Imaging mass spectrometry reveals heterogeneity of proliferation and metabolism in atherosclerosis
Christelle Guillermier, … , Matthew L. Steinhauser, Jonathan D. Brown
Christelle Guillermier, … , Matthew L. Steinhauser, Jonathan D. Brown
Published June 6, 2019
Citation Information: JCI Insight. 2019;4(11):e128528. https://doi.org/10.1172/jci.insight.128528.
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Technical Advance Vascular biology

Imaging mass spectrometry reveals heterogeneity of proliferation and metabolism in atherosclerosis

Abstract

Atherosclerotic plaques feature local proliferation of leukocytes and vascular smooth muscle cells (VSMCs) and changes in cellular metabolism. Yet the relationship between glucose utilization and proliferation has been technically impossible to study directly in cells of atherosclerotic plaques in vivo. We used multi-isotope imaging mass spectrometry (MIMS), a quantitative imaging platform, to measure coincident cell division and glucose utilization at suborganelle resolution in atherosclerotic plaques. In established plaques, 65% of intimal foam cells and only 4% of medial VSMCs were labeled with 15N-thymidine after 1 week of isotope treatment. Dividing cells demonstrated heightened glucose labeling. MIMS detected 2H-glucose label in multiple subcellular compartments within foam cells, including lipid droplets, the cytosol, and chromatin. Unexpectedly, we identified an intensely focal region of 2H-label in VSMCs underlying plaques. This signal diminished in regions of aorta without atherosclerosis. In advanced plaques, 15N-thymidine and 2H-glucose labeling in foam cells and VSMCs significantly decreased. These data demonstrate marked heterogeneity in VSMC glucose metabolism that was dependent on both proliferative status and proximity of VSMCs to plaques. Furthermore, these results reveal how quantitative mass spectrometry coupled with isotope imaging can complement other methods used to study cell biology directly in the growing atherosclerotic plaque in vivo.

Authors

Christelle Guillermier, Sean P. Doherty, Adam G. Whitney, Vladimir R. Babaev, MacRae F. Linton, Matthew L. Steinhauser, Jonathan D. Brown

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Figure 3

VSMCs underlying plaque are characterized by increased 2H-glucose labeling in the absence of augmented proliferation.

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VSMCs underlying plaque are characterized by increased 2H-glucose labeli...
(A) MIMS mosaic images of plaque demonstrate intense 2H-glucose labeling of VSMCs in the central area underneath the plaque (white arrow). Scale bar: 20 μm. (B) 2H glucose labeling distributions of VSMCs relative to foam cells, demonstrating higher glucose utilization by VSMCs in each mouse analyzed (n = 3 mice). Each dot denotes an individual cell. Bars denote median ± interquartile range. Significance assessed by Mann-Whitney U test. (C) 2H glucose labeling distributions of nucleated VSMCs as a function of whether they divided (15N-thymidine labeled, 15N+) during the labeling period. Data expressed as relative to the undivided (15N–) fraction. VSMCs from n = 3 mice were pooled. Each dot denotes an individual cell. Bars denote median ± interquartile range. Significance was assessed by Mann-Whitney U test. (D) Graph of VSMC 2H-glucose labeling from A as a function of distance from plaque center (denoted by white arrow in A). Each dot denotes an individual cell. Black line, linear regression model. (E) Representative MIMS images of regions of aortic wall without overlying visible plaque but from the same section and adjacent to regions that contained plaque. Scale bar: 10 μm. (F) VSMC 2H-glucose labeling in cells underneath plaque, relative to regions from the same section without visible plaque. Each dot represents mean VSMC labeling for the indicated region from a single mouse. n = 3 mice. Significance was assessed by paired t test.