In mammalian species, profibrogenic cells are activated to become myofibroblasts in response to liver damage. Few studies have examined hepatic myofibroblasts and their role in liver damage in teleosts. The aim of the present study was to investigate the involvement of myofibroblast-like cells in rainbow trout (Oncorhynchus mykiss) with hepatic damage induced by aflatoxin B1 (AFB1). Histopathological and immunohistochemical analyses characterized alterations in the liver stroma during the carcinogenic process. Anti-human α-smooth muscle actin (SMA) and anti-human desmin primary antibodies were used in immunohistochemistry. Only the anti-SMA reagent labelled cells in trout liver. In the livers of control fish, only smooth muscle in blood vessels and around bile ducts was labelled. In the livers from AFB1-treated fish, SMA-positive cells were present in the stroma surrounding neoplastic lesions and in areas of desmoplastic reaction. These observations indicate that in teleosts, as in mammals, the myofibroblast-like cell is involved in fibrosis associated with liver injury. Chronic liver injury induced in trout by aflatoxin may provide a useful model system for study of the evolution of such mechanisms. © 2013 Elsevier Ltd.15002/03/15258265Ahmad, A., Ahmad, R., Understanding the mechanism of hepatic fibrosis and potential therapeutic approaches (2012) Saudi Journal of Gastroenterology, 18, pp. 155-167Arana, S., Dagli, M.L.Z., Sabino, M., Tabata, Y.A., Rigolino, M.G., Evaluation of the efficacy of hydrated sodium aluminosilicate in the prevention of aflatoxin-induced hepatic cancer in rainbow trout (2011) Pesquisa Veterinária Brasileira, 31, pp. 751-755Arana, S., Tabata, Y., Sabino, M., Rigolino, M.G., Hernandez-Blazquez, F.J., Differential effect of chronic aflatoxin B1 intoxication on the growth performance and incidence of hepatic lesions in triploid and diploid rainbow trout (Oncorhynchus mykiss) (2002) Archivos de Medicina Veterinária, 4, pp. 253-263Bailey, G.S., Williams, D.E., Hendricks, J.D., Fish models for environmental carcinogenesis: the rainbow trout (1996) Environmental Health Perspective, 104, pp. 5-19Bataller, R., Brenner, D.A., Liver fibrosis (2005) Journal of Clinical Investigation, 115, pp. 209-218Benyon, R.C., Iredale, J.P., Is liver fibrosis reversible? (2000) Gut, 46, pp. 443-446Bioulac-Sage, P., Blanc, J.F., Lepreux, S., Balabaud, C., Rosenbaum, J., Cirrhosis: forever? (2000) Gastroenterologie Clinique et Biologique, 24, pp. 877-882Bunton, T.E., Expression of actin and desmin in experimentally induced hepatic lesions and neoplasm from medaka (Oryzias Latipes) (1995) Carcinogenesis, 16, pp. 1059-1063Choi, S.S., Omenetti, A., Witek, R.P., Moylan, C.A., Syn, W.K., Hedgehog pathway activation and epithelial-to-mesenchymal transitions during myofibroblastic transformation of rat hepatic cells in culture and cirrhosis (2009) American Journal of Physiology: Gastrointestinal and Liver Physiology, 297, pp. G1093-G1106Couch, J.A., Spongiosis hepatis: chemical induction, pathogenesis, and possible neoplastic fate in a teleost fish model (1991) Toxicologic Pathology, 19, pp. 237-250Couch, J.A., Courtney, L.A., N-nitrosodiethylamine-induced hepatocarcinogenesis in estuarine sheepshead minnow (Cyprinodon variegatus) neoplasms and related lesions compared with mammalian lesions (1987) Journal of the National Cancer Institute, 79, pp. 297-321Friedman, S.L., Hepatic stellate cells: protean, multifunctional, and enigmatic cells of the liver (2008) Physiology Reviews, 88, pp. 125-172Hendricks, J.D., Meyers, T.R., Shelton, D.W., Histological progression of hepatic neoplasia in rainbow trout (Salmo gairdneri) (1984) National Cancer Institute Monographs, 65, pp. 321-336Hendricks, J.D., Shelton, D.W., Loveland, P.M., Pereira, C.B., Bailey, G.S., Carcinogenicity of dietary dimethylnitrosomorpholine, N-methyl-N'-nitro-N-nitrosoguanidine, and dibromoethane in rainbow trout (1995) Toxicologic Pathology, 23, pp. 447-457Hinton, D.E., Couch, J.A., Architectural pattern, tissue and cellular morphology in livers of fishes: relationship to experimentally-induced neoplastic responses (1998) Fish Ecotoxicology, pp. 141-163. , Birkhäuser Verlag, Basel, T. Braunbeck, D.E. Hinton, B. Streit (Eds.)Hobbie, K.R., DeAngelo, A.B., George, M.H., Law, J.M., Neoplastic and non-neoplastic liver lesions induced by dimethylnitrosamine in Japanese medaka fish (2012) Veterinary Pathology, 49, pp. 372-385Iwaisako, K., Brenner, D.A., Kisseleva, T., What's new in liver fibrosis? The origin of myofibroblasts in liver fibrosis (2012) Journal of Gastroenterology and Hepatology, 27, pp. 65-68Li, C., Kong, Y., Wang, H., Wang, S., Yu, H., Homing of bone marrow mesenchymal stem cells mediated by sphingosine 1-phosphate contributes to liver fibrosis (2009) Journal of Hepatology, 50, pp. 