Isolation of a morphologically and functionally distinct smooth muscle cell type from the intimal aspect of the normal rat aorta. Evidence for smooth muscle cell heterogeneity

Abstract

Recent studies indicate that the neointima of injured rat arteries is composed of a subpopulation of smooth muscle cells (SMCs) distinct from medial smooth muscle cells. However, SMC diversity in normal adult aorta has remained elusive. This study characterizes two morphologically and functionally distinct SMC types isolated from different anatomic regions of the normal rat aorta. Rat aortic medial smooth muscle cells (MSMCs) were isolated from the media after removal of the intimal and adventitial cells. Rat aortic intimal smooth muscle cells (ISMCs) were isolated from the intimal aspect of everted rat aortas. The two cell types were characterized morphologically and immunohistochemically and were compared for their capacity to contract collagen gels in response to endothelin-1. MSMCs were spindle-shaped and grew in hills and valleys showing features previously described for vascular SMCs. Conversely, ISMCs displayed a polygonal and epitheloid shape, grew mainly as a monolayer, and had a higher proliferative rate. Both cell types expressed alpha-smooth muscle actin and were negative for Factor VIII-RAg. ISMCs produced large amounts of a laminin and type IV collagen-rich extracellular matrix which had a characteristic pericellular distribution. ISMCs, but not MSMCs, rapidly contracted collagen gels in response to endothelin-1. This study indicates that the normal rat aorta contains two types of SMCs located in anatomically distinct regions of the vessel wall. Because of their functional characteristics, the SMCs isolated from the intimal aspect of the aorta may play an important role in physiologic as well as pathologic conditions.

Enhanced H 2 O 2 -Induced Cytotoxicity in “Epithelioid” Smooth Muscle Cells

“…Although the majority of medial SMCs in adult animals can be classified as fusiform, epithelioid SMCs have been derived from the media of blood vessels of several species of animals and maintained in culture through multiple passages. [3][4][5][6][7][8] These cell lines exhibit distinct morphological features, display unique profiles of SMC proteins, and possess characteristic growth patterns. Moreover, epithelioid SMCs may play an important role in neointimal formation.…”

“…3,4 Using this method, we established 5 cell lines from 1 rat aorta, 3 of which appeared to be fusiform and 1 epithelioid, according to the criteria published by Bochaton-Piallat et al 4 The fifth cell line had some features of both fusiform and epithelioid cells. Two of the cell lines, 1 fusiform and 1 epithelioid, have been propagated through 20 passages and have retained their distinct morphological characteristics.…”

“…[3][4][5][6][7][8][9]15 To compare the effects of H 2 O 2 on neointimal versus medial SMCs in situ, the thoracic aorta was removed 15 days after balloon or sham injury. Segments of aorta were incubated with 0 to 300 mol/L H 2 O 2 for 15 hours in culture medium, stained with Hoechst 33342, and then examined by UV microscopy.…”

“…Key Words: smooth muscle cells Ⅲ apoptosis Ⅲ reactive oxygen species Ⅲ hydrogen peroxide Ⅲ neointima R ecent reports by several groups indicate that smooth muscle cells (SMCs) within the arterial wall comprise a variety of distinct phenotypes that possess unique biochemical and functional properties. [1][2][3][4][5][6][7][8] In general, clonally derived SMC lines can be classified as "fusiform" or "epithelioid," corresponding to the appearance and growth pattern of the cells in culture. 2,9 Fusiform SMCs, which are elongated and exhibit the classic "hills-and-valleys" pattern of growth, are predominant in the arterial media of adult animals.…”

“…[1][2][3][4][5][6][7][8] In general, clonally derived SMC lines can be classified as "fusiform" or "epithelioid," corresponding to the appearance and growth pattern of the cells in culture. 2,9 Fusiform SMCs, which are elongated and exhibit the classic "hills-and-valleys" pattern of growth, are predominant in the arterial media of adult animals.…”