George A. Alba

Loss of glypican-3 Function Causes Growth Factor-dependent Defects in Cardiac and Coronary Vascular Development

Glypican-3 (Gpc3) is a heparan sulfate proteoglycan (HSPG) expressed widely during vertebrate development. Loss-of-function mutations cause Simpson-Golabi-Behmel syndrome (SGBS), a rare and complex congenital overgrowth syndrome with a number of associated developmental abnormalities including congenital heart disease. We found that Gpc3-deficient mice display a high incidence of congenital cardiac malformations like ventricular septal defects, common atrioventricular canal and double outlet right ventricle. In addition we observed coronary artery fistulas, which have not been previously reported in SGBS. Coronary artery fistulas are noteworthy because little is known about the molecular basis of this abnormality. Formation of the coronary vascular plexus in Gpc3-deficient embryos was delayed compared to wild-type, and consistent with GPC3 functioning as a co-receptor for fibroblast growth factor-9 (FGF9), we found a reduction in Sonic Hedgehog (Shh) mRNA expression and signaling in embryonic mutant hearts. Interestingly, we found an asymmetric reduction in SHH signaling in cardiac myocytes, as compared with perivascular cells, resulting in excessive coronary artery formation in the Gpc3-deficient animals. We hypothesize that the excessive development of coronary arteries over veins enables the formation of coronary artery fistulas. This work has broad significance to understanding the genetic basis of coronary development and potentially to molecular mechanisms relevant to revascularization following ischemic injury to the heart.

Faculty staff-guided versus self-guided ultrasound training for internal medicine residents

Ultrasonography is of growing importance within internal medicine (IM), but the optimal method of training doctors to use it is uncertain. In this study, the authors provide the first objective comparison of two approaches to training IM residents in ultrasonography.

Optimising debriefing for technology-enhanced simulation.

The last two decades have witnessed sweeping changes in the American health care system, a landscape largely unchanged since it was revolutionised in 1910 by Abraham Flexner’s famous report. The limitations imposed on resident physician duty hours, changes in hospital reimbursement models, and the increased focus on health care quality and safety combine to highlight the growing emphasis on how health care professionals are trained. Modern-day technologyenhanced simulation (TES) emerged in the late 1960s within anaesthesiology – although its roots arguably derive from the use of birthing manikins in 17th century France – and it has become an increasingly popular modality to help teach health care professionals in varying stages of training or practice. It has been specifically lauded for providing trainees with opportunities to learn in environments that do not hamper patient safety and for enabling educators to structure simulation experiences that foster deliberate practice, focused assessment, feedback and reflection. Increased focus on health care quality and safety highlights the growing emphasis on how health care professionals are trained

Network Analysis to Risk Stratify Patients With Exercise IntoleranceNovelty and Significance

Rationale: Current methods assessing clinical risk because of exercise intolerance in patients with cardiopulmonary disease rely on a small subset of traditional variables. Alternative strategies incorporating the spectrum of factors underlying prognosis in at-risk patients may be useful clinically, but are lacking. Objective: Use unbiased analyses to identify variables that correspond to clinical risk in patients with exercise intolerance. Methods and Results: Data from 738 consecutive patients referred for invasive cardiopulmonary exercise testing at a single center (2011–2015) were analyzed retrospectively (derivation cohort). A correlation network of invasive cardiopulmonary exercise testing parameters was assembled using |r|>0.5. From an exercise network of 39 variables (ie, nodes) and 98 correlations (ie, edges) corresponding to P<9.5e−46 for each correlation, we focused on a subnetwork containing peak volume of oxygen consumption (pVO2) and 9 linked nodes. K-mean clustering based on these 10 variables identified 4 novel patient clusters characterized by significant differences in 44 of 45 exercise measurements (P<0.01). Compared with a probabilistic model, including 23 independent predictors of pVO2 and pVO2 itself, the network model was less redundant and identified clusters that were more distinct. Cluster assignment from the network model was predictive of subsequent clinical events. For example, a 4.3-fold (P<0.0001; 95% CI, 2.2–8.1) and 2.8-fold (P=0.0018; 95% CI, 1.5–5.2) increase in hazard for age- and pVO2-adjusted all-cause 3-year hospitalization, respectively, were observed between the highest versus lowest risk clusters. Using these data, we developed the first risk-stratification calculator for patients with exercise intolerance. When applying the risk calculator to patients in 2 independent invasive cardiopulmonary exercise testing cohorts (Boston and Graz, Austria), we observed a clinical risk profile that paralleled the derivation cohort. Conclusions: Network analyses were used to identify novel exercise groups and develop a point-of-care risk calculator. These data expand the range of useful clinical variables beyond pVO2 that predict hospitalization in patients with exercise intolerance.

A 57-Year-Old Man With Insidious Dyspnea and Nonpleuritic Chest and Back Pain

A 57-year-old man with a history of DVT and pulmonary embolism, transient ischemic attacks, prior 60 pack-year smoking history, and oxygen-dependent COPD presented with insidiously worsening dyspnea associated with new pleuritic chest and back pain.

