Collagen proportionate area correlates to hepatic venous pressure gradient in non-abstinent cirrhotic patients with alcoholic liver disease

Fibrosis and steatosis of the liver graft: Are non-invasive tests useful? A short review

As life expectancy of liver transplanted patients improves, new questions are arising to avoid progressive graft loss. The spectrum of chronic inflammation and fibrosis are known to be important triggers in the alteration of graft function. Liver biopsy remains the gold standard to better understand progressive, normal, and abnormal histological modifications of the graft. In parallel, the interest for metabolic steatosis development in post-transplantation is also growing. Long-term survival of these patients involves the management of comorbidities including metabolic syndrome and cardiovascular diseases. Early detection of altered graft parenchyma, and monitoring of its evolution are undoubtedly essential. Non-invasive methods including transient elastography and fibrosis biomarkers are attractive tools to avoid drawbacks and complications of liver biopsy. Accuracy of these methods are well-known in a pre-transplantation setting, but evidence is lacking in post-transplantation setting. We review current knowledge of progressive liver fibrosis and steatosis development after transplantation and non-invasive methods of their assessment.

In Vivo Comparison of Synthetic Macroporous Filamentous and Sponge-like Skin Substitute Matrices Reveals Morphometric Features of the Foreign Body Reaction According to 3D Biomaterial Designs

Synthetic macroporous biomaterials are widely used in the field of skin tissue engineering to mimic membrane functions of the native dermis. Biomaterial designs can be subclassified with respect to their shape in fibrous designs, namely fibers, meshes or fleeces, respectively, and porous designs, such as sponges and foams. However, synthetic matrices often have limitations regarding unfavorable foreign body responses (FBRs). Severe FBRs can result in unfavorable disintegration and rejection of an implant, whereas mild FBRs can lead to an acceptable integration of a biomaterial. In this context, comparative in vivo studies of different three-dimensional (3D) matrix designs are rare. Especially, the differences regarding FBRs between synthetically derived filamentous fleeces and sponge-like constructs are unknown. In the present study, the FBRs on two 3D matrix designs were explored after 25 days of subcutaneous implantation in a porcine model. Cellular reactions were quantified histopathologically to investigate in which way the FBR is influenced by the biomaterial architecture. Our results show that FBR metrics (polymorph-nucleated cells and fibrotic reactions) were significantly affected according to the matrix designs. Our findings contribute to a better understanding of the 3D matrix tissue interactions and can be useful for future developments of synthetically derived skin substitute biomaterials.

Principles of diagnosis and treatment of alcohol-induced liver fibrosis

Alcohol-related liver diseases are one of the leading causes of death worldwide, primarily due to complications of liver cirrhosis (LC). Early detection of alcohol-induced liver fibrosis (LF) is a difficult task, since often  alcoholic liver disease (ALD) is clinically manifested only at late stages. Given that not all alcoholic suffer from ALD, the widespread use of liver biopsy to verify the diagnosis is not advisable. Despite the variety of proposed non-invasive methods for assessing the severity of LF in patients with ALD, none of them has sufficient validation and therefore cannot be recommended for widespread use in clinical practice. The most well-studied transient elastography, due to its suboptimal specificity, can be effectively used only to exclude clinically significant LF or LC. The only proven approach to treat ALD is persistent and total alcohol abstinence. While the therapeutic options for patients with severe forms of acute hepatitis remain unchanged since the 70s of the last century and are based mainly on the use of corticosteroids, currently, there are no approaches to antifibrotic therapy of ALD approved by the guidelines. At the same time, modern achievements in understanding the pathophysiological mechanisms  of this disease  have served  as an impetus  for  the development  of ways to solve  the problem. In particular, providing intestinal eubiosis may be an important goal for the prevention and treatment of alcohol-induced LF. Randomized controlled multicenter trials involving a large number of patients are needed to confirm this and other hypotheses related to antifibrotic therapy of ALD and to accept them as a standard of medical care.

