Platelet-Rich Fibrin Decreases the Inflammatory Response of Mesenchymal Cells.

Chronic inflammation is a pathological process where cells of the mesenchymal lineage become a major source of inflammatory mediators. Platelet-rich fibrin (PRF) has been shown to possess potent anti-inflammatory activity in macrophages, but its impact on mesenchymal cells has not been investigated. The aim of this study was, therefore, to expose mesenchymal cells to inflammatory cytokines together with lysates generated from liquid platelet-poor plasma (PPP), the cell-rich buffy coat layer (BC; concentrated-PRF or C-PRF), and the remaining red clot layer (RC), following centrifugation of blood. Heating PPP generates an albumin gel (Alb-gel) that when mixed back with C-PRF produces Alb-PRF. Membranes prepared from solid PRF were also subjected to lysis. We report here that lysates of PPP, BC, and PRF decreased the cytokine-induced expression of interleukin 6 (IL6) and nitric oxide synthase (iNOS) in the bone marrow-derived ST2 cells. Consistently, PPP, BC, and PRF greatly decreased the phosphorylation and nuclear translocation of p65 in ST2 cells. The inflammatory response caused by Pam3CSK4 was reduced accordingly. Moreover, PPP, BC, and PRF reduced the enhanced expression of inflammatory mediators IL6 and iNOS in 3T3-L1 pre-adipocyte mesenchymal cells, and iNOS and CCL5 in murine calvarial cells. Surprisingly, PRF lysates were not effective in reducing the inflammatory response of human gingival fibroblasts and HSC2 epithelial cells. The data from the present study suggest that both liquid PRF and solid PRF exert potent anti-inflammatory activity in murine mesenchymal cells.

Downregulation of SERINC5 expression in buffy coats of HIV-1-infected patients with detectable or undetectable viral load.

Among the host restriction factors against HIV, SERINC5 has been described in vitro, but the mRNA level of SERINC5 in vivo has been little studied. We compare SERINC5 expression in subjects with HIV-1 (highly active antiretroviral treatment (HAART) and HAART-naïve) with and without suppression of viral load. A cross-sectional study was performed with 107 individuals distributed as follows: 24 with HAART-naïve and detectable viral load (> 50 copies/mL), 13 with HAART and detectable viral load (> 50 copies/mL), 50 with HAART and undetectable viral load (≤ 50 copies/mL), and 20 without HIV-1. SERINC5 expression in buffy coats was determined using RT-qPCR. The viral load was determined using real-time PCR and the amount of CD4 + and CD8 + T-lymphocytes was measured using flow cytometry. The data were normalized with the Shapiro-Wilk test and the Kruskal-Wallis test was subsequently performed. The relative expression was compared with a T-test and the remaining data with the Mann-Whitney U-test. ANCOVA multiple linear regression analysis was performed between characteristics of patients with SERINC5 expression. The mean and SD of the SERINC5 expression in the three groups with HIV-1 was 0.9 ± 0.2 and without HIV-1 was 1.7 ± 0.14 (P < 0.001). Multiple linear regression did not show the participation of CD4 +, CD8 + , viral load, infection time, or treatment time. No differences in the SERINC5 expression were found among the studied groups of patients with HIV-1. When comparing the groups with and without HIV-1 infection, SERINC5 was downregulation in the HIV-1 groups.

Cryopreserved buffy-coat-derived platelets reconstituted in platelet additive solution: A safe and available product with sufficient haemostatic effectiveness.

BACKGROUND: Platelets (PLTs) stored at 20-24 °C have a short shelf life of only 5 days, which can result in their restricted availability. PLT cryopreservation extends the shelf life to 2 years. METHODS: We implemented a method of PLT freezing at -80 °C in 5-6% dimethyl sulfoxide. Buffy-coat-derived leucodepleted fresh PLTs blood group O (FP) were used for cryopreservation. Cryopreserved pooled leucodepleted PLTs (CPP) were thawed at 37 °C, reconstituted in PLT additive solution SSP + and compared to FP regarding PLT content, PLT concentration, pH, volume, PLT loss, anti-A/B antibody titre, total protein, plasma content, and PLT swirling. Clot properties were evaluated via rotational thromboelastometry. PLT microparticle number and surface receptor phenotype were assessed via flow cytometry. RESULTS: CPP met the required quality parameters. The mean freeze-thaw PLT loss was 22.24 %. Anti-A/B antibody titre and plasma content were significantly lower in CPP. CPP were characterised by faster clot initiation and form stable PLT clots. The number of PLT microparticles increased 25 times in CPP and there were more particles positive for the activation marker CD62 P compared to FP. CONCLUSION: Thawing and reconstitution are easy and fast processes if platelet additive solution is used. Low anti-A/B antibody titre and plasma content make possible the use of CPP of blood group O reconstituted in SSP + as universal ABO products, including clinical situations where washed PLTs are required. Clot properties evaluated via rotational thromboelastometry demonstrated that CPP retain a significant part of their activity compare to FP and are haemostatically effective.

