Citations

Circulating extracellular vesicles (EVs) are a novel and emerging biomarker for nonalcoholic steatohepatitis (NASH). It has been demonstrated that total circulating EVs and hepatocyte‐derived EVs are elevated in male mice with diet‐induced NASH. How hepatocyte‐derived EVs change over time and other cellular sources of EVs in NASH have not been determined. Our objective was to define the quantitative evolution of hepatocyte‐derived, macrophage‐derived, neutrophil‐derived, and platelet‐derived EVs in male and female mice with dietary NASH. Fluorescently labeled antibodies and a nanoscale flow cytometer were used to detect plasma levels of EVs. Asialoglycoprotein receptor 1 (ASGR1) and cytochrome P450 family 2 subfamily E member 1 (CYP2E1) are markers of hepatocyte‐derived EVs; galectin 3 is a marker of macrophage‐derived EVs; common epitope on lymphocyte antigen 6 complex, locus G/C1 (Ly‐6G and Ly‐6C) is a marker of neutrophil‐derived EVs; and clusters of differentiation 61 (CD61) is a marker of platelet‐derived EVs. Nonalcoholic fatty liver disease activity score (NAS) was calculated using hematoxylin and eosin‐stained liver sections, and magnetic resonance imaging (MRI) was used for measurement of the fat fraction and elastography. Hepatocyte‐derived EVs increased in both male and female mice at 12 and 10 weeks of feeding, respectively, and remained elevated at 24 weeks in both male and female mice and at 48 weeks in male mice and 36 weeks in female mice. Macrophage‐ and neutrophil‐derived EVs were significantly elevated at 24 weeks of dietary feeding concomitant with the histologic presence of inflammatory foci in the liver. In fat‐, fructose‐, and cholesterol‐ (FFC) fed male mice, platelet‐derived EVs were elevated at 12, 24, and 48 weeks, whereas in female mice, platelet derived EVs were significantly elevated at 24 weeks. Hepatocyte‐, macrophage‐ and neutrophil‐derived EVs correlated well with the histologic NAS. Conclusion: Circulating cell‐type‐specific EVs may be a novel biomarker for NASH diagnosis and longitudinal follow up.

The lack of reliable, noninvasive methods to diagnose early nonalcoholic steatohepatitis (NASH) is a major unmet need. We aimed to determine the diagnostic accuracy of three‐dimensional magnetic resonance elastography (3D‐MRE), with shear stiffness measured at 60 Hz, damping ratio at 40 Hz, and magnetic resonance imaging proton density fat fraction (MRI‐PDFF) in the detection of NASH in individuals undergoing bariatric surgery. Obese adults at risk for NASH were enrolled between 2015 and 2017 (prospective cohort, n = 88) and 2010 and 2013 (retrospective cohort, n = 87). The imaging protocol consisted of multifrequency 3D‐MRE (mf3D‐MRE) with shear waves delivered at different frequencies to explore parameters that best correlated with histologic NASH, and MRI‐PDFF to estimate steatosis. The prospective cohort was used to establish the optimal mf3D‐MRE technical parameters for NASH detection. The two cohorts were then combined to derive predictive models of NASH and disease activity by nonalcoholic fatty liver disease activity score (NAS) using the three imaging parameters that correlated with NASH. A total of 175 patients (median age 45, 81% women, and 81 [46%] with histologic NASH) were used for model derivation. From the complex shear modulus output generated by mf3D‐MRE, the damping ratio at 40 Hz and shear stiffness at 60 Hz best correlated with NASH. The fat fraction obtained from MRI‐PDFF correlated with steatosis ( P < 0.05 for all). These three parameters were fit into a logistic regression model that predicted NASH with cross‐validated area under the receiver operating characteristic curve (AUROC) = 0.73, sensitivity = 0.67, specificity = 0.80, positive predictive value = 0.73 and negative predictive value = 0.74, and disease activity by NAS with cross‐validated AUROC = 0.82. Conclusion: The mf3D‐MRE allows identification of imaging parameters that predict early NASH and disease activity. This imaging biomarker represents a promising alternative to liver biopsy for NASH diagnosis and monitoring. The results provide motivation for further studies in nonbariatric cohorts.

