cis-4-[18F]fluoro-L-proline Molecular Imaging Experimental Liver Fibrosis

[18F]AlF-ND-bisFAPI PET imaging of fibroblast activation protein as a biomarker to monitor the progression of liver fibrosis

BACKGROUND

Hepatic fibrosis is a progressive disease, which is reversible in the early stages. The current monitoring methods have notable limitations that pose a challenge to early detection. In this study, we evaluated the utility of [18F]AlF-ND-bisFAPI positron emission tomography imaging of fibroblast activation protein (FAP) to monitor the progression of liver fibrosis.

METHODS

Two mouse models of liver fibrosis were established by bile duct ligation and carbon tetrachloride administration, respectively. Positron emission tomography imaging was performed with the FAP-specific radiotracer [18F]AlF-ND-bisFAPI for the evaluation of rat HSCs and mouse models of fibrosis and combined with histopathology, immunohistochemical staining, and immunoblotting to elucidate the relationships among radioactivity uptake, FAP levels, and liver fibrosis progression. Furthermore, [18F]AlF-ND-bisFAPI autoradiography was performed to assess tracer binding in liver sections from patients with varying degrees of liver fibrosis.

RESULTS

Cell experiments demonstrated that [18F]AlF-ND-bisFAPI uptake was specific in activated HSCs. Compared with control mice, [18F]AlF-ND-bisFAPI uptake in livers increased in the early stages of fibrosis and increased significantly further with disease progression. Immunohistochemistry and western blot analyses demonstrated that FAP expression increased with fibrosis severity. In accordance with the findings in animal models, ex vivo autoradiography on human fibrotic liver sections showed that radioactivity increased as fibrosis progressed from mild to severe.

CONCLUSIONS

[18F]AlF-ND-bisFAPI positron emission tomography imaging is a promising noninvasive method for monitoring the progression of liver fibrosis.

Metabolic Profile Reflects Stages of Fibrosis in Patients with Non-Alcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is a leading cause of chronic liver disease worldwide, with fibrosis stage being the main predictor for clinical outcomes. Here, we present the metabolic profile of NAFLD patients with regards to fibrosis progression. We included all consecutive new referrals for NAFLD services between 2011 and 2019. Demographic, anthropometric and clinical features and noninvasive markers of fibrosis were recorded at baseline and at follow-up. Significant and advanced fibrosis were defined using liver stiffness measurement (LSM) as LSM ≥ 8.1 kPa and LSM ≥ 12.1 kPa, respectively. Cirrhosis was diagnosed either histologically or clinically. Fast progressors of fibrosis were defined as those with delta stiffness ≥ 1.03 kPa/year (25% upper quartile of delta stiffness distribution). Targeted and untargeted metabolic profiles were analysed on fasting serum samples using Proton nuclear magnetic resonance (¹H NMR). A total of 189 patients were included in the study; 111 (58.7%) underwent liver biopsy. Overall, 11.1% patients were diagnosed with cirrhosis, while 23.8% were classified as fast progressors. A combination of metabolites and lipoproteins could identify the fast fibrosis progressors (AUROC 0.788, 95% CI: 0.703-0.874, p < 0.001) and performed better than noninvasive markers. Specific metabolic profiles predict fibrosis progression in patients with nonalcoholic fatty liver disease. Algorithms combining metabolites and lipids could be integrated in the risk-stratification of these patients.

Automated Radiosynthesis of cis- and trans-4-[18F]Fluoro-l-proline Using [18F]Fluoride

The positron emission tomography imaging agents cis- and trans-4-[18F]fluoro-l-proline are used for the detection of numerous diseases such as pulmonary fibrosis and various carcinomas. These imaging agents are typically prepared by nucleophilic fluorination of 4-hydroxy-l-proline derivatives, with [18F]fluoride, followed by deprotection. Although effective radiofluorination reactions have been developed, the overall radiosynthesis process is suboptimal due to deprotection methods that are performed manually, require multiple steps, or involve harsh conditions. Here we describe the development of two synthetic routes that allow access to precursors, which undergo highly selective radiofluorination reactions and rapid deprotection, under mild acidic conditions. These methods were found to be compatible with automation, avoiding manual handling of radioactive intermediates.

LECT2, A Novel and Direct Biomarker of Liver Fibrosis in Patients With CHB

Chronic hepatitis B (CHB) patients with severe liver fibrosis would be more likely to progress to a poorer prognosis. Treatment is considered once the liver fibrosis reaches significant liver fibrosis (≥S2). Leukocyte cell-derived chemotaxin-2 (LECT2) has been shown to contribute to liver fibrosis progression. No research has focused on the role of LECT2 in liver fibrosis in CHB patients. This study enrolled 227 CHB patients and divided them into the training group (n = 147) and validation group (n = 80), respectively. The expression of LECT2 in serum, protein and mRNA of the human liver tissues was detected to analyze the possible associations between LECT2 and liver fibrosis. A receiver operating characteristic curve (ROC) was used to estimate the efficacy of LECT2 for predicting liver fibrosis. The data showed that there was a positive relationship between LECT2 and the progression of liver fibrosis. In the training group, LECT2 was demonstrated to have better effectiveness than APRI and FIB-4. The AUC was 0.861, 0.698, and 0.734 for significant liver fibrosis, and 0.855, 0.769, and 0.752 for advanced liver fibrosis. Besides, the efficacy of LECT2 in different statuses of patients with CHB was examined and the effectiveness of LECT2 had also been confirmed in the validation group. All the results confirmed that LECT2 could act as a perfect predictor and thus offers a novel and direct biomarker to estimate liver fibrosis more accurately.

Steam Explosion-Assisted Extraction of Protein from Fish Backbones and Effect of Enzymatic Hydrolysis on the Extracts

The development of an efficient pretreatment, prior to enzymatic hydrolysis, is a good strategy for the sustainable use of refractory fish byproducts. This study compared hydrothermal pretreatments at 159 °C for 2 min, followed by water extraction (steam explosion-assisted extraction, SE) and 121 °C for 70 min (hot-pressure extraction, HPE), for the recovery of proteins from fish backbones. The effect of enzymatic hydrolysis on the properties of the obtained fish bone protein (FBP) was also evaluated. The results demonstrated that FBP had high contents of protein (81.09-84.88 g/100 g) and hydroxyproline (70-82 residues/1000 residues). After hydrolysis with Flavourzyme, for 3 h, the FBP hydrolysates that were pretreated with SE (SFBP-H) exhibited a better degree of hydrolysis (DH) and nitrogen recovery (NR), and a higher level of umami taste free amino acids (151.50 mg/100 mL), compared with the HPE-treated samples. The obtained SFBP-H mainly distributed below 3000 Da and had strong scavenging effects on 1,1-diphenyl-2-picrylhydrazy (DPPH) (IC₅₀ = 4.24 mg/mL) and 2,2-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) (IC₅₀ = 1.93 mg/mL) radicals. Steam explosion-assisted extraction is a promising route for recovering proteins from native fish bone materials, and improving the flavor and antioxidant activity of the hydrolysates.