Molecular MRI of liver fibrosis by a peptide-targeted contrast agent in an experimental mouse model

Advances in Noninvasive Molecular Imaging Probes for Liver Fibrosis Diagnosis

Liver fibrosis is a wound-healing response to chronic liver injury, which may lead to cirrhosis and cancer. Early-stage fibrosis is reversible, and it is difficult to precisely diagnose with conventional imaging modalities such as magnetic resonance imaging, positron emission tomography, single-photon emission computed tomography, and ultrasound imaging. In contrast, probe-assisted molecular imaging offers a promising noninvasive approach to visualize early fibrosis changes in vivo, thus facilitating early diagnosis and staging liver fibrosis, and even monitoring of the treatment response. Here, the most recent progress in molecular imaging technologies for liver fibrosis is updated. We start by illustrating pathogenesis for liver fibrosis, which includes capillarization of liver sinusoidal endothelial cells, cellular and molecular processes involved in inflammation and fibrogenesis, as well as processes of collagen synthesis, oxidation, and cross-linking. Furthermore, the biological targets used in molecular imaging of liver fibrosis are summarized, which are composed of receptors on hepatic stellate cells, macrophages, and even liver collagen. Notably, the focus is on insights into the advances in imaging modalities developed for liver fibrosis diagnosis and the update in the corresponding contrast agents. In addition, challenges and opportunities for future research and clinical translation of the molecular imaging modalities and the contrast agents are pointed out. We hope that this review would serve as a guide for scientists and students who are interested in liver fibrosis imaging and treatment, and as well expedite the translation of molecular imaging technologies from bench to bedside.

Cancer-associated fibroblasts: Origin, function, imaging, and therapeutic targeting

The tumor microenvironment (TME) is emerging as one of the primary barriers in cancer therapy. Cancer-associated fibroblasts (CAF) are a common inhabitant of the TME in several tumor types and play a critical role in tumor progression and drug resistance via different mechanisms such as desmoplasia, angiogenesis, immune modulation, and cancer metabolism. Due to their abundance and significance in pro-tumorigenic mechanisms, CAF are gaining attention as a diagnostic target as well as to improve the efficacy of cancer therapy by their modulation. In this review, we highlight existing imaging techniques that are used for the visualization of CAF and CAF-induced fibrosis and provide an overview of compounds that are known to modulate CAF activity. Subsequently, we also discuss CAF-targeted and CAF-modulating nanocarriers. Finally, our review addresses ongoing challenges and provides a glimpse into the prospects that can spearhead the transition of CAF-targeted therapies from opportunity to reality.

Engineered Molecular Therapeutics Targeting Fibrin and the Coagulation System: a Biophysical Perspective

The coagulation cascade represents a sophisticated and highly choreographed series of molecular events taking place in the blood with important clinical implications. One key player in coagulation is fibrinogen, a highly abundant soluble blood protein that is processed by thrombin proteases at wound sites, triggering self-assembly of an insoluble protein hydrogel known as a fibrin clot. By forming the key protein component of blood clots, fibrin acts as a structural biomaterial with biophysical properties well suited to its role inhibiting fluid flow and maintaining hemostasis. Based on its clinical importance, fibrin is being investigated as a potentially valuable molecular target in the development of coagulation therapies. In this topical review, we summarize our current understanding of the coagulation cascade from a molecular, structural and biophysical perspective. We highlight single-molecule studies on proteins involved in blood coagulation and report on the current state of the art in directed evolution and molecular engineering of fibrin-targeted proteins and polymers for modulating coagulation. This biophysical overview will help acclimatize newcomers to the field and catalyze interdisciplinary work in biomolecular engineering toward the development of new therapies targeting fibrin and the coagulation system.

Extracellular Matrix Components as Diagnostic Tools in Inflammatory Bowel Disease

Simple Summary

For decades, the extracellular matrix (ECM) has been defined as a structure component playing a rather neglected role in the human body. In recent years, research has shed light on the role of ECM within cellular processes, including proliferation, migration and differentiation, as well as in inflammation. In inflammation, ECM composition is constantly being remodeled and undergoes dynamic and rapid changes. Tracking these changes could serve as a novel diagnostic tool. Inflammatory bowel disease is accompanied by complications such as fibrosis, stenosis and fistulas. All of these structural complications involve excessive synthesis or degradation of ECM. With this review, we explored whether the analysis of ECM composition can be of support in diagnosing inflammatory bowel disease and whether changes within ECM can help to predict a complicated disease course early on.

