Human Aneurysms Research Articles

Monocyte Chemotactic Protein-1-Interleukin-6-Osteopontin Pathway of Intra-Aneurysmal Tissue Healing.

We have previously demonstrated that the local delivery of monocyte chemotactic protein-1 (MCP-1) via an MCP-1-releasing poly(lactic-co-glycolic acid)-coated coil promotes intra-aneurysmal tissue healing. In this study, we demonstrate that interleukin-6 (IL-6) and osteopontin are downstream mediators in the MCP-1-mediated aneurysm-healing pathway. Murine carotid aneurysms were created in C57BL/6 mice. Drug-releasing coils (MCP-1, IL-6, and osteopontin) and control poly(lactic-co-glycolic acid) coils were created and then implanted into the aneurysms to evaluate their intra-aneurismal-healing capacity. To investigate the downstream mediators for aneurysm healing, blocking antibodies for IL-6 receptor and osteopontin were given to the mice implanted with the MCP-1-releasing coils. A histological analysis of both murine and human aneurysms was utilized to cross-validate the data. We observed increased expression of IL-6 in MCP-1-coil-treated aneurysms and not in control-poly(lactic-co-glycolic acid)-only-treated aneurysms. MCP-1-mediated intra-aneurysmal healing is inhibited in mice given blocking antibody to IL-6 receptor. MCP-1-mediated intra-aneurysmal healing is also inhibited by blocking antibody to osteopontin. The role of IL-6 in intra-aneurysmal healing is in recruiting of endothelial cells and fibroblasts. Local delivery of osteopontin to murine carotid aneurysms via osteopontin-releasing coil significantly promotes intra-aneurysmal healing, but IL-6-releasing coil does not, suggesting that IL-6 cannot promote aneurysm healing independent of MCP-1. In the MCP-1-mediated aneurysm healing, osteopontin expression is dependent on IL-6; inhibition of IL-6 receptor significantly inhibits osteopontin expression in MCP-1-mediated aneurysm healing. Our findings suggest that IL-6 and osteopontin are key downstream mediators of MCP-1-mediated intra-aneurysmal healing.

The water channel AQP1 is expressed in human atherosclerotic vascular lesions and AQP1 deficiency augments angiotensin II-induced atherosclerosis in mice.

The water channel aquaporin 1 (AQP1) promotes endothelial cell migration. It was hypothesized that AQP1 promotes neovascularization and growth of atherosclerotic plaques. AQP1 immunoreactivity and protein abundance was examined in human and murine atherosclerotic lesions and aortic aneurysms. Apolipoprotein E (ApoE) knockout (-/-) and AQP1-/-ApoE-/- mice were developed and fed Western diet (WD) for 8 and 16weeks to accelerate the atherosclerosis process. In ApoE-/- and AQP1-/-ApoE-/- mice abdominal aortic aneurysms (AAA) were induced by angiotensin II (ANGII) infusion by osmotic minipumps for 4weeks. In human atherosclerotic lesions and AAA, AQP1 immunoreactive protein was associated with intralesional small vessels. In ApoE-/- mouse aorta, APQ1 mRNA levels were increased with time on WD (n=7-9, P<0.003). Both in murine lesions at the aortic root and in the abdominal aortic aneurysmal wall, AQP1 immunoreactivity was associated with microvascular structures. The atherosclerotic lesion burden was enhanced significantly in ANGII-infused AQP1-/-ApoE-/- mice compared with ApoE-/- mice, but neither incidence nor progression of AAA was different. The aortic lesion burden increased with time on WD but was not different between ApoE-/- and AQP1-/-ApoE-/- mice at either 8 or 16weeks (n=13-15). Baseline blood pressure and ANGII-induced hypertension were not different between genotypes. AQP1 is expressed in atherosclerotic lesion neovasculature in human and mouse arteries and AQP1 deficiency augments lesion development in ANGII-promoted atherosclerosis in mice. Normal function of AQP1 affords cardiovascular protection.

Prostaglandin E2-EP2-NF-κB signaling in macrophages as a potential therapeutic target for intracranial aneurysms.

