the LRO. The molecular characterization of patients and knowledge derived from animal models of HPS contribute to the understanding of biogenesis and function of the LRO. This paper describes a patient with a novel homozygous nonsense mutation causing HPS and provides a review of the literature focusing on recent advances in the molecular characterization and physiopathology of HPS.

GPI-anchor and GPI-anchored protein expression in PMM2-CDG patients

BACKGROUND

Mutations in PMM2 impair phosphomannomutase-2 activity and cause the most frequent congenital disorder of glycosylation, PMM2-CDG. Mannose-1-phosphate, that is deficient in this disorder, is also implicated in the biosynthesis of glycosylphosphatidyl inositol (GPI) anchors.

OBJECTIVE

To evaluate whether GPI-anchor and GPI-anchored proteins are defective in PMM2-CDG patients.

METHODS

The expression of GPI-anchor and seven GPI-anchored proteins was evaluated by flow cytometry in different cell types from twelve PMM2-CDG patients. Additionally, neutrophil CD16 and plasma hepatic proteins were studied by Western blot. Transferrin glycoforms were evaluated by HPLC.

RESULTS

Patients and controls had similar surface expression of GPI-anchor and most GPI-anchored proteins. Nevertheless, patients displayed a significantly diminished binding of two anti-CD16 antibodies (3G8 and KD1) to neutrophils and also of anti-CD14 (61D3) to monocytes. Interestingly, CD16 immunostaining and asialotransferrin levels significantly correlated with patients' age. Analysis by flow cytometry of CD14 with MΦP9, and CD16 expression in neutrophils by Western blot using H-80 ruled out deficiencies of these antigens.

CONCLUSIONS

PMM2 mutations do not impair GPI-anchor or GPI-anchored protein expression. However, the glycosylation anomalies caused by PMM2 mutations might affect the immunoreactivity of monoclonal antibodies and lead to incorrect conclusions about the expression of different proteins, including GPI-anchored proteins. Neutrophils and monocytes are sensitive to PMM2 mutations, leading to abnormal glycosylation in immune receptors, which might potentially affect their affinity to their ligands, and contribute to infection. This study also confirms less severe hypoglycosylation defects in older PMM2-CDG patients.

IgM monoclonal component associated with type I Gaucher disease resolved after enzyme replacement therapy: a case report

The frequency of monoclonal gammopathy of undetermined significance (MGUS) is higher in patients with type I Gaucher disease (GD I) than in the general population. Although enzyme replacement therapy is effective in the control of the disease, its effect on MGUS is still controversial. We present the case of a 65-year-old woman with extensive GD I associated with IgM MGUS, in whom enzyme replacement therapy succeeded in eradicating the monoclonal component. This observation further supports the idea that enzyme replacement therapy decreases the chronic antigenic stimulation responsible for gammopathies in Gaucher disease.

Differential effects of quercetin, apigenin and genistein on signalling pathways of protease-activated receptors PAR(1) and PAR(4) in platelets

BACKGROUND AND PURPOSE

The modulation by flavonoids of platelet responses induced by thrombin has been little investigated, and the antiplatelet activity, as well as possible inhibitory mechanisms of these compounds on thrombin signalling, has not yet been elucidated. We explored whether flavonoids affect platelet signalling pathways triggered by thrombin and by the selective activation of its protease-activated receptors (PARs) 1 and 4, and analysed the antagonism of these polyphenols at thrombin receptors.

EXPERIMENTAL APPROACH

We investigated the effect of a range of polyphenolic compounds on platelet aggregation, 5-HT secretion, intracellular calcium mobilization, protein kinase activity and tyrosine phosphorylation, triggered by thrombin and PAR agonist peptides (PAR-APs). The ability of these flavonoids to bind to thrombin receptors was investigated by competitive radioligand binding assays using (125)I-thrombin.

KEY RESULTS

Quercetin, apigenin and genistein impaired platelet aggregation, as well as 5-HT release and calcium mobilization, induced by thrombin and PAR-APs. Quercetin and apigenin were inhibitors of protein kinases, but genistein exhibited a minimal ability to suppress platelet phosphorylation. Binding assays did not establish any kind of interaction between thrombin receptors and any of the flavonoids tested.

CONCLUSIONS AND IMPLICATIONS

Quercetin, apigenin and genistein did not inhibit thrombin responses by interacting with thrombin receptors, but by interfering with intracellular signalling. While inhibition by genistein may be a consequence of affecting calcium mobilization, subsequent platelet secretion and aggregation, for quercetin and apigenin, inhibition of kinase activation may also be involved in the impairment of platelet responses.

Apigenin inhibits platelet adhesion and thrombus formation and synergizes with aspirin in the suppression of the arachidonic acid pathway