Comparative analysis of platelet concentrates prepared after two hours and overnight storage of buffy coat at room temperature.

INTRODUCTION: The overnight storage of the buffy coat (BC) at room temperature has logistic and operational advantages for the blood centre. The present study aimed to evaluate the impact of an overnight hold (stored) of BC at room temperature in comparison with the 2-hour hold (fresh) of buffy coats on the platelet concentrate (PC) characteristics. METHODS: A total of 60 BCs were included in the study, 30 PCs (fresh) were prepared after two hours holding time of the BCs and the other 30 PCs (stored) were prepared after the overnight BC storage at room temperature. The primary endpoint of PCs evaluation was the platelet yield, volume, pH, WBC count, RBC count, and platelet swirling in the PC and the secondary endpoints were glucose concentration, lactate, LDH, and sterility of the PCs. All the tests were performed on the day+1 of the blood collection. RESULTS: There was no difference concerning the volume, RBC count, and swirling between the two groups (P>0.05). The PCs from the fresh BC had higher pH and glucose concentration (P<0.05). On the other hand, the overnight hold of BC produced higher platelet counts, WBC counts, lactate, and LDH levels (P<0.05). All the 60 PCs did not record any bacterial growth on the culture media for the sterility results. CONCLUSION: The overnight hold of BC produces a higher platelet yield with higher storage lesions. This may also allow better supervision, ensuring better quality control.

Relative Centrifugal Force (RCF; G-Force) Affects the Distribution of TGF-ß in PRF Membranes Produced Using Horizontal Centrifugation.

Solid platelet-rich fibrin (PRF) is produced with centrifugation tubes designed to accelerate clotting. Thus, activated platelets may accumulate within the fibrin-rich extracellular matrix even before centrifugation is initiated. It can thus be assumed that platelets and their growth factors such as transforming growth factor-ß (TGF-ß) are trapped within PRF independent of their relative centrifugal force (RCF), the gravitation or g-force. To test this assumption, we prepared PRF membranes with tubes where clotting is activated by a silicone-coated interior. Tubes underwent 210 g, 650 g and 1500 g for 12 min in a horizontal centrifuge. The respective PRF membranes, either in total or separated into a platelet-poor plasma and buffy coat fraction, were subjected to repeated freeze-thawing to prepare lysates. Gingival fibroblasts were exposed to the PRF lysates to provoke the expression of TGF-ß target genes. We show here that the expression of interleukin 11 (IL11) and NADPH oxidase 4 (NOX4), and Smad2/3 signaling were similarly activated by all lysates when normalized to the size of the PRF membranes. Notably, platelet-poor plasma had significantly less TGF-ß activity than the buffy coat fraction at both high-speed protocols. In contrast to our original assumption, the TGF-ß activity in PRF lysates produced using horizontal centrifugation follows a gradient with increasing concentration from the platelet-poor plasma towards the buffy coat layer.

Buffy coat-derived platelets cryopreserved using a new method: Results from a pivotal clinical trial on thrombocytopenic patients with acute leukaemia.

The administration of cryopreserved platelets (PLTs) may overcome the limits of platelet shortage and availability, especially during some seasons or in specific contexts like rural areas. After in vitro validation studies, ad hoc prepared buffy coat-derived pooled platelet concentrates (BC-PLTs), treated with dimethyl sulphoxide (DMSO) and cryopreserved (CRY BC-PLTs) at -80 °C with a modified Valeri method, were transfused in patients with severe thrombocytopenia secondary to chemotherapy for acute leukaemia (AL). Five inpatients were enrolled in the pivotal clinical trial NCT02032134: 4 males and 1 female with a mean age of 71 years (range: 65-80). Four patients were diagnosed with acute myeloid leukaemia and 1 had acute lymphoblastic leukaemia.Transfusion of one Unit of CRY BC-PLTs resulted effective in active bleeding control in two patients without any adverse reaction or concomitant antihaemorrhagic therapies. CRY BC-PLTs met the currently accepted criteria for cryopreserved PLTs, their transfusion in patients with AL was safe. (Clinical trial: NCT02032134).

