Early growth response 1 exacerbates thoracic aortic aneurysm and dissection of mice by inducing the phenotypic switching of vascular smooth muscle cell through the activation of Krüppel-like factor 5.

Vascular smooth muscle cell (VSMC) phenotypic switching has been reported to regulate vascular function and thoracic aortic aneurysm and dissection (TAAD) progression. Early growth response 1 (Egr1) is associated with the differentiation of VSMCs. However, the mechanisms through which Egr1 participates in the regulation of VSMCs and progression of TAAD remain unknown. This study aimed to investigate the role of Egr1 in the phenotypic switching of VSMCs and the development of TAAD. Wild-type C57BL/6 and SMC-specific Egr1-knockout mice were used as experimental subjects and fed β-aminopropionitrile for 4 weeks to construct the TAAD model. Ultrasound and aortic staining were performed to examine the pathological features in thoracic aortic tissues. Transwell, wound healing, CCK8, and immunofluorescence assays detected the migration and proliferation of synthetic VSMCs. Egr1 was directly bound to the promoter of Krüppel-like factor 5 (KLF5) and promoted the expression of KLF5, which was validated by JASPAR database and dual-luciferase reporter assay. Egr1 expression increased and was partially co-located with VSMCs in aortic tissues of mice with TAAD. SMC-specific Egr1 deficiency alleviated TAAD and inhibited the phenotypic switching of VSMC. Egr1 knockdown prevented the phenotypic switching of VSMCs and subsequently suppressed the migration and proliferation of synthetic VSMCs. The inhibitory effects of Egr1 deficiency on VSMCs were blunted once KLF5 was overexpressed. Egr1 aggravated the development of TAAD by promoting the phenotypic switching of VSMCs via enhancing the transcriptional activation of KLF5. These results suggest that inhibition of SMC-specific Egr1 expression is a promising therapy for TAAD.

Han X ，Xu S ，Hu K ，Yu Y ，Wang X ，Qu C ，Yang B ，Liu X ... -  《-》

ER stress dependent microparticles derived from smooth muscle cells promote endothelial dysfunction during thoracic aortic aneurysm and dissection.

The degeneration of vascular smooth muscle cell(s) (SMC) is one of the key features of thoracic aortic aneurysm and dissection (TAAD). We and others have shown that elevated endoplasmic reticulum (ER) stress causes SMC loss and TAAD formation, however, the mechanism of how SMC dysfunction contributes to intimal damage, leading to TAAD, remains to be explored. In the present study, in vitro assay demonstrated that elevated mechanical stretch (18% elongation, 3600 cycles/h) stimulated the ER stress response and microparticle(s) (MP) production from both SMC and endothelial cell(s) (EC) in a time-dependent manner. Treatment of EC with isolated MP led to anoikis, which was determined by measuring the fluorescence of the ethidium homodimer (EthD-1) and Calcein AM cultured in hydrogel-coated plates and control plates. MP stimulation of EC also up-regulated the mRNA levels of inflammatory molecules (i.e. Vascular cellular adhesion molecular-1 (VCAM-1)), intercellular adhesion molecular-1 (ICAM-1), interleukin-1β (IL-1β), and interleukin-6 (IL-6)). Use of an ER stress inhibitor or knockout of CHOP decreased mechanical stretch-induced MP production in SMC. In vivo, administration of an ER stress inhibitor or knockout of CHOP suppressed both apoptosis of EC and the infiltration of inflammatory cells. Moreover, TAAD formation was also suppressed by the administration of an ER stress inhibitor. In conclusion, our study demonstrates that elevated mechanical stretch induces MP formation in SMC leading to endothelial dysfunction, which is ER stress dependent. The inhibition of ER stress suppressed EC apoptosis, inflammation in the aorta, and TAAD development.

Jia LX ，Zhang WM ，Li TT ，Liu Y ，Piao CM ，Ma YC ，Lu Y ，Wang Y ，Liu TT ，Qi YF ，Du J ... -  《-》

Dexamethasone attenuated thoracic aortic aneurysm and dissection in vascular smooth muscle cell Tgfbr2-disrupted mice with CCL8 suppression.

