Phagocytosis of collagen by mouse decidual cells

Collagen fibrils were present within membrane‐bound vacuoles in the cytoplasm of mouse‐decidual cells on the 7th day of pregnancy. The space between the vacuole membranes and the fibrils was narrow and frequently filled with a granular electron‐dense material. The loss of banding of the collagen fibrils, their association with lysosomelike bodies, and the demonstration of acid phosphatase activity in the vacuoles indicate that the fibrils were internalized by the decidual cells and were being digested. It is suggested that phagocytosis of collagen is a mechanism of remodeling of the mouse decidua.