Intracranial aneurysms are common but are generally untreated, and their rupture can lead to subarachnoid hemorrhage. Because of the poor prognosis associated with subarachnoid hemorrhage, preventing the progression of intracranial aneurysms is critically important. Intracranial aneurysms are caused by chronic inflammation of the arterial wall due to macrophage infiltration triggered by monocyte chemoattractant protein-1 (MCP-1), macrophage activation mediated by the transcription factor nuclear factor κB (NF-κB), and inflammatory signaling involving prostaglandin E2 (PGE2) and prostaglandin E receptor subtype 2 (EP2). We correlated EP2 and cyclooxygenase-2 (COX-2) with macrophage infiltration in human intracranial aneurysm lesions. Monitoring the spatiotemporal pattern of NF-κB activation during intracranial aneurysm development in mice showed that NF-κB was first activated in macrophages in the adventitia and in endothelial cells and, subsequently, in the entire arterial wall. Mice with a macrophage-specific deletion of Ptger2 (which encodes EP2) or macrophage-specific expression of an IκBα mutant that restricts NF-κB activation had fewer intracranial aneurysms with reduced macrophage infiltration and NF-κB activation. In cultured cells, EP2 signaling cooperated with tumor necrosis factor-α (TNF-α) to activate NF-κB and synergistically induce the expression of proinflammatory genes, including Ptgs2 (encoding COX-2). EP2 signaling also stabilized Ccl2 (encoding MCP-1) by activating the RNA-stabilizing protein HuR. Rats administered an EP2 antagonist had reduced macrophage infiltration and intracranial aneurysm formation and progression. This signaling pathway in macrophages thus facilitates intracranial aneurysm development by amplifying inflammation in intracranial arteries. These results indicate that EP2 antagonists may therefore be a therapeutic alternative to surgery.

EFFECTS OF HYPERTENSION AND PRESSURE GRADIENT IN A HUMAN CEREBRAL ANEURYSM USING FLUID STRUCTURE INTERACTION SIMULATIONS

Fluid–structure interaction (FSI) simulations were carried out in a human cerebral aneurysm model with the objective of quantifying the effects of hypertension and pressure gradient on the behavior of fluid and solid mechanics. Six FSI simulations were conducted using a hyperelastic Mooney–Rivlin model. Important differences in wall shear stress (WSS), wall displacements, and effective von Mises stress are reported. The hypertension increases wall stress and displacements in the aneurysm region; however, the effects of hypertension on the hemodynamics in the aneurysm region were small. The pressure gradient affects the WSS in the aneurysm and also the displacement and wall stress on the aneurysm. Maximum wall stress with hypertension in the range of rupture strength was found.

Abstract WP83: Wall Shear Stress Strength Over the Cerebral Aneurysm is Drastically Affected by Aneurysm Location While the Magnitude of Disturbed Flow is Closely Related to Aneurysm Size and Surface Area

Background and purpose: The rupture rate of cerebral aneurysms varies according to the aneurysm size and location. Although several reports suggest hemodynamic involvement in the mechanisms, there still remains to be clarified. Using computational fluid dynamics, we elucidated here differences in hemodynamics according to size and location of human cerebral aneurysms. Methods: Patient-specific inflow velocities and arterial geometries of 39 MCA aneurysms and anterior communicating artery (Acom) aneurysms were acquired from patients who consented to participate in the multi-institutional prospective clinical study, CFD ABO Study. Pulsatile blood flow was simulated using ANSYS-CFX, based on the Navier-Stokes equations for incompressible fluid. Aneurysms were divided into 3 groups by their size; less than 5mm, less than 7mm and more than 5mm, and more than 7mm. Results: Wall shear stress (WSS) was significantly lower in Acom aneurysms than MCA aneurysms (p=0.00075) while there was no significant difference in WSS according to aneurysm size. In contrast, indicators for disturbed flow, oscillatory shear index (OSI) and normalized transverse WSS (NtransWSS) were significantly higher over the aneurysms of the size less than 7mm and more than 5mm compared to those less than 5mm (p=0.021 and 0.014, respectively). Moreover, there were strong or moderate positive correlations between aneurysm surface area and OSI and NtransWSS, but not WSS. However, there was no significant difference in OSI or NtransWSS between MCA and Acom aneurysms. Conclusions: The data suggest that WSS strength over the cerebral aneurysm is drastically affected by the aneurysm location while the magnitude of disturbed flow is closely related to aneurysm size and surface area. A significant lower WSS in Acom aneurysms compared to MCA aneurysms may be associated with higher rupture rate in Acom aneurysms. In contrast, disturbed flow may be involved in aneurysm enlargement.

