Biology subjects

Graf, D. B.

Publications and source records attributed to Graf, D. B..

3 recordsLinked to original sources

bioRxiv2025

Cardiac Hemorrhage Precedes Hypertension-induced Fibrosis inPlasminogen Activator Inhibitor-1 Deficient Mice

AimsPlasminogen activator inhibitor-1 (PAI-1) regulates plasmin-mediated proteolysis, thereby influencing vascular stability and tissue remodeling. Angiotensin II (AngII) induces an increase in PAI-1 during the development of ascending thoracic aortic aneurysm (ATAA). The initial purpose of this study was to determine whether deletion of PAI-1 influenced development of ATAA. Subsequently, this study aimed to define the early pathological events preceding cardiac fibrosis in PAI-1 deficiency and the structural domain responsible for its protective effect. Methods and resultsAngII was infused for 4 weeks in whole-body PAI-1 deficient (PAI-1-/-) mice and their wild-type littermates (PAI-1+/+) to examine the role of PAI-1 in ATAA. PAI-1 deficiency did not alter AngII-induced aortopathy but revealed a striking cardiac phenotype characterized by replacement fibrosis predominantly within the epicardium and posterior septum. Ferric iron, indicative of prior hemorrhage, was coincident with fibrosis. Similar phenotypes were observed in PAI-1-/- mice infused with norepinephrine for 4 weeks. To define the pathological events preceding cardiac fibrosis, either AngII or norepinephrine was infused for 1 week in PAI-1+/+ or -/- mice. Both infusions induced extensive epicardial hemorrhage and posterior septal fibrosis in PAI-1-/- mice. To explore the initiation of cardiac pathology, AngII was infused for approximately 1 day. PAI-1-/- mice developed diffuse hemorrhage and cardiomyocyte injury localized to the posterior septum, pathologic changes that preceded overt fibrosis. Finally, to determine the protective domain of PAI-1, saline or AngII was administered to mice harboring loss-of-function point mutations in the protease inhibitory (PAI-1Ala/Ala) or somatomedin B-binding domains (PAI-1AK/AK). Compared to saline infusion, 1 week of AngII induced hemorrhage and heterogeneous fibrosis in PAI-1Ala/Ala, but not PAI-1AK/AK mice. ConclusionsThese findings support that, under hemodynamic stress, PAI-1 deficiency promotes early cardiac hemorrhage and cardiomyocyte injury that lead to fibrosis. Mutational studies implicate dysregulated plasmin generation as an initiator of cardiac injury and fibrosis. TRANSLATIONAL PERSPECTIVECardiac fibrosis has been reported in a human population with PAI-1 deficiency and currently lacks targeted therapy. Our findings demonstrate that in animal models, PAI-1 deficiency confers susceptibility to cardiac injury in response to hemodynamic stress, which may accelerate fibrotic remodeling. Mutational disruption of the protease-inhibitory domain of PAI-1 induced similar pathology, supporting a protective role for this function. These observations suggest that interventions aimed at controlling hypertension, promoting endothelial integrity, or regulating plasmin activation could reduce fibrotic remodeling in this population.

pathology↗

bioRxiv2025

Smooth Muscle Cells and Fibroblasts in the Proximal Thoracic Aorta Exhibit Minor Differences Between Embryonic Origins in Angiotensin II-driven Transcriptional Alterations

BackgroundThoracic aortopathy is influenced by angiotensin II (AngII) and exhibits regional heterogeneity with the proximal region of the thoracic aorta being susceptible. Smooth muscle cells (SMCs) and selected fibroblasts in this region are derived from two embryonic origins: second heart field (SHF) and cardiac neural crest (CNC). While our previous study revealed a critical role of SHF-derived cells in AngII-mediated aortopathy formation, the contribution of CNC-derived cells remains unclear. MethodsMef2c-Cre R26RmT/mG mice were infused with AngII (1,000 ng/kg/min). Proximal thoracic aortas were harvested at baseline or after 3 days of infusion, representing the prepathological phase. Cells were sorted by origins using mGFP (SHF-derived) and mTomato (other origins, nSHF-derived) signals, respectively. After sorting cells by origin, single-cell RNA sequencing was performed and analyzed. ResultsShort-term AngII infusion induced significant transcriptomic changes in both SHF- and nSHF-derived SMCs, but differences between origins were modest. Fibroblast transcriptomes also underwent notable changes by AngII infusion, but differences between SHF and nSHF origins remained modest. Interestingly, AngII infusion resulted in the emergence of a new fibroblast sub-population. Several molecules related to the extracellular matrix, such as Eln and Col3a1, were downregulated in SHF-derived fibroblasts compared to nSHF-derived fibroblasts in the new subcluster. ConclusionFibroblasts in the new subcluster exhibited lineage-specific differences in extracellular matrix-related genes; however, overall transcriptomic differences between origins in SMCs and fibroblasts in response to AngII were modest in the pre-pathological phase of AngII-induced thoracic aortopathy. GRAPHIC ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=174 SRC="FIGDIR/small/610985v1_ufig1.gif" ALT="Figure 1"> View larger version (38K): org.highwire.dtl.DTLVardef@17c2e3corg.highwire.dtl.DTLVardef@1bf9517org.highwire.dtl.DTLVardef@d51aedorg.highwire.dtl.DTLVardef@dac951_HPS_FORMAT_FIGEXP M_FIG C_FIG

pathology↗

bioRxiv2023

β-aminopropionitrile Induces Distinct Pathologies in the Ascending and Descending Thoracic Aortic Regions of Young Mice

BACKGROUND{beta}-aminopropionitrile (BAPN) is a pharmacological inhibitor of lysyl oxidase and lysyl oxidase-like proteins. Administration of BAPN promotes aortopathies, although there is a paucity of data on experimental conditions to generate pathology. The objective of this study was to define experimental parameters and determine whether equivalent or variable aortopathies were generated throughout the aortic tree during BAPN administration in mice. METHODSBAPN was administered in drinking water for a period ranging from 1 to 12 weeks. The impacts of BAPN were first assessed with regard to dose, strain, age, and sex. BAPN-induced aortic pathological characterization was conducted using histology and immunostaining. To investigate the mechanistic basis of regional heterogeneity, ascending and descending thoracic aortas were harvested after one week of BAPN administration before the appearance of overt pathology. RESULTSBAPN-induced aortic rupture predominantly occurred or originated in the descending thoracic aorta in young C57BL/6J or N mice. No apparent differences were found between male and female mice. For mice surviving 12 weeks of BAPN administration, profound dilatation was consistently observed in the ascending region, while there were more heterogeneous changes in the descending thoracic region. Pathological features were distinct between the ascending and descending thoracic regions. Aortic pathology in the ascending region was characterized by luminal dilatation and elastic fiber disruption throughout the media. The descending thoracic region frequently had dissections with false lumen formation, collagen deposition, and remodeling of the wall surrounding the false lumen. Cells surrounding the false lumen were predominantly positive for -smooth muscle actin. One week of BAPN administration compromised contractile properties in both regions equivalently, and RNA sequencing did not show obvious differences between the two aortic regions in smooth muscle cell markers, cell proliferation markers, and extracellular components. CONCLUSIONSBAPN-induced pathologies show distinct, heterogeneous features within and between ascending and descending aortic regions in mice.

pathology↗