β-Aminopropionitrile-induced aortic aneurysm and dissection in mice

Circ_0000006 and circ_0000160 regulate hsa-let-7e-5p/UBQLN4 axis in aortic dissection progression

Aortic aneurysms (AA) and aorta dissection (AD) are life-threatening conditions with a rising incidence and high mortality rate. Recent research has linked non-coding RNAs to the regulation of AA and AD progression. In this study, we performed circRNA sequencing, microRNA (miRNA) sequencing, and messenger RNA (mRNA) sequencing on plasma samples from AA and AD patients to identify the key circRNA-miRNA-mRNA axis involved in the transition from AA to AD. Our results showed elevated levels of circ_0000006 and circ_0000160, along with decreased levels of hsa-let-7e-5p in AD samples compared to AA samples. Predictive analysis suggested that circ_0000006 and circ_0000160 potentially target hsa-let-7e-5p, which in turn may bind to the mRNA of Ubiquilin 4 (UBQLN4). In an AD cell model using vascular smooth muscle cells (VSMCs), silencing circ_0000006 and circ_0000160 attenuated the effects of platelet-derived growth factor (PDGF)-induced phenotypic changes, proliferation, and migration. This effect was partially reversed by inhibiting hsa-let-7e-5p. Furthermore, we found that overexpression of UBQLN4 counteracted the effects of hsa-let-7e-5p, suggesting UBQLN4 as a downstream mediator of hsa-let-7e-5p. In an animal model of AD, knockdown of circ_0000006 and circ_0000160 also showed protective effects against aortic septation. Overall, our findings indicate that the upregulation of circ_0000006 and circ_0000160 contributes to the progression from AA to AD by influencing abnormal phenotypic changes, migration, and proliferation of VSMCs. The Hsa-let-7e-5p/UBQLN4 axis may play a critical role in AD development. Targeting circ_0000006 and circ_0000160 could be a potential therapeutic strategy for preventing the progression of AD.

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

BACKGROUND

β-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.

METHODS

BAPN 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.

RESULTS

BAPN-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 α-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.

CONCLUSIONS

BAPN-induced pathologies show distinct, heterogeneous features within and between ascending and descending aortic regions in mice.

Angiotensinogen as a Therapeutic Target for Cardiovascular and Metabolic Diseases

AGT (angiotensinogen) is the unique precursor for the generation of all the peptides of the renin-angiotensin system, but it has received relatively scant attention compared to many other renin-angiotensin system components. Focus on AGT has increased recently, particularly with the evolution of drugs to target the synthesis of the protein. AGT is a noninhibitory serpin that has several conserved domains in addition to the angiotensin II sequences at the N terminus. Increased study is needed on the structure-function relationship to resolve many unknowns regarding AGT metabolism. Constitutive whole-body genetic deletion of Agt in mice leads to multiple developmental defects creating a challenge to use these mice for mechanistic studies. This has been overcome by creating Agt-floxed mice to enable the development of cell-specific deficiencies that have provided considerable insight into a range of cardiovascular and associated diseases. This has been augmented by the recent development of pharmacological approaches targeting hepatocytes in humans to promote protracted inhibition of AGT synthesis. Genetic deletion or pharmacological inhibition of Agt has been demonstrated to be beneficial in a spectrum of diseases experimentally, including hypertension, atherosclerosis, aortic and superior mesenteric artery aneurysms, myocardial dysfunction, and hepatic steatosis. This review summarizes the findings of recent studies utilizing AGT manipulation as a therapeutic approach.

Cannabidiol protects against acute aortic dissection by inhibiting macrophage infiltration and PMAIP1-induced vascular smooth muscle cell apoptosis

