Mice expressing nonpolymerizable fibrinogen have reduced arterial and venous thrombosis with preserved hemostasis.

ABSTRACT: Elevated circulating fibrinogen levels correlate with increased risk for both cardiovascular and venous thromboembolic diseases. In vitro studies show that formation of a highly dense fibrin matrix is a major determinant of clot structure and stability. Here, we analyzed the impact of nonpolymerizable fibrinogen on arterial and venous thrombosis as well as hemostasis in vivo using FgaEK mice that express normal levels of a fibrinogen that cannot be cleaved by thrombin. In a model of carotid artery thrombosis, FgaWT/EK and FgaEK/EK mice were protected from occlusion with 4% ferric chloride (FeCl3) challenges compared with wild-type (FgaWT/WT) mice, but this protection was lost, with injuries driven by higher concentrations of FeCl3. In contrast, fibrinogen-deficient (Fga-/-) mice showed no evidence of occlusion, even with high-concentration FeCl3 challenge. Fibrinogen-dependent platelet aggregation and intraplatelet fibrinogen content were similar in FgaWT/WT, FgaWT/EK, and FgaEK/EK mice, consistent with preserved fibrinogen-platelet interactions that support arterial thrombosis with severe challenge. In an inferior vena cava stasis model of venous thrombosis, FgaEK/EK mice had near complete protection from thrombus formation. FgaWT/EK mice also displayed reduced thrombus incidence and a significant reduction in thrombus mass relative to FgaWT/WT mice after inferior vena cava stasis, suggesting that partial expression of nonpolymerizable fibrinogen was sufficient for conferring protection. Notably, FgaWT/EK and FgaEK/EK mice had preserved hemostasis in multiple models as well as normal wound healing times after skin incision, unlike Fga-/- mice that displayed significant bleeding and delayed healing. These findings indicate that a nonpolymerizable fibrinogen variant can significantly suppress occlusive thrombosis while preserving hemostatic potential in vivo.

4D intravital imaging studies identify platelets as the predominant cellular procoagulant surface in a mouse model of hemostasis.

Interplay between platelets, coagulation/fibrinolytic factors, and endothelial cells (ECs) is necessary for effective hemostatic plug formation. This study describes a novel four-dimensional (4D) imaging platform to visualize and quantify hemostatic plug components with high spatiotemporal resolution. Fibrin accumulation following laser-induced endothelial ablation was observed at the EC-platelet plug interface, controlled by the antagonistic balance between fibrin generation and breakdown. Phosphatidylserine (PS) was first detected in close physical proximity to the fibrin ring, followed by exposure across the endothelium. Impaired PS exposure in cyclophilinD -/- mice resulted in a significant reduction in fibrin accumulation. Adoptive transfer and inhibitor studies demonstrated a key role for platelets, but not ECs, in fibrin generation during hemostatic plug formation. Inhibition of fibrinolysis with tranexamic acid (TXA) led to increased fibrin accumulation in WT mice, but not in cyclophilinD -/- mice or WT mice treated with antiplatelet drugs. These studies implicate platelets as the functionally dominant procoagulant surface during hemostatic plug formation. In addition, they suggest that impaired fibrin formation due to reduced platelet procoagulant activity is not reversed by TXA treatment.

Protease-activated receptors and glycoprotein VI cooperatively drive the platelet component in thromboelastography.