Distinct structural and dynamic components of portal hypertension in different animal models and human liver disease etiologies

BACKGROUND AND AIMS

Liver fibrosis is the static and main (70%-80%) component of portal hypertension (PH). We investigated dynamic components of PH by a three-dimensional analysis based on correlation of hepatic collagen proportionate area (CPA) with portal pressure (PP) in animals or HVPG in patients.

APPROACH AND RESULTS

Different animal models (bile duct ligation: n = 31, carbon tetrachloride: n = 12, thioacetamide: n = 12, choline-deficient high-fat diet: n = 12) and patients with a confirmed single etiology of cholestatic (primary biliary cholangitis/primary sclerosing cholangitis: n = 16), alcohol-associated (n = 22), and metabolic (NASH: n = 19) liver disease underwent CPA quantification on liver specimens/biopsies. Based on CPA-to-PP/HVPG correlation, potential dynamic components were identified in subgroups of animals/patients with lower-than-expected and higher-than-expected PP/HVPG. Dynamic PH components were validated in a patient cohort (n = 245) using liver stiffness measurement (LSM) instead of CPA. CPA significantly correlated with PP in animal models (Rho = 0.531; p < 0.001) and HVPG in patients (Rho = 0.439; p < 0.001). Correlation of CPA with PP/HVPG varied across different animal models and etiologies in patients. In models, severity of hyperdynamic circulation and specific fibrosis pattern (portal fibrosis: p = 0.02; septa width: p = 0.03) were associated with PH severity. In patients, hyperdynamic circulation (p = 0.04), vascular dysfunction/angiogenesis (VWF-Ag: p = 0.03; soluble vascular endothelial growth factor receptor 1: p = 0.03), and bile acids (p = 0.04) were dynamic modulators of PH. The LSM-HVPG validation cohort confirmed these and also indicated IL-6 (p = 0.008) and hyaluronic acid (HA: p < 0.001) as dynamic PH components.

CONCLUSIONS

The relative contribution of "static" fibrosis on PH severity varies by type of liver injury. Next to hyperdynamic circulation, increased bile acids, VWF-Ag, IL-6, and HA seem to indicate a pronounced dynamic component of PH in patients.

Semiautomated quantification of the fibrous tissue response to complex three-dimensional filamentous scaffolds using digital image analysis

Fibrosis represents a relevant response to the implantation of biomaterials, which occurs not only at the tissue-material interface (fibrotic encapsulation) but also within the void fraction of complex three-dimensional (3D) biomaterial constructions (fibrotic ingrowth). Usual evaluation of the biocompatibility mostly depicts fibrosis at the interface of the biomaterial using semiquantitative scores. Here, the relations between encapsulation and infiltrating fibrotic growth are poorly represented. Virtual pathology and digital image analysis provide new strategies to assess fibrosis in a more differentiated way. In this study, we adopted a method previously used to quantify fibrosis in visceral organs to the quantification of fibrosis to 3D biomaterials. In a proof-of-concept study, we transferred the "Collagen Proportionate Area" (CPA) analysis from hepatology to the field of biomaterials. As one task of an experimental animal study, we used CPA analysis to quantify the fibrotic ingrowth into a filamentous scaffold after subcutaneous implantation. We were able to demonstrate that the application of the CPA analysis is well suited as an additional fibrosis evaluation strategy for new biomaterial constructions. The CPA method can contribute to a better understanding of the fibrotic interactions between 3D scaffolds and the host tissue responses.

Second-harmonic generation (SHG) microscopy and hepatic venous pressure gradient-based validation of a novel histological staging system for alcoholic hepatitis

