Biology subjects

Daugherty, A.

Publications and source records attributed to Daugherty, A..

3 recordsLinked to original sources

bioRxiv2020

Functional Importance of Second Heart Field-derived Cells During Thoracic Aortic Aneurysm Formation

BackgroundThe ascending aorta is a common location for aneurysm and dissection. This aortic region is populated by a mosaic of medial and adventitial cells that are embryonically derived from either the second heart field (SHF) or the cardiac neural crest. SHF-derived cells populate areas that coincide with the spatial specificity of thoracic aortopathies. The purpose of this study was to determine whether and how SHF-derived cells contribute to ascending aortopathies. MethodsAscending aortic pathologies were examined in patients with sporadic thoracic aortopathies and angiotensin II (AngII)-infused mice. Ascending aortas without overt pathology from AngII-infused mice were subjected to mass spectrometry assisted proteomics, and molecular features of SHF-derived cells were determined by single cell transcriptomic analyses. Genetic deletion of either low-density lipoprotein receptor-related protein 1 (Lrp1) or transforming growth factor-{beta} receptor 2 (Tgfbr2) in SHF- derived cells was conducted to examine the impact of SHF-derived cells on vascular integrity. ResultsPathologies in human ascending aortic aneurysmal tissues were predominant in outer medial layers and adventitia. This gradient was mimicked in mouse aortas following AngII infusion that was coincident with the distribution of SHF-derived cells. Proteomics indicated that brief AngII infusion, prior to overt pathology, evoked downregulation of SMC proteins and differential expression of extracellular matrix proteins, including several LRP1 ligands. LRP1 deletion in SHF-derived cells augmented AngII-induced ascending aortic aneurysm and rupture. Single cell transcriptomic analysis revealed that brief AngII infusion decreased Lrp1 and Tgfbr2 mRNA abundance in SHF-derived cells and induced a unique fibroblast population with low abundance of Tgfbr2 mRNA. SHF-specific Tgfbr2 deletion led to embryonic lethality at E12.5 with dilatation of the outflow tract and retroperitoneal hemorrhage. Integration of proteomic and single cell transcriptomics results identified plasminogen activator inhibitor 1 (PAI1) as the most increased protein in SHF-derived SMCs and fibroblasts during AngII infusion. Immunostaining revealed a transmural gradient of PAI1 in both ascending aortas of AngII-infused mice and human ascending aneurysmal aortas that mimicked the gradient of medial and adventitial pathologies. ConclusionSHF-derived cells exert a critical role in maintaining vascular integrity through LRP1 and TGF-{beta} signaling associated with increases of aortic PAI1. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=89 SRC="FIGDIR/small/930917v6_ufig1.gif" ALT="Figure 1"> View larger version (34K): org.highwire.dtl.DTLVardef@185e3d9org.highwire.dtl.DTLVardef@131d702org.highwire.dtl.DTLVardef@11afa42org.highwire.dtl.DTLVardef@242786_HPS_FORMAT_FIGEXP M_FIG C_FIG Clinical PerspectiveO_ST_ABSWhat is new?C_ST_ABS- SHF-derived SMCs and fibroblasts associate with AngII-induced aortic pathologies. - AngII induces a distinct fibroblast sub-cluster that is less abundant for mRNAs related to major extracellular components and TGF{beta} ligands and receptors, but more abundant for proliferative genes. - TGFBR2 deletion in SHF-derived cells are embryonic lethal with significant dilatation of the outflow tract in mice. - SHF-specific deletion of LRP1 leads to aortic pathologies in mice, supporting the importance of SHF-derived cells in maintaining ascending aortic wall integrity. What are the clinical implications?- Heterogeneity of the embryonic origins of SMCs and fibroblasts contributes to complex mechanisms of vasculopathy formation, which should be considered when investigating the pathogenesis of thoracic aortopathies.

pathology↗

bioRxiv2020

Hypercholesterolemia Accelerates the Initiation and Progression of Angiotensin II-induced Abdominal Aortic Aneurysms