Previous studies using washed platelets demonstrated that certain flavonoids inhibit platelet function through several mechanisms including blockade of TxA(2) receptors (TPs). We aimed to analyze the binding capacity of flavonoids to TPs in platelet rich plasma (PRP), investigated their effect in flowing blood, and evaluated the ability of apigenin to improve the efficacy of aspirin in the inhibition of platelet aggregation. The binding of flavonoids to TPs in PRP was explored using binding assays and the TP antagonist [ (3)H]SQ29548. Effects of flavonoids on platelet adhesion were assessed using arterial subendothelium with annular plate perfusion chambers, and global evaluation of apigenin on high-shear-dependent platelet function was determined by the PFA-100. To evaluate the ability of apigenin to potentiate the effect of aspirin, arachidonic acid-induced platelet aggregation was measured prior to and after consumption of subaggregatory doses of aspirin in the presence or absence of apigenin. Binding assays revealed that apigenin was an efficient competitor of [ (3)H]SQ29548 binding to PRP ( K i = 155.3 +/- 65.4 microM), and perfusion studies showed that apigenin, genistein, and catechin significantly diminished thrombus formation when compared to control (26.2 +/- 3.8, 33.1 +/- 5.2, and 26.2 +/- 5.2 vs 76.6 +/- 2.6%, respectively; p < 0.05). Apigenin, similarly to the TP antagonist SQ29548, significantly prolonged collagen epinephrine-induced PFA-100 closure time in comparison to the control and, when added to platelets that had been exposed in vivo to aspirin, potentiated its inhibitory effect on platelet aggregation. The inhibitory effect of some flavonoids in the presence of plasma, particularly apigenin, might in part rely on TxA(2) receptor antagonism. There is a clear increase in the ex vivo antiplatelet effect of aspirin in the presence of apigenin, which encourages the idea of the combined use of aspirin and certain flavonoids in patients in which aspirin fails to properly suppress the TxA(2) pathway.

Flavonoids inhibit platelet function through binding to the thromboxane A2 receptor

BACKGROUND

Dietary flavonoids are known for their antiplatelet activity resulting in cardiovascular protection, although the specific mechanisms by which this inhibition occurs has not been fully established.

OBJECTIVE

The aim of this study was to investigate the interaction of nine flavonoids representative of various chemical classes, with platelet responses dependent on thromboxane A(2) (TxA(2)) generation and on receptor antagonism, and to analyze the structural requirements for such effects.

METHODS

The effect of several types of flavonoids on platelet aggregation, serotonin release, and TxA(2) generation was investigated. Competitive radioligand binding assays were used to screen for affinity of these compounds to TxA(2) receptors.

RESULTS

Flavones (apigenin and luteolin) and isoflavones (genistein) abrogated arachidonic acid and collagen-induced platelet responses, such as aggregation and secretion, with a less substantial effect on TxA(2) synthesis. These compounds were identified as specific ligands of the TxA(2) receptor in the micromol L(-1) range, this effect accounting for antiplatelet effects related to stimulation with those agonists. Tight binding of flavonoids to the human TxA(2) receptor relies on structural features such as the presence of the double bond in C2-C3, and a keto group in C4.

CONCLUSIONS

The inhibition by specific flavonoids of in vitro platelet responses induced by collagen or arachidonic acid seems to be related, to a great extent, to their ability to compete for binding to the TxA(2) receptor. Therefore, antagonism of this TxA(2) receptor may represent an additional mechanism for the inhibitory effect of these compounds in platelet function.

Evaluation of refrigerated platelet concentrates supplemented with low doses of second messenger effectors

With the goal of producing haemostatically effective platelet concentrates (PCs) with a longer shelf-life, we aimed to identify a simple combination of platelet inhibitors, with a low pharmacological load, which could avoid the unacceptable loss of platelets stored under refrigerated conditions. PCs stored with different combinations of second messenger effectors were analysed at days 5, 10 and 15 of storage and compared with those supplemented with ThromboSol--a combination of six platelet inhibitors that protects cells from cold damage. The following parameters were analysed: platelet counts, biochemical parameters (glucose, pH, bicarbonate, lactate), cell lysis (lactic dehydrogenase, LDH), membrane glycoproteins (GPs), platelet aggregation, fibrinogen binding and hypotonic shock response. We characterized the combination of amiloride and sodium nitroprusside (at 1/2 the dose included in ThromboSol). This was found to be similar to ThromboSol and superior to nontreated units in the prevention of cold-induced platelet aggregation at day 15 of storage (maintenance of 78% and 80% of initial platelet counts, respectively), preservation of GPIbalpha (11% and 12% better maintenance of mean fluorescence intensity compared with control units, respectively), and reduced cell lysis (13% and 11% decrease in supernatant LDH, respectively). The reduced pharmacological load with the identified solution compared with ThromboSol is an argument in favour of the potential use of these agents when designing strategies to improve PC storage.

Evaluation of a new whole-blood filter that allows preparation of platelet concentrates by platelet-rich plasma methods

BACKGROUND

A novel WBC-reduction in-line whole-blood (WB) filter that does not retain platelets was evaluated to assess the filtration performance and, after processing WB by the platelet-rich plasma (PRP) method, to analyze the storage quality of filtered platelet concentrate (PC) units.

STUDY DESIGN AND METHODS

To analyze the filter retention, blood was collected from random donors into quadruple blood packs with an integral in-line filter (Imuflex WB-SP, Terumo; n = 25) or in standard triple bag systems (n = 30). To assess the in vitro storage characteristics of platelets, 26 WB units were pooled in pairs and redistributed into 13 units that underwent WBC reduction and 13 units that were not WBC reduced. In all cases, WB was separated into RBCs, PCs, and plasma by the PRP method and platelet function was compared.

RESULTS

The filtration procedure led to RBC and PC WBC-reduced products that met the AABB and European requirements. The average filtration time was 30 minutes, the filter retained about 45 mL of WB, and there was no further loss of RBCs during the fractionation procedure. In vitro PC storage characteristics of the filtered units were similar to those of the nonfiltered units.

CONCLUSION

A 4- and 3-log WBC reduction was observed in RBC and PC units that were produced by the PRP method, with a mean residual WBC content of 0.24 +/- 0.38 x 106 and 0.02 +/- 0.03 x 106 per unit, respectively. The procedure, performed under relatively simple logistics, results in good-quality, standard components that may reduce costs and ease the process of WBC reduction in transfusion services.