Acute aortic dissection (AAD) progresses rapidly and is associated with high mortality; therefore, there remains an urgent need for pharmacological agents that can protect against AAD. Herein, we examined the therapeutic effects of cannabidiol (CBD) in AAD by establishing a suitable mouse model. In addition, we performed human AAD single-cell RNA sequencing and mouse AAD bulk RNA sequencing to elucidate the potential underlying mechanism of CBD. Pathological assays and in vitro studies were performed to verify the results of the bioinformatic analysis and explore the pharmacological function of CBD. In a β-aminopropionitrile (BAPN)-induced AAD mouse model, CBD reduced AAD-associated morbidity and mortality, alleviated abnormal enlargement of the ascending aorta and aortic arch, and suppressed macrophage infiltration and vascular smooth muscle cell (VSMC) apoptosis. Bioinformatic analysis revealed that the pro-apoptotic gene PMAIP1 was highly expressed in human and mouse AAD samples, and CBD could inhibit Pmaip1 expression in AAD mice. Using human aortic VSMCs (HAVSMCs) co-cultured with M1 macrophages, we revealed that CBD alleviated HAVSMCs mitochondrial-dependent apoptosis by suppressing the BAPN-induced overexpression of PMAIP1 in M1 macrophages. PMAIP1 potentially mediates HAVSMCs apoptosis by regulating Bax and Bcl2 expression. Accordingly, CBD reduced AAD-associated morbidity and mortality and mitigated the progression of AAD in a mouse model. The CBD-induced effects were potentially mediated by suppressing macrophage infiltration and PMAIP1 (primarily expressed in macrophages)-induced VSMC apoptosis. Our findings offer novel insights into M1 macrophages and HAVSMCs interaction during AAD progression, highlighting the potential of CBD as a therapeutic candidate for AAD treatment.

Inhibiting Lysyl Oxidases prevents pathologic cartilage calcification

Lysyl oxidases (LOX(L)) are enzymes that catalyze the formation of cross-links in collagen and elastin fibers during physiologic calcification of bone. However, it remains unknown whether they may promote pathologic calcification of articular cartilage, an important hallmark of debilitating arthropathies. Here, we have studied the possible roles of LOX(L) in cartilage calcification, related and not related to their cross-linking activity. We first demonstrated that inhibition of LOX(L) by β-aminoproprionitrile (BAPN) significantly reduced calcification in murine and human chondrocytes, and in joint of meniscectomized mice. These BAPN's effects on calcification were accounted for by different LOX(L) roles. Firstly, reduced LOX(L)-mediated extracellular matrix cross-links downregulated Anx5, Pit1 and Pit2 calcification genes. Secondly, BAPN reduced collagen fibrotic markers Col1 and Col3. Additionally, LOX(L) inhibition blocked chondrocytes hypertrophic differentiation (Runx2 and COL10), pro-inflammatory IL-6 release and reactive oxygen species (ROS) production, all triggers of chondrocyte calcification. Through unbiased transcriptomic analysis we confirmed a positive correlation between LOX(L) genes and genes for calcification, hypertrophy and extracellular matrix catabolism. This association was conserved throughout species (mouse, human) and tissues that can undergo pathologic calcification (kidney, arteries, skin). Overall, LOX(L) play a critical role in the process of chondrocyte calcification and may be therapeutic targets to treat cartilage calcification in arthropathies.

68Ga-labeled WVP peptide as a novel PET probe for molecular biological diagnosis of unstable thoracic aortic aneurysm and early dissection: an animal study

Objective

Type IV collagen (Col-IV) is a prospective biomarker for diagnosing and treating of unstable thoracic aortic aneurysm and dissection (TAAD). This study aims to evaluate the feasibility of ⁶⁸Ga-labeled WVP peptide (⁶⁸Ga-DOTA-WVP) as a novel Col-IV-targeted probe for TAAD biological diagnosis using PET/CT.

Methods

WVP peptide was modified with bifunctional chelator DOTA for ⁶⁸Ga radiolabeling. Immunohistochemical staining was used to evaluate the expression and location of Col-IV and elastin in aortas treated with 3-aminopropionitrile fumarate (BAPN) at different time points (0, 2, and 4 weeks). The imaging performance of ⁶⁸Ga-DOTA-WVP was investigated using Micro-PET/CT in a BAPN-induced TAAD mouse model. The relationship between ⁶⁸Ga-DOTA-WVP uptake in aortic lesions and the serum levels of TAAD-related biomarkers including D-dimer, C-reactive protein (CRP), and serum soluble suppression of tumorigenicity-2 (sST2) was also analyzed.

Results

⁶⁸Ga-DOTA-WVP was readily prepared with high radiochemical purity and stability in vitro. ⁶⁸Ga-DOTA-WVP Micro-PET/CT could detect Col-IV exposure of unstable aneurysms and early dissection in BAPN-induced TAAD mice, but little ⁶⁸Ga-DOTA-WVP uptake was shown in the control group at each imaging time point. The differences of Col-IV expression and distribution of ⁶⁸Ga-DOTA-WVP both in TAAD and control groups further verified the imaging efficiency of ⁶⁸Ga-DOTA-WVP PET/CT. Additionally, a higher sST2 level was found in the imaging positive (n = 14) than the negative (n = 8) group (9.60 ± 1.14 vs. 8.44 ± 0.52, P = 0.014).