BackgroundPreoperative prediction of tumor recurrence is important in the management of patients with hepatocellular carcinoma (HCC).PurposeTo investigate whether tumor stiffness derived by magnetic resonance elastography (MRE) could predict early recurrence of HCC after hepatic resection.Study TypeRetrospective.PopulationIn all, 99 patients with pathologically confirmed HCCs after surgical resection.Field Strength/Sequence3.0T; preoperative MRE with 60‐Hz mechanical vibrations using an active acoustic driver.AssessmentRegions of interest (ROIs) were manually drawn in the tumors to measure mean tumor stiffness. Surgical specimens were reviewed for histological grade, capsule, vascular invasion, and surgical margins. The early recurrence of HCC was defined as that occurring within 2 years after resection.Statistical TestsCox proportional hazard models were used to evaluate risk factors associated with the time to early recurrence.ResultsHCCs with recurrence had higher tumor stiffness, higher rate of advanced T stage, vascular invasion, lower rate of capsule formation, larger tumor size, higher aspartate aminotransferase (AST), and hepatitis B virus (HBV)‐DNA level and aspartate aminotransferase / alanine aminotransferase ratio (P = 0.031, 0.007, 0.01, <0.001, 0.015, 0.034, 0.01, and 0.014, respectively) than HCCs without recurrence. Vascular invasion (hazard ratio [HR] = 2.922; 95% confidence interval [CI]: [1.079, 7.914], P = 0.035) and mean tumor stiffness (HR = 1.163; 95% CI: [1.055, 1.282], P = 0.002) were risk factors associated with early recurrence. Each 1‐kPa increase in tumor stiffness was associated with a 16.3% increase in the risk for tumor recurrence.Data ConclusionThe mean stiffness of HCCs may be a useful, noninvasive, quantitative biomarker for the prediction of early HCC recurrence after hepatic resection.Level of Evidence: 4Technical Efficacy: Stage 5J. Magn. Reson. Imaging 2019;49:719–730.

PurposeTo assess the success rate, image quality, and the ability to stage liver fibrosis of a standard 2D gradient‐recalled echo (GRE) and four different spin‐echo (SE) magnetic resonance elastography (MRE) sequences in patients with different liver iron concentrations.Materials and MethodsA total of 332 patients who underwent 3T MRE examinations that included liver fat and iron quantification were enrolled, including 136 patients with all five MRE techniques. Thirty‐four patients had biopsy results for fibrosis staging. The liver stiffness, region of interest area, image quality, and success rate of the five sequences were compared in 115/136 patients. The area under the receiver operating characteristic curves (AUCs) and the accuracies for diagnosing early‐stage fibrosis and advanced fibrosis were compared. The effect of BMI (body mass index), the R2* relaxation time, and fat fraction on the image quality and liver stiffness measurements were analyzed.ResultsThe success rates were significantly higher in the four SE sequences (99.1–100%) compared with GRE MRE (85.3%) (all P < 0.001). There were significant differences of the mean ROI area between every pair of sequences (all P < 0.0001). There were no significant differences in the AUC of the five MRE sequences for discriminating advanced fibrosis (10 P‐values ranging from 0.2410–0.9171). R2* had a significant effect on the success rate and image quality for the noniron 2D echo‐planar imaging (EPI), 3D EPI and 2D GRE (all P < 0.001) sequences. BMI had a significant effect on the iron 2D EPI (P = 0.0230) and iron 2D SE (P = 0.0040) sequences.ConclusionAll five techniques showed good diagnostic performance in staging liver fibrosis. The SE MRE sequences had higher success rates and better image quality than GRE MRE in 3T clinical hepatic imaging.Level of Evidence: 3Technical Efficacy: Stage 5J. Magn. Reson. Imaging 2018;47:976–987.

Magnetic resonance elastography (MRE) is a promising technique for noninvasive assessment of fibrosis, a major determinant of outcome in nonalcoholic fatty liver disease (NAFLD). However, data in children are limited. The purpose of this study was to determine the accuracy of MRE for the detection of fibrosis and advanced fibrosis in children with NAFLD and to assess agreement between manual and novel automated reading methods. We performed a prospective, multicenter study of two‐dimensional (2D) MRE in children with NAFLD. MR elastograms were analyzed manually at two reading centers, and using a new automated technique. Analysis using each approach was done independently. Correlations were determined between MRE analysis methods and fibrosis stage. Thresholds for classifying the presence of fibrosis and of advanced fibrosis were computed and cross‐validated. In 90 children with a mean age of 13.1 ± 2.4 years, median hepatic stiffness was 2.35 kPa. Stiffness values derived by each reading center were strongly correlated with each other (r = 0.83). All three analyses were significantly correlated with fibrosis stage (center 1, ρ = 0.53; center 2, ρ = 0.55; and automated analysis, ρ = 0.52; P < 0.001). Overall cross‐validated accuracy for detecting any fibrosis was 72.2% for all methods (95% confidence interval [CI], 61.8%‐81.1%). Overall cross‐validated accuracy for assessing advanced fibrosis was 88.9% (95% CI, 80.5%‐94.5%) for center 1, 90.0% (95% CI, 81.9%‐95.3%) for center 2, and 86.7% (95% CI, 77.9%‐92.9%) for automated analysis. Conclusion : 2D MRE can estimate hepatic stiffness in children with NAFLD. Further refinement and validation of automated analysis techniques will be an important step in standardizing MRE. How to best integrate MRE into clinical protocols for the assessment of NAFLD in children will require prospective evaluation. (H epatology 2017;66:1474–1485)

