Ultrastructure of Primary Culture Amnion Cells and Transformed FL Cells in Continuous Culture2

Abstract

Human amnion cells in primary culture and transformed amnion cells (strain FL) in continuous culture differ considerably in morphology when observed in thin sections with the electron microscope. Primary amnion cells are characterized by organized layers of organelles and bands of fine filaments in the cytoplasmic matrix. FL cells of young cultures contain uniform, small free vesicles within multivesicular bodies, hypertrophied Golgi complex, large mitochondria, and abundant ergastoplasm. FL cells of older cultures contain a cytoplasm abundantly filled with small mitochondria, unorganized endoplasmic reticulum, and dispersed Golgi zones. While multivesicular bodies are rare in older cultures, isolated, dense, membrane-limited particles, and concentric-membraned vesicular bodies, of several different morphologic types, are commonly observed in the cytoplasm and at the cell border. The multivesicular bodies could be either cellular reactions related to the malignancy factors of the FL cells or normal cellular components related to rapid growth. The membrane-limited particles of the older FL cultures are most logically assumed to be related to the transformation of normal human amnion cells into malignant cells.