Conclusion

⁶⁸Ga-DOTA-WVP could trace the exposure and abnormal deposition of Col-IV in enlarged and early injured aortas, showing a potential for biological diagnosis, whole-body screening, and progression monitoring of TAAD.

Low Zinc Alleviates the Progression of Thoracic Aortic Dissection by Inhibiting Inflammation

Vascular inflammation triggers the development of thoracic aortic dissection (TAD). Zinc deficiency could dampen tissue inflammation. However, the role of zinc as a nutritional intervention in the progression of TAD remains elusive. In this study, we employed a classical β-aminopropionitrile monofumarate (BAPN)-induced TAD model in mice treated with low zinc and observed that the TAD progression was greatly ameliorated under low zinc conditions. Our results showed that low zinc could significantly improve aortic dissection and rupture (BAPN + low zinc vs. BAPN, 36% vs. 100%) and reduce mortality (BAPN + low zinc vs. BAPN, 22% vs. 57%). Mechanically, low zinc attenuated the infiltration of macrophages and inhibited the expression of inflammatory cytokines, suppressed the phenotype switch of vascular smooth muscle cells from contractile to synthetic types, and eventually alleviated the development of TAD. In conclusion, this study suggested that low zinc may serve as a potential nutritional intervention approach for TAD prevention.

Periadventitial β-aminopropionitrile-loaded nanofibers reduce fibrosis and improve arteriovenous fistula remodeling in rats

Background

Arteriovenous fistula (AVF) postoperative stenosis is a persistent healthcare problem for hemodialysis patients. We have previously demonstrated that fibrotic remodeling contributes to AVF non-maturation and lysyl oxidase (LOX) is upregulated in failed AVFs compared to matured. Herein, we developed a nanofiber scaffold for the periadventitial delivery of β-aminopropionitrile (BAPN) to determine whether unidirectional periadventitial LOX inhibition is a suitable strategy to promote adaptive AVF remodeling in a rat model of AVF remodeling.

Methods

Bilayer poly (lactic acid) ([PLA)-]- poly (lactic-co-glycolic acid) ([PLGA)] scaffolds were fabricated with using a two-step electrospinning process to confer directionality. BAPN-loaded and vehicle control scaffolds were wrapped around the venous limb of a rat femoral-epigastric AVF during surgery. AVF patency and lumen diameter were followed monitored using Doppler ultrasound surveillance and flow was measured before euthanasia. AVFs were harvested after 21 days for histomorphometry and immunohistochemistry. AVF compliance was measured using pressure myography. RNA from AVF veins was sequenced to analyze changes in gene expression due to LOX inhibition.

Results

Bilayer periadventitial nanofiber scaffolds extended BAPN release compared to the monolayer design (p < 0.005) and only released BAPN in one direction. Periadventitial LOX inhibition led to significant increases in AVF dilation and flow after 21 days. Histologically, BAPN trended toward increased lumen and significantly reduced fibrosis compared to control scaffolds (p < 0.01). Periadventitial BAPN reduced downregulated markers associated with myofibroblast differentiation including SMA, FSP-1, LOX, and TGF-β while increasing the contractile marker MYH11. RNA sequencing revealed differential expression of matrisome genes.

Conclusion

Periadventitial BAPN treatment reduces fibrosis and promotes AVF compliance. Interestingly, the inhibition of LOX leads to increased accumulation of contractile VSMC while reducing myofibroblast-like cells. Periadventitial LOX inhibition alters the matrisome to improve AVF vascular remodeling.

Aortic Stress Activates an Adaptive Program in Thoracic Aortic Smooth Muscle Cells That Maintains Aortic Strength and Protects Against Aneurysm and Dissection in Mice

BACKGROUND

When aortic cells are under stress, such as increased hemodynamic pressure, they adapt to the environment by modifying their functions, allowing the aorta to maintain its strength. To understand the regulation of this adaptive response, we examined transcriptomic and epigenomic programs in aortic smooth muscle cells (SMCs) during the adaptive response to AngII (angiotensin II) infusion and determined its importance in protecting against aortic aneurysm and dissection (AAD).

METHODS

We performed single-cell RNA sequencing and single-cell sequencing assay for transposase-accessible chromatin (scATAC-seq) analyses in a mouse model of sporadic AAD induced by AngII infusion. We also examined the direct effects of YAP (yes-associated protein) on the SMC adaptive response in vitro. The role of YAP in AAD development was further evaluated in AngII-infused mice with SMC-specific Yap deletion.