Application of a new enzyme-linked immunosorbent assay for detection of total hepatitis C virus core antigen in blood donors

Recent studies have shown that total hepatitis C virus (HCV) core antigen, both free and antibody bound, is an accurate indirect marker of viral replication that can be used in clinical practice. The aim of the present study was to evaluate the performance of a new total HCV core antigen enzyme-linked immunosorbent assay (ELISA) for detection and quantification of total core antigen in blood donors, testing positive for anti-HCV antibodies and for prospective low-risk population screening. A population comprising 257 samples, from blood donors detected reactive for anti-HCV antibodies [137 recombinant immunoblot assay (RIBA) positive and 120 RIBA indeterminate], were tested by using a new total HCV core antigen ELISA. HCV-RNA was quantified by using quantitative polymerase chain reaction (PCR) assays in all RIBA-positive samples and RIBA-indeterminate samples that were positive for the total core antigen. Specificity of the assay was studied in 1070 healthy blood donors negative for anti-HCV antibodies. Compared with quantitative PCR assays, the total HCV core antigen assay showed 97.37% sensitivity. The three HCV-RNA-positive samples, which tested negative for the total core antigen, had a low viral load (< 1.4 x 10(4) IU mL(-1)). All samples with more than 1.4 x 10(4) IU mL(-1) of viral RNA were positive for total core antigen, independent of the HCV genotype. Concentration of total core antigen correlated significantly with those of HCV-RNA (r = 0.614, P < 0.0001). Overall specificity in freshly collected blood donor specimens was 99.63%. Our data indicate that the total HCV core antigen ELISA has a sensitivity close to PCR assays in diagnosing HCV infection in blood donors with anti-HCV antibodies and shows an excellent specificity in volunteer donors. This assay, in combination with anti-HCV antibodies screening tests, could be an alternative to molecular assays for HCV infection screening in blood donors.

Platelet aggregation through prothrombinase activation induced by non-aggregant doses of platelet agonists

Activation of the prothrombinase complex, which catalyzes the formation of thrombin from prothrombin, is crucial for the (patho)physiological processes of hemostasis and thrombosis. We here report that washed platelets supplemented with prothrombin can be irreversibly aggregated with otherwise non-aggregant doses of adenosine diphosphate (10 micromol/l), thrombin (0.06 U/ml), or collagen (1 microg/ml). Prothrombinase-catalyzed prothrombin to thrombin conversion most probably supports this aggregation response, since inhibitors of thrombin (hirudin or heparin) and an inhibitor of activated factor X (DX-9065a) impair the response. A certain degree of agonist-induced platelet activation seems to be required for this prothrombin-supported aggregation response, since prothrombin alone does not induce aggregation, and blockade of glycoprotein Ia/IIa with a specific antibody inhibits the platelet aggregation response to collagen and prothrombin. These results may suggest that activation of the prothrombinase complex could be a common step of the platelet response to distinct agonists, which may be achieved at low levels of platelet stimulation.

Polymorphisms of P-selectin glycoprotein ligand-1 are associated with neutrophil-platelet adhesion and with ischaemic cerebrovascular disease

P-selectin glycoprotein ligand (PSGL-1) shares common features with platelet glycoprotein Ibalpha. A recently described polymorphism in this receptor that results in a variable number of tandem repeats (VNTR) sequence present either 16, 15 or 14 times (alleles A, B or C) could, similar to GPIbalpha, be functionally relevant. The allelic frequency of this polymorphism was investigated in 469 individuals from the south of Spain, and was similar to that previously described in other Caucasian populations: 85% A, 14% B and 1% C alleles. We identified two new polymorphisms genetically linked to the C isoform, resulting in the Ser273Phe and Met274Val changes. To assess the functional consequence of the polymorphisms in the receptor, we performed flow cytometric analysis of P-selectin dependent neutrophil-platelet interaction. Neutrophils carrying the shortest C allele and the amino acid variations in residues 273 and 274 exhibited a significantly lower capacity to bind activated platelets than A/B and A/A samples (mean fluorescence intensity of CD42b+ neutrophils 262 versus 303 and 319 respectively, P < 0.05). The distribution of the VNTR was analysed in three case-control studies including 104 cerebrovascular (CVD), 101 coronary heart disease (CHD) and 150 deep venous thrombosis (DVT) patients. The results showed that smaller (B and C) alleles seem to be associated with a lower risk of developing CVD (P = 0.008) but not to be related to CHD or DVT. In conclusion, polymorphisms of the PSGL-1 receptor may influence the neutrophil-platelet binding, and represent a risk factor for CVD.

Administration of post-autologous PBSCT rhG-CSF is associated with long-term low concentrations of bone marrow hematopoietic progenitor cells

Recombinant human granulocyte colony-stimulating factor (rhG-CSF) has been widely used after autologous peripheral blood stem cell transplant (APBSCT) in an attempt to reduce the duration of neutropenia, but whether this treatment has any influence on long-term engraftment remains unknown. We have retrospectively analyzed data from breast cancer patients to compare post-APBSCT rhG-CSF administration in terms of the short-term benefit and myeloid marrow regeneration after 1 year. Group A included 10 patients not treated with post-APBSCT rhG-CSF, while groups B and C comprised 15 and 13 patients treated with this drug from days +1 and +6, respectively. No differences among the three groups were found in age, diagnosis, previous chemo-radiotherapy, CD34+/CD71- cell concentration in pre-transplant bone marrow (BM), mobilization schedule, CD34+ cell yield, conditioning regimen and post-transplant radiotherapy. Post-APBSCT rhG-CSF was shown to accelerate neutrophil recovery, but there were no significant differences in platelet recovery, transfusion requirements, days of fever, antibiotic administration or inhospital stay. With regard to BM hematopoietic precursors 1 year after APBSCT, significantly lower concentrations of total CD34+ cells, committed CD34+/CD33+ subsets, and more immature CD34+/CD71- cells were found in both groups B and C compared with patients not having received the cytokine (group A). Thus, post-APBSCT rhG-CSF administration does not appear to beneficially affect procedure outcome, and might even impair long-term marrow hematopoiesis.

