Conclusions

HSCs that lie in the space between PCs and SECs play pivotal roles in the regulation of homeostasis of vitamin A in the whole body. HSCs in top predators of Arctic animals store vitamin A which is 20-100 times the levels normally found in other animals, including humans. The existence of a gradient of vitamin A-storing capacity in the liver was reported and it is independent on the vitamin A amount in the organ. This gradient was expressed as a symmetrical biphasic distribution starting at the periportal zone, peaking at the middle zone, and sloping down toward the central zone

FIGURE 15. Stellate cells in the pyloric cecum. The pyloric cecum of the arrowtooth halibut (Atheresthes evermanni Jordan et Starks) was observed by Sudan III staining (A), differential interference microscopy (B), and fluorescence microscopy (C) for detecting autofluorescence of vitamin A. Scale bars indicate 100 mm.

FIGURE 15. Stellate cells in the pyloric cecum. The pyloric cecum of the arrowtooth halibut (Atheresthes evermanni Jordan et Starks) was observed by Sudan III staining (A), differential interference microscopy (B), and fluorescence microscopy (C) for detecting autofluorescence of vitamin A. Scale bars indicate 100 mm.

in the liver lobule. In pathological conditions such as liver cirrhosis, their phenotype changes from that of star-shaped SCs to that of fibroblasts or myofibroblasts. The 3D structure of the ECM can reversibly regulate the morphology, proliferation, and functions of the SCs. Molecular mechanisms in the regulation of the SCs by 3D structure of the ECM imply cell surface integrin binding to the matrix components followed by signal transduction processes and cytoskeleton assembly. HSCs play key roles in the regeneration of the liver. The SC system consists of hepatic and extrahepatic SCs and regulates vitamin A homeostasis of the whole body.

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