Diffusion-compensated tofts model suggests contrast leakage through aneurysm wall.

The purpose of this study was to investigate the diffusional transport of contrast agent and its effects on kinetic modeling of dynamic contrast enhanced (DCE) images. We performed simulations of our diffusion-compensated model and compared these results to human intracranial aneurysms (IAs). We derive an easy-to-use parameterization of diffusional effects that can provide an accurate estimate of diffusion corrected contrast agent leakage rates (ktrans ). Finally, we performed re-ansalysis of an existing data set to determine whether diffusion-corrected kinetic parameters improve the identification of high-risk IAs, thereby providing a new MRI-based imaging metric of IA stability based on wall integrity. Probability distributions of simulated versus measured data show contrast leakage away from the aneurysm wall. Parameterization of diffusional effects on ktrans showed high correlation with long-chain methods in both surrounding tissue and near the aneurysm wall (r2 = 0.91 and r2 = 0.90, respectively). Finally, size, ktrans , and ( ktrans-kDCtrans) showed significant univariate relationships with rupture risk (P < 0.05). We report the first evidence of diffusion-compensated permeability modeling in intracranial aneurysms and propose a parameterization of diffusional effects on ktrans . Furthermore, a comparison of measured versus simulated data suggests that contrast leakage occurs across the aneurysm wall. Magn Reson Med 78:2388-2398, 2017. © 2017 International Society for Magnetic Resonance in Medicine.

脳動脈瘤破裂メカニズム解明に向けた未破裂・破裂瘤における壁厚と壁細胞の病理工学的検討

脳動脈瘤破裂メカニズム解明に向けた未破裂・破裂瘤における壁厚と壁細胞の病理工学的検討

The Role Matrix Metalloproteinases in the Production of Aortic Aneurysm.

Matrix metalloproteinases (MMPs) have been implicated in the pathogenesis of aortic aneurysm because the histology of thoracic aortic aneurysm (TAA) and abdominal aortic aneurysm (AAA) is characterized by the loss of smooth muscle cells in the aortic media and the destruction of extracellular matrix (ECM). Furthermore, AAA have evidence of inflammation and the cellular elements involved in inflammation such as macrophages can produce and/or activate MMPs This chapter focuses on human aortic aneurysm that are not due to specific known genetic causes because this type of aneurysm is the more common type. This chapter will also focus on MMP protein expression rather than on genetic data which may not necessarily translate to increased MMP protein expression. There are supporting data that certain MMPs are increased in the aortic wall. For TAA, it is most notably MMP-1, -9, -12, and -14 and MMP-2 when a bicuspid aortic valve is present. For AAA, it is MMP-1, -2, -3, -9, -12, and -13. The data are weaker or insufficient for the other MMPs. Several studies of gene polymorphisms support MMP-9 for TAA and MMP-3 for AAA as potentially important factors. The signaling pathways in the aorta that can lead to MMP activation include JNK, JAK/stat, osteopontin, and AMP-activated protein kinase alpha2. Substrates in the human vasculature for MMP-3, MMP-9, or MMP-14 include collagen, elastin, ECM glycoprotein, and proteoglycans. Confirmed and potential substrates for MMPs, maintain aortic size and function so that a reduction in their content relative to other components of the aortic wall may produce a failure to maintain aortic size leading to dilatation and aneurysm formation.

A New Mouse Model for Introduction of Aortic Aneurysm by Implantation of Deoxycorticosterone Acetate Pellets or Aldosterone Infusion in the Presence of High Salt.

