The versatility of microvascular pericytes: from mesenchyme to smooth muscle?

V Nehls, D Drenckhahn - Histochemistry, 1993 - Springer
V Nehls, D Drenckhahn
Histochemistry, 1993Springer
Microvessels basically consist of two cell types: endothelial cells which line the vascular
lumen and smooth muscle cells which are located on the abluminal side of endothelial cells.
Towards the smallest branches of the microcirculation, the capillaries, the smooth muscle
cells gradually become replaced by pericytes (Sims 1986; Diaz-Flores et al. 1991).
Pericytes, like smooth muscle cells, are surrounded by their own basal lamina (Majno 1965;
Bfir and Wolf 1972; Forbes et al. 1976; Cohen et al. 1980; Archer and Gardiner 1981; …
Microvessels basically consist of two cell types: endothelial cells which line the vascular lumen and smooth muscle cells which are located on the abluminal side of endothelial cells. Towards the smallest branches of the microcirculation, the capillaries, the smooth muscle cells gradually become replaced by pericytes (Sims 1986; Diaz-Flores et al. 1991). Pericytes, like smooth muscle cells, are surrounded by their own basal lamina (Majno 1965; Bfir and Wolf 1972; Forbes et al. 1976; Cohen et al. 1980; Archer and Gardiner 1981; Carlson et al. 1988). Within the intercellular space located between the endothelium and the attached pericytes (and their processes) the basal laminae of both cells often fuse to form a common basal lamina (Fig. 1). It is generally accepted that under certain conditions (see below) pericytes are able to leave their basal membrane pockets, thus acquiring characteristics of" extramural" pericytes, which in contrast to" intramural" pericytes, are not surrounded by basal lamina material (Ashton and DeOliveira 1966). Pericytes are found on capillaries of almost all organs, although in some tissues, ie capillaries of the lung microvasculature, they are less conspicuous and thus have been discovered comparatively recently (Weibel 1974). Typical pericytes are absent from venulae rectae of the kidney medulla and from sinusoids of the liver, spleen and bone marrow. It is possible, howeve r, that in the latter three locations pericytes have developed in or been replaced by specialized perivascular cell types, as for example Ito-cells of the liver or parasinusoidal reticular cells of spleen and bone marrow (Fujimoto and Singer 1987). Glomerular mesangial cells of the kidney have also been proposed to be a specialized type of pericytes (Schl6ndorff 1987). Like other midcapillary pericytes mesangial cells in situ lack the smooth muscle isoform of actin (see below), but begin to express this actin isoform when proliferating in situ or in vitro (Drenckhahn et al. 1990; Johnson et al. 1991; Elger et al. 1993).
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