Print E-mail
Volume 51, Number 2, April 2018

Toll-like receptor 7 agonist induces hypoplasia of the biliary system in a neonatal mouse model 


Ying-Hsien Huang, Hsiang-Hung Shih, Mao-Meng Tiao, Chao-Cheng Huang, Kuang-Che Kuo, Fu-Chen Huang, Ya-Ling Yang, Jiin-Haur Chuang


 

Background and purpose: 

Viral infections and innate immunity signaling, especially Toll-like receptor 7 (TLR7) have been implicated in the pathogenesis of biliary atresia (BA). Administration of rhesus rotavirus-type A to newborn Balb/c mice produces inflammatory obstruction of bile ducts, which resembles human BA. However, whether activation of TLR7 signaling plays a role in neonatal hepatobiliary injury remains to be investigated. 



 

Methods:

TLR7 agonist, imiquimod (R837), was intraperitoneally administered to Balb/c mice within 24 hours of birth and then every other day. Morphological and histological injuries of liver and gallbladder were examined at 2 weeks. Hepatic messenger RNA expression of TLR7 signaling was studied. Terminal deoxynucleotidyl transferase 2′-deoxyuridine 5′-triphosphate nick end labeling staining was used to delineate hepatobiliary apoptosis upon TLR7 stimulation. 



 

Results:

TLR7 agonist, imiquimod, induced hypoplasia of the biliary system of neonatal Balb/c mice both in atrophic gallbladder and in paucity of intrahepatic bile ducts. There was significantly higher hepatic expression of TLR7 and downstream innate immunity-mediated interferon regulatory factor 7, interferon-α, and tumor necrosis factor-α. In addition, terminal deoxynucleotidyl transferase 2′-deoxyuridine 5′-triphosphate nick end labeling-positive cells in the liver were increased after injections of TLR7 agonist. 



 

Conclusion:

The results demonstrate that TLR7 activation may trigger innate immunity pathways and induce apoptosis and hypoplasia of neonatal biliary trees in Balb/c mice. The novel findings give an implication of pathogenesis of infantile cholestasis, such as BA. 



 

Key words:

animal model, Balb/c mice, biliary atresia, infantile cholestasis, innate immunity, toll-like receptor 7