BACKGROUND: Thromboelastography (TEG) is used for real-time determination of hemostatic status in patients with acute risk of bleeding. Thrombin is thought to drive clotting in TEG through generation of polymerized fibrin and activation of platelets through protease-activated receptors (PARs). However, the specific role of platelet agonist receptors and signaling in TEG has not been reported. OBJECTIVES: Here, we investigated the specific receptors and signaling pathways required for platelet function in TEG using genetic and pharmacologic inhibition of platelet proteins in mouse and human blood samples. METHODS: Clotting parameters (R time, α-angle [α], and maximum amplitude [MA]), were determined in recalcified, kaolin-triggered citrated blood samples using a TEG 5000 analyzer. RESULTS: We confirmed the requirement of platelets, platelet contraction, and αIIbß3 integrin function for normal α and MA. Loss of the integrin adaptor Talin1 in megakaryocytes/platelets (Talin1mKO) also reduced α and MA, but only minimal defects were observed in samples from mice lacking Rap1 GTPase signaling. PAR4mKO samples showed impaired α but normal MA. However, impaired TEG traces similar to those in platelet-depleted samples were observed with samples from PAR4mKO mice depleted of glycoprotein VI on platelets or with addition of a Syk inhibitor. We reproduced these results in human blood with combined inhibition of PAR1, PAR4, and Syk. CONCLUSION: Our results demonstrate that standard TEG is not sensitive to platelet signaling pathways critical for integrin inside-out activation and platelet hemostatic function. Furthermore, we provide the first evidence that PARs and glycoprotein VI play redundant roles in platelet-mediated clot contraction in TEG.

The CalDAG-GEFI/Rap1/αIIbß3 axis minimally contributes to accelerated platelet clearance in mice with constitutive store-operated calcium entry.

Circulating platelets maintain low cytosolic Ca2+ concentrations. At sites of vascular injury, agonist-induced Ca2+ release from platelet intracellular stores triggers influx of extracellular Ca2+, a process known as store-operated Ca2+ entry (SOCE). Stromal interaction molecule 1 (Stim1) senses reduced Ca2+ stores and triggers SOCE. Gain-of-function (GOF) mutations in Stim1, such as described for Stormorken syndrome patients or mutant mice (Stim1Sax), are associated with marked thrombocytopenia and increased platelet turnover. We hypothesized that reduced platelet survival in Stim1Sax/+ mice is due to increased Rap1/integrin signaling and platelet clearance in the spleen, similar to what we recently described for mice expressing a mutant version of the Rap1-GAP, Rasa3 (Rasa3hlb/hlb). Stim1Sax/+ mice were crossed with mice deficient in CalDAG-GEFI, a critical calcium-regulated Rap1-GEF in platelets. In contrast to Rasa3hlb/hlb x Caldaggef1-/- mice, only a small increase in the peripheral platelet count, but not platelet lifespan, was observed in Stim1Sax/+ x Caldaggef1-/- mice. Similarly, inhibition of αIIbß3 integrin in vivo only minimally raised the peripheral platelet count in Stim1Sax/+ mice. Compared to controls, Stim1Sax/+ mice exhibited increased platelet accumulation in the lung, but not the spleen or liver. These results suggest that CalDAG-GEFI/Rap1/integrin signaling contributes only minimally to accelerated platelet turnover caused by constitutive SOCE.

What do we know? Platelets are small blood cells which act to prevent blood loss, which circulate in a resting state but are rapidly activated upon exposure to ligands at the site of vascular injuryCalcium (Ca²⁺) is critical for platelet activation, especially for activation of integrins which support platelet­platelet interactionsIf platelet activation occurs in circulation, platelets can be prematurely cleared from blood and unable to function in hemostasisDisorders of Ca²⁺ dysregulation such as Stormorken syndrome are associated with reduced platelet counts (thrombocytopenia) and bleedingWhat did we discover? We used a mouse model expressing a mutation causing higher Ca²⁺ levels in cells including platelets (Stim1^Sax), and investigated whether thrombocytopenia is due to stimulation of a specific pathway for integrin activation, mediated by a protein called Rap1 GTPaseWe crossed Stim1^Sax mice with mice lacking an important activator of Rap1, the Ca²⁺-regulated protein CalDAG-GEFI, and saw no major improvement in thrombocytopeniaWe also observed more Stim1^Sax platelets in the lung but not the liver or spleen, in contrast to mice with activation of platelet integrins in circulationWhat is the impact? Our results rule out activation of the CalDAG-GEFI/Rap1/integrin pathway as a major cause of thrombocytopenia in Stim1^Sax miceOur findings help to narrow down potential causes of thrombocytopenia in disorders such as Stormorken syndrome.

