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(Arteriosclerosis, Thrombosis, and Vascular Biology. 2000;20:52.)
© 2000 American Heart Association, Inc.

Vascular Biology

Retrovirus-Mediated, Stable Scavenger-Receptor Gene Transfer Leads to Functional Endocytotic Receptor Expression, Foam Cell Formation, and Increased Susceptibility to Apoptosis in Rabbit Aortic Smooth Muscle Cells

Pauliina Lehtolainen; Motohiro Takeya; Seppo Ylä-Herttuala

From the A.I. Virtanen Institute (P.L., S.Y.-H.) and the Department of Medicine (S.Y.-H.), University of Kuopio, Kuopio, Finland, and the Kumamoto University School of Medicine (M.T.), Kumamoto, Japan.

Correspondence to Seppo Ylä-Herttuala, MD, PhD, A.I. Virtanen Institute, University of Kuopio, PO Box 1627, Neulaniementie 2, FIN-70211 Kuopio, Finland. E-mail Seppo.Ylaherttuala{at}uku.fi

Abstract—The type II, class A macrophage scavenger receptor (SR-A) plays an important role in the pathogenesis of atherosclerosis and foam cell formation. However, its role in nonmacrophage cell lines remains unknown. To test the hypothesis that SR-A activity leads to proatherogenic changes in nonmacrophage cell lines, we generated Moloney murine leukemia virus– and vesicular stomatitis virus G protein–pseudotyped retroviruses containing SR-A type II cDNA, which were used for stable transfection of SR-A activity into mouse fibroblasts and rabbit aortic smooth muscle cells (SMCs). ß-Galactosidase–transfected cell lines were used as controls. Transfected cell lines expressed functional SR-A mRNA and protein. Expression of SR-A activity was stable for at least 9 months. By electron microscopy, transfected receptors were located in coated pits and in intracellular structures resembling endocytotic vesicles. Expression of SR-A on the cell surface was verified by flow cytometry and by uptake and degradation of ¹²⁵I-labeled acetylated low density lipoprotein (LDL). Increases of 5- to 25-fold and of 6- to 8-fold in the rate of acetylated LDL degradation were observed in transfected fibroblasts and SMCs, respectively, compared with ß-galactosidase–transfected control cell lines. Incubation of the transfected SMCs and fibroblasts with acetylated or oxidized LDL led to foam cell formation. Incubation with oxidized LDL also led to increased apoptosis and cell death. An altered morphology with increased cell size and granularity was observed in the most active SR-A SMC clones. It is concluded that stable overexpression of SR-A leads to foam cell formation and other proatherogenic changes in nonmacrophage cell lines. Stable SMC and fibroblast cell lines can be used as models for foam cell formation. The results also suggest that increased SR activity may play an important role in SMC-related pathology in atherosclerotic arteries.

Key Words: atherogenesis • gene transfer • retrovirus • oxidized LDL

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