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Abstract Background Platelets and erythrocytes constitute over 95% of all hematopoietic stem cell output. However, the clonal dynamics of HSC contribution to these lineages remains largely unexplored. Results We use lentiviral genetic labeling of mouse hematopoietic stem cells to quantify output from all lineages, nucleate, and anucleate, simultaneously linking these with stem and progenitor cell transcriptomic phenotypes using single-cell RNA-sequencing. We observe dynamic shifts of clonal behaviors through time in same-animal peripheral blood and demonstrate that acute platelet depletion shifts the output of multipotent hematopoietic stem cells to the exclusive production of platelets. Additionally, we observe the emergence of new myeloid-biased clones, which support short- and long-term production of blood cells. Conclusions Our approach enables kinetic studies of multi-lineage output in the peripheral blood and transcriptional heterogeneity of individual hematopoietic stem cells. Our results give a unique insight into hematopoietic stem cell reactivation upon platelet depletion and of clonal dynamics in both steady state and under stress.

Platelets are key mediators of thrombus formation and inflammation during the acute phase of ischaemic stroke. Particularly, the platelet glycoprotein (GP) receptors GPIbα and GPVI have been shown to mediate platelet adhesion and activation in the ischaemic brain. GPIbα and GPVI blockade could reduce infarct volumes and improve functional outcome in mouse models of acute ischaemic stroke, without concomitantly increasing intracerebral haemorrhage. However, the functional role of platelets during long-term stroke recovery has not been elucidated so far.Thus, we here examined the impact of platelet depletion on post-stroke recovery after transient middle cerebral artery occlusion (tMCAO) in adult male mice. Platelet depleting antibodies or isotype control were applied from day 3–28 after tMCAO in mice matched for infarct size. Long-term functional recovery was assessed over the course of 28 days by behavioural testing encompassing motor and sensorimotorical functions, as well as anxiety-like or spontaneous behaviour. Whole brain flow cytometry and light sheet fluorescent microscopy were used to identify resident and infiltrated immune cell types, and to determine the effects of platelet depletion on the cerebral vascular architecture, respectively.We found that delayed platelet depletion does not improve long-term functional outcome in the tMCAO stroke model. Immune cell abundance, the extent of thrombosis and the organisation of the cerebral vasculature were also comparable between platelet-depleted and control mice. Our study demonstrates that, despite their critical role in the acute stroke setting, platelets appear to contribute only marginally to tissue reorganisation and functional recovery at later stroke stages.

ObjectiveTo explore the risk factors and predictive indexes of severe thrombocytopenia during concurrent radio-chemotherapy of nasopharyngeal carcinomas.MethodsRetrospective analysis was performed from the hospitalized patients with nasopharyngeal carcinoma from August 2014 to July 2017, and induction chemotherapy and concurrent radio-chemotherapy were completed. According to the lowest platelet count during concurrent chemotherapy, patients were divided into observation and control groups. General information and laboratory examinations were recorded and analyzed by univariate analysis, multivariate regression analysis, and ROC curve analysis.ResultsFactors, including age, PLT, IBIL, APTT at first visit, WBC, RBC, HGB, PLT, NEUT, APTT, IBIL, FFA, Crea, and urea before radio-chemotherapy, which are significant in univariate analysis into multivariate regression analysis, were taken. It turned out that RBC (OR = 10.060, 95% CI 2.679–37.777, p = 0.001), PLT (OR = 1.020, 95% CI 1.006–1.034, p = 0.005), and IBIL (OR = 0.710, 95% CI 0.561–0.898, p = 0.004) are independent predictors of severe TP in NPC. ROC analysis showed that the AUC of RBC, IBIL, PLT, and AGE is 0.746 (p < 0.001), 0.735 (p < 0.001), 0.702 (p = 0.001), and 0.734 (p < 0.001). New variables called joint predictors were calculated by a regression equation (Y = 2.309 * RBC - 0.343 * IBIL + 0.02 * PLT - 10.007), the AUC of which is 0.8700 (p < 0.001); best truncation value is >5.87 mmol/l.ConclusionsLower RBC, PLT, and higher IBIL before concurrent radio-chemotherapy are independent risk factors causing severe TP during concurrent radio-chemotherapy of NPC. The RBC, PLT, and IBIL before concurrent radio-chemotherapy and joint predictor have a good predictive value to evaluate the risk of severe TP during concurrent radio-chemotherapy of NPC.