Ezetimibe inhibits intestinal cholesterol absorption and lowers low‐density lipoprotein cholesterol. Uncontrolled studies have suggested that it reduces liver fat as estimated by ultrasound in nonalcoholic steatohepatitis (NASH). Therefore, we aimed to examine the efficacy of ezetimibe versus placebo in reducing liver fat by the magnetic resonance imaging‐derived proton density‐fat fraction (MRI‐PDFF) and liver histology in patients with biopsy‐proven NASH. In this randomized, double‐blind, placebo‐controlled trial, 50 patients with biopsy‐proven NASH were randomized to either ezetimibe 10 mg orally daily or placebo for 24 weeks. The primary outcome was a change in liver fat as measured by MRI‐PDFF in colocalized regions of interest within each of the nine liver segments. Novel assessment by two‐dimensional and three‐dimensional magnetic resonance elastography was also performed. Ezetimibe was not significantly better than placebo at reducing liver fat as measured by MRI‐PDFF (mean difference between the ezetimibe and placebo arms ‐1.3%, P = 0.4). Compared to baseline, however, end‐of‐treatment MRI‐PDFF was significantly lower in the ezetimibe arm (15%‐11.6%, P < 0.016) but not in the placebo arm (18.5%‐16.4%, P = 0.15). There were no significant differences in histologic response rates, serum alanine aminotransferase and aspartate aminotransferase levels, or longitudinal changes in two‐dimensional and three‐dimensional magnetic resonance elastography‐derived liver stiffness between the ezetimibe and placebo arms. Compared to histologic nonresponders (25/35), histologic responders (10/35) had a significantly greater reduction in MRI‐PDFF (‐4.35 ± 4.9% versus ‐0.30 ± 4.1%, P < 0.019). Conclusions : Ezetimibe did not significantly reduce liver fat in NASH. This trial demonstrates the application of colocalization of MRI‐PDFF‐derived fat maps and magnetic resonance elastography‐derived stiffness maps of the liver before and after treatment to noninvasively assess treatment response in NASH. (H epatology 2015;61:1239–1250)

Chronic passive hepatic congestion (congestive hepatopathy) leads to hepatic fibrosis; however, the mechanisms involved in this process are not well understood. We developed a murine experimental model of congestive hepatopathy through partial ligation of the inferior vena cava (pIVCL). C57BL/6 and transgenic mice overexpressing tissue factor pathway inhibitor (SM22α‐TFPI) were subjected to pIVCL or sham. Liver and blood samples were collected and analyzed in immunohistochemical, morphometric, real‐time polymerase chain reaction, and western blot assays. Hepatic fibrosis and portal pressure were significantly increased after pIVCL concurrent with hepatic stellate cell (HSC) activation. Liver stiffness, as assessed by magnetic resonance elastography, correlated with portal pressure and preceded fibrosis in our model. Hepatic sinusoidal thrombosis as evidenced by fibrin deposition was demonstrated both in mice after pIVCL as well as in humans with congestive hepatopathy. Warfarin treatment and TFPI overexpression both had a protective effect on fibrosis development and HSC activation after pIVCL. In vitro studies show that congestion stimulates HSC fibronectin (FN) fibril assembly through direct effects of thrombi as well as by virtue of mechanical strain. Pretreatment with either Mab13 or Cytochalasin‐D, to inhibit β‐integrin or actin polymerization, respectively, significantly reduced fibrin and stretch‐induced FN fibril assembly. Conclusion : Chronic hepatic congestion leads to sinusoidal thrombosis and strain, which in turn promote hepatic fibrosis. These studies mechanistically link congestive hepatopathy to hepatic fibrosis. (H epatology 2015;61:648‐659)

PurposeTo investigate the influence of portal pressure on the shear stiffness of the liver and spleen in a well‐controlled in vivo porcine model with magnetic resonance elastography (MRE). A significant correlation between portal pressure and tissue stiffness could be used to noninvasively assess increased portal venous pressure (portal hypertension), which is a frequent clinical condition caused by cirrhosis of the liver and is responsible for the development of many lethal complications.Materials and MethodsDuring multiple intraarterial infusions of Dextran‐40 in three adult domestic pigs in vivo, 3D abdominal MRE was performed with left ventricle and portal catheters measuring blood pressure simultaneously. Least‐squares linear regressions were used to analyze the relationship between tissue stiffness and portal pressure.ResultsLiver and spleen stiffness have a dynamic component that increases significantly following an increase in portal or left ventricular pressure. Correlation coefficients with the linear regressions between stiffness and pressure exceeded 0.8 in most cases.ConclusionThe observed stiffness–pressure relationship of the liver and spleen could provide a promising noninvasive method for assessing portal pressure. Using MRE to study the tissue mechanics associated with portal pressure may provide new insights into the natural history and pathophysiology of hepatic diseases and may have significant diagnostic value in the future. J. Magn. Reson. Imaging 2013;38:809–815. © 2013 Wiley Periodicals, Inc.