Project description:The goal of these studies was to delineate mechanisms of crosstalk between the atherosclerotic arterial wall of the aorta and the peripheral nervous system (PNS) in aged hyperlipidemic ApoE-deficient mice. We had observed by immunohistochemistry and morphometry that axon density of the PNS in adventitia segments that were located adjacent to advanced atherosclerotic plaques of aged hyperlipidemic ApoE-deficient mice were markedly higher than those adventitia segments that did not show adjacent atherosclerotic plaques in the intima layer. It is noteworthy in this connection that neither the media nor the intimal layer are innervated by axon endings. However, the adventitia layer of arteries is a conduit for axons and nerves of the PNS connecting the peripheral ganglia and peripheral organs including the spleen. In addition, we discovered (see references below) that atherosclerosis is sensed by the immune system of aged ApoE-deficient mice resulting in the formation of artery tertiary lymphoid organs in the adventitia layer of the arterial wall. To examine potential molecular mechanisms of the crosstalk between the disease aorta and the PNS, we isolated adventitia tissues and media tissues from aortas of ApoE-deficient mice and used wild-type mice as controls. Moreover, we observed that the sympathetic nervous system paraaortic and periaortic ganglia in aged ApoE-deficient but not of aged wild-type mice were infiltrated by leukocytes indicating that atherosclerosis is associated with major alterations of the PNS including axonogenesis and ganglionitis. To identify potential molecules involved in the crosstalk, we isolated respective tissues (media, adventitia, ganglia) by laser capture microdissection and generated large scale mRNA expression arrays to construct transcript maps that were assembled into transcript atlases. Publications related to this approach: Artery Tertiary Lymphoid Organs Control Aorta Immunity and Protect against Atherosclerosis via Vascular Smooth Muscle Cell Lymphotoxin β Receptors. Hu D, Mohanta SK, Yin C, Peng L, Ma Z, Srikakulapu P, Grassia G, MacRitchie N, Dever G, Gordon P, Burton FL, Ialenti A, Sabir SR, McInnes IB, Brewer JM, Garside P, Weber C, Lehmann T, Teupser D, Habenicht L, Beer M, Grabner R, Maffia P, Weih F, Habenicht AJ. Immunity. 2015 Jun 16;42(6):1100-15. doi: 10.1016/j.immuni.2015.05.015. Artery tertiary lymphoid organs contribute to innate and adaptive immune responses in advanced mouse atherosclerosis. Mohanta SK, Yin C, Peng L, Srikakulapu P, Bontha V, Hu D, Weih F, Weber C, Gerdes N, Habenicht AJ. Circ Res. 2014 May 23;114(11):1772-87. doi: 10.1161/CIRCRESAHA.114.301137. Review. Control of dichotomic innate and adaptive immune responses by artery tertiary lymphoid organs in atherosclerosis. Weih F, Gräbner R, Hu D, Beer M, Habenicht AJ. Front Physiol. 2012 Jul 6;3:226. doi: 10.3389/fphys.2012.00226. Laser-capture microdissection of hyperlipidemic/ApoE⁻/⁻ mouse aorta atherosclerosis. Beer M, Doepping S, Hildner M, Weber G, Grabner R, Hu D, Mohanta SK, Srikakulapu P, Weih F, Habenicht AJ. Methods Mol Biol. 2011;755:417-28. doi: 10.1007/978-1-61779-163-5_35.

