Regularities of plaque stabilization in various scenarios of neointimal calcification and vascularization

Aim. To study the relationships between phenotypes of extracranial arteries' plaques (stable/unstable), their calcification and its causes, in particular, vascularization.

Material and methods. The study included 88 patients: patients (n=44) with ischemic stroke and those (n=44) with chronic brain ischemia. In all subjects, the parameters of systemic mineral homeostasis were assessed (total and ionized calcium, phosphate, total protein, albumin, and calcification propensity). Atherosclerotic plaques have been obtained during carotid endarterectomy, fixed in formalin, postfixed in 1% osmium tetroxide, stained in 2% osmium tetroxide, dehydrated in ascending ethanol series and acetone, stained with 2% alcoholic uranyl acetate and embedded into epoxy resin with its further polymerization. Epoxy resin blocks were grinded, polished, counterstained with Reynolds' lead citrate and sputter coated with carbon. Sample visualization was performed employing backscattered scanning electron microscopy. Number and area of calcium deposits and neointimal vessels were quantified using ImageJ. Statistical analysis was carried out using Mann-Whitney U-test and Spearman's rank correlation coefficient.

Results. It was found that area of neointimal calcification, but not number of calcium deposits, was associated with the stable plaque phenotype. The stabilizing effect of calcification was manifested in retarding stenosis associated with plaque rupture and stroke. Calcification extent directly correlated with total and local plaque vascularization, which have been associated with unstable and stable plaque phenotype, respectively. In addition, plaque calcification negatively correlated with total protein and albumin, thereby reflecting the impaired systemic mineral homeostasis.

Conclusion. Atherosclerotic plaque calcification and active local vascularization reduce stenosis extent and stabilize plaque. In contrast, total plaque calcification contributes to the atherosclerosis progression and promotes major acute cardiovascular events.

1. Każmierski P, Pająk M, Kruś-Hadała J, et al Screening test for extracranial carotid lesions' detection in patients of an outpatient vascular clinic. Pol Przegl Chir. 2019;91(5):5-11. doi:10.5604/01.3001.0013.4520.

2. Ragino YuI, Volkov AM, Chernyavskiy AM. Stages of atherosclerotic plaque development and unstable plaque types: pathophysiologic and histologic characteristics. Russian Journal of Cardiology. 2013;18(5):88-95. (In Russ.) doi:10.15829/1560-4071-2013-5-88-95.

3. Nicoll R, Henein M. Arterial calcification: A new perspective? Int J Cardiol. 2017;228:11-22. doi:10.1016/j.ijcard.2016.11.099.

4. Mukhamadiyarov RA, Kutikhin AG. Structure of calcificates in human carotid artery atherosclerotic plaques by means of backscattered scanning electron microscopy. Atherosclerosis. 2020;16(2):5-15. (In Russ.) doi:10.15372/ATER20200201.

5. Mukhamadiyarov RA, Kutikhin AG. Backscattered scanning electron microscopy approach to assess microvessels in health and disease. Bulletin of Experimental Biology and Medicine. 2020;169(4):514-20. (In Russ.)

6. Mukhamadiyarov RA, Kutikhin AG. Histology and histopathology of blood vessels: backscattered scanning electron microscopy approach. Fundamental and Clinical Medicine. 2019;4(1):6-14. (In Russ.) doi:10.23946/2500-0764-2019-4-1-6-14.

7. Galis ZS, Lessner SM. Will the real plaque vasculature please stand up? Why we need to distinguish the vasa plaquorum from the vasa vasorum. Trends Cardiovasc Med. 2009;19(3):87-94. doi:10.1016/j.tcm.2009.06.001.

8. Shioi A, Ikari Y. Plaque Calcification During Atherosclerosis Progression and Regression. J Atheroscler Thromb. 2018;25(4):294-303. doi:10.5551/jat.RV17020.

9. Jinnouchi H, Sato Y, Sakamoto A, et al. Calcium deposition within coronary atherosclerotic lesion: Implications for plaque stability. Atherosclerosis. 2020;14:S0021-9150(20)30291-4. doi:10.1016/j.atherosclerosis.2020.05.017.

10. Otsuka F, Sakakura K, Yahagi K, et al. Has our understanding of calcification in human coronary atherosclerosis progressed? Arterioscler Thromb Vasc Biol. 2014;34(4):724-36. doi:10.1161/ATVBAHA.113.302642.

11. Karlof E, Seime T, Dias N, et al. Correlation of computed tomography with carotid plaque transcriptomes associates calcification with lesion-stabilization. Atherosclerosis. 2019;288:175-85. doi:10.1016/j.atherosclerosis.2019.05.005.

12. Xu C, Yuan C, Stutzman E, et al. Quest for the Vulnerable Atheroma: Carotid Stenosis and Diametric Strain — A Feasibility Study. Ultrasound Med Biol. 2016;42(3):699-716. doi:10.1016/j.ultrasmedbio.2015.11.002.

13. Yahagi K, Kolodgie FD, Lutter C, et al. Pathology of Human Coronary and Carotid Artery Atherosclerosis and Vascular Calcification in Diabetes Mellitus. Arterioscler Thromb Vasc Biol. 2017;37(2):191-204. doi:10.1161/ATVBAHA.116.306256.

14. Akers EJ, Nicholls SJ, Di Bartolo BA. Plaque Calcification: Do Lipoproteins Have a Role? Arterioscler Thromb Vasc Biol. 2019;39(10):1902-10. doi:10.1161/ATVBAHA.119.311574.

15. Bentzon JF, Otsuka F, Virmani R, et al. Mechanisms of plaque formation and rupture. Circ Res. 2014;114(12):1852-66. doi:10.1161/CIRCRESAHA.114.302721.