Transdifferentiation of mouse aortic smooth muscle cells to a macrophage-like state after cholesterol loading.
Mouse aortic smooth muscle cells (SMCs) were loaded for 72 h with cholesterol by using cholesterol:methyl-beta-cyclodextrin complexes, leading to approximately 2-fold and approximately 10-fold increases in the contents of total cholesterol and cholesteryl ester, respectively. Foam-cell formation was demonstrated by accumulation of intracellular, Oil Red O-stained lipid droplets. Immunostaining showed decreased protein levels of smooth muscle alpha-actin and alpha-tropomyosin and increased levels of macrophage markers CD68 and Mac-2 antigen. Quantitative real-time RT-PCR revealed that after cholesterol loading, the expression of SMC-related genes alpha-actin, alpha-tropomyosin, myosin heavy chain, and calponin H1 decreased (to 11.5 +/- 0.5%, 29.3 +/- 1.4%, 23.8 +/- 1.4%, and 3.8 +/- 0.5% of unloaded cells, respectively; P < 0.05 for all), whereas expression of macrophage-related genes CD68, Mac-2, and ABCA1 mRNA increased (to 709 +/- 84%, 330 +/- 11%, and 207 +/- 13% of unloaded cells, respectively; P < 0.05 for all), thereby demonstrating that the protein changes were regulated at the mRNA level. Furthermore, these changes were accompanied by a gain in macrophage-like function as assessed by phagocytotic activity. Expression of vascular cell adhesion molecule 1 and monocyte chemoattractant protein 1, known responders to inflammation, were not changed. In conclusion, cholesterol loading of SMC causes phenotypic changes regulated at the mRNA level that result in a transdifferentiation to a macrophage-like state. This finding suggests that not all foam cells in lesions may have a macrophage origin, despite what is indicated by immunostaining for macrophage-related markers. Furthermore, inflammatory changes in foam cells observed in vivo may not be simple consequences of cholesterol accumulation.
Rong
James X
JX
Department of Medicine and The Zena and Michael A. Wiener Cardiovascular Institute, Mount Sinai School of Medicine, New York, NY 10029, USA.
Shapiro
Mark
M
Trogan
Eugene
E
Fisher
Edward A
EA
D000199:Actins / Q000378:metabolism; D000818:Animals; D015703:Antigens, CD / Q000096:biosynthesis; D015214:Antigens, Differentiation, Myelomonocytic / Q000096:biosynthesis; D001011:Aorta / Q000378:metabolism*; D001391:Azo Compounds / Q000494:pharmacology; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism*; D002788:Cholesterol Esters / Q000378:metabolism; D004396:Coloring Agents / Q000494:pharmacology; D003505:Cyclodextrins / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005487:Foam Cells; D037502:Galectin 3 / Q000096:biosynthesis; D007150:Immunohistochemistry; D008264:Macrophages / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D032389:Myocytes, Smooth Muscle / Q000166:cytology*; D041681:NIH 3T3 Cells; D010586:Phagocytes / Q000378:metabolism; D010587:Phagocytosis; D010641:Phenotype; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D014335:Tropomyosin / Q000378:metabolism; D019010:Vascular Cell Adhesion Molecule-1 / Q000378:metabolism; D000097382:CD68 Molecule
D000199:Actins; D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; D001391:Azo Compounds; D002784:Cholesterol; D002788:Cholesterol Esters; D004396:Coloring Agents; D003505:Cyclodextrins; D037502:Galectin 3; D012333:RNA, Messenger; D014335:Tropomyosin; D019010:Vascular Cell Adhesion Molecule-1; C067980:CD68 antigen, human; D000097382:CD68 Molecule; C011049:oil red O