The extravascular contractile system in the human placenta

Abstract

In the human placenta, besides the fetal blood vessel system a second extravascular contractile system exists. It is localized in the chorionic plate and runs in a longitudinal direction and adjacent to fetal blood vessels into the stem villi, where it forms perivascular contractile sheaths. Characteristically, cells of the extravascular contractile system are extremely long and spindle-shaped and give rise to fine cell processes, by which they obviously contact each other or insert into the basement membrane of the trophoblast. They show immunoreactivity with desmin, vimentin, alpha-actin, myosin, nitric oxide synthase type I (brain form) and dipeptidyl peptidase IV. The ultrastructure suggests that cells of the extravascular contractile system are related to smooth muscle cells, including subpopulations with myofibroblastic features. In stem villi a few cells are nitric oxide synthase type I immunoreactive. These cells are thought to be specialized smooth-muscle-like cells of the extravascular contractile system or cells of the extravascular contractile system related to paraneurons that generate nitric oxide, which, in turn, may modulate the tone of perivascular contractile sheaths. The high dipeptidyl peptidase IV activity suggests that modulation of the extravascular contractile system may also occur by substance P.

α-Tropomyosin mutations Asp175Asn and Glu180Gly affect cardiac function in transgenic rats in different ways

“…In 1922, Naujoks (11) proposed the hypothesis that the human placenta is capable of contraction and Krantz and Arey (11) later demonstrated that these cells in the placenta have all the morphological characteristics of smooth muscle. More recently, Graf et al (5) confirmed the presence of myofibroblasts in stem villi by demonstrating the immunolocalization of vimentin, desmin, ␣-actin, ␥-actin, and myosin in these cells (5). Those investigators also proposed that the change in villus length is an active process (5).…”

Phenotype of cultured fetal perivascular cells from human placenta studied by scanning electron microscopy

“…The exclusion of fibroblasts has been facilited by using chorioplacental vessels instead of intravillous vessels, which are known to present a gradient of differentiation from fibroblast to myofibroblast extending from the trophoblast to the axial vessels. The deepest cells form sheaths surrounding the vessels (Graf et al 1995). The CAM cultured in this study derived from the media of chorioplacental arteries, since the adventitia, which contains fibroblasts, was removed by forceps.…”

Collagen III (Reticulin) – A Location Marker of Pre-Sinusoid Arteriole Sphincters in the Villous System of Human Placenta

“…Graf et al (1994) [5] have described "perivascular contractile sheaths" in the stem villi, also called "extra-vascular contractile system". Ultrastructural studies have suggested the association at this level of smooth muscle cells and subpopulations of microfibroblasts differentited from the perivascular mesenchimal stroma [26,27].…”

“…Initially the cells similar to those in the smooth muscle were defined [1][2][3][4] and later these contractile elements were integrated in the "extra-vascular contractile system'' at the level of stem villi, associated with the extra-cellular matrix of villose stroma [5,6]. The correlations between smooth muscle cells and the elastic fibres with the collagen fibres in a myofibroelastic anatomical-functional unit are well known [6].…”