Project description:Tertiary lymphoid organs (TLOs) emerge in response to nonresolving inflammation but their roles in adaptive immunity remain unknown. Here, we explored artery TLOs (ATLOs) to delineate atherosclerosis T cell responses in apoe-/- mice during aging. Though the T cell repertoire showed systemic age-associated contractions in size and modifications in subtype composition and activation, wt and apoe-/- mice were equally affected. In contrast, ATLOs - but not wt aortae, apoe-/- aorta segments without ATLOs or atherosclerotic plaques - promoted T cell recruitment, altered characteristics of T cell motility, primed and imprinted T cells in situ, generated CD4+/FoxP3-, CD4+/FoxP3+, CD8+/FoxP3- effector and central memory cells, and converted naïve CD4+/FoxP3- T cells into induced Treg cells. ATLOs also showed substantially increased antigen presentation capability by conventional dendritic cells (DCs) and monocyte-derived DCs but not by plasmacytoid DCs. Thus, the senescent immune system specifically employs ATLOs to control dichotomic atherosclerosis T cell immune responses. We assembled transcriptome maps of wt and apoe-/- aortae and aorta-draining RLNs and identified ATLOs as major sites of atherosclerosis-specific T cell responses during aging: Transcriptome atlases of wt and apoe-/- abdominal aortae and associated draining RLNs were constructed from laser capture microdissection (LCM)-based whole genome mRNA expression microarrays yielding 6 maps: wt adventitia (tissue-1); wt RLN (tissue-2); apoe-/- ATLOs (tissue-3); apoe-/- RLN (tissue-4); apoe-/- adventitia without adjacent plaques (tissue-5), and plaques (tissue-6). Several two-tissue comparisons within the transcriptome atlases are noteworthy: Unexpectedly, transcriptomes of wt and apoe-/- RLNs were virtually identical; additonal data revealed that transcriptomes of RLNs were strikingly similar to those of inguinal LNs which do not drain the aorta adventitia (as shown of India ink injection experiments of surgically exposed aortae); in sharp contrast, wt adventitia versus ATLOs revealed 1405 differentially expressed transcripts many of which encoded members of GO terms immune response and inflammatory response; the ATLO-plaque comparison also showed > 1000 differentially expressed transcripts; however, wt adventitia versus apoe-/- adventitia without plaque showed few genes (< 5 % of differentially expressed transcripts of the wt adventitia-ATLO comparison). Thus, the aorta transcriptome atlases support the conclusion that neither aorta-draining apoe-/- RLNs nor ILNs participate in atherosclerosis-specific T cell responses. In addition, they demonstrate that T cell responses in the diseased aorta are highly territorialized. Finally, these data show that the immune responses carried out in ATLOs differ significantly from those carried out in plaques. We next identified three major clusters within the transcriptome atlases through ANOVA analyses and application of strict filters: An adventitia cluster, a plaque/ATLO cluster, and a LN/plaque cluster. The total number of differentially expressed genes in each cluster were examined for GO terms immune response, inflammatory response, T cell activation, positive regulation of T cell response, and T cell proliferation. Within the adventitia cluster, similarities of transcriptomes of wt adventitia and apoe-/- adventitia without associated plaque versus ATLOs indicate that a robust number of immune response-regulating genes are selectively expressed in ATLOs which are located within a distance of few µm of the adventitia without associated plaques indicating a very high degree of territoriality of the atherosclerosis T cell response. Furthermore, unlike the total number of differentially regulated transcripts, the majority of transcripts among GO terms immune response and inflammatory response, was up-regulated. Inspection of the plaque/ATLO cluster provided further information: The majority of immune response regulating genes where expressed at a higher level in ATLOs when compared to plaques though plaques also contained a significant number of immune response regulating genes; the reverse is true for genes regulating inflammation. Finally, the lymph node cluster revealed that though the majority of immune response regulating genes resides in both wt and apoe-/- RLNs (with little differences between them) ATLOs express a selected set of immune response regulating genes at a higher level when compared to LNs. In addition, the inflammatory component of ATLOs when compared to LNs is documented by the finding that many more genes regulating inflammation reside in ATLOs even when compared to those of plaques. Key words: T cell response in atherosclerosis; Laser capture microdissection; transcriptome atlas of atherosclerosis. Citations: Gräbner R. et al. Lymphotoxin beta receptor signaling promotes tertiary lymphoid organogenesis in the aorta adventitia of aged ApoE-/- mice. J Exp Med 2009 Jan 16;206(1):233-48. PMID: 19139167; Moos M. et al. The lamina adventitia is the major site of immune cell accumulation in standard chow-fed apolipoprotein E-deficient mice. Arterioscler Thromb Vasc Biol. 2005 Nov;25(11):2386-91. Epub 2005 Sep 22. PMID: 16179593; Beer M. et al. Laser-capture microdissection of hyperlipidemic/ApoE-/- mouse aorta atherosclerosis. Methods Mol Biol. 2011;755:417-28. PMID: 21761324; Weih F. et al. Control of Dichotomic Innate and Adaptive Immune Responses by Artery Tertiary Lymphoid Organs in Atherosclerosis. Front Physiol. 2012;3:226. Epub 2012 Jul 6. PMID: 22783198. Wild-type and apoE-deficient mice on the C57BL/6J genetic background were maintained on a standard mouse chow. Total aortae were removed at the age of 6 (n=3), 32 (n=3), or 78 (n=3) w and microarrays were prepared from total RNA extracts or extracts of atherosclerotic lesions and adventitiae obtained by the use of a laser dissection microscope. In addition, aorta associated LNs or distant LNs were prepared from both mouse genotypes.