ObjectiveThis study determined whether hypercholesterolemia would contribute to both the initiation and progression of angiotensin (Ang)II-induced abdominal aortic aneurysms (AAAs) in mice. Methods and ResultsTo determine whether hypercholesterolemia accelerates the initiation of AAAs, male low-density lipoprotein (LDL) receptor -/- mice were either fed one week of Western diet prior to starting AngII infusion or initiated Western diet one week after starting AngII infusion. During the first week of AngII infusion, mice fed normal diet had less luminal expansion of the suprarenal aorta compared to those initiated Western diet after the first week of AngII infusion. The two groups achieved comparable luminal dilation on week 2 through week 6 of AngII infusion as monitored by ultrasound. To determine whether hypercholesterolemia contributed to the progression of established AAAs, male LDL receptor -/- mice were fed Western diet and infused with AngII for 4 weeks. Mice with established AAAs were then stratified into two groups based on luminal diameters measured by ultrasound. While AngII infusion was continued for another 8 weeks in both groups, mice in one group were continuously fed Western diet, but diet in the other group was switched to normal laboratory diet. In the latter group, plasma cholesterol concentrations were reduced rapidly to approximately 500 mg/dl within one week after the diet was switched from Western diet to normal laboratory diet. Luminal expansion progressed constantly in mice continuously fed Western diet, whereas no continuous expansion was detected in mice that were switched to normal laboratory diet. ConclusionsHypercholesterolemia accelerates both the initiation of AAAs and progression of established AAAs in AngII-infused male LDL receptor -/- mice. Clinical RelevanceHypercholesterolemia is modestly associated with AAAs in observational or retrospective clinical studies. It is not feasible to study whether hypercholesterolemia contributes to the initiation of AAAs or progression of established AAAs in human. This study using AngII-induced AAA mouse model provides solid evidence that hypercholesterolemia contributes to both the initiation and progression of AAAs, supporting that statin therapy at any stage of AAA development may be beneficial to hypercholesterolemic patients with AAAs.

pathology↗

bioRxiv2019

The Two Amino Acids Proximate to the Renin Cleavage Site of Human Angiotensinogen Do Not Affect Angiotensin II-mediated Functions in Mice

ObjectiveRenin cleavage of angiotensinogen (AGT) has species specificity. Since the residues at positions 11 and 12 of AGT are different between human and mouse AGT, we determined whether these two residues in AGT affect renin cleavage and angiotensin II-mediated functions using an adeno-associated viral (AAV) approach for manipulating AGT in vivo. Approach and ResultsHepatocyte-specific AGT deficient (hepAGT-/-) mice in an LDL receptor -/- background were infected with AAVs containing a null insert, human AGT, or mouse AGT expressing the same residues of the human protein at positions 11 and 12 [mouse AGT (L11V;Y12I)]. Expression of human AGT in hepAGT-/- mice led to high plasma human AGT concentrations without changes in plasma mouse endogenous AGT, plasma renin concentrations, blood pressure, or atherosclerosis. This is consistent with human AGT not being cleaved by mouse renin. To determine whether the residues at positions 11 and 12 in human AGT lead to the inability of mouse renin to cleave human AGT, hepAGT-/- mice were injected with AAV encoding mouse AGT (L11V;Y12I). Expression of mouse AGT (L11V;Y12I) resulted in increased plasma mouse AGT concentrations, reduced renin concentrations, and increased renal AngII concentrations that were comparable to their concentrations in hepAGT+/+ mice. This mouse AGT variant increased blood pressure and atherosclerosis in hepAGT-/- mice to the magnitude of hepAGT+/+ mice. ConclusionReplacement of L11 and Y12 to V11 and I12, respectively, in mouse AGT does not affect renin cleavage and AngII-mediated functions in mice. HIGHLIGHTSO_LIHuman AGT is not cleaved by mouse renin and does not change AngII-mediated functions in hepatocyte-specific AGT -/- mice. C_LIO_LIReplacement of the N-terminal amino acids at 11 and 12 positions from mouse to human AGT does not affect renin cleavage and AngII-mediated functions in hepatocyte-specific AGT -/- mice. C_LI

pathology↗