RESULTS

In wild-type mice, AngII infusion increased medial thickness in the thoracic aorta. Single-cell RNA sequencing analysis revealed an adaptive response in thoracic SMCs characterized by upregulated genes with roles in wound healing, elastin and collagen production, proliferation, migration, cytoskeleton organization, cell-matrix focal adhesion, and PI3K-PKB/Akt (phosphoinositide-3-kinase-protein kinase B/Akt) and TGF-β (transforming growth factor beta) signaling. ScATAC-seq analysis showed increased chromatin accessibility at regulatory regions of adaptive genes and revealed the mechanical sensor YAP/transcriptional enhanced associate domains as a top candidate transcription complex driving the expression of these genes (eg, Lox, Col5a2, Tgfb2). In cultured human aortic SMCs, cyclic stretch activated YAP, which directly bound to adaptive gene regulatory regions (eg, Lox) and increased their transcript abundance. SMC-specific Yap deletion in mice compromised this adaptive response in SMCs, leading to an increased AAD incidence.

CONCLUSIONS

Aortic stress triggers the systemic epigenetic induction of an adaptive response (eg, wound healing, proliferation, matrix organization) in thoracic aortic SMCs that depends on functional biomechanical signal transduction (eg, YAP signaling). Our study highlights the importance of the adaptive response in maintaining aortic homeostasis and preventing AAD in mice.

Inhibition of the Renin-Angiotensin System Fails to Suppress β-Aminopropionitrile-Induced Thoracic Aortopathy in Mice-Brief Report

BACKGROUND

Cross-linking of lysine residues in elastic and collagen fibers is a vital process in aortic development. Inhibition of lysyl oxidase by BAPN (β-aminopropionitrile) leads to thoracic aortopathies in mice. Although the renin-angiotensin system contributes to several types of thoracic aortopathies, it remains unclear whether inhibition of the renin-angiotensin system protects against aortopathy caused by the impairment of elastic fiber/collagen crosslinking.

METHODS

BAPN (0.5% wt/vol) was started in drinking water to induce aortopathies in male C57BL/6J mice at 4 weeks of age for 4 weeks. Five approaches were used to investigate the impact of the renin-angiotensin system. Bulk RNA sequencing was performed to explore potential molecular mechanisms of BAPN-induced thoracic aortopathies.

RESULTS

Losartan increased plasma renin concentrations significantly, compared with vehicle-infused mice, indicating effective angiotensin II type 1 receptor inhibition. However, losartan did not suppress BAPN-induced aortic rupture and dilatation. Since losartan is a surmountable inhibitor of the renin-angiotensin system, irbesartan, an insurmountable inhibitor, was also tested. Although increased plasma renin concentrations indicated effective inhibition, irbesartan did not ameliorate aortic rupture and dilatation in BAPN-administered mice. Thus, BAPN-induced thoracic aortopathies were refractory to angiotensin II type 1 receptor blockade. Next, we inhibited angiotensin II production by pharmacological or genetic depletion of AGT (angiotensinogen), the unique precursor of angiotensin II. However, neither suppressed BAPN-induced thoracic aortic rupture and dilatation. Aortic RNA sequencing revealed molecular changes during BAPN administration that were distinct from other types of aortopathies in which angiotensin II type 1 receptor inhibition protects against aneurysm formation.

CONCLUSIONS

Inhibition of either angiotensin II action or production of the renin-angiotensin system does not attenuate BAPN-induced thoracic aortopathies in mice.

Progress in murine models of ruptured abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a focal dilation of the aorta that is prevalent in aged populations. The progressive and unpredictable expansion of AAA could result in aneurysmal rupture, which is associated with ~80% mortality. Due to the expanded screening efforts and progress in diagnostic tools, an ever-increasing amount of asymptomatic AAA patients are being identified yet without a cure to stop the rampant aortic expansion. A key barrier that hinders the development of effective AAA treatment is our incomplete understanding of the cellular and molecular basis of its pathogenesis and progression into rupture. Animal models provide invaluable mechanistic insights into AAA pathophysiology. However, there is no single experimental model that completely recapitulate the complex biology behind AAA, and different AAA-inducing methodologies are associated with distinct disease course and rupture rate. In this review article, we summarize the established murine models of ruptured AAA and discuss their respective strengths and utilities.