Fibrosis Disease Models
CCl4 Induced Liver Fibrosis
Carbon tetrachloride (CCl4) has been widely used to experimentally induce liver injury in rodents as a model for the human chronic liver injury process.
CCl4 is a chemical inducer of acute inflammation. A single dose of CCl4 leads to centrizonal necrosis and steatosis, while prolonged administration leads to liver fibrosis, cirrhosis, and HCC.
Following 4 weeks of CCl4 or vehicle model induction dosing, mice are enrolled into the efficacy study based on body weight & clinical signs, so that mean body weights/clinical signs are approximately equivalent across all treatment groups
CCl4 or vehicle dosing continues during the efficacy phase, PO BIW
Dosing for the efficacy study as listed in Table 1 begins on Day 0, and continues for 4 weeks
Body weights & clinical signs are collected 2x/week during the dosing period
Following 4 weeks of dosing, mice are euthanized and samples collected
Bile Duct Ligation Induced Liver Fibrosis
The liver produces bile that is necessary to emulsify absorbed fats and enable the digestion of lipids in the small intestine as well as to excrete bilirubin and other metabolic products.
In the liver, the experimental obstruction of the extrahepatic biliary system initiates a complex cascade of pathological events that leads to cholestasis and inflammation resulting in a strong fibrotic reaction originating from the periportal fields.
Surgical ligation of the common bile duct has become the most commonly used model to induce obstructive cholestatic injury in mice and rats and to study the molecular and cellular events that underlie these pathophysiological mechanisms induced by inappropriate bile flow.
The most frequently used model is the complete obstruction of the common bile duct that induces a strong fibrotic response after 21 to 28 days.
Twice common bile duct ligation (1 cm distal to duodenum to avoid parabiliary pancreatic ductuli) is performed with 5/0 silk suture and common bile duct resection between the ligatures.
Approximately 3 weeks following the BDL or sham surgery, mice are enrolled into efficacy treatment groups
Diet Induced NAFLD/NASH
A variety of dietary models for induction of NASH in rodents have been characterized. The Methionine and Choline Deficiency (MCD) diet contains high sucrose and fat but lacks methionine and choline, which are essential for hepatic β-oxidation and production of VLDL. In addition, choline deficiency impairs hepatic VLDL secretion.
As a result, lipid is deposited in the liver. Furthermore, oxidative stress and changes in cytokines and adipocytokines occur, contributing to the liver injury. Antagonizing oxidative stress by increasing antioxidant capacities attenuates the degree of steatohepatitis and stresses the importance of reactive oxygen species in this model.
Serum alanine aminotransferase (ALT) level is consistently increased after MCD-diet feeding in mice. When fed to genetically altered mouse models of obesity and diabetes, the histopathology and pathophysiology of MCD diet model more closely resembles those of human NAFLD.
UUO Induced Renal Fibrosis
Renal fibrosis is the common pathway for most forms of progressive renal disease. The Unilateral Ureteral Obstruction (UUO) model is used to cause renal fibrosis, where the primary feature of UUO is tubular injury as a result of obstructed urine flow.
The UUO-obstructed kidney (UUO-OK) is characterized by tubular dilation, interstitial expansion, loss of proximal tubular mass, hypertrophy, hydronephrosis, infiltration of leukocytes, tubular epithelial cell death and presence of fibroblasts.
These alterations are a result of molecular processes such as hemodynamic change by mechanical stretching, epithelial tubular cell apoptosis, oxidative stress and inflammation; which altogether lead to progressive renal tubulointerstitial fibrosis.
Bleomycin Induced Lung Fibrosis
Idiopathic pulmonary fibrosis (IPF) is a chronic interstitial lung disease with high lethality, a fatal prognosis, and a lack of effective medical therapies. The pathological characteristics of IPF mainly include the disruption of the pulmonary parenchymal matrix and replacement with fibrotic tissues.
The bleomycin-induced model of pulmonary fibrosis is induced by either intratracheal, iv or ip administration of bleomycin.
For studies designed to assess pulmonary inflammation, a 14 day observation period is typical. Treatment with the test agent would usually begin 24hrs prior to challenge and continue for the 14 day study period.
For the assessment of antifibrotic agents, the experimental period would be extended for up to 50 days, although 21 days is most commonly used. Treatment with the test agent could begin prior to challenge or at any time following administration of bleomycin.