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  • 1
    ISSN: 1432-0878
    Keywords: Key words: Elastic fibres ; Placental stem villi ; Extravascular smooth muscle cells ; Adhesion plaques ; Talin immunoreactivity ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. The stroma of human placental stem villi is believed to consist only of reticular and collagen fibres. In the present study we were able to show for the first time by light (orcein staining) and electron microscopy large amounts of elastic fibres in the stem villous stroma. Electron microscopically, homogeneous elastin was found alone or in association with microfibrils. In addition, microfibrils were observed forming long bands. These three structures, generally known to form elastic connective tissue, were seen in close connection with placental extravascular smooth muscle cells, which belong to the perivascular contractile sheath (PVCS) of stem villi. Elastin was associated with these smooth muscle cells and connected to collagen fibres via microfibrils. Collagen fibres were additionally interconnected by spike-like structures. Extravascular smooth muscle cells revealed numerous adhesion plaques which occupied conspicuously long cytoplasmic faces of the plasma membrane. In cryostat sections, immunoreactivity of talin, an attachment protein of adhesion plaques linking intracellular α-actin filaments with extracellular fibronectin, was detected in extravascular and vascular (media) smooth muscle cells. The arrangement of placental extravascular smooth muscle cells, elastic and collagen fibres suggests a functional myofibroelastic unit within the PVCS, which surrounds the large foetal blood vessels possibly contributing to elasticity and supporting tensile and/or contracting forces within the stem villi.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0878
    Keywords: Key words: Placental stem villi ; Perivascular contractile sheath ; Molecules of adhesion plaques ; Extracellular matrix molecules ; Immunocytochemistry ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. In previous studies, we have shown that smooth muscle cells and myofibroblast subpopulations of the perivascular stem villous sheath of the human placenta contain focal adhesion plaques and talin immunoreactivity. The close association of these cells to elastic and collagen fibres have led to the assumption of a functional myofibroelastic unit within the perivascular stem villous sheath. Interactions between the extracellular matrix and smooth muscle cells depend on a variety of structural protein assemblies. In the present study, we examined, by immunocytochemistry, whether the molecular assembly of extracellular matrix proteins and molecules of focal adhesions, known to be essential for signal transduction in smooth muscle cells, are also found in smooth muscle cells of the perivascular stem villous sheath of the human placenta. Vascular and extravascular smooth muscle cells were immunoreactive for α-actinin, vinculin, paxillin and tensin, the integrin chains α1 and β1, and the basement membrane components laminin and heparan/-chondroitin sulfate proteoglycan perlecan. pp125FAK did not react. In the extracellular matrix of blood vessel walls and the perivascular stem villous sheath, we found immunoreactivity of fibronectin and collagen types I, VI and undulin (collagen type XIV). From our data we conclude that within the perivascular stem villous sheath, there exists a system of signal transduction molecules, indicating a cross talk between the smooth muscle cells of this sheath and their surrounding extracellular matrix.
    Type of Medium: Electronic Resource
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