A randomized trial comparing diet and delivery strategies for weight management in adolescents with intellectual disabilities.

BACKGROUND: The literature evaluating multi-component interventions for long-term weight loss in adolescents with intellectual disabilities (ID) is extremely limited. OBJECTIVES: To compare the effectiveness of two delivery strategies, face-to-face (FTF) or remote delivery (RD), and two diets, enhanced Stop Light diet (eSLD) or conventional diet (CD) on weight change across 12 and 18 months. in response to an 18 months. weight management intervention (6 months Weight loss/12 months. Weight maintenance) in adolescents with ID. METHODS: Adolescents with ID were randomized to one of three arms: FTF /CD, RD/CD, RD/eSLD and asked to attend individual education sessions with a health educator which were delivered during FTF home visits or remotely using video conferencing. The CD followed the US dietary guidelines. The eSLD utilized the Stop Light guide and was enhanced with portion-controlled meals. Participants were also asked to increase their physical activity (PA) and to self-monitor diet, PA and body weight across the 18-month. RESULTS: Weight was obtained from 92(84%) and 89(81%) randomized adolescents at 12 and 18 months, respectively. Weight change across 12 months. Differed significantly by diet (RD/eSLD: -7.0% vs. RD/CD: -1.1%, p = 0.002) but not by delivery strategy (FTF/CD: +1.1% vs. RD/CD: -1.1%, p = 0.21). Weight change across 18 months. Was minimal in all intervention arms and did not differ by diet (RD/eSLD: -2.6% vs. RD/CD: -0.5%; p = 0.28) or delivery strategy (FTF/CD: +1.6% vs. RD/CD: -0.5%; p = 0.47). CONCLUSIONS: Additional research is required to identify effective strategies to improve long-term weight loss in adolescents with ID.

Rasa3 deficiency minimally affects thrombopoiesis but promotes severe thrombocytopenia due to integrin-dependent platelet clearance.

Platelet homeostasis is dependent on a tight regulation of both platelet production and clearance. The small GTPase Rap1 mediates platelet adhesion and hemostatic plug formation. However, Rap1 signaling is also critical for platelet homeostasis as both Rap1 deficiency and uninhibited Rap1 signaling lead to marked thrombocytopenia in mice. Here, we investigated the mechanism by which deficiency in Rasa3, a critical negative regulator of Rap1, causes macrothrombocytopenia in mice. Despite marked morphological and ultrastructural abnormalities, megakaryocytes in hypomorphic Rasa3hlb/hlb (R3hlb/hlb) or Rasa3-/- mice demonstrated robust proplatelet formation in vivo, suggesting that defective thrombopoiesis is not the main cause of thrombocytopenia. Rather, we observed that R3hlb/hlb platelets became trapped in the spleen marginal zone/red pulp interface, with evidence of platelet phagocytosis by macrophages. Clearance of mutant platelets was also observed in the liver, especially in splenectomized mice. Platelet count and platelet life span in Rasa3-mutant mice were restored by genetic or pharmacological approaches to inhibit the Rap1/talin1/αIIbß3 integrin axis. A similar pattern of splenic clearance was observed in mice injected with anti-αIIbß3 but not anti-glycoprotein Ibα platelet-depleting antibodies. In summary, we describe a potentially novel, integrin-based mechanism of platelet clearance that could be critical for our understanding of select inherited and acquired thrombocytopenias.

Both G protein-coupled and immunoreceptor tyrosine-based activation motif receptors mediate venous thrombosis in mice.

