Heterogeneity of microvascular pericytes for smooth muscle type alpha-actin.

Abstract

Abstract. Microvascular pericytes are believed to be involved in various functions such as regulation of capillary blood flow and endothelial proliferation. Since pericytes represent a morphologically heterogeneous cell population ranging from circular smooth musclelike to elongated fibroblast-like morphology it is possible that regulation of blood flow (via contractility) and control of endothelial proliferation (as well as other metabolic functions) may be accomplished by different subsets of pericytes. In the present study we provide evidence for heterogeneity of pericytes at the molecular level by using two novel technical approaches. These are (a) immunostaining of whole mounts of the microvascular beds of the rat mesentery and bovine retina and (b) immunoblotting studies of microdissected retinal microvessels. We show that pericytes of true capillaries (midcapiUaries) apparently lack the smooth muscle isoform of tx-actin whereas transitional pericytes of pre-and postcapillary microvascular segments do express this isoform. Thus, regulation of capillary blood flow may be accomplished by the smooth muscle-related pre-and postcapillary pericytes whereas the nonmuscle pericytes of true capillaries may play a role in other functions.

Pericytes and Endothelial Precursor Cells: Cellular Interactions and Contributions to Malignancy

“…The expression of several cell surface markers characteristic of pericytes in tissues has been confirmed by flow cytometry in pericytes maintained as a primary culture (24)(25)(26)(27)(28). The expression of characteristic cell surface endothelial markers on EPC has been described previously (8); the EPC are CD45 negative but express CD31, VEGFR2, and VE-cadherin.…”

“…The distinction between pericytes and other cells types in the vasculature of tissues is often made through immunohistochemical staining for desmin. Other markers expressed by pericytes include NG2, aSMA, and VCAM (24)(25)(26)(27)(28). The expression of some markers can vary depending upon the tissue in which the pericytes reside.…”

Chapter 12 Structure of Microvascular Networks in Genetic Hypertension

“…For example, SM α-actin can be expressed by pericytes, immature smooth muscle cells, which express SM α-actin and not SM myosin heavy chain, and mature smooth muscle cells, which express both contractile proteins (Nehls and Drenckhahn, 1991;Price et al, 1994;Van Gieson et al, 2003;Yoshida and Owens, 2005). Desmin and PDGF-β can also be expressed by smooth muscle cells and interstitial fibroblasts (Nehls et al, 1992).…”

Low-grade Sarcomas with CD34-Positive Fibroblasts and Low-Grade Myofibroblastic Sarcomas

“…Variable features include micropinocytosis, microfilaments with dense bodies, and junctions. Their immunophenotype varies with location: those around precapillary and postcapillary vessels express smooth muscle actin (SMA), whereas pericytes around capillaries are SMA negative [64]. The latter perivascular cell has been considered to represent a persistent primitive mesenchymal cell that can, according to circumstance and specific location, differentiate into (vascular) smooth muscle cells, glomus cells, preadipocytes, and osteoblasts [65].…”