1174-1183Lu, J.W., Hsia, Y., Tu, H.C., Hsiao, Y.C., Yang, W.Y., Liver development and cancer formation in zebrafish (2011) Birth Defects Research (Part C), 3, pp. 157-172Makovicky, P., Dudova, M., Tumova, E., Rajmon, R., Vodkova, Z., Experimental study of non-alcoholic fatty liver disease (NAFLD) on a model of starving chickens: is generalization of steatosis accompanied by fibrosis of the liver tissue? (2011) Pathology Research and Practice, 207, pp. 151-155Neaud, V., Faouzi, S., Guirouilh, J., Le Bail, B., Balabaud, C., Human hepatic myofibroblasts increase invasiveness of hepatocellular carcinoma cells: evidence for a role of hepatocyte growth factor (1997) Hepatology, 26, pp. 1458-1466Neaud, V., Hisaka, T., Monvoisin, A., Bedin, C., Balabaud, C., Paradoxical pro-invasive effect of the serine proteinase inhibitor tissue factor pathway inhibitor-2 on human hepatocellular carcinoma cells (2000) Journal of Biological Chemistry, 275, pp. 35565-35569Ochiai, K., Handharyani, E., Umemura, T., Idiopathic hepatic fibrosis with cholestasis in broiler chickens: immunohistochemistry of hepatic stellate cells (2003) Avian Pathology, 32, pp. 425-458Okihiro, M.S., Hinton, D.E., Progression of hepatic neoplasia in medaka (Oryzias latipes) exposed to diethylnitrosamine (1999) Carcinogenesis, 20, pp. 933-940Okihiro, M.S., Hinton, D.E., Partial hepatectomy and bile duct ligation in rainbow trout, (Oncorhynchus mykiss). Histologic, immunohistochemical and enzyme histochemical characterization of hepatic regeneration and biliary hyperplasia (2000) Toxicologic Pathology, 28, pp. 342-356Otranto, M., Sarrazy, V., Bonté, F., Hinz, B., Gabbiani, G., The role of the myofibroblast in tumor stroma remodeling (2012) Cell Adhesion and Migration, 6, pp. 203-219Parola, M., Marra, F., Pinzani, M., Myofibroblast-like cells and liver fibrogenesis: emerging concepts in a rapidly moving scenario (2008) Molecular Aspects of Medicine, 29, pp. 58-66Rahimi, R.S., Rockey, D.C., Complications of cirrhosis (2012) Current Opinion in Gastroenterology, 28, pp. 223-229Rekha, R.D., Amali, A.A., Her, G.M., Yeh, Y.H., Gong, H.Y., Thioacetamide accelerates steatohepatitis, cirrhosis and HCC by expressing HCV core protein in transgenic zebrafish, Danio rerio (2008) Toxicology, 243, pp. 11-22Schmitt-Gräff, A., Krüger, S., Bochard, F., Gabbiani, G., Denk, H., Modulation of alpha-smooth muscle actin and desmin expression in perisinusoidal cells of normal and diseased human livers (1991) American Journal of Pathology, 138, pp. 1233-1242Senda, T., Nomura, R., The expression of cytokeratin in hepatic stellate cells of the cod (2003) Archives of Histology and Cytology, 66, pp. 437-444Soares, L.M.V., Rodriguez-Amaya, D.B., Survey of aflatoxins, ochratoxin A, zearalenone and sterigmatocystin in some Brazilian foods by using multi-toxin thin-layer chromatographic method (1989) Journal of the Association of Official Analytical Chemists, 72, pp. 22-26Starkel, P., Leclercq, I.A., Animal models for the study of hepatic fibrosis (2011) Best Practice and Research in Clinical Gastroenterology, 25, pp. 319-333Tilton, S.C., Gerwick, L.G., Hendricks, J.D., Rosato, C.S., Corley-Smith, G., Use of a rainbow trout oligonucleotide microarray to determine transcriptional patterns in aflatoxin B1-induced hepatocellular carcinoma compared to adjacent liver (2005) Toxicological Sciences, 88, pp. 319-330Van Wettere, A.J., Law, J.M., Hinton, D.E., Kullman, S.W., Anchoring hepatic gene expression with development of fibrosis and neoplasia in a toxicant-induced fish model of liver injury (2013) Toxicologic Pathology, 41, pp. 744-760Williams, D.E., The rainbow trout liver cancer model: response to environmental chemicals and studies on promotion and chemoprevention (2012) Comparative Biochemistry and Physiology Part C, 155, pp. 121-127Williams, D.E., Bailey, G.S., Reddy, A., Hendricks, J.D., Oganesian, A., The rainbow trout (Oncorhynchus mykiss) tumor model: recent applications in low-dose exposures to tumor initiators and promoters (2003) Toxicologic Pathology, 31 (SUPPL. 1), pp. 58-61Wolf, J.C., Wolfe, M.J., A brief overview of non-neoplastic hepatic toxicity in fish (2005) Toxicologic Pathology, 33, pp. 75-85Yamamoto, H., Itoh, F., Adachi, Y., Sakamoto, H., Adachi, M., Relation of enhanced secretion of active matrix metalloproteinases with tumor spread in human hepatocellular carcinoma (1997) Gastroenterology, 112, pp. 1290-1296Yamamoto, K., Sargent, P.A., Fisher, M.M., Youson, J.H., Periductal fibrosis and lipocytes (fat-storing cells or Ito cells) during biliary atresia in the lamprey (1986) Hepatology, 6, pp. 54-59Yokoi, Y., Namihisa, T., Kuroda, H., Komatsu, I., Miyazaki, A., Immunocytochemical detection of desmin in fat-storing cells (Ito cells) (1984) Hepatology, 4, pp. 709-714Zhao, L., Burt, A.D., The diffuse stellate cell system (2007) Journal of Molecular Histology, 38, pp. 53-64