Changes in collagen fiber content and hepatic stellate cell distribution in the liver of chick embryos and growing chickens

The content of collagen and the distribution of hepatic stellate cells (HSCs) were studied to elucidate the occurrence of sex-dependent variations in the liver of developing embryos and growing chickens. Chick embryos from embryonic days (e) 12 to e20 and chicks at 1, 4 and 8weeks were analyzed. Liver tissue was processed using NaOH maceration and freeze-dried to obtain the collagen fiber specimens. HSCs were identified by double fluorescent immunohistochemistry for desmin and vimentin. There were no sex-dependent variations in the percentage of collagen fiber per liver weight and HSC area during embryonic stages. However, the content of collagen fiber increased during embryonic development in both sexes. On the other hand, the area of HSCs significantly increased in growing males but did not show any change in females. Importantly, sex differences were observed in both collagen fiber content and HSC area in the liver at 8weeks. These results indicate that the occurrence of collagen content variations takes place at 8weeks in chicken liver, suggesting that a sex-dependent hormone may play an important role on the collagen production of HSCs in the growing chicken liver.