Microvessel precursor smooth muscle cells express head-inserted smooth muscle myosin heavy chain (SM-B) isoform in hyperoxic |
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Authors: | R Jones Wolfgang Steudel Sheryl White Margaretha Jacobson Robert Low |
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Institution: | (1) Department of Anesthesia and Critical Care, Molecular and Cell Biology Laboratory, Massachusetts General Hospital East, Harvard Medical School, 149 East 13th Street, Charlestown, MA 02129, USA Tel.: +1 617 726 4178; Fax: +1 617 726 4176, US;(2) Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, Vermont, USA, US |
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Abstract: | The present study analyzes smooth muscle myosin heavy chain (SMMHC) expression as lung microvascular precursor smooth muscle
cells (PSMCs), cells derived from fibroblasts and intermediate cells (immature SMCs), acquire a smooth muscle phenotype in
anin vivo model of pulmonary hypertension (PH). Because of the unique contractile properties of the SMMHC isoform SM-B, we
analyzed its expression in the microvessels (<100 μm diameter) and in larger vessels (100–700 μm) quantitatualy by the labeled
strept]avidin-biotin technique (day 1–28), and related this to cell phenotype by transmission microscopy and protein A-gold
labeling (at day 28). Airway SMCs of the normal and hypertensive lung uniformly expressed SM-B whereas vascular SMC expression
was heterogeneous. Thus, in some large arteries (and veins) SMCs contained cells expressing SM-B while in others all the cells
were immunonegative. Microvascular cells expressing SM-B (arteries and veins) were rare in normal lung and numerous in PH,
increasing as wall muscle developed in smaller segments with time. As in large vessels, some microvessels had immunopositive
cells and others only negative ones. Ultrastructural analysis confirmed that the SMCs of bronchial vessels, and the septal
SMCs adjoining alveolar ducts, contained dense filament arrays decorated with SM-B. While the PSMC processes of the normal
lung contained sparse filaments decorated with SM-B, these cells expressed dense filament arrays in PH. Fibroblasts migrating
to align around the microvessels also expressed SM-B but in the absence of a filament network. For the first time,we demonstrate
in vivo that newly developed microvascular PSMCs express the SMMHC SM-B isoform in PH.
Received: 9 April 1998 / Accepted: 9 September 1998 |
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Keywords: | Rat lung Fibroblasts and microvessels Smooth muscle cell differentiation |
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