Modeling Principle

The Beagle Cirrhosis Model is a SCI gold-standard large-animal pathological model of liver cirrhosis established by combined intervention of subcutaneous injection of carbon tetrachloride (CCl₄) olive oil solution plus ethanol drinking water. It accurately recapitulates the complete pathological cascade of end-stage progression from chronic viral hepatitis, alcoholic liver disease and drug-induced liver injury in clinic, including repeated hepatocellular degeneration and necrosis, sustained activation of hepatic stellate cells, massive collagen fiber deposition, hepatic lobule structural disintegration, pseudolobule formation, portal hypertension and liver failure, and compensates for experimental defects of rodent animals with tremendous differences from humans in small liver volume, rapid hepatic fibrosis progression, underdeveloped portal system and hepatic metabolic enzyme spectrum.

The hepatic lobular anatomy, hepatocyte cytochrome P450 metabolic enzyme system, distribution and activation mechanism of hepatic stellate cells (HSC), portal circulation hemodynamics, bile secretion pathway and hepatic detoxification metabolic pathway of young Beagle dogs are highly homologous to humans. CCl₄ is metabolized by hepatic CYP2E1 to generate trichloromethyl free radicals, which directly attack hepatocyte lipid membranes to cause hepatocellular oxidative damage, degeneration and necrosis. Repeated liver injury activates hepatic stellate cells, and the TGF-β1/Smad pathway is persistently overactivated to secrete massive type Ⅰ and type Ⅲ collagen fibers with excessive extracellular matrix deposition. Combined with ethanol drinking water to aggravate hepatocyte oxidative stress and accelerate hepatic fibrosis progression. With prolonged modeling cycle, fibrous septa gradually widen and surround residual hepatic lobules to form typical pseudolobule structures, the liver becomes hard with nodular uneven surface, accompanied by portal hypertension, splenomegaly, ascites and progressive deterioration of liver function. This model fully recapitulates the classic pathogenic cascade of human liver cirrhosis: repeated hepatocyte necrosis-sustained inflammatory activation-hepatic stellate cell activation-collagen fiber deposition-pseudolobule formation-liver function decompensation.

Beagle dogs possess sufficient liver volume with well-developed portal system. The progression of hepatic fibrosis is slow and controllable with minimal individual dispersion and no spontaneous liver diseases. It can clearly distinguish three-stage lesions including early hepatic fibrosis stage (4 weeks), middle fibrous septum formation stage (8 weeks) and terminal liver cirrhosis stage with pseudolobule formation (12 weeks), serving as a standardized large-animal gold-standard model for translational research on liver cirrhosis pathogenesis, anti-fibrotic drugs, portal hypertension intervention, liver regeneration repair and artificial liver support system.

Modeling Success Criteria

Macroscopic Gross Hepatic and General Phenotype

Animals in blank control group were active with normal food intake and clear light yellow urine. The liver was ruddy, soft, smooth-surfaced and intact in lobulation without nodules or fibrous hyperplasia. At Week 12 terminal point, animals in model group showed listlessness, decreased appetite, weight loss and dark yellow urine. Anatomical observation showed reduced liver volume, hard texture, diffuse nodular uneven surface with nodules of different sizes, blunt edges, gray-white fibrous septa surrounding yellow-brown liver parenchyma on cut surface, splenomegaly and ascites formation. The macroscopic liver cirrhosis phenotype was typical with extremely significant difference from blank group, confirming preliminary successful construction of liver cirrhosis model.

Quantitative Biochemical Gold-Standard Indexes of Serum

Serum ALT, AST and TBIL in model group were extremely significantly higher than blank group; albumin ALB decreased sharply with inverted albumin/globulin A/G ratio; all four hepatic fibrosis markers including hyaluronic acid HA, laminin LN, procollagen type Ⅲ PC-Ⅲ and type Ⅳ collagen Ⅳ-C were significantly elevated; serum pro-inflammatory factors TNF-α, IL-1β and IL-6 were upregulated; accumulation of MDA in hepatic tissues and serum increased while antioxidant activity of SOD decreased significantly, fully matching the core biochemical diagnostic characteristics of clinical liver cirrhosis: persistent hepatocellular injury, decompensated liver function, massive collagen fiber deposition, systemic inflammatory activation and disordered oxidative stress.