Alcoholic hepatitis (AH) lacks specific histological staging. A novel fibrosis staging that encompasses perisinusoidal fibrosis and cirrhosis sub-stages, substantiated by Hepatic venous pressure gradient (HVPG) and automated fibrosis quantification, is imperative. To correlate novel histological staging system of AH with second-harmonic generation microscopy (SHG)-based q-fibrosis, HVPG, and activated hepatic stellate cells (HSCs). Liver biopsies of AH (n = 175) were staged semi-quantitatively as F0, F1, F2, F3A and F3B and Laennec substages of cirrhosis 4A, 4B and 4C. Stages were correlated with SHG q-fibrosis parameters, HVPG and HSCs. Mean age 41.2 ± 9.4 years, 96.6% males, bilirubin 20.58 ± 8.0 mg/dl and Maddrey's discriminant function 78.9 ± 36.7 displayed advanced fibrosis in 98.6%. With increasing histological stages, an increase in q-fibrosis indices and mean HVPG (p < 0.0001) were recorded; stage 4C showed the most significant difference from other stages (p < 0.000). Stages 3A and 3B were comparable with the stages 4A and 4B, respectively, for q-fibrosis (p = 1) and HVPG (p = 1). HSCs (> 30%) were significantly higher in stage 3 (75%) compared with 4 (49%) and 2 (59%), p = 0.018. Overall agreement for histological staging was excellent for all stages (0.82). SHG quantified fibrosis and HVPG corroborates the novel histological staging of AH. Expansive PCF matches with collagen content and clinical severity to early sub-stages of cirrhosis. This highlights the need for an accurate quantification and inclusion of PCF as a separate stage. SHG-based quantification can be a useful adjunct to histological fibrosis staging systems.

Relationship between hemodynamic parameters and portal venous pressure in cirrhosis patients with portal hypertension

Cirrhosis caused by viral and alcoholic hepatitis is an essential cause of portal hypertension (PHT). The incidence of PHT complication is directly proportional to portal venous pressure (PVP), and the clinical research of PVP and its hemodynamic indexes is of great significance for deciding the treatment strategy of PHT. Various techniques are currently being developed to decrease portal pressure but hemodynamic side effects may occur. In this article, the hemodynamic indexes of cirrhotic PHT patients were studied to explore the correlation between the index and PVP and to evaluate the clinical value of Doppler ultrasound in measuring PVP in patients with PHT. This was achieved by selecting 90 cirrhotic PHT patients who underwent transjugular intrahepatic portosystemic shunt in our hospital from June 2015 to September 2019. Fifty healthy people who had a physical examination in the hospital in the same period were selected as the control group. The liver hemodynamic parameters of two groups were measured by Doppler ultrasound, and the cirrhotic PHT patients were graded by the Child–Pugh grading method to evaluate the liver function and measure the PVP value. The results showed that both the central portal vein velocity (PVV) and splenic vein velocity (SVV) of the PHT group were lower than those of the control group. Also, the portal vein diameter (PVD), portal venous flow and splenic vein diameter (SVD) were higher than those of the control group (all Ps < 0.05). Among liver function graded PHT patients, the PVD, PVV, SVD and SVV were significantly different (all Ps < 0.05). Furthermore, the PVP of patients with liver function grades A, B and C was 38.9 ± 1.4, 40.6 ± 5.1 and 42.5 ± 4.8 cmH₂O, respectively, with a significant difference. It can be concluded from this study that Doppler ultrasound can be used as a tool for clinical assessment of PHT in cirrhosis patients. Doppler ultrasound showed a good prospect in noninvasive detection of PHT in cirrhosis; however, this technique needs application on large sample population study to validate the results.

Quantification of Liver Fibrosis—A Comparative Study

Liver disease has been targeted as the fifth most common cause of death worldwide and tends to steadily rise. In the last three decades, several publications focused on the quantification of liver fibrosis by means of the estimation of the collagen proportional area (CPA) in liver biopsies obtained from digital image analysis (DIA). In this paper, early and recent studies on this topic have been reviewed according to these research aims: the datasets used for the analysis, the employed image processing techniques, the obtained results, and the derived conclusions. The purpose is to identify the major strengths and “gray-areas” in the landscape of this topic.

