Clonally expanding smooth muscle cells promote atherosclerosis by escaping efferocytosis and activating the complement cascade

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 117; no. 27; pp. 15818 - 15826
• Main Authors: Wang, Ying, Nanda, Vivek, Direnzo, Daniel, Ye, Jianqin, Xiao, Sophia, Kojima, Yoko, Howe, Kathryn L., Jarr, Kai-Uwe, Flores, Alyssa M., Tsantilas, Pavlos, Tsao, Noah, Rao, Abhiram, Newmane, Alexandra A. C., Eberhard, Anne V., Priest, James R., Ruusalepp, Arno, Pasterkamp, Gerard, Maegdefessel, Lars, Miller, Clint L., Lind, Lars, Koplev, Simon, Björkegren, Johan L. M., Owense, Gary K., Ingelsson, Erik, Weissmanr, Irving L., Leeper, Nicholas J.
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 07.07.2020
• Subjects: Anaphylatoxins; Animals; Arteriosclerosis; Atherosclerosis; Atherosclerosis - metabolism; Biological Sciences; Cardiovascular diseases; CD47; CD47 Antigen - metabolism; Cell Lineage; Cell Proliferation; Cholesterol; clonality; Cloning, Molecular; Complement; Complement Activation; Complement C3 - genetics; Complement C3 - metabolism; efferocytosis; Female; Genomic analysis; Humans; Immunosurveillance; Inflammation; Macrophages; Macrophages - metabolism; Male; Medicin och hälsovetenskap; Mice, Knockout, ApoE; Muscles; Myocardial infarction; Myocytes, Smooth Muscle - cytology; Myocytes, Smooth Muscle - metabolism; Opsonization; Pathogenesis; Phagocytes; Phagocytosis - physiology; Plaque, Atherosclerotic - metabolism; Plaques; Sequence Analysis, RNA; Smooth muscle; smooth muscle cells; Up-Regulation; atherosclerosis; smooth muscle cells; clonality; CD47; efferocytosis
• ISSN: 0027-8424; 1091-6490; 1091-6490
• DOI: 10.1073/pnas.2006348117

Atherosclerosis is the process underlying heart attack and stroke. Despite decades of research, its pathogenesis remains unclear. Dogma suggests that atherosclerotic plaques expand primarily via the accumulation of cholesterol and inflammatory cells. However, recent evidence suggests that a substantial portion of the plaque may arise from a subset of “dedifferentiated” vascular smooth muscle cells (SMCs) which proliferate in a clonal fashion. Herein we use multicolor lineage-tracing models to confirm that the mature SMC can give rise to a hyperproliferative cell which appears to promote inflammation via elaboration of complement-dependent anaphylatoxins. Despite being extensively opsonized with prophagocytic complement fragments, we find that this cell also escapes immune surveillance by neighboring macrophages, thereby exacerbating its relative survival advantage. Mechanistic studies indicate this phenomenon results from a generalized opsoninsensing defect acquired by macrophages during polarization. This defect coincides with the noncanonical up-regulation of so-called don’t eat me molecules on inflamed phagocytes, which reduces their capacity for programmed cell removal (PrCR). Knockdown or knockout of the key antiphagocytic molecule CD47 restores the ability of macrophages to sense and clear opsonized targets in vitro, allowing for potent and targeted suppression of clonal SMC expansion in the plaque in vivo. Because integrated clinical and genomic analyses indicate that similar pathways are active in humans with cardiovascular disease, these studies suggest that the clonally expanding SMC may represent a translational target for treating atherosclerosis.