Platelets are critical in hemostasis and a major contributor to arterial thrombosis (AT). (Pre)clinical studies suggest platelets also contribute to venous thrombosis (VT), but the mechanisms are largely unknown. We hypothesized that in VT, platelets use signaling machinery distinct from AT. Here we aimed to characterize the contributions of platelet G protein-coupled (GPCR) and immunoreceptor tyrosine-based activation motif (ITAM) receptor signaling to VT. Wild-type (WT) and transgenic mice were treated with inhibitors to selectively inhibit platelet-signaling pathways: ITAM-CLEC2 (Clec2mKO), glycoprotein VI (JAQ1 antibody), and Bruton's tyrosine kinase (ibrutinib); GPCR-cyclooxygenase 1 (aspirin); and P2Y12 (clopidogrel). VT was induced by inferior vena cava stenosis. Thrombin generation in platelet-rich plasma and whole-blood clot formation were studied ex vivo. Intravital microscopy was used to study platelet-leukocyte interactions after flow restriction. Thrombus weights were reduced in WT mice treated with high-dose aspirin + clopidogrel (dual antiplatelet therapy [DAPT]) but not in mice treated with either inhibitor alone or low-dose DAPT. Similarly, thrombus weights were reduced in mice with impaired ITAM signaling (Clec2mKO + JAQ1; WT + ibrutinib) but not in Clec2mKO or WT + JAQ1 mice. Both aspirin and clopidogrel, but not ibrutinib, protected mice from FeCl3-induced AT. Thrombin generation and clot formation were normal in blood from high-dose DAPT- or ibrutinib-treated mice; however, platelet adhesion and platelet-neutrophil aggregate formation at the vein wall were reduced in mice treated with high-dose DAPT or ibrutinib. In summary, VT initiation requires platelet activation via GPCRs and ITAM receptors. Strong inhibition of either signaling pathway reduces VT in mice.

Deletion of platelet CLEC-2 decreases GPIbα-mediated integrin αIIbß3 activation and decreases thrombosis in TTP.

Microvascular thrombosis in patients with thrombotic thrombocytopenic purpura (TTP) is initiated by GPIbα-mediated platelet binding to von Willebrand factor (VWF). Binding of VWF to GPIbα causes activation of the platelet surface integrin αIIbß3. However, the mechanism of GPIbα-initiated activation of αIIbß3 and its clinical importance for microvascular thrombosis remain elusive. Deletion of platelet C-type lectin-like receptor 2 (CLEC-2) did not prevent VWF binding to platelets but specifically inhibited platelet aggregation induced by VWF binding in mice. Deletion of platelet CLEC-2 also inhibited αIIbß3 activation induced by the binding of VWF to GPIbα. Using a mouse model of TTP, which was created by infusion of anti-mouse ADAMTS13 monoclonal antibodies followed by infusion of VWF, we found that deletion of platelet CLEC-2 decreased pulmonary arterial thrombosis and the severity of thrombocytopenia. Importantly, prophylactic oral administration of aspirin, an inhibitor of platelet activation, and therapeutic treatment of the TTP mice with eptifibatide, an integrin αIIbß3 antagonist, reduced pulmonary arterial thrombosis in the TTP mouse model. Our observations demonstrate that GPIbα-mediated activation of integrin αIIbß3 plays an important role in the formation of thrombosis in TTP. These observations suggest that prevention of platelet activation with aspirin may reduce the risk for thrombosis in patients with TTP.

Genetic deletion of platelet PAR4 results in reduced thrombosis and impaired hemostatic plug stability.

