Immunological Analysis of Human Atherosclerotic Plaques in ex vivo Culture System

Abstract

to analyze the dynamics of lymphocytic composition of human atherosclerotic plaques in ex vivo culture system. The study included 15 atherosclerotic plaques obtained from patients who underwent carotid endarterectomy. Plaques were cultured as ring-shaped explants on collagen rafts in culture medium of special composition in CO2 incubator according to the previously developed technique. On day 0, and also on the 4th and 19th days of culture we extracted cells from plaque explants and analyzed B- and T-lymphocytic content of the tissue, as well as the percentage of CD16+ natural killer (NK) cells, using multichromatic flow cytometry. For this purpose we digested the explants with an original enzymatic cocktail, which allows preservation of cell surface markers, and we stained extracted cells with fluorescence-labelled monoclonal antibodies against CD45, CD3, CD19, CD4, CD8, CD16. In addition, we estimated the amount of interleukin 2 (IL-2) and interferon-gamma (IFN-)-producing T-cells by means of flow cytometry. After 4 days of culture the amount of lymphocytes in plaques explants decreased, however live lymphocytes were still preserved (2619.3 [1680.4, 3478.2] cells/100mg tissue). Viable lymphocytes population included T cells (2123.4 [484.9; 3181.2] cells/100 mg tissue), B cells (5.6 [3.4, 27.9] cell/100 mg tissue) and CD16+ NK cells (10.6 [1.8, 23.7] cell/100mg tissue). On the 4th day of culture T cells were presented by CD4+CD8- (797 [475.5, 1000.7] cells/100mg tissue, 37.5 [32.1; 46.3]%) and CD4-CD8+ (686.2 [423.6; 1158.4] cells/100 mg tissue, 45.6 [38.1; 47.9]%) populations. The percentage of CD4+CD8- T cell population decreased compared to the 1st day of culture, and this decrease correlated with the increase in CD4-CD8- T cells content (p<0.05). Additionally, after 4 days of culture we found in tissue explants both CD8+ (17.5[13.3;19.9]%) and CD8- (9.9 [6.4; 14]%) IFN--producing T-cells, however, their percentage, as well as the percentage of IL-2-producing T cells tended to decrease. After 19 days of culture explants of atherosclerotic plaques also contained lymphocytes (2830.1 [2350.3, 5900.2] cells/100mg tissue). Lymphocytes population included T cells (2594.5 [2035.7, 5306.7] cells/100mg tissue), presented by CD4+CD8- (1016.8 [671.2, 2201.7] cells/100mg tissue, 42.3 [34.3; 47.8]%) and CD4-CD8+ (1534.3 [813.8; 2207.2] cells/100mg tissue, 50.8 [45.6; 56.5]%) subsets, B cells (31 [18.3; 64.4] cell/100 mg tissue) and CD16+ NK cells (44.9 [33.4; 138.9] cells/100 mg of tissue). An ex vivo model of human atherosclerotic plaque culture that we previously developed enables to preserve viability of various lymphocyte subsets for up to 19 days. We also found that cultured tissue explants retain T cells that can maintain T-helper-1-dependent immune response, which demonstrates inflammation in atherosclerotic plaques. Our results allow to perform experiments on immunological mechanisms of atherogenesis and to develop new approaches for treatment of atherosclerosis, devoted to the suppression of local inflammatory processes in atherosclerotic plaques. An ex vivo model of human atherosclerotic plaque preserves CD4+CD8- and CD4-CD8+ T cells, B cells, and CD16+ NK cells for a long time. Moreover, after 4 days of culture tissue explants also retain IFN-++ T cells.