Abstract 20127: Fluorescence-Activated Cell Sorting Confirms the Majority of Foam Cells in Human Coronary and Aortic Atherosclerosis Are Not Leukocyte-Derived
Introduction: Smooth muscle cells (SMCs) comprise the majority of cells in human arterial intima, but their role in foam cell development and regression has received little attention compared to macrophages. Using immunohistochemical methods we previously reported that foam cells staining strongly for smooth muscle (SM) α-actin comprise at least 50% of all foam cells in human coronary atherosclerosis. This estimate did not include SMCs with a lower level or complete absence of SM α-actin expression. In the current studies we utilized fluorescence-activated cell sorting (FACS) on digested tissues to quantitate the contribution of non-leukocytes and leukocytes to total foam cells in human coronary and aortic atherosclerosis. We also explored further the relative expression of the rate-limiting mediator of cholesterol efflux from foam cells, ATP-binding cassette transporter A1 (ABCA1).
Methods: OCT-fixed human arterial tissues from explanted hearts and abdominal aorta were scraped to remove endothelial cells, cut into small pieces, and subjected to gentle tissue digestion using Roche Liberase™. Isolated cells were stained for SM α-actin, CD45, BODIPY (to stain intracellular lipids), and ABCA1.
Results: Tissue digestion resulted in liberation of intact cells from the artery wall. FACS was used to isolate foam cells (BODIPY+) and separate them into SM α-actin+ or - or into leukocyte- (CD45+) and non-leukocyte-lineage (CD45-) clusters, with no CD45 expression found in cultured or isolated arterial SMCs. In coronary artery 48.7±6.9% of foam cells expressed SM α-actin. 64.9±5.3% were CD45- (mean ± SEM, n=8) (p<0.01 relative to CD45+ foam cells). In abdominal aorta only 21.8±4.9% of foam cells were SM α-actin+. 63.8±5.5% were CD45- (n=11), (p<0.01 relative to CD45+ foam cells). ABCA1 expression was significantly lower in non-leukocyte- compared to leukocyte-derived foam cells in coronary and aortic arteries.
Conclusion: FACS isolation suggests non-leukocytes are the origin of the majority of foam cells in coronary and aortic human atherosclerosis. Studies are underway to confirm the SMC lineage of the non-leukocyte foam cells. Lower expression of ABCA1 provides a potential reason for the larger contribution of this population to foam cell formation.
Author Disclosures: S. Allahverdian: None. Y. Wang: None. V. Ollivier: None. J.A. Dubland: None. J. Michel: None. M.A. Seidman: None. G.A. Francis: None.
- © 2016 by American Heart Association, Inc.