Some new findings about Hofbauer cells in the chorionic villi of the human placenta.

The cytological structure of the Hofbauer cells was investigated in human placentas of the first and second trimesters of gestation. These cells are found in the stromal channel system of the chorionic villi core. Their walls, which are supported by collagen fiber bundles, are produced by reticulum cells and fibroblasts. The cytoplasmic processes of the Hofbauer cells are in contact with the walls of the channels without being associated with them by desmosomal complexes. Some of these cells have features in common with macrophages, such as cytoplasmic processes, larger vacuoles, many pinocytotic vesicles and intracytoplasmic granules. This system of vacuoles and vesicles enables micropinocytotic activity and phagocytosis. This type of Hofbauer cell resembles the typical macrophages. These cells may play a role in the regulation of stromal water content, transportation of ions and the flow of interstitial fluid. The most original finding of this study are long tubes observed in some Hofbauer cells and extending between the nucleus and the extracellular ground substance through the cytoplasm. One of these tubular formations resembles a cilium in structure with three limiting membranes and is filled with a slightly electron-dense substance. This type of Hofbauer cell may transport information between the nucleus and the extracellular ground substance by means of these tubular structures.