Challenges in the Multivariate Analysis of Mass Cytometry Data: The Effect of Randomization.

Cytometry by time-of-flight (CyTOF) has emerged as a high-throughput single cell technology able to provide large samples of protein readouts. Already, there exists a large pool of advanced high-dimensional analysis algorithms that explore the observed heterogeneous distributions making intriguing biological inferences. A fact largely overlooked by these methods, however, is the effect of the established data preprocessing pipeline to the distributions of the measured quantities. In this article, we focus on randomization, a transformation used for improving data visualization, which can negatively affect multivariate data analysis methods such as dimensionality reduction, clustering, and network reconstruction algorithms. Our results indicate that randomization should be used only for visualization purposes, but not in conjunction with high-dimensional analytical tools. © 2019 The Authors. Cytometry Part A published by Wiley Periodicals, Inc. on behalf of International Society for Advancement of Cytometry.

Overcoming the deceptively low viability of CD45+ cells in thawed cord blood unit segments.

BACKGROUND AND OBJECTIVES: There is no standard methodology for post-thaw sample preparation for viability analysis of umbilical cord blood units (CBU). A common challenge faced by CB bank is for their product to meet the post-thaw cell viability threshold for CD45+ cells set at 40% by NetCord-FACT. The objective of this work was to improve the post-thaw staining method to maximize CD45+ cell viability so that clinically valuable samples meet the NetCord-FACT threshold criteria for CD45+ and CD34+ cell viabilities. MATERIALS AND METHODS: Samples of CBU buffy coats and CBU segments were thawed and taken for staining. Various parameters were evaluated on CD45+ and CD34+ cell viability as measured by 7-actinomycin D (7-AAD) staining. RESULTS: The results revealed that initiating the staining at 20 min post-thaw instead of 30, shortening the red cell lysis treatment, or performing lysis on ice and removing this step all together, all improved the viability of CD45+ cells. Using CBU segments, it was shown that the most effective approach in increasing the viability of CD45+ cells was the complete omission of red cell lysis step. However, removal of the lysis step can create technical artefacts during flow cytometry acquisition that results in an underestimation of the viability of CD34+ cells. This can be avoided and CD34+ cell viability restored with additional thresholding on CD45 signal. CONCLUSION: CB CD45+ cells are sensitive to red cell lysis treatment post-thaw; omission of this step provides the best viability and ultimately better reflects the quality of cells used for transplantation.

CXCL16/CXCR6-mediated adhesion of human peripheral blood mononuclear cells to inflamed endothelium.

The endothelial chemokine CXC motif ligand 16 (CXCL16) is involved in the recruitment and firm adhesion of CXCR6+ cells to the atherosclerosis-prone aortic vessel wall. Recently we showed that CXCR6+ platelets from flowing blood attach to CXCL16 expressed by activated endothelium on the luminal side of the blood vessel. With this study we supplement these findings with the observation that platelets bound to the inflamed endothelium are presenting CXCR6 to CXCL16-positive peripheral blood mononuclear cells (PBMCs) and, thus, are mediating an increased adhesion of PBMCs to the arterial wall. Furthermore we identified endothelial CXCL16 as an important adhesion molecule promoting the firm adhesion of CXCR6-positive PBMCs to inflamed endothelium. Our results demonstrate that endothelial CXCL16 as well as platelet CXCR6 are acting as potent PBMC-adhesion ligands, inducing PBMC-adhesion to the atherosclerosis-prone vessel wall and thus promoting the progression of atherosclerosis.

Soluble CD40L and CD62P levels differ in single-donor apheresis platelet concentrates and buffy coat-derived pooled platelet concentrates.

