Liver reconstruction on the chorioallantoic membrane of the chick embryo.

The liver from a 6-day-old chick embryo was transplanted on the chorioallantoic membrane of a 9-day-old chick embryo to observe the process of liver regeneration histologically. When a piece of the liver was implanted on the chorioallantoic membrane, only cells in the superficial zone of the graft adhering to the chorioallantoic membrane survived. Eventually, these surviving cells in the superficial zone proliferated with hematopoiesis, resulting in the formation of clusters of blood cells surrounded by the hepatocytes (or hepatic parenchymal cells). Semi-thin serial sections showed that these clusters of blood cells were confined to the space formed by hepatocytes. Furthermore, structures similar to the hepatic cord, sinusoid, central vein, and bile duct appeared in the reconstructed liver eleven days after transplantation. Meanwhile, when a pellet of the dissociated liver cells was transplanted onto the chorioallantoic membrane, two types of liver like structures were reconstructed: one was clusters of hepatocytes accompanied by sinusoids after hematopoiesis, and the other was a simple accumulation of hepatocytes without any sinusoids or hematopoiesis. The sinusoids found in the former type became clear following the connection between the space in the transplant and vessels of the chorioallantoic membrane. These findings indicated that the reconstructed liver was primarily produced by the accumulation of hepatocytes accompanied by hematopoietic cells, followed by the formation of sinusoidal spaces. We therefore consider that hematopoiesis is important for liver regeneration with a normal structure. Transplantation of the liver in the chorioallantoic membrane could be also useful for research into liver regeneration.