Elevated homocysteine in human abdominal aortic aneurysmal tissues.

An abnormally high level of homocysteine (Hcy) has been consistently observed in the blood of abdominal aortic aneurysm (AAA) patients. However, the expression of Hcy in human AAA tissues has not been investigated. In this study, the expression of Hcy in aneurysmal tissues from AAA patients ( n=30) was compared with non-aneurysmal tissues from organ donors ( n=31) by dot blotting and immunohistochemistry. A significantly higher expression of Hcy was observed in AAA than control tissues ( p<0.001). Furthermore, the associations of methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism, detected by polymerase chain reaction-restriction fragment length polymorphism, with both AAA and tissue Hcy expression were evaluated. Our results showed MTHFR C677T polymorphism was not significantly associated with AAA or tissue Hcy expression. Lastly, the expression of Hcy in vascular smooth muscle cells (VSMCs), which were isolated from human aortic tissues by explant culture, and their release to cultured media was investigated by dot blotting. The AAA VSMCs expressed and released a significantly higher level of Hcy than the control VSMCs ( p<0.001). In summary, our novel findings showed Hcy expression was abnormally elevated in human AAA tissues, which may not be dependent on MTHFR C677T polymorphism.

Abdominal Aortic Aneurysm-Associated MicroRNA-516a-5p Regulates Expressions of Methylenetetrahydrofolate Reductase, Matrix Metalloproteinase-2, and Tissue Inhibitor of Matrix Metalloproteinase-1 in Human Abdominal Aortic Vascular Smooth Muscle Cells.

BACKGROUND: MicroRNAs (miRNAs or miRs) have been highlighted to be involved in abdominal aortic aneurysm (AAA) with the emergence of recent miRNA microarray profiling studies. miR-516a-5p has been shown to be significantly overexpressed in vascular smooth muscle cells (VSMCs) from human AAA tissues from our previous microarray study, suggesting its crucial association with AAA. In addition, further bioinformatics analysis predicted methylenetetrahydrofolate reductase (MTHFR), which regulates homocysteine (Hcy) metabolism and is proposed to be a risk gene for AAA formation and to be the downregulation target of miR-516a-5p. However, the pathogenic role of miR-516a-5p in VSMCs for AAA formation remains unresolved. This study aims to investigate the role of miR-516a-5p in human VSMCs for AAA pathogenesis. METHODS: miR-516a-5p was stably overexpressed and knocked down in VSMCs explant cultured from human abdominal aortic tissues by means of lentiviral system. The MTHFR protein expression was first examined by Western blotting. In addition, the protein expressions of several key components involved in AAA pathogenic features are as follows: matrix metalloproteinase (MMP)-2, MMP-9, tissue inhibitor of matrix metalloproteinase (TIMP)-1 and TIMP-2 for elastin degradation; collagen type 1 alpha 1 for compensatory collagen synthesis; monocyte chemoattractant protein-1 for inflammation, were also evaluated. Apoptotic level of VSMCs was examined by terminal deoxynucleotidyl transferase dUTP nick end labeling assay. RESULTS: Results showed that protein expression of MTHFR was significantly downregulated on miR-516a-5p overexpression (P < 0.05) in VSMCs, whereas it was significantly upregulated on miR-516a-5p knockdown (P < 0.05). Of all the AAA key components investigated, only MMP-2 and TIMP-1 protein expressions were found altered. A significant increase in MMP-2 (P < 0.05) and decrease in TIMP-1 (P < 0.05) expressions were observed on miR-516a-5p overexpression in VSMCs. Apoptosis was not promoted on miR-516a-5p overexpression or knockdown in VSMCs. CONCLUSIONS: Our findings suggested that miR-516a-5p may regulate MTHFR, MMP-2, and TIMP-1 expressions in human VSMCs, possibly promoting the disruption of Hcy metabolism and proteolytic degradation of elastin for AAA formation.

Geometric Alteration of Renal Arteries After Fenestrated Grafting and the Impact on Renal Function.