Effect of cold-storage in the accumulation of bioreactive substances in platelet concentrates treated with second messenger effects

BACKGROUND AND OBJECTIVES

The mandatory 5-day of shelf-life platelet concentrates (PCs) creates outdating and inventory control problems in blood banking. Moreover, storage of PCs at 22-24 degrees C has been associated with a time-dependent accumulation of pyrogenic cytokines, potentially harmful for recipients. Previous studies have shown that supplementation of PCs with ThromboSol, a mixture of second-messengers effectors, might allow storage of functionally active platelets at refrigerated temperature to be extended. This study further investigates this storage approach by comparing the accumulation of bioactive compounds in standard and refrigerated PCs.

DESIGN AND METHODS

The PCs were supplemented with ThromboSol or a control solution and stored in parallel at 24 degrees C with continuous agitation or undisturbed at 4 degrees C. Samples were removed on days 1, 5, 9 of storage, and assayed for their content of interleukin (IL)-6, IL-8, tumour necrosis factor (TNF)-alpha, transforming growth factor (TGF)-beta1, and anaphylatoxins C3a and C4a.

RESULTS

Throughout storage, refrigerated PCs, both ThromboSol-treated and untreated units, displayed a slightly lower level of IL-6 and significantly lower concentration of IL-8 than conventionally stored PCs. ThromboSol slightly reduced the level of these cytokines in PCs. Throughout storage at 22 degrees C, an accumulation of anaphylatoxins C3a and C4a was seen both in both control and ThromboSol-treated PCs. This accumulation was significantly reduced in control PCs stored at 4 degrees C, but not in refrigerated PCs supplemented with ThromboSol. Cold-storage, with or without ThromboSol, had a minor effect on the accumulation of TGF-beta1 in PCs.

INTERPRETATION AND CONCLUSIONS

Our data confirm that release of bioactive compounds during in vitro storage of PCs is a temperature-sensitive process. The ThromboSol-refrigeration system could be a useful alternative for extending storage of PCs, without increasing the accumulation of cytokines (IL-6, IL-8), known to be involved in febrile reactions in recipients. Nevertheless, this storage system has no benefit on the level of other bioactive compounds (TGF-beta1, anaphylatoxins C3a and C4a) in PCs.

Binding of recombinant apolipoprotein(a) to human platelets and effect on platelet aggregation

The interaction of lipoprotein(a) [Lp(a)] with platelets is not well defined, particularly with regards to the individual contribution of the protein components of Lp(a), the apo B-100 and the apolipoprotein apo(a). This study investigated the binding of different recombinant apo(a) [r-apo(a)] isoforms, to human platelets and its effect on platelet aggregation. Scatchard analysis of saturation binding experiments demonstrated that human platelets display a single class of high affinity r-apo(a) binding sites (71 +/- 46 molec./platelet, Kd = 5.6 +/- 2.0 nmol/L). Platelet activation with strong agonists (thrombin, arachidonic acid) increased 2- to 10-fold the r-apo(a) binding, without affecting the affinity. Competition assays showed that the binding sites are highly specific for r-apo(a) and Lp(a). At high concentration t-PA could also bind to the r-apo(a) binding sites. By contrast, neither fibrinogen nor plasminogen inhibited to the r-apo(a) binding. The lysine analogue EACA inhibits the binding of r-apo(a) to platelets, thus suggesting the involvement of lysine residues in that interaction. Moreover, the r-apo(a) binding to platelets is unlikely mediated by GPIIb/IIIa-attached fibrin since it is not affected by platelet treatment with either LJ-CP8, a monoclonal antibody that specifically blocks fibrinogen binding to GPIIb/IIIa, nor GPRP, an inhibitor of fibrin polymerisation. Finally, we show that the distinct recombinant apo(a) proteins, as well as native Lp(a), promote an aggregation response of platelets to otherwise subaggregant doses of arachidonic acid. This proaggregant effect of r-apo(a) is dependent on its binding to platelets since it requires a minimum incubation time, and it is prevented by EACA at concentration inhibiting the r-apo(a)-platelet interaction. These results suggest that the prothrombotic action of Lp(a) may be in part mediated by modulating the platelet function through the interaction of its apo(a) subunit with a specific receptor at the platelet surface.

Platelet GP Ib/IX/V complex: physiological role

Platelets play an essential role in primary hemostasis and in thrombotic events, particularly in arterial vessels, as rheological conditions originate closer interactions between platelets and endothelium than lower shear rates. In response to vascular injury, platelets adhere to the subendothelial matrix by membrane receptors potentiating the generation of thrombin, become activated, and a series of biochemical processes induce platelet aggregation and liberation of intracellular metabolic products to the extracelular medium. Among platelet receptors, glycoprotein (GP) Ib/IX/V complex is peculiar, as it binds adhesive proteins, mainly von Willebrand factor (vWF), and thrombin, the main platelet agonist. Platelet adhesion and subsequent aggregation under conditions of high shear flow, essentially relies upon this receptor's capacity of binding to the subendothelial matrix, initiating signal transduction. Two proteins associated to GP Ib/IX/V, actin-binding protein (ABP) 280 and 14-3-3zeta, are potential mediators of signal transduction by the complex, but their specific contribution in this process is not yet fully understood. Additionally, two proteins implicated in signal transduction by immune stimuli, FcgammaRIIA and FcR gamma-chain, associate with GPIb/IX/V complex, and increasing data indicate a potential role in GPIbalpha mediated signal transduction.