Dysfunction of the renin-angiotensin-aldosterone system (RAAS) has been implicated in the etiologies of many cardiovascular diseases, including aortic aneurysm. In particular, the infusion of angiotensin II (Ang II) in the apolipoprotein E-deficient mice (apoE-/-) and low density lipoprotein receptor knockout mice (LDLR-/-) to induce aortic aneurysm has been extensively used in the field. In contrast, whether aldosterone (Aldo), an essential component of RAAS and a downstream effector of Ang II, is involved in aortic aneurysm is largely unknown. Here, we describe a new animal model for induction of aortic aneurysm in mice in which administration of deoxycorticosterone acetate (DOCA) and high salt or aldosterone and high salt, but not DOCA or high salt alone, to C57BL/6 male mice can potently induce aortic aneurysm formation and rupture in an age-dependent manner. This new aortic aneurysm mouse model is different from Ang II infusion mouse model and exhibits several unique features that mimic human aortic aneurysm.

Genetic and Epigenetic Regulation of Aortic Aneurysms.

Aneurysms are characterized by structural deterioration of the vascular wall leading to progressive dilatation and, potentially, rupture of the aorta. While aortic aneurysms often remain clinically silent, the morbidity and mortality associated with aneurysm expansion and rupture are considerable. Over 13,000 deaths annually in the United States are attributable to aortic aneurysm rupture with less than 1 in 3 persons with aortic aneurysm rupture surviving to surgical intervention. Environmental and epidemiologic risk factors including smoking, male gender, hypertension, older age, dyslipidemia, atherosclerosis, and family history are highly associated with abdominal aortic aneurysms, while heritable genetic mutations are commonly associated with aneurysms of the thoracic aorta. Similar to other forms of cardiovascular disease, family history, genetic variation, and heritable mutations modify the risk of aortic aneurysm formation and provide mechanistic insight into the pathogenesis of human aortic aneurysms. This review will examine the relationship between heritable genetic and epigenetic influences on thoracic and abdominal aortic aneurysm formation and rupture.

脳動脈瘤の発症解明に向けた瘤発症分岐部と未発症分岐部の病理特徴の検討

脳動脈瘤の発症解明に向けた瘤発症分岐部と未発症分岐部の病理特徴の検討

Pathological engineering study for identifying the rupture mechanism of human cerebral aneurysms

Pathological engineering study for identifying the rupture mechanism of human cerebral aneurysms

脳動脈瘤菲薄メカニズム解明に向けた平滑筋細胞と血行動態の病理工学的検討

脳動脈瘤菲薄メカニズム解明に向けた平滑筋細胞と血行動態の病理工学的検討

Haem-Enzymes Predictive of Coronary Artery Disease Are Present in Thoracic and Abdominal Aortic Aneurysm

Purpose: A reliable plasma biomarker for aortic aneurysm has proven elusive. Elevated plasma levels of the oxidative or immune regulatory haem-enzymes myeloperoxidase (MPO) or indoleamine 2,3-dioxygenase (IDO) can predict disease prevalence and clinical risk in coronary artery disease patients. We therefore studied the relationship of MPO and IDO with thoracic or abdominal aortic aneurysm. Methodology: In patients undergoing elective surgical or endovascular repair of thoracic (n = 14) or abdominal (n = 18) aortic aneurysm, preoperative plasma was analysed for MPO protein levels by ELISA or IDO activity (indexed as a ratio of IDO's product kynurenine and substrate tryptophan) and compared with healthy controls (n = 15). Plasma levels of other inflammatory markers (CRP, neutrophil elastase) were also measured. Surgically resected aortic wall samples were analysed for MPO protein by immunohistochemistry. Results: Patients with abdominal aneurysms [72 yrs (67-76)] were significantly older than those with thoracic aneurysms [57 yrs (52-70)] and healthy controls [31 years (29-36)] and more likely to have atherosclerosis as the aetiology of aortic disease (88.9% vs. 28.6% in thoracic aneurysm). Plasma IDO activity and CRP levels, but not MPO or elastase, were significantly elevated in patients with aortic aneurysm vs. healthy controls. MPO protein, however, was expressed in the intima and media of all aortic aneurysm specimens but not non-diseased aorta. Conclusion: The haem-enzymes MPO and IDO may be involved in human aortic aneurysm and their roles warrant further study in experimental animal models of aneurysm. Measurement of plasma IDO activity and CRP, but not MPO, may represent potential useful biomarkers for aortic aneurysm.