BACKGROUND: This study aims to investigate the degree of geometric change on renal arteries and its impact on renal function after fenestrated endovascular aortic repair (fEVAR). METHODS: Twenty-five patients with fEVAR were included. There were 47 renal arteries target vessels, and 43 of these (22 left and 21 right vessels) stented successfully. Their preoperative and first postoperative follow-up computed tomography (CT) images were reconstructed using the Aquarius workstation (TeraRecon, San Mateo, CA, USA). The superior mesenteric artery (SMA) or celiac axis (if SMA was stented) was appointed as reference origin. The longitudinal orientation of a renal artery or a stent was represented by a takeoff angle (ToA) between the renal artery or stent and the distal abdominal aorta. The postoperative stent ToAs were compared with those of preoperative renal arteries. Preoperative and short-term postoperative serum creatinine levels were measured. Renal function impairment was indicated as a >30% or >2.0 mg/dL rise in serum creatinine compared to the preoperative level. The relationship between postoperative renal function impairment and the stent orientation or geometric changes in renal arteries was correlated. RESULTS: The patency rate of renal arteries was 100% at the first postoperative CT review. The average ToAs of both renal arteries were significantly enlarged after stenting (P < 0.05). Seven stent deformations (16.3%) in four patients (16.0%) were observed. They were attributed to caudal misalignment of the fenestrated stent graft (n = 6) or inaccurate graft sizing (n = 1). There was no stent fracture or target vessel loss. Postoperatively, nine patients (36.0%) at day 1 and 10 patients (41.7%) after 3 months suffered the renal function impairment. This was found not to be associated with the stent angulation or angular change of the renal arteries (both P > 0.05). The three patients with stent deformation due to misalignment suffered postoperative renal function impairment and continuing deterioration in renal function. CONCLUSIONS: Implanted renal stents could angulate renal arteries more cephalad after fenestrated stenting. Postoperative renal function impairment was not associated with the stent orientation and changes in vessel orientation. Accurate fenestrated alignment is important to maintain stent performance and preserve renal function.

Clearance of matrix metalloproteinase-9 is dependent on low-density lipoprotein receptor-related protein-1 expression downregulated by microRNA-205 in human abdominal aortic aneurysm.

OBJECTIVE: Low-density lipoprotein receptor-related protein-1 (LRP1) has been suggested to be a crucial regulator in the pathogenesis of abdominal aortic aneurysm (AAA) from previous genome association and animal studies. Our prior study using human aortic samples has further revealed a significant reduction of LRP1 protein expression associated with AAA. However, the downregulation of LRP1 in the pathophysiology of AAA remained unresolved. We hypothesized that LRP1 downregulation may be mediated by microRNA (miR) and that LRP1 may function as a scavenger of matrix metalloproteinase-9 (MMP-9), a well-known protease for degradation of extracellular matrix proteins at the aortic wall for AAA pathogenesis. This study investigated the cause of LRP1 downregulation and its potential effect on AAA pathogenesis. METHODS: An observational study of LRP1 protein, LRP1 messenger RNA (mRNA), and its three predicted miR candidates (miR-205, miR-338-5p, and miR-545-3p) was first performed in AAA compared with nonaneurysmal tissues from humans, followed by a functional study testing the effect on LRP1 expression of miR-205 overexpression and knockdown in human vascular smooth muscle cells (VSMCs) explant cultured from human abdominal aortic tissues. Lastly, another functional study was performed to test for the clearance of exogenous MMP-9 upon silencing of LRP1 in human VSMCs. RESULTS: From the observational study, significantly higher miR-205 (P < .001) and lower LRP1 protein (P < .001) expressions were found in human AAA tissues compared with nonaneurysmal aortic tissues, and no significant difference in LRP1 mRNA expression was observed. Further statistical analysis showed a significant negative correlation between miR-205 and LRP1 protein expressions (r = -0.65; P < .01). For the functional study, a significant downregulation of LRP1 protein expression was shown in miR-205-overexpressing VSMCs (P < .05), without any alteration in LRP1 mRNA expression. Moreover, a significantly reduced clearance of exogenous MMP-9 was observed in LRP1-silenced VSMCs (P < .05), and this difference in MMP-9 clearance was completely abolished with a pretreatment of anti-LRP1 antibody. CONCLUSIONS: Our study revealed the downregulation of LRP1 protein expression may be tightly regulated by miR-205 through translational inhibition in human VSMCs. Also, such LRP1 down-regulation in VSMCs may hinder the removal of pericellular MMP-9, leading to excess MMP-9 remaining in the extracellular matrix. Hence, the integrity of the vascular wall may be disrupted, promoting AAA formation.