Abstract

Work from the last years indicates that the extracellular matrix (ECM) plays a direct role in various cellular processes, including proliferation, migration and differentiation. Besides homeostatic processes, its regulatory function in inflammation becomes more and more evident. In inflammation, such as inflammatory bowel disease, the ECM composition is constantly remodeled, and this can result in a structuring of fistulizing disease course. Thus, tracking early ECM changes might bear the potential to predict the disease course. In this review, we provide an overview of relevant diagnostic methods, focusing on ECM changes.

Advances in functional and molecular MRI technologies in chronic liver diseases

MRI has emerged as the most comprehensive non-invasive diagnostic tool for liver diseases. In recent years, the value of MRI in hepatology has been significantly enhanced by a wide range of contrast agents, both clinically available and under development, that add functional information to anatomically detailed morphological images, or increase the distinction between normal and pathological tissues by targeting molecular and cellular events. Several classes of contrast agents are available for contrast-enhanced hepatic MRI, including i) conventional non-specific extracellular fluid contrast agents for assessing tissue perfusion; ii) hepatobiliary-specific contrast agents that are taken up by functioning hepatocytes and excreted through the biliary system for evaluating hepatobiliary function; iii) superparamagnetic iron oxide particles that accumulate in Kupffer cells; and iv) novel molecular contrast agents that are biochemically targeted to specific molecular/cellular processes for staging liver diseases or detecting treatment responses. The use of different functional and molecular MRI methods enables the non-invasive assessment of disease burden, progression, and treatment response in a variety of liver diseases. A high diagnostic performance can be achieved with MRI by combining imaging biomarkers.

Molecular Probes for Imaging Fibrosis and Fibrogenesis

Fibrosis, or the accumulation of extracellular matrix molecules that make up scar tissue, is a common result of chronic tissue injury. Advances in the clinical management of fibrotic diseases have been hampered by the low sensitivity and specificity of noninvasive early diagnostic options, lack of surrogate end points for use in clinical trials, and a paucity of noninvasive tools to assess fibrotic disease activity longitudinally. Hence, the development of new methods to image fibrosis and fibrogenesis is a large unmet clinical need. Herein, an overview of recent and selected molecular probes for imaging of fibrosis and fibrogenesis by magnetic resonance imaging, positron emission tomography, and single photon emission computed tomography is provided.

Molecular imaging of fibrosis: recent advances and future directions

Fibrosis, the progressive accumulation of connective tissue that occurs in response to injury, causes irreparable organ damage and may result in organ failure. The few available antifibrotic treatments modify the rate of fibrosis progression, but there are no available treatments to reverse established fibrosis. Thus, more effective therapies are urgently needed. Molecular imaging is a promising biomedical methodology that enables noninvasive visualization of cellular and subcellular processes. It provides a unique means to monitor and quantify dysregulated molecular fibrotic pathways in a noninvasive manner. Molecular imaging could be used for early detection, disease staging, and prognostication, as well as for assessing disease activity and treatment response. As fibrotic diseases are often molecularly heterogeneous, molecular imaging of a specific pathway could be used for patient stratification and cohort enrichment with the goal of improving clinical trial design and feasibility and increasing the ability to detect a definitive outcome for new therapies. Here we review currently available molecular imaging probes for detecting fibrosis and fibrogenesis, the active formation of new fibrous tissue, and their application to models of fibrosis across organ systems and fibrotic processes. We provide our opinion as to the potential roles of molecular imaging in human fibrotic diseases.

Antifibrotics in chronic liver disease: tractable targets and translational challenges

Chronic liver disease prevalence is increasing globally. Iterative liver damage, secondary to any cause of liver injury, results in progressive fibrosis, disrupted hepatic architecture, and aberrant regeneration, which are defining characteristics of liver cirrhosis. Liver transplantation is an effective treatment for end-stage liver disease; however, demand greatly outweighs donor organ supply, and in many parts of the world liver transplantation is unavailable. Hence, effective antifibrotic therapies are urgently required. In the past decade, rapid progress has been made in our understanding of the pathophysiology of liver fibrosis and a large number of potential cellular and molecular antifibrotic targets have been identified. This has led to numerous clinical trials of antifibrotic agents in patients with chronic liver disease. However, none of these have resulted in a robust and reproducible effect on fibrosis. It is therefore imperative that the ongoing translational challenges are addressed, to convert scientific discoveries into potent antifibrotics and enable bridging of the translational gap between putative therapeutic targets and effective treatments for patients with chronic liver disease.

