Liver fibrosis often progresses to cirrhosis. The evolution of cirrhosis is slow (decades) and monitoring of progression by frequent liver biopsies is both unethical and subject to sampling error. Fibrosis results from a dysbalance of the dynamic processes of fibrolysis (removal of matrix) in favor of fibrogenesis (deposition of matrix). There exist no noninvasive markers to measure hepatic fibrogenesis and fibrolysis. Due to the lack of such markers it has been impossible to quantify the individual risk of liver patients to progress to cirrhosis, or to develop proven antifibrotic drugs that can inhibit progression or induce fibrosis reversal. [unreadable] [unreadable] In our preliminary work we established models of progression in rats with secondary biliary cirrhosis and with panlobular cirrhosis due to thioacetamide intoxication. Cirrhosis in these animals reverses after biliodigestive anastomosis and the antifibrotic agent halofuginone, respectively. We defined specific liver gene expression profiles associated with fibrosis progression and reversal. By applying advanced serum proteomics we found first serum proteins associated with fibrogenesis and fibrolysis. [unreadable] [unreadable] We hypothesize that by using homogeneous groups of rats with progression or reversal of liver fibrosis, we can 1. relate differential serum proteomic patterns to the activity of hepatic fibrogenesis or fibrolysis as verified in the paired liver samples, and 2. identify the differentially expressed proteins. To reach these goals we pursue the following aims: 1. to thoroughly characterize the dynamics of our rat models of biliary and panlobular fibrosis progression and reversal, 2. to use quantitative proteomics with isobaric protein tags to identify serum markers of hepatic fibrogenesis and fibrolysis. [unreadable] [unreadable] To achieve these aims, we will attach 4 (8) different isobaric peptide labels (iTRAQ) to trypsin digests of 4 pools of fractionated sera from groups representing the evolution of hepatic fibrogenesis and fibrolysis after removal of abundant serum proteins. Differentially expressed proteins will be identified by 2D Nano-liquid chromatography and MALDI-TOF/TOF mass spectrometry. Based on the findings of this proposal, ELISAs for serum markers of portal vs. lobular fibrogenesis and fibrolysis will be developed in a future application. Adaptation to the human proteome and prospective validation shall allow noninvasive monitoring of fibrosis progression and regression in patients with liver diseases. [unreadable] [unreadable] [unreadable]