Fibrosis and alcohol-related liver disease

Histological fibrosis stage is one of the most important prognostic factors in compensated and decompensated alcohol-related liver disease (ALD). Morphological assessment of fibrosis is useful for patient stratification, enabling individualised management, and for evaluation of treatment effects in clinical studies. In contrast to most chronic liver diseases where fibrosis is portal-based, fatty liver disease (FLD) of alcoholic or non-alcoholic aetiology (NAFLD) is associated with a centrilobular pattern of injury which leads to perivenular fibrosis and/or pericellular fibrosis. Progression of FLD drives expansive pericellular fibrosis, linking vascular structures and paving the way for the development of cirrhosis. At the cirrhotic stage, ongoing tissue damage leads to increasing fibrosis severity due to parenchymal loss and proliferation of fibrous scars. Histologic fibrosis staging systems have been devised, based on topography and the extent of fibrosis, for most chronic liver diseases. The utility of histological staging is reflected in different risks associated with individual fibrosis stages which cannot be reliably distinguished by non-invasive fibrosis assessment. In contrast to NAFLD, ALD-specific staging systems that enable the standardised prognostication required for clinical management and trials are lacking. Although morphological similarities between NAFLD and ALD exist, differences in clinical and histological features may substantially limit the utility of established NAFLD-specific staging systems for prognostication in ALD. This review summarises morphological features of fibrosis in ALD and compares them to other chronic liver diseases, particularly NAFLD. ALD-related fibrosis is examined in the context of pathogenetic mechanisms of fibrosis progression, regression and clinical settings that need to be considered in future prognostically relevant ALD staging approaches.

Hemodynamic measurements with an abdominal 4D flow MRI sequence with spiral sampling and compressed sensing in patients with chronic liver disease

BACKGROUND

The test-retest/interobserver repeatability and diagnostic value of 4D flow MRI in liver disease is underreported.

PURPOSE

To determine the reproducibility/repeatability of flow quantification in abdominal vessels using a spiral 4D flow MRI sequence; to assess the value of 4D flow parameters in diagnosing cirrhosis and degree of portal hypertension.

STUDY TYPE

Prospective.

SUBJECTS

Fifty-two patients with chronic liver disease.

FIELD STRENGTH/SEQUENCE

1.5T/spiral 4D flow acquired in one breath-hold.

ASSESSMENT

Thirteen abdominal vessels were identified and segmented by two independent observers to measure maximum and time-averaged through-plane velocity, net flow, and vessel cross-section area. Interobserver agreement and test-retest repeatability were evaluated in 15 and 4 cases, respectively. Prediction of the presence and severity of cirrhosis and portal hypertension was assessed using 4D flow parameters.

STATISTICAL TESTS

Cohen's kappa coefficient, coefficient of variation (CV), Bland-Altman, Mann-Whitney tests, logistic regression.

RESULTS

For all vessels combined, measurements showed acceptable agreement between observers, with Cohen's kappa = 0.70 (P < 0.001), CV < 21%, Bland-Altman bias <5%, but high limits of agreement ([-75%,75%]). Test-retest repeatability was excellent in large vessels (CV = 1-15%, bias = 1-25%, Bland-Altman limits of agreement [BALA] = [4%,150%]), and poor in small vessels (CV = 7-130%, bias = 10-200%, BALA = [8%,190%]). Average velocity in the right hepatic vein and average area of the splenic vein were higher in cirrhosis (P = 0.027/0.0039). Flow in the middle hepatic vein strongly correlated with Child-Pugh score (ρ = 0.84, P = 0.0238), while flow in the splenic vein (ρ = 0.43, P = 0.032), time-average (ρ = 0.46, P = 0.02) and peak velocity in the superior mesenteric vein (ρ = 0.45, P = 0.032), and peak velocity in the infrarenal IVC (ρ = 0.39, P = 0.032) positively correlated with an imaging-based portal hypertension score. Average area of the splenic vein predicted cirrhosis (P = 0.019; area under the curve AUC [95% confidence interval, CI] = 0.87 [0.71,1.00]) and clinically significant portal hypertension (P = 0.042; AUC [95% CI] = 0.78 [0.57-0.99]).

DATA CONCLUSION

Spiral 4D flow allows comprehensive assessment of abdominal vessels in one breath-hold, with substantial interobserver reproducibility, but variable test-retest repeatability. 4D flow may potentially reflect vascular changes due to cirrhosis and portal hypertension.

LEVEL OF EVIDENCE

2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;49:994-1005.