[18F]-Alfatide PET Imaging of Nonalcoholic steatohepatitis (NASH) Through Noninvasive Measurement of Integrin αvβ3 in Preclinical Models

139 Background: Hepatic stellate cell (HSC) activation, which is accompanied by increased expression of integrin αvβ3, is an important factor in liver fibrogenesis. Molecular imaging targeting the integrin αvβ3 could provide a non-invasive method for evaluating the expression and the function of the integrin αvβ3 on activated HSCs (aHSCs) in the injured liver, and thus provide important prognostic information. [18F]-Alfatide ([18F]-FAl-NOTA-RGD2) is a radiotracer specific for integrin αvβ3. In this study, we sought to compare differences in uptake of the [18F]-Alfatide between normal and injured liver to evaluate its utility for assessment of fibrogenesis. Methods: We used PET/CT to assess changes in integrin αvβ3 binding of [18F]-Alfatide in the livers of mice with 12 weeks CDAHFD (L-amino acid diet with 60 kcal% fat with 0.1% methionine without added choline) diet induced NASH compared with controls. We performed HE and Oil red O staining to assess steatosis, and Sirius red staining to assess liver fibrosis, immunofluorescence to identify the location of integrin αvβ3 expressed in NASH liver, and measured protein and messenger RNA expression of integrin αvβ3 and alpha smooth muscle actin (α-SMA) in control and fibrotic livers. Results: HE, Oil red O and Sirius red staining showed a significant steatosis and liver fibrosis, indicating an advanced NASH (Fig. 1A). 60 min [18F]-Alfatide PET preformation demonstrated high uptake in NASH liver compared with controls. The accumulation of radioactivity in the livers increased significantly in all treatment groups compared with that of normal controls (Fig. 1B). Immunofluorescence-stained integrin αvβ3 (red), α-SMA (green) and DAPI (blue) shown that integrin αvβ3 have a high co-expression with α-SMA, which consisted FITC-RGD2 (green) staining (Fig. 1C). To our knowledge, this is the first study that systematically validates [18F]-Alfatide /PET imaging in NASH disease by performing a spatially precise correlative analysis of PET imaging, histopathology, integrin αvβ3 expression in preclinical rodent models Conclusions: [18F]-Alfatide is a promising candidate for noninvasive imaging of NASH in the integrin αvβ3 signaling pathway.