99m Tc-3PRGD2 scintigraphy to stage liver fibrosis and evaluate reversal after fibrotic stimulus withdrawn

Combining T1rho and advanced diffusion MRI for noninvasively staging liver fibrosis: an experimental study in rats

PURPOSE

To investigate the value of imaging parameters derived from T1 relaxation times in the rotating frame (T1ρ or T1rho), diffusion kurtosis imaging (DKI) and intravoxel incoherent motion (IVIM) in assessment of liver fibrosis in rats and propose an optimal diagnostic model based on multiparametric MRI.

METHODS

Thirty rats were divided into one control group and four fibrosis experimental groups (n = 6 for each group). Liver fibrosis was induced by administering thioacetamide (TAA) for 2, 4, 6, and 8 weeks. T1ρ, mean kurtosis (MK), mean diffusivity (MD), perfusion fraction (f), true diffusion coefficient (D), and pseudo-diffusion coefficient (D*) were measured and compared among different fibrosis stages. An optimal diagnostic model was established and the diagnostic efficiency was evaluated by receiver operating characteristic (ROC) curve analysis.

RESULTS

The mean AUC values, sensitivity, and specificity of T1ρ and MD derived from DKI across all liver fibrosis stages were comparable but much higher than those of other imaging parameters (0.954, 92.46, 91.85 for T1ρ; 0.949, 92.52, 91.24 for MD). The model combining T1ρ and MD exhibited better diagnostic performance with higher AUC values than any individual method for staging liver fibrosis (≥ F1: 1.000 (0.884-1.000); ≥ F2: 0.935 (0.782-0.992); ≥ F3: 0.982 (0.852-1.000); F4: 0.986 (0.859-1.000)).

CONCLUSION

Among the evaluated imaging parameters, T1ρ and MD were superior for differentiating varying liver fibrosis stages. The model combining T1ρ and MD was promising to be a credible diagnostic biomarker to detect and accurately stage liver fibrosis.

Automated whole slide image analysis for a translational quantification of liver fibrosis

Current literature highlights the need for precise histological quantitative assessment of fibrosis which cannot be achieved by conventional scoring systems, inherent to their discontinuous values and reader-dependent variability. Here we used an automated image analysis software to measure fibrosis deposition in two relevant preclinical models of liver fibrosis, and established correlation with other quantitative fibrosis descriptors. Longitudinal quantification of liver fibrosis was carried out during progression of post-necrotic (CCl₄-induced) and metabolic (HF-CDAA feeding) models of chronic liver disease in mice. Whole slide images of picrosirius red-stained liver sections were analyzed using a fully automated, unsupervised software. Fibrosis was characterized by a significant increase of collagen proportionate area (CPA) at weeks 3 (CCl₄) and 8 (HF-CDAA) with a progressive increase up to week 18 and 24, respectively. CPA was compared to collagen content assessed biochemically by hydroxyproline assay (HYP) and by standard histological staging systems. CPA showed a high correlation with HYP content for CCl₄ (r = 0.8268) and HF-CDAA (r = 0.6799) models. High correlations were also found with Ishak score or its modified version (r = 0.9705) for CCl₄ and HF-CDAA (r = 0.9062) as well as with NASH CRN for HF-CDAA (r = 0.7937). Such correlations support the use of automated digital analysis as a reliable tool to evaluate the dynamics of liver fibrosis and efficacy of antifibrotic drug candidates in preclinical models.

Enhanced US/CT/MR imaging of integrin αvβ3 for liver fibrosis staging in rat

Liver fibrosis is a global health challenge with high morbidity and mortality rates, and diagnostic sensitivity of liver fibrosis tests can be increased using multimodal molecular agents. We designed cyclic arginine-glycine-aspartic acid (cRGD)-modified nanoparticles (NPs) using ultrasound (US)/computed tomography (CT)/magnetic resonance (MR) triple-modality imaging to evaluate liver fibrosis stages. In vitro and in vivo studies were conducted using primary hepatic stellate cells (HSCs) and a rat model of liver fibrosis induced by carbon tetrachloride (CCl4). Our results showed cRGD-poly(lactic-co-glycolic acid)-Fe3O4-perfluorocarbon bromide (cRGD-PLGA-Fe3O4-PFOB) NPs were preferentially internalised by activated HSCs (aHSCs). The main cell types expressing integrin αvβ3 during liver fibrogenesis were the aHSCs. The protein levels of αv and β3 expressed on aHSCs increased with the progression of liver fibrosis. After intravenous injection of cRGD-PLGA-Fe3O4-PFOB NPs, the echo intensity (EI) values, CT values, and T2 values of liver parenchyma correlated well with liver fibrosis severity. cRGD-PLGA-Fe3O4-PFOB NPs as multifunction contrast agents showed great potential to reflect the degree of HSC activation and distinguish among different liver fibrotic stages. The ligand-directed and integrin αvβ3-mediated accumulation provides active and passive targeting capabilities, permitting the targeted multimodal imaging of cRGD-PLGA-Fe3O4-PFOB NPs, which delivers accurate non-invasive diagnosis and real-time monitoring of liver fibrosis development.