BACKGROUND: Platelet storage lesions are structural and biochemical changes in platelet concentrates (PCs), and depend on variables in collection and processing, as well as secondary procedures and storage conditions; such lesions can be mitigated by the use of platelet additive solutions (PASs). STUDY DESIGN AND METHODS: This study investigated release of the inflammatory markers sCD40L and sCD62P by single-donor apheresis platelet concentrates (SDA-PCs) and buffy coat-derived pooled platelet concentrates (PPCs) before and after storage. SDA-PC and PPC samples (n = 9089) processed by various methods and stored for different durations were obtained following production in one regional setting, the French National Blood Service. Soluble factors were quantified in PC supernatants immediately after processing and at the time of delivery, using biological testing technology (Luminex). RESULTS: SDA-PCs appeared more activated than PPCs at the end of the production step (i.e., prior to storage); however, proinflammatory soluble factors exhibited greater increases in PPCs than in SDA-PCs during storage. In SDA-PCs, PAS-D (65%) led to reduced secretion of sCD62P, but favored secretion of sCD40L, compared with the alternative PAS-E. CONCLUSION: These data stress the importance of the production (processing) steps of PC manufacture and of storage. The extent to which they affect patient outcomes awaits further investigation in clinical studies.

Buffy coat-derived platelets cryopreserved using a new method: Results from in vitro studies.

Cryopreservation for the long-term storage of platelets (PLTs) is a useful method to overcome the limits of platelet shortage. This is an in vitro prospective study to evaluate the count, viability, and function of buffy coat-derived pooled platelet concentrates (BC-PLTs), treated with dimethyl sulphoxide (DMSO) and cryopreserved (CRY BC-PLTs) at -80 °C with a modified Valeri method. PLTs were stored in 6% DMSO with a patented kit. Overall, 49 BC-PLTs from 245 healthy volunteer donors were prepared, cryopreserved, and analysed before and after 3, 6, and 9 months of storage. In flow cytometry, a statistically significant reduction in CD 42b (92.7 ± 4.29% at T0 vs. 23.6 ± 27.5% at T3, 16.38 ± 12.54% at T6, and 17.3 ± 9.6% at T9) and PAC-1 (1.9 ± 1.34% at T0 vs. 0.62 ± 0.4% at T3, 0.63 ± 0.83% at T6, and 0.49 ± 0.48% at T9) was observed after storage. CRY BC-PLTs showed a good and stable endogenous thrombin generation potential (nM min): 529.25 ± 98.64 at T0 vs. 533.04 ± 103.15 at T9 months. CRY BC-PLTs showed a good viability in vitro, according to currently accepted criteria for cryopreserved PLTs.

Flow cytometry analysis of platelet populations: usefulness for monitoringthe storage lesion in pooled buffy-coat platelet concentrates.

BACKGROUND: Early detection of the platelet storage lesion is still a challenge in transfusion practice. Using flow cytometry, we evaluated the appearance of the storage lesion, based on the expression of platelet activation markers, in total platelets and platelet populations. MATERIALS AND METHODS: Buffy-coat-derived platelet concentrates were stored under standard conditions for 5 days. The expression of activation antigens CD42b, CD36, CD62p and phosphatidylserine on total platelets and populations of small, medium-sized and large platelets was analysed by flow cytometry on storage days 1, 3 and 5. RESULTS: The activation/lesion on total platelets and each platelet population was detected on storage day 3, by the increased expression of CD36. On the same day, increased expression of CD42b and CD62p was detected, but only on large platelets. Small and medium-sized platelets had increased CD62p expression only on day 5. Externalisation of phosphatidylserine was not detected. DISCUSSION: Evaluation of the level of expression of various activation markers on different platelet populations could be an additional valid analysis in cell quality control of platelet concentrates, and in the assessment of novel approaches to platelet concentrate manipulation.

Platelet storage lesion in interim platelet unit concentrates: A comparison with buffy-coat and apheresis concentrates.

Platelet storage lesion is characterized by morphological changes and impaired platelet function. The collection method and storage medium may influence the magnitude of the storage lesion. The aim of this study was to compare the newly introduced interim platelet unit (IPU) platelet concentrates (PCs) (additive solution SSP+, 40% residual plasma content) with the more established buffy-coat PCs (SSP, 20% residual plasma content) and apheresis PCs (autologous plasma) in terms of platelet storage lesions. Thirty PCs (n=10 for each type) were assessed by measuring metabolic parameters (lactate, glucose, and pH), platelet activation markers, and in vitro platelet aggregability on days 1, 4, and 7 after donation. The expression of platelet activation markers CD62p (P-selectin), CD63 (LAMP-3), and phosphatidylserine was measured using flow cytometry and in vitro aggregability was measured with multiple electrode aggregometry. Higher platelet activation and lower in vitro aggregability was observed in IPU than in buffy-coat PCs on day 1 after donation. In contrast, metabolic parameters, expression of platelet activation markers, and in vitro aggregability were better maintained in IPU than in buffy-coat PCs at the end of the storage period. Compared to apheresis PCs, IPU PCs had higher expression of activation markers and lower in vitro aggregability throughout storage. In conclusion, the results indicate that there are significant differences in platelet storage lesions between IPU, buffy-coat, and apheresis PCs. The quality of IPU PCs appears to be at least comparable to buffy-coat preparations. Further studies are required to distinguish the effect of the preparation methods from storage conditions.

