Feldstein, Ariel E.

Chronic liver diseases can lead to fibrotic changes that may progress to the development of cirrhosis, which poses a significant risk for morbidity and increased mortality rates. Metabolic dysfunction-associated steatotic liver disease (MASLD), alcohol-associated liver disease (ALD), and viral hepatitis are prevalent liver diseases that may lead to cirrhosis. The advanced stages of cirrhosis can be further complicated by cancer development or end-stage liver disease and liver failure. Hence, early detection and diagnosis of liver fibrosis is crucial for preventing the progression to cirrhosis and improving patient outcomes. Traditionally, invasive liver biopsy has been considered the gold standard for diagnosing and staging liver fibrosis. In the last decade, research has focused on non-invasive methods, known as liquid biopsies, which involve the identification of disease-specific biomarkers in human fluids, such as blood. Among these alternative approaches, extracellular vesicles (EVs) have emerged as promising diagnostic and therapeutic tools for various diseases, including chronic liver diseases. EVs are released from stressed or damaged cells and can be isolated and quantified. Moreover, EVs facilitate cell-to-cell communication by transporting various cargo, and they have shown the potential to reduce the expression of profibrogenic markers, making them appealing tools for novel anti-fibrotic treatments. This review focuses on the impact of EVs in chronic liver diseases and exploring their potential applications in innovative therapeutic and diagnostic approaches.

Nonalcoholic fatty liver disease (NAFLD) is currently one of most common forms of chronic liver disease globally. NAFLD represents a wide spectrum of liver involvement from nonprogressive isolated steatosis to nonalcoholic steatohepatitis (NASH), characterized by liver necroinflammation and fibrosis and currently one of the top causes of end‐stage liver disease and hepatocellular carcinoma. At present, there is a lack of effective treatments, and a central barrier to the development of therapies is the requirement for an invasive liver biopsy for diagnosis of NASH. Discovery of reliable, noninvasive biomarkers are urgently needed. In this study, we tested whether circulating extracellular vesicles (EVs), cell‐derived small membrane‐surrounded structures with a rich cargo of bioactive molecules, may serve as reliable noninvasive “liquid biopsies” for NASH diagnosis and assessment of disease severity. Total circulating EVs and hepatocyte‐derived EVs were isolated by differential centrifugation and size‐exclusion chromatography from serum samples of healthy individuals, patients with precirrhotic NASH, and patients with cirrhotic NASH. EVs were further characterized by flow cytometry, electron microscopy, western blotting, and dynamic light scattering assays before performing a proteomics analysis. Our findings suggest that levels of total and hepatocyte‐derived EVs correlate with NASH clinical characteristics and disease severity. Additionally, using proteomics data, we developed understandable, powerful, and unique EV‐based proteomic signatures for potential diagnosis of advanced NASH. Conclusion: Our study shows that the quantity and protein constituents of circulating EVs provide strong evidence for EV protein–based liquid biopsies for NAFLD/NASH diagnosis.

Abstract—Hypercholesterolemia (HC) is often associated with impaired peripheral and coronary vascular responses to endothelium-dependent vasodilators, which are probably due to low bioavailability of nitric oxide. To examine the effect of HC on renal vascular and tubular function, 22 domestic pigs were studied after being fed a 12-week normal (n=11) or HC (n=11) diet. Renal regional perfusion and intratubular contrast media concentration in each nephron segment (representing fluid reabsorption) were quantified in vivo with electron-beam computed tomography before and after a suprarenal infusion of either acetylcholine (6 pigs of each diet) or sodium nitroprusside (SNP; 5 pigs of each diet). An increase in cortical perfusion, observed in normal pigs with acetylcholine (+35±6%,P=0.002) and SNP (+12±4%,P=0.005), was blunted in the HC group (+8.8±4.0,P=0.01, and −4.6±4.0%,P=0.1, respectively,P=0.003 andP=0.005 compared with normal) as was an increase in medullary perfusion (+58±21 in normal versus +24±11% in HC,P=0.04). A decrease in the intratubular contrast media concentration in the distal tubule and collecting duct of normal pigs was observed in all tubular segments (and was significantly enhanced in the proximal tubule and Henle’s loop) in the HC group, which was associated with increased sodium excretion. The tubular and renal excretory responses to SNP were similar between the groups. In conclusion, early experimental HC in the pig attenuates renal perfusion response to both endothelium-dependent and -independent vasodilators possibly because of decreased bioavailability or decreased vascular responsiveness to nitric oxide. This vascular impairment may play a role in maladjusted renovascular responses and contribute to renal damage in later stages of atherosclerosis.

ABSTRACTBackground:The relations between hepatic steatosis and histological features of hepatocyte injury in children with nonalcoholic fatty liver disease have yet to be examined. The aims of the present study were to establish associations between steatosis amount, type, and distribution in a well‐characterized group of children with biopsy‐proven nonalcoholic fatty liver disease (NAFLD).Patients and Methods:One hundred eight children with NAFLD seen in 5 centers were studied. Clinical and laboratory data were collected. Hematoxylin‐eosin and Masson trichrome stains were evaluated by 2 expert liver pathologists. Steatosis grade (0–3), type (macrovesicular, microvesicular, or mixed), and zone (1, 3, azonal, or panacinar) were determined. The NAFLD activity score and fibrosis stage were determined.Results:Median patient age was 12 years and median body mass index was 31 kg/m2. Fibrosis was present in 87%. The median NAFLD activity score was 4. Mild, moderate, and severe steatosis were present in 42%, 34%, and 24% of biopsies, respectively. Macrovesicular steatosis was present in 81% and mixed steatosis was present in 19%. Panacinar distribution of steatosis was most frequent (40%), followed by azonal (27%). Steatosis grade positively correlated with portal inflammation (P = 0.018). Azonal distribution positively correlated with presence of hepatocyte ballooning (P = 0.03). Biopsies with mixed steatosis were approximately 20 times more likely to have megamitochondria than those with macrovesicular steatosis alone (95% confidence interval 2.3–204.9). There was no relation between steatosis amount, type, or distribution to fibrosis stage.Conclusions:Specific histological patterns of steatosis in children are associated with histological markers of steatohepatitis. Ballooning and portal inflammation correlated well with features of steatosis.