Re-mobilization of peripheral blood progenitor cells within a short time interval fails to achieve effective progenitor cell yields

We report the case of a healthy donor who was mobilized for the purpose of performing an unrelated donor transplantation with subcutaneous injections of rhG-CSF. Because of accidental loss of progenitors, 3 days after completing the first collection, the donor was mobilized again with rhG-CSF, and progenitors were collected. While a similar increase in the pre-apheresis leukocyte count was observed in both procedures, fewer mononuclear cells were mobilized during the second rhG-CSF course, resulting in a poor CD34+ yield. These data suggest that an 8-day interval between commencement of rhG-CSF mobilizations is insufficient to predict an efficient collection of hematopoietic progenitors to ensure engraftment after bone marrow transplantation.

Evaluation of pooled platelet concentrates using prestorage versus poststorage WBC reduction: impact of filtration timing

BACKGROUND

Concern for the undesirable consequences of transfusing passenger WBCs is leading to the general use of WBC-reduced platelet concentrates (PCs). However, the impact of prestorage versus poststorage WBC reduction on the quality of platelet products has not been clearly defined.

STUDY DESIGN AND METHODS

Pooled PCs were WBC reduced before or after 5-day storage, by use of a WBC filter (PXL-8, Pall Corp.). Samples from pools were taken on days 1 and 5, before and after filtration, and on Day 9 of storage and assessed for cell counts, biochemical values, expression of platelet glycoproteins, thrombin generation, and content of IL-6, IL-8, TNFalpha, transforming growth factor beta1 (TGFbeta1), and anaphylatoxins C3a and C4a.

RESULTS

Filtration of fresh and 5-day-stored pooled PCs via a PXL-8 filter was similarly efficient, rendering pools with low WBC counts (<1 x 10(6) cells) and high platelet recovery (>95%). No major changes were found in the metabolic behavior or the expression of platelet GPIb, GPIIb/IIIa, CD62, and CD63 in PCs filtered before or after storage. Filtration, either before or after storage, increased by less than 5 percent the proportion of CD62+ platelets. Moreover, no changes were found in the concentration of prothrombin fragments 1 and 2 and thrombin-antithrombin complexes in the pooled PCs derived from the time of filtration. Finally, prestorage WBC reduction abrogated the accumulation of IL-6 and IL-8, but it did not prevent that of anaphylatoxins C3a and C4a nor of TGFbeta1. However, filtration through a PXL-8 filter significantly reduced (40-90%) the amount of IL-8, C3a, and C4a in the filtrate.

CONCLUSIONS

The timing of PXL-8 filtration of PCs has little impact on the efficiency of WBC reduction and on platelet recovery, and it does not seem to affect the quality of platelets or the generation of thrombin in the PCs. As regards the goal of reducing the amount of bioactive products in PCs, it remains uncertain as to whether prestorage WBC reduction fully eliminates the need for poststorage filtration. Prestorage filtration leads to low levels of IL-6 and IL-8 in PCs, but it does not impair the poststorage content of TGFbeta1 or anaphyla-toxins. By contrast, poststorage PXL-8 filtration removes significant amounts of C3a and C4a, and thus it might provide clinical benefits beyond those of prestorage WBC reduction.

Mobilization of hematopoietic progenitor cells with paclitaxel (taxol) as a single chemotheraupetic agent, associated with rhG-CSF

We assessed the mobilization capacity of taxol with rhG-CSF, both as a single chemotherapeutic agent and in the presence of cyclophosphamide (CY), and compared the effect with yields achieved when mobilization was performed solely with rhG-CSF. Fifteen patients with breast cancer received taxol 170 mg/m2 (continuous infusion, day 1) and rhG-CSF (8 microg/kg/day, from day 2 until the end of apheresis) (T-G group), while seven breast cancer patients were additionally treated with CY (4 g/m2) on day 2, followed by rhG-CSF starting at similar doses on day 3 (T-CY-G group). The PBSC collections after taxol with/without CY were compared with those of 30 breast cancer patients who had received rhG-CSF (8 microg/kg/day) for mobilization. No differences were found in the characteristics of patients included in any of the three mobilization groups. The median yield of CD34+ cells from all patients included in taxol containing schedules was 9 x 106/kg (range 2-26) collected with a median of one apheresis procedure (range 1-4). Leukaphereses began earlier in the T-G group (median day 8, range 7-10) than in the T-CY-G group (median day 13, range 11-17). In most patients (20 out of 22) who received taxol containing regimens, more than 2.5 x 106 CD34+ cells/kg, a threshold considered to be sufficient for hematopoietic reconstitution, were collected with a single apheresis. Those patients in the T-G group experienced less neutropenic and thrombocytopenic days, with all neutropenic fever episodes developing in patients treated with the T-CY-G schedule (43%). When considering priming with rhG-CSF alone in our historical cohort of 30 breast cancer patients, a significant detrimental effect was observed in comparison with taxol mobilizing schedules, in the number of aphereses performed, in the total yield CD34+cells and in the number of patients who achieved the target dose of 2.5 x 106/kg CD34+ cells within the first collection procedure. We conclude that taxol containing schedules are effective in mobilizing PBSC and facilitate the collection of high yields of CD34+ cells (usually more than 5 x 106/kg recipient body weight) with a reduced number of apheresis procedures. Taxol, as a single agent with rhG-CSF, exhibits less hematological toxicity than the combination chemotherapy mobilization regimen including CY. Bone Marrow Transplantation (2000) 25, 231-235.