NEDD9 targets COL3A1 to promote endothelial fibrosis and pulmonary arterial hypertension

TGF-β–independent oxidative modification of NEDD9 at Cys18 promotes vascular fibrosis and the pathobiology of pulmonary arterial hypertension. In silico sleuthing for pulmonary hypertension Cell proliferation and fibrosis (the accumulation of excess connective tissue) cause arterioles to thicken during pulmonary arterial hypertension (PAH). Aldosterone, a hormone involved in reactive oxygen species generation, wound healing, and fibrosis, is also increased in PAH. Samokhin et al. used in silico analysis to identify NEDD9 as a critical protein involved in vascular remodeling, fibrosis, and pulmonary hypertension. Oxidative modification of NEDD9 impaired its degradation and promoted collagen production. Mice lacking NEDD9 were protected from pulmonary hypertension, and collagen deposition, vascular remodeling, and cardiopulmonary metrics were normalized in a rat model of PAH treated with siRNA targeting NEDD9. This work suggests that therapeutic targeting of NEDD9 may be effective for combating vascular fibrosis in PAH. Germline mutations involving small mothers against decapentaplegic–transforming growth factor–β (SMAD–TGF-β) signaling are an important but rare cause of pulmonary arterial hypertension (PAH), which is a disease characterized, in part, by vascular fibrosis and hyperaldosteronism (ALDO). We developed and analyzed a fibrosis protein-protein network (fibrosome) in silico, which predicted that the SMAD3 target neural precursor cell expressed developmentally down-regulated 9 (NEDD9) is a critical ALDO-regulated node underpinning pathogenic vascular fibrosis. Bioinformatics and microscale thermophoresis demonstrated that oxidation of Cys18 in the SMAD3 docking region of NEDD9 impairs SMAD3-NEDD9 protein-protein interactions in vitro. This effect was reproduced by ALDO-induced oxidant stress in cultured human pulmonary artery endothelial cells (HPAECs), resulting in impaired NEDD9 proteolytic degradation, increased NEDD9 complex formation with Nk2 homeobox 5 (NKX2-5), and increased NKX2-5 binding to COL3A1. Up-regulation of NEDD9-dependent collagen III expression corresponded to changes in cell stiffness measured by atomic force microscopy. HPAEC-derived exosomal signaling targeted NEDD9 to increase collagen I/III expression in human pulmonary artery smooth muscle cells, identifying a second endothelial mechanism regulating vascular fibrosis. ALDO-NEDD9 signaling was not affected by treatment with a TGF-β ligand trap and, thus, was not contingent on TGF-β signaling. Colocalization of NEDD9 with collagen III in HPAECs was observed in fibrotic pulmonary arterioles from PAH patients. Furthermore, NEDD9 ablation or inhibition prevented fibrotic vascular remodeling and pulmonary hypertension in animal models of PAH in vivo. These data identify a critical TGF-β–independent posttranslational modification that impairs SMAD3-NEDD9 binding in HPAECs to modulate vascular fibrosis and promote PAH.

Tense ascites in a postpartum woman.

Question: A 36-year-old woman originally from Haiti presented to the emergency department with 2 weeks of abdominal distention, diarrhea, and blood-tinged emesis. She had given birth to her first child by uncomplicated caesarean section 9.5 weeks earlier. There was no history of recent travel, diet change, or sick contacts. She denied alcohol, tobacco, or illicit drug use and was not taking any medications or supplements. She was allergic to chloroquine (itchiness) and had no history of atopy. She was not aware of any family history of liver disease or allergy, although her paternal history was unknown. Upon being admitted to the general medicine service, the patient was afebrile and hemodynamically stable. She did not have any stigmata of chronic liver disease. Her abdomen was distended and diffusely tender with rebound tenderness and guarding (Figure A). Serum studies were notable for white blood cell count of 14.5 k/ L with 46% eosinophils (absolute count 6660/mm3). Other alues, including serum human chorionic gonadotropin, were normal. Computed tomography of the abdomen and pelvis (Figure B) showed a large amount of abdominal and pelvic ascites (arrow) with ild small bowel wall thickening. There was no evidence of organomegaly or vessel thrombosis. Subsequent diagnostic paracentesis emonstrated an exudative effusion with total nucleated cells 4545/mL, with 82% eosinophils. Large-volume paracentesis of 4000 L of straw-colored fluid relieved the patient’s abdominal pain. Fluid bacterial and tuberculosis cultures were negative, and cytology howed no evidence of malignancy. Peripheral blood smear was unremarkable. Stool culture, stool ova and parasites, urine culture, nd blood culture were all negative. Because of these findings, the gastroenterology service was consulted. Esophagoduodenoscopy and colonoscopy showed mild ectal mucosal erythema (arrow) without masses, bleeding, ulcers, or polyps (Figure C). What is the diagnosis? What is the appropriate management? Look on page 467 for the answer and see the GASTROENTEROLOGY web site (www.gastrojournal.org) for more information on submitting your favorite image to Clinical Challenges and Images in GI. Acknowledgments: The authors thank Dr Jay Luther for his guidance and manuscript review and Dr Daniel Pratt for obtaining images.