BACKGROUND: Protease-activated receptor 4 (PAR4) is expressed by a wide variety of cells, including megakaryocytes/platelets, immune cells, cardiomyocytes, and lung epithelial cells. It is the only functional thrombin receptor on murine platelets. A global deficiency of PAR4 is associated with impaired hemostasis and reduced thrombosis. OBJECTIVE: We aimed to generate a mouse line with a megakaryocyte/platelet-specific deletion of PAR4 (PAR4fl/fl ;PF4Cre+ ) and use the mouse line to investigate the role of platelet PAR4 in hemostasis and thrombosis in mice. METHODS: Platelets from PAR4fl/fl ;PF4Cre+ were characterized in vitro. Arterial and venous thrombosis was analyzed. Hemostatic plug formation was analyzed using a saphenous vein laser injury model in mice with global or megakaryocyte/platelet-specific deletion of PAR4 or wild-type mice treated with thrombin or glycoprotein VI (GPVI) inhibitors. RESULTS: PAR4fl/fl ;PF4Cre+ platelets were unresponsive to thrombin or specific PAR4 stimulation but not to other agonists. PAR4-/- and PAR4fl/fl ;PF4Cre+ mice both exhibited a similar reduction in arterial thrombosis compared to their respective controls. More importantly, we show for the first time that platelet PAR4 is critical for venous thrombosis in mice. In addition, PAR4-/- mice and PAR4fl/fl ;PF4Cre+ mice exhibited a similar impairment in hemostatic plug stability in a saphenous vein laser injury model. Inhibition of thrombin in wild-type mice gave a similar phenotype. Combined PAR4 deficiency on platelets with GPVI inhibition did not impair hemostatic plug formation but further reduced plug stability. CONCLUSION: We generated a novel PAR4fl/fl ;PF4Cre+ mouse line. We used this mouse line to show that PAR4 signaling in platelets is critical for arterial and venous thrombosis and hemostatic plug stability.

Novel Interdisciplinary Approach to GERD: Concomitant Laparoscopic Hiatal Hernia Repair with Transoral Incisionless Fundoplication.

BACKGROUND: Transoral incisionless fundoplication (TIF) is an endoscopic alternative for the treatment of GERD. However, TIF does not address the hiatal hernia (HH). We present a novel approach with a laparoscopic HH repair followed by same-session TIF, coined concomitant transoral incisionless fundoplication (cTIF). The aim of this study was to assess the efficacy, safety, and feasibility of cTIF in a collaborative approach between Gastroenterology and surgery. STUDY DESIGN: Patients with confirmed GERD and >2 cm HH who underwent cTIF between 2018 and 2020 were included. Symptoms were assessed using the Reflux Disease Questionnaire, GERD Health-Related Quality of Life Index, and the Reflux Symptom Index pre and post cTIF. One-way ANOVA and paired samples t-test were used for statistical analysis. RESULTS: Sixty patients underwent cTIF (53% were men, mean age was 59.3 years) with 100% technical success. Mean ± SD HH measurement on endoscopy was 2.9 ± 1.5 cm. Scores on Reflux Disease Questionnaire for symptom frequency and symptom severity improved significantly from before to 6 months after cTIF (17.4 to 4.72; p < 0.01 and 16.7 to 4.56; p < 0.05, respectively). According to the GERD Health-Related Quality of Life Index, significant decreases were seen post cTIF in heartburn (23.26 to 7.37; p < 0.01) and regurgitation (14.26 to 0; p = 0.05). Reflux Symptom Index similarly decreased after cTIF (17.7 to 8.1 post cTIF; p < 0.01). Mean DeMeester score decreased from 43.7 to 4.9 and acid exposure time decreased from 12.7% to 1.28% post cTIF (p = 0.06). CONCLUSIONS: We present a novel multidisciplinary approach to GERD using a combined endoscopic and surgical approach with close collaboration between Gastroenterology and surgery. Our results suggest that cTIF is safe and effective in reducing reflux symptoms in a large spectrum of GERD patients.

Cost-effectiveness of a telehealth intervention for in-home dementia care support: Findings from the FamTechCare clinical trial.