Renal blood perfusion in GK rats using targeted contrast enhanced ultrasonography

OBJECTIVE

To explore application of targeted contrast enhanced ultrasonography in diagnosis of early stage vascular endothelial injury and diabetic nephropathy.

METHODS

Targeted SonoVue-TM microbubble was prepared by attaching anti-TM monoclonal antibody to the surface of ordinary microbubble SonoVue by biotin - avidin bridge method and ultrasonic instrument was used to evaluate the developing situation of targeted microbubble in vitro. Twenty 12-week-old male GK rats and 20 Wistar rats were enrolled in this study, and were randomly divided into targeted angiography group and ordinary angiography group. Targeted microbubbles SonoVue-TM or general microbubble SonoVue were rapidly injected to the rats via tail vein; the developing situation of the two contrast agents in rats kidneys was dynamically observed. Time-intensity curve was used to analyze rat kidney perfusion characteristics in different groups.

RESULTS

Targeted ultrasound microbubble SonoVue-TM was successfully constructed, and it could be used to develop an external image. Targeted microbubbles SonoVue-TM enabled clear development of experimental rat kidney. Time-intensity curve shapes of rat kidney of the two groups showed as single apex with steep ascending and slowly descending branch. Compared with the control group, the rising slope of the GK rat renal cortex, medulla in targeted angiography group increased (P < 0.05); the peak intensity of medulla increased (P < 0.05), and the total area under the curve of medulla increased (P < 0.05). Compared with control group, the ascending branch of the GK rat in renal cortex, medulla in ordinary angiography group increased (P < 0.05). The peak intensity of the curve increased (P < 0.05), and the total area under the curve increased (P < 0.05). Compared with the ordinary angiography group, the peak of GK rat medulla curve in targeted angiography group intensity increased (P < 0.05), and the total area under the curve increased (P < 0.05).

CONCLUSIONS

Targeted microbubbles SonoVue-TM can make a clear development of experimental rat kidney, its stable performance meet the requirement of ultrasonic observation time limit, and it can reflect early changes of blood perfusion in GK rat kindey.

MRI and (1)H MRS findings of hepatobilary changes and cholangiocarcinoma development in hamsters infected with Opisthorchis viverrini and treated with N-nitrosodimethylamine

3 T MRI and (1)H MRS were useful for quantitative investigation of the serial development of hepatobiliary changes in Opisthorchis viverrini infection in hamsters, and the differential diagnosis of cholangiocacinoma (CCA) development from bile duct changes and normal condition is unclear. In this study, we investigated the serial development of hepatobiliary changes and CCAgenesis in O. viverrini-infected and N-nitrosodimethylamine (NDMA) treated hamsters (ON group) using 3 T MRI and (1)H MRS and the results were compared with those either in the O. viverrini-infected group (OV group) and uninfected normal controls. In the ON group, CCAs were first found at 9 weeks post-infection, with sizes of ~2 mm. The typical MR signal characteristics of CCA were hypo- and occasionally isointensity signal on T1-weighted images, and mild-moderate to hyper-intensity signal on T2-weighted images compared to the liver parenchyma. T2-weighted images with fat suppression revealed dilatation of the intra- and extrahepatic bile ducts, and often defined the anatomical level of biliary obstruction, cystic lesions, liver abscesses, and CCA which was starting seen of these noticeable abnormalities at 5 weeks onwards. The results of fibrosis grading using MR images showed a positive correlation (r=0.90, P<0.038 by Spearman's rank correlation test) with those of the histopathological grading. In addition, 3.0 T (1)H MRS showed elevated choline and decreased lipids levels in the liver tissues of the ON group. In conclusion, MRI and (1)H MRS are useful for the quantitative investigation of the serial development of hepatobilary changes and CCA in hamsters, and are potentially useful as early diagnostic tools for CCA.

Recent advances in molecular magnetic resonance imaging of liver fibrosis

Liver fibrosis is a life-threatening disease with high morbidity and mortality owing to its diverse causes. Liver biopsy, as the current gold standard for diagnosing and staging liver fibrosis, has a number of limitations, including sample variability, relatively high cost, an invasive nature, and the potential of complications. Most importantly, in clinical practice, patients often reject additional liver biopsies after initiating treatment despite their being necessary for long-term follow-up. To resolve these problems, a number of different noninvasive imaging-based methods have been developed for accurate diagnosis of liver fibrosis. However, these techniques only reflect morphological or perfusion-related alterations in the liver, and thus they are generally only useful for the diagnosis of late-stage liver fibrosis (liver cirrhosis), which is already characterized by "irreversible" anatomic and hemodynamic changes. Thus, it is essential that new approaches are developed for accurately diagnosing early-stage liver fibrosis as at this stage the disease may be "reversed" by active treatment. The development of molecular MR imaging technology has potential in this regard, as it facilitates noninvasive, target-specific imaging of liver fibrosis. We provide an overview of recent advances in molecular MR imaging for the diagnosis and staging of liver fibrosis and we compare novel technologies with conventional MR imaging techniques.