In vitro analysis of platelet concentrates stored in the presence of modulators of 3',5' adenosine monophosphate, and organic anions

The storage of conventional platelet concentrates (PCs) under standard blood bank conditions is limited to five days, in part because longer storage periods lead to increasing damage in platelet integrity and functionality. The growing demand of PCs for clinical use, raises the interest to develop agents that would potentially permit a more extended period of storage. We have evaluated and compared the in vitro quality of PCs treated with: (1) Modulators of levels of cAMP (PGE1, foskolin, theophylline and isobutyl-methyl-xanthine [IBMX]); and (2) organic anions that function as alternative substrates of platelets (pyruvate and acetate). Platelet rich plasma (PRP) from pools (n = 6) of PCs was distributed into storage bags, and the agents to be tested were added, using saline as a control substance. PCs were stored at 22 degrees C with continuous agitation for up to 10 days. At 0, 5 and 10 days of storage, samples were analyzed for platelet counts, mean platelet volume (MPV), metabolic markers, and expression of glycoproteins (GPs). The addition of modulators of levels of cAMP, at the concentration used in the study, did not lead to substantial improvement in the parameters being evaluated, with respect to those in control units. The supplementation with organic anions, while not affecting the surface levels of GPs, favored the maintenance of metabolic values, such as pH, PCO2, and bicarbonate concentrations, as well as the preservation of MPV (p values < 0.05 respect to control units both at 5 and 10 days of storage). Our results indicate that while the use of modulators of levels of cAMP do not provide substantial benefit in the prevention of platelet storage lesions, organic anions have some advantageous effect in the storage promoted metabolic changes of PCs. These data might be considered when designing strategies to improve PC storage.

A common polymorphism flanking the ATG initiator codon of GPIb alpha does not affect expression and is not a major risk factor for arterial thrombosis

The platelet membrane glycoprotein (GP) Ib alpha plays a key role in the initial formation of thrombi. Polymorphisms (VNTR and HPA-2) in this receptor are associated with increased risk of coronary heart disease (CHD) and cerebral vascular disease (CVD). We investigated whether a recently described polymorphism (S/R), due to a single base change (T-->C) five nucleotides upstream the initiator codon of GPIb alpha, might influence the expression of the protein, and be implicated in the development of arterial thrombosis. One hundred and thirty nine healthy individuals provided blood samples for DNA analysis of platelet GPIb alpha polymorphisms, and for flow cytometric analysis of the surface expression of the receptor. A group of 20 S/R normal individuals and an identical number of S/S participants, age and sex matched, was investigated for the analysis of the density of various platelet receptors. The distribution of the S/R polymorphism was also analyzed in two case/control studies including 104 CVD patients, 101 CHD patients, and one control age, sex, and environmental risk factors matched for each case patient. Surface density of GPIb alpha showed no wide variations between individuals, was not influenced by the presence of S or R alleles, nor associated with the VNTR or HPA-2 polymorphisms. The prevalence of the S/R genotype among CVD and CHD patients was not distinct from that in the control groups. We conclude that the S/R polymorphism of GPIb alpha, flanking the initiator codon of the receptor, does not seem to be associated with surface levels of the protein, and is not an independent risk factor for arterial thrombosis.

Platelet cryopreservation using a reduced dimethyl sulfoxide concentration and second-messenger effectors as cryopreserving solution

Cryopreservation of platelets is of great interest since it could extend to years the shelf life of therapeutic platelet concentrates (PCs) and facilitate stockpiling and inventory control in blood banking. We have compared the cryopreservation of PCs by the standard method using 6% Me(2)SO as cryoprotectant with the method of freezing employing low concentrations of Me(2)SO (2%) plus ThromboSol, a mixture of second-messenger effectors that protect platelets from cold damage. PC pools were treated either with 6% Me(2)SO or with ThromboSol and 2% Me(2)SO and then placed directly in a -80 degrees C freezer or in the vapor phase of a liquid nitrogen freezer (-120 degrees C). After storage for 1 week or for 3 months, samples were removed, thawed, and analyzed. Measurements included cell recovery, biochemical parameters, membrane glycoproteins (GPs), platelet aggregation, and binding of radiolabeled von Willebrand factor (vWF) and fibrinogen. PCs cryopreserved with ThromboSol and 2% Me(2)SO displayed a platelet recovery (90%) equivalent to those frozen with 6% Me(2)SO. Following either cryopreservation procedure, platelets showed increased surface expression of P-selectin and moderate loss of GP Ibalpha in comparison to fresh platelets. The aggregatory response to ristocetin and the binding of vWF were similar in platelets frozen by either procedure. Finally, both methods promoted comparable impairment of the reactivity of platelets to thrombin, aggregation and binding of fibrinogen and vWF, compared to that of fresh platelets. In summary, cryopreservation of PCs using reduced Me(2)SO concentration and ThromboSol yields platelets with in vitro functional characteristics equivalent to those of cells frozen with the conventional method using 6% Me(2)SO.

[The education of type-2 diabetics: why not in groups?]