Objective: To explore the risk factors and predictive indexes of severe thrombocytopenia during concurrent radio-chemotherapy of nasopharyngeal carcinomas. Methods: Retrospective analysis was performed from the hospitalized patients with nasopharyngeal carcinoma from August 2014 to July 2017, and induction chemotherapy and concurrent radio-chemotherapy were completed. According to the lowest platelet count during concurrent chemotherapy, patients were divided into observation and control groups. General information and laboratory examinations were recorded and analyzed by univariate analysis, multivariate regression analysis, and ROC curve analysis. Results: Factors, including age, PLT, IBIL, APTT at first visit, WBC, RBC, HGB, PLT, NEUT, APTT, IBIL, FFA, Crea, and urea before radio-chemotherapy, which are significant in univariate analysis into multivariate regression analysis, were taken. It turned out that RBC (OR = 10.060, 95% CI 2.679–37.777, p = 0.001), PLT (OR = 1.020, 95% CI 1.006–1.034, p = 0.005), and IBIL (OR = 0.710, 95% CI 0.561–0.898, p = 0.004) are independent predictors of severe TP in NPC. ROC analysis showed that the AUC of RBC, IBIL, PLT, and AGE is 0.746 (p < 0.001), 0.735 (p < 0.001), 0.702 (p = 0.001), and 0.734 (p < 0.001). New variables called joint predictors were calculated by a regression equation (Y = 2.309 * RBC - 0.343 * IBIL + 0.02 * PLT - 10.007), the AUC of which is 0.8700 (p < 0.001); best truncation value is >5.87 mmol/l. Conclusions: Lower RBC, PLT, and higher IBIL before concurrent radio-chemotherapy are independent risk factors causing severe TP during concurrent radio-chemotherapy of NPC. The RBC, PLT, and IBIL before concurrent radio-chemotherapy and joint predictor have a good predictive value to evaluate the risk of severe TP during concurrent radio-chemotherapy of NPC. [ABSTRACT FROM AUTHOR]

Dengue hemorrhagic fever is shown to correlate with secondary infection with a virus serotype different from the previous infection. However, only a small fraction of secondary infections leads to hemorrhagic fever. A recent Science paper suggests that the fucosylation state and isotype of IgGs elicited in patients may enhance disease severity. [ABSTRACT FROM AUTHOR]

The hemorrhagic syndrome of leptospirosis was studied in guinea pigs. The study correlates hematological, histopathological and immunohistochemical alterations in sixty animals inoculated by the intraperitoneal route with lml of the culture of virulent strain of Leptospira interrogans serovar copenhageni. Leptospirae antigens were detected by immunoperoxidase, chiefly in liver, kidney and heart muscle capillaries. Possible pathogenic mechanisms responsible for hemorrhagic syndrome are discussed with emphasis on toxic and anoxic attacks causing damage to endothelia, platelet depletion and alterations to hemostasia rates: prothrombin time [FT], partial thromboplastin time [PIT] and fibrinogen concentrations. Tide clinical-laboratoiy picture is compatible with the histopathological observation of disseminated intravascular coagulation [D1C] in most of the guinea pigs from day 4 of infection.Os autores estudam a síndrome hemorrágica da leptospirose em cobaios inoculados com amostra virulenta de Leptospira interrogans sorovar copenhageni. São abordados aspectos hematológicos, hístopatolôgicos e imuno- histoquímicos. Aumento do tempo de protrombina (PT) e do tempo parcial tromboplastina (PTT), bem como redução do número de plaquetas e do fibrinogênio acompanharam-se de congestão vascular, hemorragias e coagulação intravascular no fígado, rim, coração, músculo esquelético e pulmão. O antígetzo de Leptospira foi detectado principalmente em tecido hepático, renal e cardíaco. São discutidos possíveis mecanismos patogênicos responsáveis pela síndrome hemorrágica, com ênfase na agressão tóxico- anóxica do endotêlio vascular, que propiciaria a instalação de coagulação intravascular disseminada (CIVD) observada, sobretudo, nos cobaios dos grupos 4, 5 e 6.

Tissue injury following ischemia-reperfusion (I/R) occurs as a consequence of actions of soluble factors and immune cells. Growing evidence supports a role for platelets in the manifestation of tissue damage following I/R. Spleen tyrosine kinase has been well documented to be important in lymphocyte activation and more recently in platelet activation. We performed experiments to evaluate whether inhibition of platelet activation through inhibition of spleen tyrosine kinase prevents tissue damage after mesenteric I/R injury. Platelets isolated from C57BL/6J mice fed with R788 for 10 days were transfused into C57BL/6J mice depleted of platelets 2 days before mesenteric I/R injury. Platelet-depleted mice transfused with platelets from R788-treated mice before mesenteric I/R displayed a significant reduction in the degree of remote lung damage, but with little change in the degree of local intestinal damage compared with control I/R mice. Transfusion of R788-treated platelets also decreased platelet sequestration, C3 deposition, and immunoglobulin deposition in lung, but not in the intestine, compared with control groups. These findings demonstrate that platelet activation is a requisite for sequestration in the pulmonary vasculature to mediate remote tissue injury after mesenteric I/R. The use of small-molecule inhibitors may be valuable to prevent tissue damage in remote organs following I/R injury. [ABSTRACT FROM AUTHOR]

