RESUMEN
BACKGROUND: Hepatic oval cells (HOCs) possess the potential of self-renewal, replication, and clone, proliferation and differentiation into mature hepatocytes under a certain condition. HOCs can be used as biomaterial for constructing biological artificial liver in vitro, employed for in vivo transplantation, as well as for tissue engineering as seed cells. HOCs can be widely used for improving clinical treatment of liver diseases. OBJECTIVE: To establish adult Wistar rat models of HOC proliferation, to perform/n vitro isolation and culture of HOCs, and to study the possibility of induction and differentiation of HOCs into hepatucytes. DESIGN: Observational study. SETTING: Institute of Gastroenterology, Nanfang Hospital, Southern Medical University. MATERIALS: Experiments were performed at the Laboratory of Institute of Gastroenterology of Nanfang Hospital from December 2003 to February 2006. Thirty-six healthy male Wistar rats aged 3-4 months (150-200 g) were provided by Experimental Animal Center of Southern Medical University. METHODS: Male Wistar rats were orally fed with ethionine received two-thirds partial hepatectomy (2/3 PH). HOCs were harvested and purified by two-steps perfusion and Percoll density gradient centrifugation, and then cultured in vitro and induced with hepatocyte growth factor (HGF), oncostatin M (OSM) and fibroblast growth factor-4 (FGF4). MAIN OUTCOME MEASURES: Identification and differentiation of HOCs. RESULTS: The concentration of HOCs was about 1.34×108 L-1 in each rat model after in vitro isolation. These cells were round, oval or polygon, about 1/6 1/3 the size of normal hepatocytes. The nucleus-cytoplasm ratio was relatively large. After 2 weeks, clone-like proliferation of HOCs could be observed. Laser scanning confocal microscopy indicated positive expression of stem cells markers Thy-1 and C-kit in cytoplasm and membrane of HOCs. Immunocytochemistry demonstrated positive stem cells marker alpha fetoprotein (AFP) in cytoplasm of HOCs. HOCs can stably passage and its shape gradually changed after inducing with HGF, OSM and FGF4. HOC volume became larger and HOCs lost their ability of sticking to the wall of culture flask. Apparent positive stain of cytoplasm albumin (Alb) was detected 14 days after induction, and the positive ratio increased along with the extension of inducing duration. Results of cytochemistry indicated a brown or black deposit after glucose-6-phosphotase (G-6-P) staining and red particles after periodic acid-Schiff (PAS) staining. CONCLUSION: Adult Wistar rat models of HOC proliferation are replicated by ethionine feeding combined with 2/3 PH. HOCs can be obtained through collagenase perfusion and Percoll density gradient centrifugation. Rat HOCs can be passaged and cultured in vitro. Under a certain condition, HOCs can be induced and differentiated into hepatocytes.