OBJECTIVE

To evaluate the efficacy of a programme of group education for diabetics, which succeeded in reducing base glucaemia, body mass index and glycosylated haemoglobin, stimulating insulin-treated patients' self-monitoring of glucaemia, improving their understanding of the disease, and bringing into group education 75% of the target population.

DESIGN

A controlled clinical trial with paired samples, lasting two years.

SETTING

"Las Fuentes Norte" Health Centre, Zaragoza.

PATIENTS

243 type-2 diabetics, distributed at random, with 120 in the intervention group and 123 in the control group. All patients with no history of group education in the previous two years and with no restrictions on their attending talks and monitoring were included. No-one gave up in the first year; 9 did in the second year.

INTERVENTION

Group health education workshop for two days in the first and second years.

MEASUREMENTS AND MAIN RESULTS

In the intervention group, at the end of the study, success in the survey increased by 4.2; base glucaemia dropped by 17.1 mg/dl, glycate haemoglobin went down by 0.5, and self-analysis went up by 14.2%, all with significant differences (p < 0.005 and CI 95%). The body mass index went down by 0.3 without significant differences. Knowledge was lost between the first and second year, with worse metabolic control. In the control group there were no significant differences in any variable.

CONCLUSIONS

A stable programme of group education may be effective, especially because of the increase in knowledge of the disease, fostering excellent conditions for a change to a healthier life-style.

Quality assessment of platelet concentrates supplemented with second-messenger effectors

BACKGROUND

While reducing the potential for bacterial contamination, the storage of platelet concentrates (PCs) at refrigerated temperatures is not routine, because of the induction of the so-called platelet storage lesion. As the modulation of second-messenger levels might help to overcome this drawback, a quality assessment of PCs treated with a mixture of second-messengers effectors known as ThromboSol was performed.

STUDY DESIGN AND METHODS

The PCs were supplemented with ThromboSol or phosphate-buffered saline, and stored in parallel at 22 degrees C with continuous agitation or at 4 degrees C. At 1, 5, and 9 days, an in vitro quality assessment of the PCs was performed, including measurement of cell number, metabolic and integrity markers, platelet surface expression of glycoproteins, platelet response to ristocetin and thrombin, and levels of cyclic adenosine 3', 5' monophosphate (cAMP) and thromboxane B2 (TxB2).

RESULTS

Control PCs stored at 4 degrees C underwent aggregation and displayed a significant decrease in the platelet number (40% on Day 5). By contrast, the ThromboSol-treated PCs maintained 80 percent of their initial platelet concentration after 9 days of storage at 4 degrees C. Compared to PCs stored at 22 degrees C, refrigerated PCs exhibited minor changes in metabolic values throughout storage, but the addition of ThromboSol induced a rise in metabolic rate during storage at 22 degrees C. Platelet responsiveness to both ristocetin and thrombin was maximally preserved in the ThromboSol-treated PCs stored at 4 degrees C. These units also maintained high levels of cAMP and low concentrations of TxB2 during storage.

CONCLUSION

The pharmacologic supplementation of PCs with ThromboSol significantly favors the maintenance of in vitro integrity and responsiveness of platelets during extended storage at refrigerated temperature. This protective effect seems to be a consequence of the ability of ThromboSol's components to sustain high levels of cAMP and to inhibit TxB2 production during the entire extended-storage period.

New alleles of the platelet glycoprotein Ibalpha gene

Platelet membrane glycoprotein Ibalpha (GP Ibalpha) bears two molecular polymorphisms which are in linkage disequilibrium: the C/T dimorphism at codon 145 (HPA-2) and the variable number of tandem repeats (VNTR) polymorphism in the macroglycopeptide region. The frequencies of these two polymorphisms, and of another three recently described silent polymorphisms, were investigated by genotypic identification in 729 Caucasian individuals from the south of Spain. Eight different alleles of this gene, including the longest VNTR A allele of the GP Ibalpha gene, were found in this population. Moreover, we detected an unexpected linkage between the B and A variants of the VNTR polymorphism and the HPA-2a allele in 5.9% of this population. These results suggest a new evolutionary model of GP Ibalpha, in which homologous recombination could account for the genetic diversity of the GP Ibalpha.

Polymorphisms of platelet membrane glycoprotein Ib associated with arterial thrombotic disease

Platelet membrane glycoprotein Ibalpha (GPIbalpha) is a major receptor for von Willebrand factor and thrombin, which plays a key role in the initial development of thrombi. Two polymorphisms (HPA-2 and VNTR) that affect phenotype have been described in GPIbalpha. The relevance of these polymorphisms to thrombotic disease was investigated by genotypic identification in three case-control studies: 104 case patients with acute cerebrovascular disease (CVD), 101 case patients with acute coronary heart disease (CHD), 95 patients with deep venous thrombosis (DVT), and one control age-, sex-, and race-matched for each case patient. Results show that the C/B genotype of the VNTR and the HPA-2b polymorphisms of GPIbalpha are strongly associated with increased risk of coronary heart disease and cerebral vascular disease but not with deep vein thrombosis. These two polymorphisms of GPIbalpha may represent newly identified risk factors for arterial thrombotic disease, but not for venous thrombosis.

