Hepatic fibrosis may be the wound therapeutic response to persistent hepatic injury due to different factors. TSPO appearance, and mRNA levels increased with the severity of liver damage. TSPO was a useful molecular imaging biomarker and could be used to track the progression of hepatic fibrosis to cirrhosis with PET. Hepatic fibrosis is the response to chronic hepatic injury resulting from numerous factors, such as alcohol abuse, viral contamination, or cholestasis, and is characterised by the excessive production and deposition of extracellular matrix (ECM) due BIIB021 kinase inhibitor to loss of liver cells during hepatitis. Importantly, hepatic fibrosis can progress to cirrhosis1,2. In Japan, cirrhosis is mainly caused by hepatitis computer virus, with hepatitis C computer virus accounting for 70% of cases and hepatitis B computer virus accounting for 20% of cases, as reported by the National Center for Global Health and Medicine (Chiba, Japan). Prolonged contamination in hepatitis computer virus results in progression to chronic hepatitis, cirrhosis, and hepatocellular carcinoma by 20C30 years after contamination, without a history of apparent symptoms reported by patients. Therefore, development of sensitive diagnostic methods to visualise and monitor hepatic fibrosis is needed. This information around the presence, degree and progression of liver fibrosis is useful for making therapeutic decisions or predicting disease outcomes3. In recent years, numerous evaluation methods for hepatic fibrosis have been developed, generally involving the use of serum markers and the measurement of liver stiffness (i.e., using transient elastography and magnetic resonance elastography)3,4,5,6. Positron emission tomography (PET) imaging with [18F]fluorodeoxyglucose is useful for direct, quantitative, and multispatial visualisation of physiological and cellular processes of hepatocellular carcinoma at multiple time points and at the macroscopic level7. However, no studies have reported the use of PET imaging for noninvasive diagnosis of hepatic fibrosis. Inflammation is BIIB021 kinase inhibitor usually a common feature observed during hepatic fibrogenesis in chronic liver diseases8. As the inflammatory response progresses, the expression levels of translocator protein (18?kDa) (TSPO), a receptor complex primarily expressed PR22 in mitochondria, are increased in inflammatory cells9,10. TSPO has a variety of biological functions, such as cholesterol transport, steroid hormone synthesis, apoptosis, cell proliferation, porphyrin and heme transport, anion transport, mitochondrial function, immunomodulation, and inflammation10. We have identified TSPO as a potential imaging biomarker for visualising numerous inflammatory diseases in living subjects. For example, PET studies with and mRNA expression was increased after 2 (2.2-fold), 4 (3.0-fold), 6 (6.5-fold), and 8 weeks (4.6-fold) of CCl4 treatment as compared with that in the control group. Hepatic mRNA increased with the increase in severity of liver damage. Furthermore, increased mRNA expression correlated with the increases in mRNA.Expression of hepatic (A), (B), (C), and (D) mRNA in control rats and rats treated with CCl4 for 2, 4, 6, or 8 weeks. *mRNA expression levels and (E), expression and the expression of autoradiography was performed using three rats treated with CCl4 for 6 weeks and three control rats. Histological analysis Fixed liver samples were embedded in paraffin and slice into 4-m-thick sections for staining with hematoxylin and eosin or Sirius reddish. Fibrosis was assessed histologically as follows: score 0, no fibrosis; score 1, small portion of fibrous tissue in the central venule (C); score 2, fibrous C-C septa appearance; score 3, multiple C-C fibrotic septa incompletely connected; score 4, C-C septa completely connected (pseudolobule), occasional C-P bridging appearance; score 5, moderate C-P bridging septa further dividing the pseudolobule, with a number of smaller-sized nodules comprising less than 50% (incomplete cirrhosis); score 6, multiple C-P bridging septa further dividing the pseudolobule, with a number of smaller-sized nodules comprising a lot more than 50% (comprehensive cirrhosis)18,19. Histologic evaluation was performed by two pathologists within a arbitrary, blinded way. The percentage of fibrosis was motivated from 10C15 microscopic areas (magnification, 40) of Sirius red-stained slides per pet for collagen quantification using BIIB021 kinase inhibitor Gain ROOF software program (Mitani, Tokyo, Japan) using a microscope (Olympus, Tokyo, Japan). Small-animal Family pet/CT scans Family pet scans had been performed utilizing a small-animal Inveon Family pet scanning device (Siemens, Knoxville, TN, USA), which gives 159 transaxial pieces with 0.796-mm (centre-to-centre).