Project description:Tertiary lymphoid organs (TLOs) emerge in response to nonresolving inflammation but their roles in adaptive immunity remain unknown. Here, we explored artery TLOs (ATLOs) to delineate atherosclerosis T cell responses in apoe-/- mice during aging. Though the T cell repertoire showed systemic age-associated contractions in size and modifications in subtype composition and activation, wt and apoe-/- mice were equally affected. In contrast, ATLOs - but not wt aortae, apoe-/- aorta segments without ATLOs or atherosclerotic plaques - promoted T cell recruitment, altered characteristics of T cell motility, primed and imprinted T cells in situ, generated CD4+/FoxP3-, CD4+/FoxP3+, CD8+/FoxP3- effector and central memory cells, and converted naïve CD4+/FoxP3- T cells into induced Treg cells. ATLOs also showed substantially increased antigen presentation capability by conventional dendritic cells (DCs) and monocyte-derived DCs but not by plasmacytoid DCs. Thus, the senescent immune system specifically employs ATLOs to control dichotomic atherosclerosis T cell immune responses. We assembled transcriptome maps of wt and apoe-/- aortae and aorta-draining RLNs and identified ATLOs as major sites of atherosclerosis-specific T cell responses during aging: Transcriptome atlases of wt and apoe-/- abdominal aortae and associated draining RLNs were constructed from laser capture microdissection (LCM)-based whole genome mRNA expression microarrays yielding 6 maps: wt adventitia (tissue-1); wt RLN (tissue-2); apoe-/- ATLOs (tissue-3); apoe-/- RLN (tissue-4); apoe-/- adventitia without adjacent plaques (tissue-5), and plaques (tissue-6). Several two-tissue comparisons within the transcriptome atlases are noteworthy: Unexpectedly, transcriptomes of wt and apoe-/- RLNs were virtually identical; additonal data revealed that transcriptomes of RLNs were strikingly similar to those of inguinal LNs which do not drain the aorta adventitia (as shown of India ink injection experiments of surgically exposed aortae); in sharp contrast, wt adventitia versus ATLOs revealed 1405 differentially expressed transcripts many of which encoded members of GO terms immune response and inflammatory response; the ATLO-plaque comparison also showed > 1000 differentially expressed transcripts; however, wt adventitia versus apoe-/- adventitia without plaque showed few genes (< 5 % of differentially expressed transcripts of the wt adventitia-ATLO comparison). Thus, the aorta transcriptome atlases support the conclusion that neither aorta-draining apoe-/- RLNs nor ILNs participate in atherosclerosis-specific T cell responses. In addition, they demonstrate that T cell responses in the diseased aorta are highly territorialized. Finally, these data show that the immune responses carried out in ATLOs differ significantly from those carried out in plaques. We next identified three major clusters within the transcriptome atlases through ANOVA analyses and application of strict filters: An adventitia cluster, a plaque/ATLO cluster, and a LN/plaque cluster. The total number of differentially expressed genes in each cluster were examined for GO terms immune response, inflammatory response, T cell activation, positive regulation of T cell response, and T cell proliferation. Within the adventitia cluster, similarities of transcriptomes of wt adventitia and apoe-/- adventitia without associated plaque versus ATLOs indicate that a robust number of immune response-regulating genes are selectively expressed in ATLOs which are located within a distance of few µm of the adventitia without associated plaques indicating a very high degree of territoriality of the atherosclerosis T cell response. Furthermore, unlike the total number of differentially regulated transcripts, the majority of transcripts among GO terms immune response and inflammatory response, was up-regulated. Inspection of the plaque/ATLO cluster provided further information: The majority of immune response regulating genes where expressed at a higher level in ATLOs when compared to plaques though plaques also contained a significant number of immune response regulating genes; the reverse is true for genes regulating inflammation. Finally, the lymph node cluster revealed that though the majority of immune response regulating genes resides in both wt and apoe-/- RLNs (with little differences