Ultrastructure and function of hepatic fat-storing and pit cells

Area of Science:

• Hepatology
• Cell Biology
• Immunology

Background:

• The mammalian liver contains specialized sinusoidal cells, including fat-storing cells and pit cells, with distinct ultrastructural features and functions.
• Fat-storing cells are known for vitamin A storage and extracellular matrix synthesis.
• Pit cells, resembling large granular lymphocytes, possess cytotoxic capabilities.

Purpose of the Study:

• To review the literature on the ultrastructure and function of mammalian liver sinusoidal fat-storing cells and pit cells.
• To elucidate the cellular characteristics and biological roles of these key liver cell types.

Main Methods:

• Literature review of ultrastructural and functional studies.
• Analysis of electron microscopy findings for fat-storing cells and pit cells.
• Examination of research on pit cell natural killer activity.

Main Results:

• Fat-storing cells exhibit cytoplasmic fat droplets, developed endoplasmic reticulum, Golgi complex, and synthesize collagens, fibronectin, and proteoglycans.
• Pit cells are characterized by dense granules, rod-cored vesicles, and multivesicular bodies, with organelles concentrated near the nucleus.
• Pit cells demonstrate natural killer activity against tumor cells, suggesting a role in hepatic immune surveillance.

Conclusions:

• Fat-storing cells are crucial for retinol ester storage and the synthesis of liver connective tissue components.
• Pit cells function as intrahepatic immune effector cells, potentially defending against neoplasia, metastasis, and viral infections.
• Understanding these cells' ultrastructure and function is vital for comprehending liver physiology and pathology.