Determining the cost-effectiveness of technological interventions is a crucial aspect in assuring these interventions can be adopted. The FamTechCare intervention is an innovative telehealth support that links family caregivers of persons living with dementia to tailored feedback from dementia care experts based on caregiver-initiated video recordings of challenging care situations. The FamTechCare intervention has demonstrated significant reductions in caregiver depression and increases in caregiver competence when compared to standard telephone support. The purpose of this article is to report on the cost-effectiveness of the FamTechCare telehealth intervention. Process-based costing and a cost-effectiveness analysis using the incremental cost-effectiveness ratio (ICER) was completed with 68 caregiver and person living dementia with dyads. The cost of the 12-week FamTechCare telehealth intervention was found to be greater ($48.43 per dyad per week) due to the telehealth equipment, recording application, and expert panel time compared with the telephone support intervention ($6.96 per dyad per week). The ICER was $18.51 for caregiver depression and $36.31 for caregiver competence indicating that it cost no more than $36.38 per dyad per week over 12 weeks to achieve significant improvement in depression and competence in the FamTechCare caregivers compared to the telephone support caregivers. The FamTechCare intervention appears to be cost-effective when compared to the telephone support intervention and remains near the willingness-to-pay threshold for caregivers providing in-home dementia care support.

Platelet transfusion for patients with platelet dysfunction: effectiveness, mechanisms, and unanswered questions.

PURPOSE OF REVIEW: In this review, we discuss current clinical guidelines and potential underlying mechanisms regarding platelet transfusion therapy in patients at risk of bleeding, comparing management of patients with thrombocytopenia versus those with qualitative platelet disorders. RECENT FINDINGS: Platelet transfusion therapy is highly effective in managing bleeding in patients with hypoproliferative thrombocytopenia. Clinical trials have demonstrated that platelet transfusion can be used at a lower trigger threshold and reduced platelet doses, and may be used therapeutically rather than prophylactically in some situations, although additional data are needed. In patients with inherited platelet disorders such as Glanzmann's Thrombasthenia or those with RASGRP2 mutations, platelet transfusion may be ineffective because of competition between transfused and endogenous platelets at the site of vascular injury. Successful management of these patients may require transfusion of additional platelet units, or mechanism-driven combination therapy with other pro-hemostatic agents. In patients on antiplatelet therapy, timing of transfusion and inhibitor mechanism-of-action are key in determining therapeutic success. SUMMARY: Expanding our understanding of the mechanisms by which transfused platelets exert their pro-hemostatic function in various bleeding disorders will improve the appropriate use of platelet transfusion.

Development of Optimized Tissue-Factor-Targeted Peptide Amphiphile Nanofibers to Slow Noncompressible Torso Hemorrhage.

Noncompressible torso hemorrhage accounts for a significant portion of preventable trauma deaths. We report here on the development of injectable, targeted supramolecular nanotherapeutics based on peptide amphiphile (PA) molecules that are designed to target tissue factor (TF) and, therefore, selectively localize to sites of injury to slow hemorrhage. Eight TF-targeting sequences were identified, synthesized into PA molecules, coassembled with nontargeted backbone PA at various weight percentages, and characterized via circular dichroism spectroscopy, transmission electron microscopy, and X-ray scattering. Following intravenous injection in a rat liver hemorrhage model, two of these PA nanofiber coassemblies exhibited the most specific localization to the site of injury compared to controls (p < 0.05), as quantified using immunofluorescence imaging of injured liver and uninjured organs. To determine if the nanofibers were targeting TF in vivo, a mouse saphenous vein laser injury model was performed and showed that TF-targeted nanofibers colocalized with fibrin, demonstrating increased levels of nanofiber at TF-rich sites. Thromboelastograms obtained using samples of heparinized rat whole blood containing TF demonstrated that no clots were formed in the absence of TF-targeted nanofibers. Lastly, both PA nanofiber coassemblies decreased blood loss in comparison to sham and backbone nanofiber controls by 35-59% (p < 0.05). These data demonstrate an optimal TF-targeted nanofiber that localizes selectively to sites of injury and TF exposure, and, interestingly, reduces blood loss. This research represents a promising initial phase in the development of a TF-targeted injectable therapeutic to reduce preventable deaths from hemorrhage.

Mechanism and Pathophysiology of Gastroesophageal Reflux Disease.

Gastroesophageal reflux (GER) describes a process in which gastric contents travel retrograde into the esophagus. GER can be either a physiologic phenomenon that occurs in asymptomatic individuals or can potentially cause symptoms. When the latter occurs, this represents GER disease (GERD). The process by which GER transforms into GERD begins at the esophagogastric junction. Impaired clearance of the refluxate also contributes to GERD. Reflux causes degradation of esophageal mucosal defense. The refluxate triggers sensory afferents leading to symptom generation.