What is the central question of this study? What is the relationship of chemokine (C-C motif) ligand 8 (CCL8) to thoracic aortic aneurysm and dissection (TAAD) formation in postnatal mice with vascular smooth muscle cell (VSMC) Tgfbr2 disruption, and is dexamethasone a potential treatment? What is the main finding and its importance? CCL8 was associated with the formation of TAAD in VSMC Tgfbr2-disrupted mice. Dexamethasone reduced TAAD formation and inhibited mitogen-activated protein kinase (p-p38) and nuclear factor-κB (p-p65) signalling pathways. CCL8 might be an important promoter of aortic inflammation. Dexamethasone provided potential therapeutic effects in TAAD treatment. Aortic inflammation plays a vital role in initiation and progression of thoracic aortic aneurysm and dissection (TAAD). Disturbance of the transforming growth factor-β (TGF-β) signalling pathway is believed to be one of the pathogenic mechanisms of TAAD. Initially, Myh11-CreERT2 .Tgfbr2f/f male mice were used to build a TAAD mouse model, and bioinformatic analyses revealed enriched inflammatory signal pathways and upregulated chemokine (C-C motif) ligand 8 (CCL8). So we hypothesized that vascular smooth muscle cell (VSMC) Tgfbr2 disruption in postnatal mice results in aortic inflammation associated with CCL8 secretion. Real-time quantitative PCR and serum enzyme-linked immunosorbent assay (ELISA) results confirmed that CCL8 expression began to increase after VSMC Tgfbr2 disruption. Next, we cultured mouse thoracic aortas ex vivo, and observed that the protein expression of CCL8 in culture supernatants was increased by ELISA. Subsequently, the co-localization of CCL8 with α-smooth muscle actin or CD68 was found to be significantly increased by immunofluorescence. Then, dexamethasone (DEX) was used to treat TAAD in VSMC Tgfbr2-disrupted mice; the results of histochemical, immunofluorescence and immunohistochemical staining indicated that DEX therapy reduced CCL8 secretion, inflammatory cell recruitment, aortic medial thickening, elastic fibre fragmentation, extracellular matrix degradation and contractile apparatus impairment, and thereby ameliorated TAAD formation. Western blotting showed that mitogen-activated protein kinase and nuclear factor-κB signalling pathways in aorta were overactivated after VSMC Tgfbr2 disruption, but inhibited by DEX therapy. Altogether, CCL8 might be an important promoter in TAAD formation of VSMC Tgfbr2-disrupted mice, and DEX provided potential therapeutic effects in TAAD treatment.

Wang X ，Li Q ，Li W ，Zhang T ，Li X ，Jiao Y ，Zhang X ，Jiang J ，Zhang X ，Zhang X ... -  《-》

MicroRNA-21 Knockout Exacerbates Angiotensin II-Induced Thoracic Aortic Aneurysm and Dissection in Mice With Abnormal Transforming Growth Factor-β-SMAD3 Signaling.

Thoracic aortic aneurysm and dissection (TAAD) are severe vascular conditions. Dysfunctional transforming growth factor-β (TGF-β) signaling in vascular smooth muscle cells and elevated angiotensin II (AngII) levels are implicated in the development of TAAD. In this study, we investigated whether these 2 factors lead to TAAD in a mouse model and explored the possibility of using microRNA-21 (miR-21) for the treatment of TAAD. TAAD was developed in Smad3 (mothers against decapentaplegic homolog 3) heterozygous (S3+/-) mice infused with AngII. We found that p-ERK (phosphorylated extracellular regulated protein kinases)- and p-JNK (phosphorylated c-Jun N-terminal kinase)-associated miR-21 was higher in TAAD lesions. We hypothesize that downregulation of miR-21 mitigate TAAD formation. However, Smad3+/-:miR-21-/- (S3+/-21-/-) mice exhibited conspicuous TAAD formation after AngII infusion. The vascular wall was dilated, and aortic rupture occurred within 23 days during AngII infusion. We then examined canonical and noncanonical TGF-β signaling and found that miR-21 knockout in S3+/- mice increased SMAD7 and suppressed canonical TGF-β signaling. Vascular smooth muscle cells lacking TGF-β signals tended to switch from a contractile to a synthetic phenotype. The silencing of Smad7 with lentivirus prevented AngII-induced TAAD formation in S3+/-21-/- mice. Our study demonstrated that miR-21 knockout exacerbated AngII-induced TAAD formation in mice, which was associated with TGF-β signaling dysfunction. Therapeutic strategies targeting TAAD should consider unexpected side effects associated with alterations in TGF-β signaling.

Huang X ，Yue Z ，Wu J ，Chen J ，Wang S ，Wu J ，Ren L ，Zhang A ，Deng P ，Wang K ，Wu C ，Ding X ，Ye P ，Xia J ... -  《-》

Effects of Extracellular Matrix Softening on Vascular Smooth Muscle Cell Dysfunction.

Shao Y ，Li G ，Huang S ，Li Z ，Qiao B ，Chen D ，Li Y ，Liu H ，Du J ，Li P ... -  《-》