Some New Findings about Hofbauer Cells in the Chorionic Villi of the Human Placenta

Abstract

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.

Vascular biology in implantation and placentation

“…Since at that stage no infiltration of fetal vessels and blood into the placenta has taken place, the progenitor cells are directly derived from placental mesenchymal cells [11] rather than originating from fetal blood cells. Only slightly later placental macrophages (Hofbauer cells) appear inside the villous core in direct vicinity to the vasculogenic precursor cells indicating a putative paracrine role for these cells during the early stages of placental vasculogenesis [12]. The expression patterns of angiogenic growth factors have been described mostly for later stages of pregnancy, including acidic and basic fibroblast growth factor (aFGF, bFGF) [13,14], VEGF [15--17], and placental growth factor (PlGF) [18--20].…”

Hofbauer cells morphology and density in placentas from normal and pathological gestations

“…Early studies had already found that the most striking aspects of HBCs are their highly vacuolated appearance and their granulated cytoplasm 2 . Later investigations have pointed out that HBCs are characterized by numerous membrane-bound, electron-lucent vacuoles of different sizes, possessing amorphous material of varying density, dense granules (presumably lysosomes), and short profiles of endoplasmic reticulum 1,[3][4][5][6][7] .…”

“…It has been supported that in placentas from uncomplicated pregnancies, HBCs either disappear or become scanty after the fourth to fifth month of gestation. On the other hand, in cases of pathological placentas due to intrauterine growth restriction (IUGR) or gestational diabetes mellitus their density seems to be increased 4,6,9 . However, electron microscopy studies and immunohistochemistry demonstrated their presence throughout normal uncomplicated pregnancy as well, until term, and not only in immature villi of the center of the placentone.…”

Expression of VEGF receptors VEFGR-1 and VEGFR-2, angiopoietin receptors Tie-1 and Tie-2 in chorionic villi tree during early pregnancy.

“…Moreover, the early appearance of macrophages (Hofbauer cells) in the villous core which have been affected the villous vascularisation (Demir and Erbengi, 1984) and described to regulate distinct trophoblast functions (Cervar et al, 1999) and to express angiogenic growth factors (VEGF) (Demir et al, 2004), suggests a paracrine role for these cells during the first stages of vasculogenesis (Demir et al, 1997;Seval et al, 2007).…”