The circumfusion system for multipurposeculture chambers. II. The protracted maintenance of differentiation of fetal and newborn mouse liver in vitro.

The circumfusion system is a complex in vitro pumping unit incorporating 12 multipurpose culture chambers through which a serum-supplemented fluid nutrient is recirculated at a rate of 4.5 ml/min per chamber. This system was used to study the differentiative responses of fetal and newborn mouse liver explants placed in the serum-free environment formed between the sheets of unperforated cellophane and cover glasses of the chambers. Hepatocytes (parenchymal cells) were discernible in 3-5 days. They retained many of their features of differentiation in the circumfusion system for more than 120 days of cultivation. The living morphological characteristics of the hepatocytes were studied by phase-contrast microscopy (direct viewing and time-lapse cinemicrography) and by special cytochemical staining. Electron micrographs were made of both fresh liver specimens and the cultured cells. Comparisons of the cultured parenchymal cells with their in vivo progenitors showed a remarkable preservation of their differentiated state.