Several reliable and reproducible methods are available to induce oval cells in rat liver. Effective methods often involve inhibiting proliferation in hepatocytes using an alkylating agent, then subjecting the rat to partial hepatectomy (PH). The surgery is difficult to perform reproducibly in mice. Approaches that do not include partial hepatectomy, such as administration of D-galactosamine, are ineffective in mice. We found that a choline-deficient, ethionine-supplemented (CDE) diet, which is very effective in rats, leads to high morbidity and mortality when administered to mice. This article outlines an alternative protocol by which a CDE diet can be administered to mice. This diet is shown to be highly effective for oval cell induction, without causing high mortality. It takes less time and is at least as effective as other commonly used protocols for inducing oval cells in mice. Methods for inducing liver progenitor cells, or oval cells, in rodents have greatly advanced our knowledge of liver progenitor cell biology. These include feeding carcinogens such as diethylnitrosamine 1 and diaminobenzene or its derivatives 2 ; the administration of D-galactosamine 3 ; and the modified Solt-Farber regimen, which omits diethylnitrosamine, using only acetyl aminofluorene (AAF) coupled with partial hepatectomy (PH). 4 All are highly effective in rats. In mice, the only reliable and routinely used method of inducing oval cells is the administration of an alkylating drug 1,4-Bis [N,NЈ-di-(ethylene)-phosphamide] piperazine (DIPIN), before PH. 5 However, because they are much smaller, it is difficult to perform this surgical procedure in a reproducible fashion in mice. The ever-increasing availability of transgenic mice with specific genes, which are overexpressed or ablated by gene targeting, offers opportunities to identify extracellular and intracellular signaling pathways, which are important or essential for oval cell proliferation. A choline-deficient, ethionine-supplemented (CDE) diet is often used to induce oval cells in rats. [6][7][8] This diet is simple to administer and extremely effective, and by 3 weeks, substantial numbers of oval cells are induced. It is usually provided as a solid chow, either in pelleted form or as a powder. However, our experience shows that it cannot be applied to mice, because it causes severe morbidity and mortality. This article reports modifications to the standard CDE diet that were adopted by our laboratory to successfully induce oval cells in mice. MATERIALS AND METHODSAnimals and Diet. The strain of mice used was BDF1. Two cholinedeficient (CD) diets were tested. The first was a complete 0.07% CDE diet in pellet form obtained from Teklad Test Diets (Madison, WI). The other was the modified CD diet, in powder form, produced by ICN (Costa Mesa, CA Cat. #960209). Apart from ethionine, present in the Teklad, but not the ICN formulation, these 2 diets have essentially the same composition, and both have added trace minerals. To facilitate altering the severity of choline deficiency ...

The liver regenerates after acute injury via hepatocyte cell division; during chronic injury, when hepatocyte replication is impaired or blocked, liver progenitor oval cells mediate liver regeneration. If both regeneration options are blocked in animal models, then liver failure and death ensues. The mechanisms underlying oval cell induction, proliferation, and subsequent liver regeneration remain poorly characterized. In particular, cell-signaling pathways that distinguish the alternative pathways are unknown. This study shows that in a mouse model, hepatic expression of lymphotoxin-␤ (LT␤) and interferon gamma ( T he liver has the capacity to regenerate after acute injury by hepatocyte cell division. However, in circumstances where hepatocyte proliferation is attenuated or blocked, the liver is repopulated after induction, proliferation, and differentiation of the stem cell compartment, which includes oval cells. 1 These alternative methods of liver regeneration can be modeled in mice by partial hepatectomy (PHx) and by feeding them a choline-deficient, ethionine-supplemented (CDE) diet. Surgical resection of a portion of liver mimics acute injury, stimulating a replication response from residual healthy parenchymal cells, which undergo cell division to replace the lost liver mass. 1 The CDE diet damages the liver parenchyma and prevents hepatocyte division, leading to activation and rapid induction of large numbers of oval cells in mice. 2 The replication response after PHx involves a rapid and highly coordinated series of biochemical events resulting in hepatocytes undergoing a relatively synchronized progression through the cell cycle. Immediately after the insult, immediate early genes are activated by transcription factors such as nuclear factor kappa B, activating protein 1 (AP1), and STAT-3. The immediate early phase lasts approximately 4 hours in rodents and precedes the delayed early gene response, which renders the hepatocytes responsive to growth factors that drive the

Lymphotoxin-beta (LT␤) is a proinflammatory cytokine and a member of the tumor necrosis factor (TNF) superfamily known for its role in mediating lymph node development and homeostasis. Our recent studies suggest a role for LT␤ in mediating the pathogenesis of human chronic liver disease. We hypothesize that LT␤ co-ordinates the wound healing response in liver injury via direct effects on hepatic stellate cells. This study used the choline-deficient, ethionine-supplemented (CDE) dietary model of chronic liver injury, which induces inflammation, liver progenitor cell proliferation, and portal fibrosis, to assess (1) the cellular expression of LT␤, and (2)

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