between them) ATLOs express a selected set of immune response regulating genes at a higher level when compared to LNs. In addition, the inflammatory component of ATLOs when compared to LNs is documented by the finding that many more genes regulating inflammation reside in ATLOs even when compared to those of plaques. Key words: T cell response in atherosclerosis; Laser capture microdissection; transcriptome atlas of atherosclerosis. Citations: Gräbner R. et al. Lymphotoxin beta receptor signaling promotes tertiary lymphoid organogenesis in the aorta adventitia of aged ApoE-/- mice. J Exp Med 2009 Jan 16;206(1):233-48. PMID: 19139167; Moos M. et al. The lamina adventitia is the major site of immune cell accumulation in standard chow-fed apolipoprotein E-deficient mice. Arterioscler Thromb Vasc Biol. 2005 Nov;25(11):2386-91. Epub 2005 Sep 22. PMID: 16179593; Beer M. et al. Laser-capture microdissection of hyperlipidemic/ApoE-/- mouse aorta atherosclerosis. Methods Mol Biol. 2011;755:417-28. PMID: 21761324; Weih F. et al. Control of Dichotomic Innate and Adaptive Immune Responses by Artery Tertiary Lymphoid Organs in Atherosclerosis. Front Physiol. 2012;3:226. Epub 2012 Jul 6. PMID: 22783198.

Project description:We previously observed that formation of aorta and innominate artery atherosclerotic lesions in the intima of hyperlipidemic apoE-deficient mice but not wild-type mice was accompanied by a marked age-dependent adventitial T cell infiltration. As the mice aged, adventitial T cells formed T/T cell-, T/B cell-, and T/B/dendritic cell aggregates adjacent to atherosclerotic lesions. Some of the adventitial infiltrates formed large clusters of various immune cells including T cells, B cells (centrocytes, follicular mantle cells), dendritic cells, follicular dendritic cells, and plasma cells with preferential formation in the suprarenal portion of the abdominal aorta. These data demonstrated that the immune lineage cell composition of atherosclerotic lesions and adventitia were distinct: The macrophage-foam cell-, T cell-, and SMC-dominated cell composition of atherosclerosis lesions versus the presence of immune cells capable of carrying out antigen-dependent T cell-driven humoral immune responses in the adventitia also indicated that immune reactions carried out in lesions or the adventitia are fundamentaly different. To distinguish between immunity-regulating genes in atherosclerosis lesions versus the adventitia, a combination of microarray profiling and laser capture microdissection was used. Stringent filters revealed 1163 differentially up-regulated probesets in apoE-/- mouse aortae at 78 weeks (w) versus 6 w. A fuzzy c-means cluster algorythm identified 2 clusters that significantly differed in their slope angles between time points: An apparent atherosclerosis cluster consisted of 771 probesets and an apparent adventitia cluster consisted of 392 probesets. Up-regulated genes at 32 w mirrored the influx of monocyte/macrophages into intima lesions whereas genes up-regulated between 32-78 w mirrored adventitial inflammation. To segregate both clusters into separate gene ontology (GO) molecular function groups, we determined statistically significant up-regulation (unpaired Student t-test; p < 0.05) between 6-32 w for the atherosclerosis cluster and between 32-78 w for the adventitia cluster. Among others, GO molecular function terms cytokine activity, cytokine binding, and immunoglobulin binding in the atherosclerosis cluster and cytokine activity, chemokine receptor activity, and antigen binding in the ATLO cluster suggested candidate genes in relation to inflammation triggered by macrophages or adventitia infiltration, respectively. Among other prototype atherosclerosis genes such as Itgax (complement receptor 4), Cd68, Lysz (lysozyme), Vcam1, and Icam1, the atherosclerosis cluster showed markedly overrepresented prototype macrophage/foam cell genes regulating inflammation in cytokine activity (GO: 0005125): Spp1 (osteopontin) and Il6; in cytokine binding (GO: 0019955) Cd74, Il10rb, Ccr2, and Ccr5; and in immunoglobulin binding (GO: 00119865) the proinflammatory galactose-binding lectin Lgals3, as well as genes in scavenger receptor activity and lipid transporter activity. By contrast, the adventitia cluster showed overrepresented genes regulating B cell recruitment, B cell maturation, germinal