Age influences the replicative activity and the differentiation features of cultured rat aortic smooth muscle cell populations and clones.

Abstract

The replicative activity and the differentiation features of aortic smooth muscle cells (SMCs) cultured as whole populations or clones from newborn (4-day-old), young adult (6-week-old), and old (18-month-old) rats were studied by means of cell counting, [3 H]thymidine incorporation, and measurement of the expression of cytoskeletal proteins and mRNAs. In whole populations at the fifth passage, replicative activity increased and differentiation features (ie, expression of o-smooth muscle actin, desmin, and smooth muscle myosin heavy chains) decreased with increasing age of the donor animal. SMC clones derived from newborn or young adult rats showed more differentiated cytoskeletal features than their parental populations; however, most SMC clones from old rats showed differentiated features similar to those observed in their parental populations. Our results suggest that (1) SMCs of the rat aortic media behave as a heterogeneous population; (2) cultured whole SMC populations behave differently from clones as far as their replicative activity and differentiation features are concerned; and (3) SMCs derived from old rats, whether grown as whole populations or as clones, dedifferentiate more substantially and replicate more actively than corresponding cultures from newborn or young adult rats when submitted to the same amount of serum growth factors; these differences may play a role in arterial development as well as in the formation and evolution of the atheromatous plaque. O ne of the major features of atheromatous plaque development is the increase of the intimal cell population, which is mainly due to medial smooth muscle cell (SMC) migration and proliferation (for review see References 1 to 3). The early observations of Benditt and Benditt 4 suggest that the initial SMC proliferative event must involve a small proportion of the media population, possibly one cell. This may be due to an exogenous or endogenous stimulus affecting a single (or few) cell(s) but may also depend on the fact that SMCs are heterogeneous in their replicative potentiality. It has also been shown that human and experimental atheromatous SMCs show dedifferentiated features, at least as far as their morphology (for review see Reference 5) and cytoskeletal equipment 6 " 9 are concerned, and the above considerations may apply to the acquisition of such features by SMCs. The possible heterogeneity of SMCs has been little explored until now because of the lack of experimental models. A suitable model could be based on the production of SMC clones. Ideally, these clones should be produced from human SMCs; practically, however, clones derived from SMCs of an experimental animal are relatively easy to obtain and may furnish new, useful information on the general biology of arterial SMCs.Received March 30, 1993; revision accepted June 16, 1993. From the Department of Pathology, University of Geneva, Geneva, Switzerland.Correspondence to G. Gabbiani, Department of Pathology, University of Geneva, CMU, 1 Rue Michel Servet, 1211 Geneva 4, Switzerlan...

Mechanisms of Neointima Formation and Remodeling in the Porcine Coronary Artery

“…18,24 In the present study, SMC marker expression was very similar in the populations of neointimal SMCs cultured after either stent or PTCA. Both populations maintained the expression of all markers, including smoothelin, at passage 5, indicating a SMC rather than a fibroblastic origin.…”

Rat aortic smooth muscle cells isolated from different layers and at different times after endothelial denudation show distinct biological features in vitro.

“…47 ' 48 IT-15 cells, however, showed a significantly lower contractile activity than IT-60 and control SMCs. It has recently been shown that a proportion of clones deriving from medial SMCs from old rats show dedifferentiated features, contrary to clones derived from young adult or newborn animals 13 ; this correlates with dedifferentiated features of cultured populations of SMCs from old rats. 13 Further experiments that involve cloning SMCs from intimal thickening or the underlying media at different intervals after endothelial denudation could answer the question as to whether these clones behave similarly to those produced from medial cells of young and old animals.…”

“…It is noteworthy, however, that SMC clones with different properties can be isolated from the rat aorta of normal animals at different ages. 13 Our experiments were performed to verify whether, after endothelial denudation, SMC activation (1) affects, in addition to intimal thickening, cells of the underlying media and (2) persists in intimal cells 60 days after injury, when endothelial continuity has been reestablished. Our results indicate that the replicative and phenotypic properties of cultured IT-15 cells clearly differ from those of the UM (and of course from those of the control media).…”

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

“…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.…”