Hepatic Histopathological Characteristics

Combined HE, Masson trichrome, Sirius red and α-SMA immunohistochemical staining of hepatic tissues showed characteristic temporal pathological injuries of liver cirrhosis:

1. Early stage at Week 4 after modeling: extensive hepatocellular steatosis and punctate necrosis, a small amount of inflammatory cell infiltration in portal area, slight collagen fiber hyperplasia in portal area shown by Masson staining and mild increase of α-SMA-positive hepatic stellate cells;
2. Middle stage at Week 8 after modeling: massive hepatocellular necrosis and massive inflammatory cell infiltration, fibrous septa extending from portal area into hepatic lobules to form incomplete fibrous septa and massive increase of α-SMA-positive cells;
3. Terminal stage at Week 12 after modeling: complete destruction of hepatic lobule structure, extensive fibrous septa surrounding residual hepatocyte masses to form typical pseudolobules, disordered hepatocyte arrangement, absent or deviated central veins and large-area collagen fiber deposition, which perfectly recapitulates graded pathological injury characteristics of human liver cirrhosis.

Core Hepatic Fibrosis Pathway Indexes

The hepatic TGF-β1/Smad pathway of model group was persistently overactivated with massive expression of downstream α-SMA and type Ⅰ/Ⅲ collagen. Hepatic stellate cells transformed from quiescent state to myofibroblasts, and extracellular matrix synthesis was far greater than degradation. Persistent activation of TLR4/NF-κB inflammatory pathway aggravated fibrosis progression. It accurately conforms to the complete pathogenic mechanism synergistically induced by CCl₄ combined with ethanol: repeated hepatocellular oxidative necrosis-sustained inflammatory activation-hepatic stellate cell activation-TGF-β1/Smad pathway hyperactivity-excessive collagen deposition-pseudolobule formation-liver cirrhosis, serving as core academic criterion for confirming successful modeling.

Model Advantages

This model is a well-recognized exclusive large-animal gold-standard model for CCl₄ combined ethanol-induced liver cirrhosis in hepatology SCI field. 12-week compound intervention stably forms complete liver cirrhosis phenotypes highly homologous to humans including pseudolobule structure, portal hypertension and decompensated liver function. The hepatic metabolic enzyme system, hepatic stellate cell activation mechanism and portal circulation system of Beagle dogs are close to human body, with uniform hepatic fibrosis progression gradient, extremely low intra-group data dispersion and far higher reproducibility than rodents. The modeling mechanism simulates progressive liver cirrhosis induced by repeated chronic toxin/alcohol hepatic injury in clinic, without one-sidedness caused by simple surgery or single toxin induction. It is suitable for preclinical large-animal pharmacodynamic verification of anti-fibrotic drugs, hepatoprotective preparations, portal hypertension intervention, liver regeneration repair and artificial liver support system. Multiple dynamic blood collections can be performed on single animal with sufficient hepatic tissue samples, and synchronous multi-organ sampling can evaluate secondary renal, pulmonary and cerebral injury induced by liver cirrhosis. It has extremely high clinical transformation credibility and high recognition in high-score SCI journals of hepatology, gastroenterology and pathology, suitable for National Natural Science Foundation, master/doctor project opening, graduation thesis of gastroenterology/hepatology and translational medical research on liver cirrhosis prevention and treatment.

Research Applications

The Beagle Cirrhosis Model is corely applied to basic research on CCl₄-induced hepatocellular oxidative necrosis, sustained inflammatory activation, hepatic stellate cell activation and proliferation, TGF-β1/Smad pathway hyperactivity, excessive collagen fiber deposition and portal hypertension with pseudolobule formation. It is specially used for screening and evaluating anti-fibrotic small molecules, natural plant extracts, hepatoprotective Chinese patent medicines, liver-targeted nano-preparations and portal hypertension intervention regimens with effects of alleviating hepatocellular degeneration and necrosis, inhibiting hepatic stellate cell activation, downregulating TGF-β1/Smad pathway, reducing collagen fiber deposition, promoting fibrosis reversal, improving liver function and reducing portal pressure. It is widely adopted for excavation of pathogenic fibrotic targets of liver cirrhosis, elucidation of hepatic stellate cell activation regulatory network, and large-animal preclinical in-vivo verification of anti-cirrhosis drugs and support systems, serving as a scarce and essential standardized large-animal gold-standard model in the fields of hepatology, gastroenteric pharmacology and liver regenerative medicine.

beagle dog liver cirrhosis model，CCl4 induced hepatic fibrosis，pseudolobule formation，hepatic stellate cell activation，anti-fibrotic drug preclinical evaluation