Differences in levels of platelet-derived microparticles in platelet components prepared using the platelet rich plasma, buffy coat, and apheresis procedures.

BACKGROUND: There has been an increased interest in platelet-derived microparticles (PMPs) in transfusion medicine. Little is known about PMP status during the preparation of platelet concentrates for transfusion. AIM: The aim of this study is to compare the PMP levels in platelet components prepared using the buffy coat (BC), platelet-rich plasma platelet concentrate (PRP-PC), and apheresis (AP) processes. METHODS: Platelet components were prepared using the PRP-PC and BC processes. Apheresis platelets were prepared using the Trima Accel and Amicus instruments. The samples were incubated with annexin A5-FITC, CD41-PE, and CD62P-APC. At day 1 after processing, the PMPs and activated platelets were determined using flow cytometry. RESULTS: Both the percentage and number of PMPs were higher in platelet components prepared using the Amicus instrument (2.6±1.8, 32802±19036 particles/µL) than in platelet components prepared using the Trima Accel instrument (0.5±0.4, 7568±5298 particles/µL), BC (1.2±0.6, 12,920±6426 particles/µL), and PRP-PC (0.9±0.6, 10731±5514 particles/µL). Both the percentage and number of activated platelets were higher in platelet components prepared using the Amicus instrument (33.2±13.9, 427553±196965 cells/µL) than in platelet components prepared using the Trima Accel instrument (16.2±6.1, 211209±87706 cells/µL), BC (12.9±3.2, 140624±41003 cells/µL), and PRP-PC (21.1±6.3, 265210±86257 cells/µL). CONCLUSIONS: The study suggests high variability of PMPs and activated platelets in platelet components prepared using different processes. This result may be important in validating the instruments involved in platelet blood collection and processing.

miRNAs differentially expressed by next-generation sequencing in cord blood buffy coat samples of boys and girls.

AIM: Differences in children's development and susceptibility to diseases and exposures have been observed by sex, yet human studies of sex differences in miRNAs are limited. MATERIALS & METHODS: The genome-wide miRNA expression was characterized by sequencing-based EdgeSeq assay in cord blood buffy coats from 89 newborns, and 564 miRNAs were further analyzed. RESULTS: Differential expression of most miRNAs was higher in boys. Neurodevelopment, RNA metabolism and metabolic ontology terms were enriched among miRNA targets. The majority of upregulated miRNAs (86%) validated by nCounter maintained positive-fold change values; however, only 21% reached statistical significance by false discovery rate. CONCLUSION: Accounting for host factors like sex may improve the sensitivity of epigenetic analyses for epidemiological studies in early childhood.

Quality Analysis of DNA from Cord Blood Buffy Coat: The Best Neonatal DNA Source for Epidemiological Studies?

BACKGROUND: Umbilical cord blood is an economical and easy to obtain source of high-quality neonatal genomic DNA. However, although large numbers of cord blood samples have been collected, information on the yield and quality of the DNA extracted from cord blood is scarce. Moreover, considerable doubt still exists on the utility of the buffy coat instead of whole blood as a DNA source. METHODS: We compared the sample storage and DNA extraction costs for whole blood, buffy coat, and all-cell pellet. We evaluated three different DNA purification kits and selected the most suitable one to purify 1011 buffy coat samples. We determined the DNA yield and optical density (OD) ratios and analyzed 48 single-nucleotide polymorphisms using time-of-flight mass spectrometry (TOF MS). We also analyzed eight possible preanalytical variables that may correlate with DNA yield or quality. RESULTS: Buffy coat was the most economical and least labor-intensive source for sample storage and DNA extraction. The average yield of genomic DNA from 200 µL of buffy coat sample was 16.01 ± 8.00 µg, which is sufficient for analytic experiments. The mean A260/A280 ratio and the mean A260/A230 ratio were 1.89 ± 0.09 and 1.95 ± 0.66, respectively. More than 99.5% of DNA samples passed the TOF MS test. Only hemolysis showed a strong correlation with OD ratios of DNA, but not with yield. CONCLUSION: Our findings show that cord blood buffy coat yields high-quality DNA in sufficient quantities to meet the requirements of experiments. Buffy coat was also found to be the most economic, efficient, and stable source of genomic DNA.