Tauroursodeoxycholic Acid Attenuates Angiotensin II Induced Abdominal Aortic Aneurysm Formation in Apolipoprotein E-deficient Mice by Inhibiting Endoplasmic Reticulum Stress

Abdominal aortic aneurysm (AAA) is characterised by the infiltration of smooth muscle cell (SMC) apoptosis, inflammatory cells, neovascularisation, and degradation of the extracellular matrix. Previous work has shown that endoplasmic reticulum (ER) stress and SMC apoptosis were increased both in a mouse model and human thoracic aortic aneurysm. However, whether the ER stress is activated in AAA formation and whether suppressing ER stress attenuates AAA is unknown. Human AAA and control aorta samples were collected. Expression of ER stress chaperones glucose-regulated protein (GRP)-78 and GRP-94 was detected by immunohistochemical staining. The effect of ER stress inhibitor tauroursodeoxycholic acid (TUDCA) on AAA formation in angiotensin (Ang) II induced apolipoprotein E-/- mice was explored. Elastin staining was used to observe the rupture of elastic fragmentation. Immunohistochemistry and Western blot analysis were performed, to detect the protein expression of ER stress chaperones and apoptosis molecules. There was significant upregulation of GRP-78 and GRP-94 in aneurysmal areas of human AAA and Ang II induced ApoE-/- mice (p<.05). TUDCA significantly attenuated the maximum diameters of abdominal aortas in Ang II induced ApoE-/- mice (p<.05). TUDCA significantly reduced expression of ER stress chaperones and the apoptotic cell numbers (p<.05). Furthermore, TUDCA significantly reduced expression of apoptosis molecules, such as caspase-3, caspase-12, C/EBP homologous protein, c-Jun N-terminal kinase activating transcription factor 4, X-box binding protein, and eukaryotic initiation factor 2α in Ang II induced ApoE-/- mice (p<.05). The results suggest that ER stress is involved in human and Ang II induced AAA formation in ApoE-/- mice. TUDCA attenuates Ang II induced AAA formation in ApoE-/- mice by inhibiting ER stress mediated apoptosis.

NOX isoforms in the development of abdominal aortic aneurysm

Oxidative stress plays an important role in the formation of abdominal aortic aneurysm (AAA), and we have recently established a causal role of uncoupled eNOS in this severe human disease. We have also shown that activation of NADPH oxidase (NOX) lies upstream of uncoupled eNOS. Therefore, identification of the specific NOX isoforms that are required for eNOS uncoupling and AAA formation would ultimately lead to novel therapies for AAA. In the present study, we used the Ang II infused hph-1 mice to examine the roles of NOX isoforms in the development of AAA. We generated double mutants of hph-1-NOX1, hph-1-NOX2, hph-1-p47phox, and hph-1-NOX4. After two weeks of Ang II infusion, the incidence rate of AAA substantially dropped from 76.5% in Ang II infused hph-1 mice (n=34) to 11.1%, 15.0%, 9.5% and 0% in hph-1-NOX1 (n=27), hph-1-NOX2 (n=40), hph-1-p47phox (n=21), and hph-1-NOX4 (n=33) double mutant mice, respectively. The size of abdominal aortas of the four double mutant mice, determined by ultrasound analyses, was significantly smaller than the hph-1 mice. Aortic nitric oxide and H4B bioavailabilities were markedly improved in the double mutants, while superoxide production and eNOS uncoupling activity were substantially diminished. These effects seemed attributed to an endothelial specific restoration of dihydrofolate reductase expression and activity, deficiency of which has been shown to induce eNOS uncoupling and AAA formation in both Ang II-infused hph-1 and apoE null animals. In addition, over-expression of human NOX4 N129S or T555S mutant newly identified in aneurysm patients increased hydrogen peroxide production, further implicating a relationship between NOX and human aneurysm. Taken together, these data indicate that NOX isoforms 1, 2 or 4 lies upstream of dihydrofolate reductase deficiency and eNOS uncoupling to induce AAA formation. These findings may promote development of novel therapeutics for the treatment of the disease by inhibiting NOX signaling.

