Biochemical Parameters for Longitudinal Monitoring of Liver Function in Rat Models of Partial Hepatectomy Following Liver Injury Nele Boeykens 1 , Peter Ponsaerts 2 , Dirk Ysebaert 1 *, Kathleen De Greef 1 1 Laboratory of Experimental Surgery, Antwerp Surgical Training and Research Center, University of Antwerp/University Hospital of Antwerp, Antwerp, Belgium, 2 Laboratory of Experimental Hematology, Vaccine and Infectious Disease Institute (Vaxinfectio), University of Antwerp, Antwerp, Belgium Abstract Background: While evaluation of liver function in preclinical animal studies is commonly performed at selected time-points by invasive determination of the liver/body weight ratio and histological analyses, the validation of longitudinal measurement tools for monitoring liver function are of major interest. Aims: To longitudinally evaluate serum cholinesterase (CHE) and total serum bilirubin (TSB) levels as non-invasive markers to determine injury- and partial hepatectomy (PHx)-induced alterations of liver function in rats. Methods: Male and female Lewis rats were subjected to either methionine/choline deficient (MCD) diet or treatment with FOLFOX chemotherapy prior to PHx. Body weight and CHE/TSB levels are determined weekly. Following PHx and at the study end, histological analyses of liver tissue are performed. Results: Following MCD diet, but not after FOLFOX chemotherapy treatment, results indicate gender-specific alterations in serum CHE levels and gender-independent alterations in TSB levels. Likewise, histological analyses of resected liver parts indicate significant liver injury following MCD-diet, but not following FOLFOX treatment. While TSB levels rapidly recover following MCD diet/FOLFOX treatment combined with a PHx, serum CHE levels are subject to significant model- and gender-specific differences, despite full histopathological recovery of liver tissue. Conclusions: Longitudinal measurements of serum CHE levels and TSB levels in rats are highly complementary as non- invasive parameters for evaluation of liver injury and/or recovery. Citation: Boeykens N, Ponsaerts P, Ysebaert D, De Greef K (2013) Biochemical Parameters for Longitudinal Monitoring of Liver Function in Rat Models of Partial Hepatectomy Following Liver Injury. PLoS ONE 8(6): e66383. doi:10.1371/journal.pone.0066383 Editor: Shree Ram Singh, National Cancer Institute, United States of America Received February 15, 2013; Accepted May 5, 2013; Published June 18, 2013 Copyright: ß 2013 Boeykens et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This work was supported by a BOF-NOI 2009 research grant from the University of Antwerp (granted to DY and KDG). NB holds a PhD-studentship from the Flemish Institute for Science and Technology (IWT-Vlaanderen). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: dirk.ysebaert@ua.ac.be Introduction Evaluation of induced liver injury and subsequent liver regeneration in rodents is most commonly performed on the basis of imaging techniques (MRI/CT), histological analyses, determi- nation of the body/liver weight ratio and evaluation of liver function parameters at selected time-points. However, in order to accurately determine the effect of therapeutic interventions during pre-clinical studies, longitudinal assessment of liver function is imperative to identify long-term functional deficits or impaired/ improved regeneration. For this purpose, weekly analyses of serum cholinesterase (CHE) and total serum bilirubin (TSB) levels may provide us with more information as compared to selected time- point analysis for monitoring liver function in preclinical research on liver injury and/or regeneration. In this study, we focus on the long-term assessment of liver function in two rat models of partial hepatectomy (PHx) following liver injury. With a prevalence of 10–20% in lean population and 50–75% in obese population, steatosis is the most common chronic liver disease worldwide [1]. In some patients, hepatic steatosis may progress to non-alcoholic steatohepatitis (NASH), cirrhosis and even develop hepatocellular carcinoma. Current clinical observa- tions suggest an increased risk of performing PHx in patients with severe steatosis [2,3,4]. Moreover, experimental studies have reported impaired liver regeneration in animal models of steatosis [5,6]. A methionine/choline deficient (MCD) diet has been established to mimic pathological conditions of hepatic steatosis and is frequently used in preclinical research [1]. Therefore, in this study we longitudinally evaluate liver function in rats during MCD diet (i.e. the induction of human NASH-like pathology) and during the recovery phase following PHx. Chemotherapy associated steatohepatitis (CASH) and also sinusoidal obstruction syndrome (SOS) have clinically been observed in patients subjected to preoperative chemotherapy treatment in order to downstage non-resectable liver tumors and/ PLOS ONE | www.plosone.org 1 June 2013 | Volume 8 | Issue 6 | e66383