Retrospective analysis of second-line chemotherapy outcomes with paclitaxel or docetaxel in correlation with STMN1 polymorphism in advanced non-small cell lung cancer patients

Purpose. Second-line chemotherapy of advanced non-small cell lung cancer (NSCLC) with docetaxel or pemetrexed allows to achieve objective response rate only in 5-10 % of patients. Recent studies have shown that single nucleotide polymorphisms (SNPs) in genes encoding proteins which regulate dynamics of microtubules may be considered as predictive factors of response to taxane-based chemotherapy. STMN1 gene encodes stathmin 1, which plays role in cell division by regulation of microtubules epolarisation, and this process may be associated with taxanes’ effectiveness. Materials and methods. Using HRM-PCR technique, we evaluated the −2166C>T SNP of STMN1 gene in DNA from peripheral blood leucocytes of 54 advanced NSCLC patients treated in second-line monotherapy with docetaxel or paclitaxel. Results. Patients with TT genotype of STMN1 gene demonstrated significantly longer progression-free survival (PFS) and the lower risk of early disease progression after second-line treatment compared to patients with other STMN1 genotypes (median PFS: 7 and 2 months; p = 0.0154; HR = 0.371; 95 % CI 0.184-0.743). Early disease progression during second-line chemotherapy was significantly more frequently observed in patients with CC genotype of STMN1 in contrast to patients with presence of T allele (median PFS: 2 and 4 months; p = 0.0385; HR = 1.776; 95 % CI 0.905-3.445). Conclusion. Only selected NSCLC patients could benefit from second-line chemotherapy. Therefore, investigations of novel predictive molecular factors for proper qualification of patients to second-line taxane-based chemotherapy are justified. Studied SNP of STMN1 gene may have potential predictive role in such therapy (AU)

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Use of Buffy Coat miRNA Profiling for Breast Cancer Prediction in Healthy Women.

MicroRNAs are key regulators of different biological processes and their deregulation is associated with the occurrence of many diseases among which cancer. Due to the higher stability of microRNAs and to the easiness in their detection both in organs than in biological fluids, many studies are turned toward potential use of this small molecules as biomarkers for the prediction and diagnosis of different types of cancer. Here we describe the experiment protocol that we have used for microRNA profiling analysis in buffy coat samples of women who developed breast cancer versus women who remained healthy during a 20 year follow-up period, with the aim to identify predictive microRNAs of breast cancer occurrence.

In vitro study of platelet function confirms the contribution of the ultraviolet B (UVB) radiation in the lesions observed in riboflavin/UVB-treated platelet concentrates.

BACKGROUND: Platelet inactivation technologies (PITs) have been shown to increase platelet storage lesions (PSLs). This study investigates amotosalen/ultraviolet (UV)A- and riboflavin/UVB-induced platelet (PLT) lesions in vitro. Particular attention is given to the effect of UVB alone on PLTs. STUDY DESIGN AND METHODS: Buffy coat-derived PLT concentrates (PCs) were treated with amotosalen/UVA, riboflavin/UVB, or UVB alone and compared to untreated PCs throughout storage. In vitro PLT function was assessed by blood gas and metabolite analyses, flow cytometry-based assays (CD62P, JC-1, annexin V, PAC-1), hypotonic shock response, and static adhesion to fibrinogen-coated wells. RESULTS: In our experimental conditions, riboflavin/UVB-treated PCs showed the most pronounced differences compared to untreated and amotosalen/UVA-treated PCs. The riboflavin/UVB treatment led to a significant increase of anaerobic glycolysis rate despite functional mitochondria, a significant increase of CD62P on Day 2, and a decrease of JC-1 aggregates and increase of annexin V on Day 7. The expression of active GPIIbIIIa (PAC-1) and the adhesion to fibrinogen was significantly increased from Day 2 of storage in riboflavin/UVB-treated PCs. Importantly, we showed that these lesions were caused by the UVB radiation alone, independently of the presence of riboflavin. CONCLUSION: The amotosalen/UVA-treated PCs confirmed previously published results with a slight increase of PSLs compared to untreated PCs. Riboflavin/UVB-treated PCs present significant in vitro PSLs compared to untreated PCs. These lesions are caused by the UVB radiation alone and probably involve the generation of reactive oxygen species. The impact of these observations on clinical use must be investigated.