Particularly interesting Cys-His-rich protein is highly expressed in human intracranial aneurysms and resists aneurysmal rupture.

Particularly interesting Cys-His-rich protein (PINCH) has several biological functions in cancer development, invasion and metastasis in malignant cells, and the expression of PINCH is upregulated in several cancer types, including breast cancer, gastric adenocarcinoma and rectal cancer. However, the contribution of PINCH to human cerebral aneurysms remains largely unknown. Therefore, the significance of PINCH expression in cerebral aneurysm growth and rupture was examined in the present study. The protein expression levels of alpha-smooth muscle actin, osteopontin (OPN), matrix metalloproteinase (MMP) 9 and PINCH were evaluated using immunohistochemistry and western blot analyses. The results demonstrate that the protein expression levels of OPN, MMP9 and PINCH in the unruptured intracranial aneurysm (UA) and ruptured intracranial aneurysm (RA) groups were markedly higher than those of the control group, whereas OPN and PINCH expression levels were decreased in the RA group compared to those of the UA group. In addition, there was a strong correlation between PINCH and tumor size (r=0.650 and P=0.0026), as well as between PINCH and OPN (r=0.639 and P=0.0033) in the unruptured cerebral aneurysms. However, the correlation between PINCH and tumor size (r=0.450 and P=0.1393) and between PINCH and OPN (r=0.366 and P=0.2426) revealed no obvious difference in the ruptured cerebral aneurysms. In conclusion, PINCH was highly expressed in the UAs, which may be a critical factor for preventing aneurysmal rupture. Moreover, PINCH may facilitate intracranial aneurysm progression, at least partially, through the activation of extracellular signal-regulated kinase signaling and the suppression of c-Jun N-terminal kinase signaling.

Heterogeneous histomorphology, yet homogeneous vascular smooth muscle cell dedifferentiation, characterize human aneurysm disease

ObjectiveAbdominal aortic aneurysm (AAA) is a frequent, potentially life-threatening, disease that can only be treated by surgical means such as open surgery or endovascular repair. No alternative treatment is currently available, and despite expanding knowledge about the pathomechanism, clinical trials on medical aneurysm abrogation have led to inconclusive results. The heterogeneity of human AAA based on histologic examination is thereby generally neglected. In this study we aimed to further elucidate the role of these differences in aneurysm disease. MethodsTissue samples from AAA and popliteal artery aneurysm patients were examined by histomorphologic analysis, immunohistochemistry, Western blot, and polymerase chain reaction. The results were correlated with clinical data such as aneurysm diameter and laboratory results. ResultsThe morphology of human AAA vessel wall probes varies tremendously based on the grade of inflammation. This correlates with increasing intima/media thickness and upregulation of the vascular endothelial growth factor cascade but not with any clinical parameter or the aneurysm diameter. The phenotypic switch of vascular smooth muscle cells occurred regardless of the inflammatory state and expressional changes of the transcription factors Kruppel-like factor-4 and transforming growth factor-β lead to differential protein localization in aneurysmal compared with control arteries. These changes were in similar manner also observed in samples from popliteal artery aneurysms, which, however, showed a more homogenous phenotype. ConclusionsHeterogeneity of AAA vessel walls based on inflammatory morphology does not correlate with AAA diameter yet harbors specific implications for basic research and possible aneurysm detection.