Physical activity across the curriculum (PAAC3): Testing the application of technology delivered classroom physical activity breaks.

Only 43% of children in the U.S., ages 6-11 yrs., meet current physical activity (PA) guidelines. To satisfy the MVPA requirement, schools have begun incorporating MVPA in the form of activity breaks or MVPA academic lessons. We completed two, 3 academic-yr. cluster randomized trials (DK61489, DK85317) called "Physical Activity Across the Curriculum" (PAAC) which involved increasing MVPA in the classroom. Across 3-yrs. teachers in PAAC schools delivered ~60 min/wk. (12 min/day) of MVPA. Although short of our MVPA goal (20 min/d), the PAAC approach substantially increased in-school MVPA. Teacher reluctance to devote additional time to develop and integrate PA lessons into their curriculum was the overwhelming barrier to meeting the MVPA goal. Therefore, to reduce barriers to delivery of classroom PA we developed a 3-academic yr. cluster randomized trial (2 yrs. active intervention, 1 yr. follow-up) to compare the effectiveness and sustainability of technology delivered (PAAC-R) and classroom teacher delivered (PAAC-T) activity breaks for increasing classroom MVPA in elementary school students in grades 2 and 3 at baseline who will progress to grades 4-5. NCT registration: NCT03493139.

A Prospective Multicenter Study Evaluating Endoscopy Competence Among Gastroenterology Trainees in the Era of the Next Accreditation System.

PURPOSE: The Next Accreditation System requires training programs to demonstrate competence among trainees. Within gastroenterology (GI), there are limited data describing learning curves and structured assessment of competence in esophagogastroduodenoscopy (EGD) and colonoscopy. In this study, the authors aimed to demonstrate the feasibility of a centralized feedback system to assess endoscopy learning curves among GI trainees in EGD and colonoscopy. METHOD: During academic year 2016-2017, the authors performed a prospective multicenter cohort study, inviting participants from multiple GI training programs. Trainee technical and cognitive skills were assessed using a validated competence assessment tool. An integrated, comprehensive data collection and reporting system was created to apply cumulative sum analysis to generate learning curves that were shared with program directors and trainees on a quarterly basis. RESULTS: Out of 183 fellowships invited, 129 trainees from 12 GI fellowships participated, with an overall trainee participation rate of 72.1% (93/129); the highest participation level was among first-year trainees (90.9%; 80/88), and the lowest was among third-year trainees (51.2%; 27/53). In all, 1,385 EGDs and 1,293 colonoscopies were assessed. On aggregate learning curve analysis, third-year trainees achieved competence in overall technical and cognitive skills, while first- and second-year trainees demonstrated the need for ongoing supervision and training in the majority of technical and cognitive skills. CONCLUSIONS: This study demonstrated the feasibility of using a centralized feedback system for the evaluation and documentation of trainee performance in EGD and colonoscopy. Furthermore, third-year trainees achieved competence in both endoscopic procedures, validating the effectiveness of current training programs.

Effect of individualized feedback on learning curves in EGD and colonoscopy: a cluster randomized controlled trial.