Therapeutic and diagnostic targeting of fibrosis in metabolic, proliferative and viral disorders

Fibrosis is a common denominator in many pathologies and crucially affects disease progression, drug delivery efficiency and therapy outcome. We here summarize therapeutic and diagnostic strategies for fibrosis targeting in atherosclerosis and cardiac disease, cancer, diabetes, liver diseases and viral infections. We address various anti-fibrotic targets, ranging from cells and genes to metabolites and proteins, primarily focusing on fibrosis-promoting features that are conserved among the different diseases. We discuss how anti-fibrotic therapies have progressed over the years, and how nanomedicine formulations can potentiate anti-fibrotic treatment efficacy. From a diagnostic point of view, we discuss how medical imaging can be employed to facilitate the diagnosis, staging and treatment monitoring of fibrotic disorders. Altogether, this comprehensive overview serves as a basis for developing individualized and improved treatment strategies for patients suffering from fibrosis-associated pathologies.

Imaging Fibrogenesis in a Diet-Induced Model of Nonalcoholic Steatohepatitis (NASH)

Purpose

Liver fibrosis is the hallmark of chronic nonalcoholic steatohepatitis (NASH) and is characterised by the excessive deposition of extracellular matrix proteins. Early detection and accurate staging of liver fibrosis is critically important for patient management. One of the earliest pathological markers in NASH is the activation of hepatic stellate cells (HSCs) which may be exploited as a marker of fibrogenesis. Activated HSCs secreting factors such as integrin α_vβ₃ propagate fibrosis. The purpose of the current study was to assess the utility of the integrin α_vβ₃ imaging agent [¹⁸F]FtRGD for the early detection of fibrosis in a diet-induced model of NASH longitudinally using PET imaging.

Procedures

Mice were fed with either standard chow diet (SD), high-fat diet (HFD), or a choline-deficient, L-amino acid-defined high-fat fibrogenic diet (CDAHFD) to mimic the clinical pathology of liver disease and followed longitudinally for 10 weeks to assess the development of liver fibrosis using [¹⁸F]FtRGD positron emission tomography (PET) imaging. Standard blood biochemistry, histological measures, and qPCR were used to quantify integrin α_vβ₃, smooth muscle actin, and collagen types 1 and 6 to assess the extent of NASH pathology and accurately stage liver fibrosis.

Results

The CDAHFD fibrogenic diet predictably developed hepatic inflammation and steatosis over the 10 weeks studied with little NASH pathology detected in high fat diet-treated animals. Stage 1 fibrosis was detected early by histology at day 21 and progressed to stage 2 by day 35 and stage 3 by day 56 in mice fed with CDAHFD diet only. Noninvasive imaging with [¹⁸F]FtRGD correlated well with integrin α_vβ₃ and was able to distinguish early mild stage 2 fibrosis in CDAHFD animals compared with standard chow diet-fed animals at day 35. When compared with high fat diet-fed animals, [¹⁸F]FtRGD was only able to distinguish later moderate stage 2 fibrosis in CDAHFD animals at day 49.

Conclusions

The diet-induced progression of liver fibrosis was confirmed using histology and correlated well with the mRNA of integrin α_vβ₃ and extracellular matrix protein expression. [¹⁸F]FtRGD showed very good correlation between liver uptake and integrin α_vβ₃ expression and similar detection sensitivity to the current clinical gold standard modalities for staging of liver fibrosis.

In vivo preclinical PET/CT imaging of carbon-11-labeled aminoglycerol probe for the diagnosis of liver fibrosis

OBJECTIVE

As an important membrane protein, aquaglyceroporin involves liver glycerol metabolism, which can be used to stage liver fibrosis. In this study, we synthesized a novel molecular probe carbon-11-labeled AR ([¹¹C]AR) with aminoglycerol (AR), and evaluated its preclinical performance for liver fibrosis diagnosis by positron emission tomography/computed tomography (PET/CT) imaging in vivo.

METHODS

We developed a fully automatic synthesis procedure for the preparation of [¹¹C]AR by radiolabeling glycerol analogue precursor AR with carbon-11. The liver uptake kinetics of [¹¹C]AR was investigated using a rat model by the PET/CT scanner. The dynamic PET/CT scans were performed between the control group (n = 5) and experimental group (n = 25), which was divided into three subgroups (S1, S2 + S3, S4) based on the stages of liver fibrosis. The regions of interest (ROIs) of 20 pixels were drawn in the liver area on the reconstructed images. One-way analysis of variance and independent sample t test were used to analyze the statistical difference of the maximum standardized uptake value (SUVmax) among the groups at series of scanning time points (20 s, 60 s, 90 s, 150 s, 5 min, 10 min, 20 min and 25 min).

RESULTS

The fully automatic synthesis of [¹¹C]AR was successfully achieved with high synthesis efficiency (above 50%). The uptake of [¹¹C]AR in progressive liver fibrosis tissues was significantly lower than that in healthy livers at all the imaging time points (P < 0.05), especially at early time points (before 10 min p.i.). A cut-off SUVmax value (1.1) at 150 s p.i. was set for discrimination progressive fibrosis from healthy liver. More experimental and healthy rats were tested with this new threshold to evaluate fibrosis situation. The sensitivity of detecting progressive fibrosis with [¹¹C]AR was 100% in the second cohort.

CONCLUSION

We demonstrated a new carbon-11-radiolabeled aminoglycerol PET/CT imaging probe [¹¹C]AR for liver fibrosis diagnosis and staging, which may allow potential assessment of liver fibrosis stages in a rapid and noninvasive method.