The evolution of fibrin-specific targeting strategies

Fibrin-specific targeting capabilities have been highly sought for over 50 years due to their implications for bio-molecule delivery, diagnostics, and regenerative medicine. Yet only recently has our full knowledge of fibrin's complex polymerization dynamics and biological interactions begun to be fully exploited in pursuit of this goal. This highlight will discuss the range of rapidly changing strategies for specifically targeting fibrin over the precursor fibrinogen and the advantages and disadvantages of these approaches for various applications.

Dendritic nanoglobules with polyhedral oligomeric silsesquioxane core and their biomedical applications

Dendrimers have been recognized as promising materials for biomedical applications due to their unique properties, such as well-defined unimolecular structures, precise molecular weights and high degrees of branching and surface functionality. The dendrimers with a polyhedral oligomeric silsesquioxane core – nanoglobules – have many advantageous features over traditional dendrimers, including more functional groups at the same generation of dendrimers, well-defined 3D structures and relatively compact morphologies. Various nanoglobules of polyhedral oligomeric silsesquioxane-core dendrimers have been synthesized and investigated for biomedical applications. Nanoglobules have been used as carriers for developing drug-delivery systems, gene-delivery systems and imaging contrast agents with precisely defined structures and sizes. This article summarizes the recent developments in nanoglobules for biomedical applications.

Noninvasive Biomarkers of Liver Fibrosis: Clinical Applications and Future Directions

Chronic liver disease is a significant cause of morbidity and mortality worldwide. Current strategies for assessing prognosis and treatment rely on accurate assessment of disease stage. Liver biopsy is the gold standard for assessing fibrosis stage but has many limitations. Noninvasive biomarkers of liver fibrosis have been extensively designed, studied, and validated in a variety of liver diseases. With the advent of direct acting antivirals and the rise in obesity-related liver disease, there is a growing need to establish these noninvasive methods in the clinic. In addition, it has become increasingly clear over the last few years that noninvasive biomarkers can also be used to monitor response to antifibrotic therapies and predict liver outcomes, including hepatocellular carcinoma development. This review highlights the most well-established noninvasive biomarkers to-date, with a particular emphasis on serum and imaging-based methodologies.

Comparison of magnetic resonance elastography and gadoxetate disodium-enhanced magnetic resonance imaging for the evaluation of hepatic fibrosis

OBJECTIVES

The objective of this study was to compare the diagnostic performance of magnetic resonance elastography (MRE) and gadoxetate disodium-enhanced magnetic resonance imaging (MRI) in the staging of hepatic fibrosis (HF) in patients with liver diseases.

MATERIALS AND METHODS

This retrospective study was approved by our institutional review board, and the informed consent was waived. One hundred and sixty-eight patients with chronic liver disease or suspected focal hepatic lesions underwent MRE and gadoxetate disodium-enhanced MRI at 1.5 T. Liver stiffness values were measured on quantitative shear-stiffness maps. The contrast enhancement index (CEI) was calculated as SIpost / SIpre, where SIpost and SIpre are, respectively, the liver-to-muscle signal intensity (SI) ratio on hepatobiliary phase images and on unenhanced images. The diagnostic performance of MRE and CEI for staging HF was compared using the receiver operating characteristic curve analysis on the basis of the histopathologic analysis of HF.

RESULTS

The liver stiffness values measured on MRE (r = 0.802; P < 0.0001) were more strongly correlated with the HF stage than with the CEI (r = -0.378; P < 0.0001). The areas under the receiver operating characteristic curve values of the liver stiffness values were significantly larger than those of CEI were for discriminating all stages of HF (P < 0.001 for ≥ F1, ≥ F2, ≥ F3, and ≥ F4). Magnetic resonance elastography showed higher sensitivity and specificity for predicting HF ≥ F1 (91% and 87%), ≥ F2 (87% and 91%), ≥ F3 (80% and 89%), and F4 (81% and 85%) compared with CEI (46% and 85%, 46% and 82%, 63% and 68%, and 76% and 65%, respectively).

CONCLUSIONS

Magnetic resonance elastography was superior to the gadoxetate disodium-enhancement MRI for HF staging.