Ischemia-reperfusion (I/R) injury is a leading cause of morbidity and mortality. A functional role for platelets in tissue damage after mesenteric I/R is largely unknown. The hypothesis that mesenteric I/R local and remote injury are platelet dependent was tested. Using a murine mesenteric I/R model, we demonstrate that platelets orchestrate remote lung tissue damage that follows mesenteric I/R injury and also contribute, albeit to a lesser degree, to local villi damage. While lung damage is delayed compared with villi damage, it increased over time and was characterized by accumulation of platelets in the pulmonary vasculature early, followed by alveolar capillaries and extravasation into the pulmonary space. Both villi and lung tissues displayed complement deposition. We demonstrate that villi and lung damage are reduced in mice made platelet deficient before I/R injury and that platelet transfusion into previously platelet-depleted mice before I/R increased both villi and lung tissue damage. Increased C3 deposition accompanied platelet sequestration in the lung, which was mostly absent in platelet-depleted mice. In contrast, C3 deposition was only minimally reduced on villi of platelet-depleted mice. Our findings position platelets alongside complement as a significant early upstream component that orchestrates remote lung tissue damage after mesenteric I/R and strongly suggest that reperfusion injury mitigating modalities should consider the contribution of platelets. [ABSTRACT FROM AUTHOR]

Bioincompatibility is the total of side effects during hemodialysis (HD) including, amongst others, changes in platelet (PLT) level. Deviations in PLT count, immature PLT count, PLT morphology, CD62p expression, Platelet Factor 4 (PF4), ββ-Thromboglobulin (ββ-TG), serotonin, Thrombin-Antithrombin III (TAT) and Prothrombin Fragment 1++2 (F1++2) are monitored before and during treatment with HD in order to elucidate the interaction between modifications in PLT morphology, PLT activation and markers concerning activation of coagulation. Different patterns with time indicate that there is no correlation between an increased amount of depleted PLTs and increased amounts of PLT activation markers such as CD62p, PF4, ββ-TG and serotonin. A statistically significant correlation between increased PLT activation markers and markers for increased activation of coagulation such as TAT and F1++2 has not been established. Only a weak correlation is demonstrated between the increase of markers for activation of coagulation and the decrease in PLT counts, immature PLT counts and depleted PLTs during HD treatment. The change in the extracorporeal circuit during HD is probably a more critical factor in the mechanism leading to activation of the coagulation pathway than the modifications in PLT morphology. [ABSTRACT FROM AUTHOR]

Accumulation of platelets in the microvasculature after acute myocardial ischemia may exacerbate tissue injury through the formation of microthrombi and by the release of vasoactive substances. To assess the role of platelets in myocardial ischemic injury and infarction, circulating platelets were reduced by 94±2% (mean±S.E.M.) with sheep antiserum to canine platelets. Regional myocardial ischemia was produced by occlusion of the left circumflex coronary artery (LCCA) for 90 min followed by reperfusion for 5 hours. Infarct size did not differ significantly between antiplatelet serum and nonimmune serum groups: 36±8 vs. 43±4% of the area at risk, determined by a post-mortem dual staining technique (p>0.05). A second occlusion-reperfusion control group, sacrificed at 24 hours, did not differ from 5 hr reperfused groups with regard to infarct size. Coronary sinus thromboxane B (TXB) concentrations were not altered significantly by platelet depletion. Histopathologic examination confirmed the presence of necrosis in the infarcted myocardium and revealed substantial leukocytic infiltration in both groups. The results suggest that circulating platelets are not required for the full expression of myocardial ischemic injury resulting from temporary coronary artery occlusion followed by reperfusion. [ABSTRACT FROM AUTHOR]

The stable effector functionLess (SEFL) antibody was designed as an IgG1 antibody with a constant region that lacks the ability to interact with Fcγ receptors. The engineering and stability and pharmacokinetic assessments of the SEFL scaffold is described in the accompanying article (Jacobsen, F. W., Stevenson, R., Li, C., Salimi-Moosavi, H., Liu, L., Wen, J., Luo, Q., Daris, K., Buck, L., Miller, S., Ho, S-Y., Wang, W., Chen, Q., Walker, K., Wypych, J., Narhi, L., and Gunasekaran, K. (2017) J. Biol. Chem 292). The biological properties of these SEFL antibodies were assessed in a variety of human and cynomolgus monkey in vitro assays. Binding of parent molecules and their SEFL variants to human and cynomolgus monkey FcγRs were evaluated using flow cytometry-based binding assays. The SEFL variants tested showed decreased binding affinity to human and cynomolgus FcγRs compared with the wild-type IgG1 antibody. In addition, SEFL variants demonstrated no antibody-dependent cell-mediated cytotoxicity in vitro against Daudi cells with cynomolgus monkey peripheral blood mononuclear cells, and had minimal complement-dependent cytotoxicity activity similar to that of the negative control IgG2 in a CD20 + human Raji lymphoma cell line. SEFL mutations eliminated off-target antibody-dependent monocyte phagocytosis of cynomolgus monkey platelets, and cynomolgus platelet activation in vitro These experiments demonstrate that the SEFL modifications successfully eliminated Fc-associated effector binding and functions., (© 2017 by The American Society for Biochemistry and Molecular Biology, Inc.)