BACKGROUND AND AIMS: Gastroenterology fellowships need to ensure that trainees achieve competence in upper endoscopy (EGD) and colonoscopy. Because the impact of structured feedback remains unknown in endoscopy training, this study compared the effect of structured feedback with standard feedback on trainee learning curves for EGD and colonoscopy. METHODS: In this multicenter, cluster, randomized controlled trial, trainees received either individualized quarterly learning curves or feedback standard to their fellowship. Assessment was performed in all trainees using the Assessment of Competency in Endoscopy tool on 5 consecutive procedures after every 25 EGDs and colonoscopies. Individual learning curves were created using cumulative sum (CUSUM) analysis. The primary outcome was the mean CUSUM score in overall technical and overall cognitive skills. RESULTS: In all, 13 programs including 132 trainees participated. The intervention arm (6 programs, 51 trainees) contributed 558 EGD and 600 colonoscopy assessments. The control arm (7 programs, 81 trainees) provided 305 EGD and 468 colonoscopy assessments. For EGD, the intervention arm (-.7 [standard deviation {SD}, 1.3]) had a superior mean CUSUM score in overall cognitive skills compared with the control arm (1.6 [SD, .8], P = .03) but not in overall technical skills (intervention, -.26 [SD, 1.4]; control, 1.76 [SD, .7]; P = .06). For colonoscopy, no differences were found between the 2 arms in overall cognitive skills (intervention, -.7 [SD, 1.3]; control, .7 [SD, 1.3]; P = .95) or overall technical skills (intervention, .1 [SD, 1.5]; control, -.1 [SD, 1.5]; P = .77). CONCLUSIONS: Quarterly feedback in the form of individualized learning curves did not affect learning curves for EGD and colonoscopy in a clinically meaningful manner. (Clinical trial registration number: NCT02891304.).

Impaired hemostatic activity of healthy transfused platelets in inherited and acquired platelet disorders: Mechanisms and implications.

Platelet transfusions can fail to prevent bleeding in patients with inherited platelet function disorders (IPDs), such as Glanzmann's thrombasthenia (GT; integrin αIIbß3 dysfunction), Bernard-Soulier syndrome [BSS; glycoprotein (GP) Ib/V/IX dysfunction], and the more recently identified nonsyndromic RASGRP2 variants. Here, we used IPD mouse models and real-time imaging of hemostatic plug formation to investigate whether dysfunctional platelets impair the hemostatic function of healthy donor [wild-type (WT)] platelets. In Rasgrp2-/- mice or mice with platelet-specific deficiency in the integrin adaptor protein TALIN1 ("GT-like"), WT platelet transfusion was ineffective unless the ratio between mutant and WT platelets was ~2:1. In contrast, thrombocytopenic mice or mice lacking the extracellular domain of GPIbα ("BSS-like") required very few transfused WT platelets to normalize hemostasis. Both Rasgrp2-/- and GT-like, but not BSS-like, platelets effectively localized to the injury site. Mechanistic studies identified at least two mechanisms of interference by dysfunctional platelets in IPDs: (i) delayed adhesion of WT donor platelets due to reduced access to GPIbα ligands exposed at sites of vascular injury and (ii) impaired consolidation of the hemostatic plug. We also investigated the hemostatic activity of transfused platelets in the setting of dual antiplatelet therapy (DAPT), an acquired platelet function disorder (APD). "DAPT" platelets did not prolong the time to initial hemostasis, but plugs were unstable and frequent rebleeding was observed. Thus, we propose that the endogenous platelet count and the ratio of transfused versus endogenous platelets should be considered when treating select IPD and APD patients with platelet transfusions.

Identification of a Locus in Mice that Regulates the Collateral Damage and Lethality of Virus Infection.

Arenaviruses can cause severe hemorrhagic disease in humans, which can progress to organ failure and death. The underlying mechanisms causing lethality and person-to-person variation in outcome remain incompletely explained. Herein, we characterize a mouse model that recapitulates many features of pathogenesis observed in humans with arenavirus-induced hemorrhagic disease, including thrombocytopenia, severe vascular leakage, lung edema, and lethality. The susceptibility of congenic B6.PL mice to lymphocytic choriomeningitis virus (LCMV) infection is associated with increased antiviral T cell responses in B6.PL mice compared with C57BL/6 mice and is T cell dependent. Pathogenesis imparted by the causative locus is inherited in a semi-dominant manner in F1 crosses. The locus includes PL-derived sequence variants in both poorly annotated genes and genes known to contribute to immune responses. This model can be used to further interrogate how limited genetic differences in the host can remarkably alter the disease course of viral infection.