Secreted Protein Acidic and Rich in Cysteine Modulates Molecular Arterial Homeostasis of Human Arterial Smooth Muscle Cells In Vitro

Secreted protein acidic and rich in cysteine (SPARC) is widely expressed in the vascular smooth muscle cells (VSMCs) of human intracranial aneurysms (IAs), but the effect and underlying mechanism of SPARC on VSMCs during the formation and progression of IAs needs to be probed. Human umbilical arterial smooth muscle cells (HUASMCs) were treated with a gradient concentrations of SPARC in vitro for different time. Cell counting kit-8 (CCK-8) assay, cell cycle, and cell apoptosis were used to investigate the effect of SPARC on HUASMCs. After exposure to 2 and 4μg/ml SPARC, cell viability were 89.3±2.00%, and 87.57±2.17% (P<0.05 vs. control), respectively. Induced by 2μg/ml SPARC, the proportion of cells in G0/G1 phase was 74.77±1.33% (P<0.05 vs. control), and the early and late apoptosis ratio were 7.38±1.25% and 4.86±0.81% (P<0.01 vs. control), respectively. After exposure to 2μg/ml SPARC for 2, 6, 12, 24, and 48h, Western blot analysis showed that the protein level of p21 was upregulated significantly at 2-12h (P<0.05 vs. control), while the expression of p53 remained stable within 48h. The expression of Bax protein increased markedly and peaked at 24 (P<0.01 vs. control), while Bcl2 protein decreased significantly at 48h (P<0.01 vs. control). Cleaved caspase3 was also upregulated dramatically and peaked at 24h (P<0.05 vs. control). The protein level of MMP2 increased significantly and peaked at 24h (P<0.01 vs. control), while TIMP2 remained stable and even reduced at 48h (P<0.05 vs. control). Taken together, SPARC could arrest HUASMCs in G0/G1 phase by overexpression of p21 and induce mitochondria-mediated apoptosis in vitro, which could result in the decreased cell viability. Besides, SPARC might also lead to the activation of MMP2 instead of MMP9. These results indicated SPARC could reduce the self-repair capability and increase injury of media layer and internal elastic lamina of intracranial artery, which would disrupt the normal homeostatic mechanism controlling vascular repair, thus promoting the formation and progression of IAs.

Abstract 252: Chronic Relaxin Treatment Does Not Augment Angiotensin II Induced Aortic Pathologies in Mice

Introduction: Human relaxin is being tested clinically as an acute treatment for heart failure. The effects of relaxin on extracellular matrix remodeling, among several mechanisms, may provide myocardial benefit, however, the effects of relaxin on vascular extracellular matrix-related pathology has not been examined. Human aortic aneurysm is characterized by extracellular remodeling, as well as inflammation, thrombus formation and rupture. Studying relaxin in a model of aortic aneurysm might provide insight into mechanisms of the disease but also will assess whether such agents impact the incidence/severity of aortic aneurysms (AA). Objectives: The purpose of this study was to test the effects of relaxin, an anti-fibrotic agent, on angiotensin II (AngII)-induced AA, which is characterized by enhanced activation of matrix metalloproteinases (MMPs); additionally this model mimics human pathology. Methods and Results: Vehicle or relaxin was co-infused with AngII (1.44 mg/kg/d) in either C57BL/6 mice or apoE null mice through mini osmotic pumps for 28 days. Dose-dependent plasma relaxin concentrations were noted (12-60ng/ml). Relaxin did not augment AngII-induced aortic rupture rate, the most severe consequence of AA. Maximal ex vivo diameters of suprarenal aortas were measured for abdominal aortic dilation, and ascending aortic area was measured using an en face method to determine ascending aortic dilation. Maximal aortic diameter of suprarenal aortas did not show significant difference in relaxin and AngII infused mice with either mouse strain. Relaxin also had no effect on ascending aortic dilation in both mouse strains. Conclusion: Chronic relaxin infusion for 28days does not augment aortic aneurysms in AngII-infused mice, suggesting relaxin might not impact other matrix-dependent vascular pathologies, if used as a treatment for heart failure, although additional studies are warranted. Ongoing studies interrogate the potential benefits of molecular mechanisms of relaxin response in the AngII-induced aortic pathologies.