Migraine and prothrombotic genetic risk factors

It has been suggested that during attacks of migraine both platelet activation and plasma coagulability are increased. We investigated the prevalence of several prothrombotic genetic risk factors in patients with migraine: factor V R/Q 506, factor II 20210 G/A, decanucleotide insertion/deletion in the factor VII promoter, and the platelet HPA-1 and HPA-2 alloantigenic systems, by genotypic identification in an age- and sex-matched case-control study including 106 patients with migraine (49 with aura, and 57 without aura). The prevalence of all genotypes was similar among case patients and controls. No association in relation to the type of migraine was detected in the factor II, factor VII, HPA-1, or HPA-2 polymorphisms. Our results showed a high prevalence of factor V Leiden in those patients with migraine with aura (6.1%), though that association was not statistically significant. The studied prothrombotic genetic factors do not seem to be associated with the development of migraine and, therefore, are not likely relevant in the previously reported hypercoagulability and platelet hyperaggregability in this disease.

Bone marrow steady-state CD34+/CD71- cell content is a predictive value of rG-CSF-mobilized CD34+ cells

Thirty-four patients diagnosed with breast cancer were included in a prospective study evaluating the bone marrow (BM) CD34+/CD71- cell content, as a predictive parameter of the CD34+ cell mobilization after rG-CSF administration. Analysis of the concentration of medullary CD34+/CD71- cells before priming schedules was significantly related with the collection of CD34+ cells in apheresis day 1 (P = 0.03, r = 0.36), apheresis day 1 + day 2 (P = 0.01, r = 0.42) or the total CD34+ cells collected (P = 0.005, r = 0.47). A BM CD34+/CD71- cell concentration greater than or less than a cut-off value of 30/microl was significantly associated with the yield of CD34+ cells collected by cytapheresis procedures (mean values 3.12 x 10(6)/kg, and 2.19 x 10(6)/kg, respectively, P = 0.013). These results suggest that in breast cancer patients undergoing priming with rG-CSF, steady-state BM CD34+/CD71- measurement is a relevant predictive parameter of CD34+ mobilization.

Genetic polymorphisms of factor VII are not associated with arterial thrombosis

A high plasma concentration of factor VII procoagulant activity is considered an independent risk factor for coronary heart disease. Recently, two polymorphisms of factor VII gene (insertion of a decanucleotide at -323 [A2], and the variant Q353) have been associated with 20-25% lower levels of this protein in plasma. In this study, the prevalence of these two factor VII polymorphisms were evaluated in relation to the development of acute thromboembolic events. Thus, we conducted three case-control studies of patients diagnosed with acute coronary syndromes, acute cerebrovascular events and deep venous thrombosis (101, 104 and 97 cases, respectively). No significant differences were detected in the prevalence of these polymorphisms between patients and controls, suggesting that the A1/A2 or R/Q alleles do not play an important role in the development of thromboembolic episodes.

A radioreceptor assay for mass measurement of inositol (1,4,5)-trisphosphate using saponin-permeabilized outdated human platelets

The binding of inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] to saponin-permeabilized blood-bank-outdated human platelets, 6 days old, has been characterized (Kd = 3.8 nM; Bmax = 1.7 pmol/mg protein) and used to develop a novel radioreceptor assay which allows the measurement of the Ins(1,4,5)P3 content in resting or agonist-stimulated cells. This assay is as sensitive (0.25 pmol in a 0.25 ml volume), specific, and reproducible as previously proposed methods. In addition, obtaining large batches of the Ins(1,4,5)P3 binding protein by treating outdated platelets with saponin is simple and quick and uses otherwise discarded material. Moreover, the assay is considerably cheaper than commercially available kits. Using this method we confirmed that thrombin evokes a rapid, transient, and dose-dependent increase in the platelet concentration of Ins(1,4,5)P3.

The venous thrombosis risk factor 20210 A allele of the prothrombin gene is not a major risk factor for arterial thrombotic disease

A nucleotide change (G to A transition) at position 20210 has recently been demonstrated to be a risk factor for venous thrombosis. The relevance of this polymorphism to thrombotic disease was investigated by genotypic identification in three prospective case-control studies: 101 case patients with acute coronary heart disease (CHD), 104 patients with acute cerebrovascular disease (CVD), 82 patients with a confirmed diagnosis of deep venous thrombosis (DVT), and one control age- and sex-matched for each patient. The prevalence of the genetic variation was significantly associated with the occurrence of DVT, but did not differ in patients with CHD or CVD from that in controls, suggesting that this allele should not be considered a major risk factor for arterial thrombotic disease.

HPA-1 genotype in arterial thrombosis--role of HPA-1b polymorphism in platelet function

Recently, the HPA-1b (PlA2) polymorphism of the platelet glycoprotein IIIa has been suggested as a genetic risk factor for coronary artery disease. We conducted two case-control studies of 103 patients with ischaemic cerebrovascular disease (CVD) and 101 patients with ischaemic heart disease (IHD). The groups were matched for age, race and sex. No significant differences regarding selected risk factors (hypertension, diabetes mellitus, hypercholesterolaemia and smoking) were found between case patients and controls. Moreover, we investigated 286 normal individuals from the Mediterranean area. Genotyping of HPA-1 was performed by PCR-allelic specific restriction and single-strand conformation polymorphism analysis. The prevalence of HPA-1b was similar among case patients and controls (29.2% vs. 25.3% and 26.7% vs. 34.6% for CVD and IHD case-control studies, respectively). The HPA-1b allele was found in 36.4% of the normal population. Finally, the analysis of platelet function in nine controls with the three possible HPA-1 genotypes (three a/a, three a/b and three b/b) indicates that HPA-1b genotype does not modify either the in vitro platelet aggregation and activation profile, nor the GP IIb/IIIa interaction with fibrinogen or von Willebrand factor. Our results do not support the role of HPA-1b polymorphism as an inherited risk factor for arterial thrombotic disease.