center formation, and autoimmunity in cytokine activity including Cxcl13, Ccl21, and Ltb, in CXC chemokine receptor activity the secondary lymphoid organ counterreceptor of CXCL13 Blr1 (also known as Cxcr5), Cxcr3, and Cxcr6; and in antigen binding several histocompatibility-2 loci and various markedly expressed immunoglobulin genes. As embryonic lymph node development and tertiary lymphoid organ neogenesis share common features signal intensities of genes specifying the GO molecular function term lymph node development (GO: 0048535) were examined in arrays prepared from wild-type and apoE-/- aortae. These results showed that Id2, Nfkb1, and Ltbr were constitutively expressed at significant levels in aortae of both mouse genotypes whereas other genes including Lta, Ltb, Glycam1, and the two lymphorganogenic genes Cxcl13 and Ccl21 were induced at 78 w in apoE-deficient aortae only. Thus, genes expressed by macrophage-foam cells and genes regulating ATLO neogenesis, embryonic lymph node development, or B cell maturation were constitutively expressed in the arterial wall in both genotypes or emerged in a stepwise fashion at 32 w and 78 w. To verify microarray signal intensity data, separate aortae extracts were examined by quantitative RT-PCR (QRT-PCR) analyses of wild-type and apoE-deficient mice at 32 and 78 w. These data showed that array signal values accurately reflected gene transcripts. Cell lineage analyses of the adventitial infiltrate and kinetic aorta microarray- and QRT-PCR analyses thus provided circumstantial evidence that immune responses in atherosclerosis intima lesions and the adventitia were distinct. To examine this possibility further, we selected areas of the abdominal aorta burdened with advanced lesions and separated lesions and corresponding adventitial infiltrates of 78 w old apoE-deficient mice by laser dissection microscopy. In addition, adventitiae of aorta segments that were not associated with adjacent lesions and adventitiae of wild-type mice were prepared. Consistent with the lack of a major adventitial leukocyte infiltration, wild-type adventitiae showed gene expression levels that were similar to lesion-free adventitiae of apoE-deficient mice indicating that atherosclerotic lesions directly affected adventitial inflammation in a segmental fashion. Stringent filter criteria identified genes that were differentially expressed in adventitiae and atherosclerotic lesions. Statistical analyses of overrepresented genes in GO molecular function or biological process groups were particularly instructive in cytokine activity, cytokine binding, antigen processing and presentation as well as in lymph node development. Thus, adventitiae in aorta segments with associated atherosclerotic lesions in cytokine activity showed overrepresentation of genes known to be associated with tertiary lymphoid organ formation including Cxcl13, Ccl21, and Ltb, whereas atherosclerotic lesions showed overrepresentation of prototype atherosclerosis-associated genes Ssp1 (osteopontin), Bmp4 (bone morphogenic protein 4), and Cxc3cl1 (fractalkine); in cytokine binding adventitiae showed overrepresentation of receptors implicated in B cell immunity and autoimmunity including Brl1 (counterreceptor for CXCL13), Ccr7, Tnfrsf4, and Cxcr3 whereas lesions showed overrepresentation of inflammatory mediator receptors including Tnfrs1b, Tgfbr1, and Il7r; moreover, in antigen processing and presentation, adventitiae showed overrepresentation of several histocompatibility loci; additional adventitial gene expression overrepresentations were observed in lymph node development (Fas, SpiB, Ltb, Flt3) whereas lesions showed expression of prototype macrophage genes including Tlr4, Tgfb1, and Tgfb2. These data provide comprehensive topographical transcriptome information in adventitial tissue adjacent to atherosclerotic lesions versus lesions and are expected to form the basis for future cell lineage expression analyses using single cell detection methodology including ISH. Keywords: Atherosclerosis, aorta transcriptomes, adventitia, lymphocytes, dendritic cells, immune response, tertiary lymphoid organogenesis

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Crosstalk between the diseased atherosclerotic aorta and the peripheral nervous system [Adventitia]

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