C57BL/6 Mouse Aortic Smooth Muscle Cells

TMAO Increases AngII-Induced Senescence and ROS Accumulation In Vitro

The pathology of abdominal aortic aneurysm (AAA) involves degradation of the extracellular matrix, oxidative stress, vascular inflammation, and smooth muscle cell senescence. Trimethylamine N-oxide (TMAO) is a gut microbial metabolite associated with CVD and has been shown to induce vascular inflammation and SMC senescence. The link between TMAO and AAA development has not yet been identified. Hu's team aims to investigate the association between TMAO and AAA formation and explore the underlying mechanisms.

In order to investigate the effects of TMAO on mouse aortic smooth muscle cells (SMCs), SMCs were incubated with AngII and/or TMAO before the detection of SA-β activity. SA-β staining revealed that AngII significantly increased SA-β activity, and TMAO treatment further increased the effect (Fig. 1A, C). Notably, as shown in Figure 1B, TMAO further exacerbated the AngII-induced ROS accumulation in SMCs. In contrast, TMAO treatment alone did not significantly affect SMCs (Fig. 1B, D). The expression of AAA-related MMP and senescence-related markers after TMAO treatment was further analyzed. TMAO further increased the AngII-induced expression of MMP2, MMP9, p16, and p21 in a dose-dependent manner (Fig. 1E–F). Taken together, the results suggested that TMAO exacerbates AngII-induced cellular senescence and ROS accumulation, which might be a possible mechanism by which TMAO promotes AAA formation.

Fig. 1. TMAO increases AngII-induced cellular senescence and ROS accumulation in vitro (Hu J X, Xu J M, et al., 2022).

FBLN7 in VSMCs is Associated with Vascular Remodeling

Arterial remodeling is a critical pathophysiological process of diseases like hypertension. Fibulin-7 (FBLN7) is an adhesion protein, and its function in vascular remodeling is still unclear. Here, Yao's team try to clarify whether FBLN7 regulates vascular remodeling and its mechanism.

To test whether FBLN7 was involved in vascular remodeling, they analyzed high-throughput sequencing data from two models of abdominal aortic aneurysm and hypertensive vascular remodeling from the GEO database (Fig. 2A). In the AAA model, FBLN7 expression was increased at 2 and 4 weeks after Ang II infusion than in the control group (Fig. 2B). Next, they analyzed the FBLN7 expression in vascular wall cells by single-cell sequencing data from human aortic tissue samples (Fig. 2F). The result showed that FBLN7 was highly expressed in smooth muscle cells, fibroblasts, and pericytes. They also verified the protein expression of FBLN7 in mouse aortic smooth muscle cells (MASMCs), endothelial cells (MAECs), fibroblasts (MAFs), and peritoneal macrophages (MPMs) by Western blot analysis and found that FBLN7 expression was high in MASMCs (Fig. 2G). Vascular smooth muscle cells (VSMCs) play an essential role in vascular remodeling; therefore, they tested the MASMCs stimulated by Ang II and found that FBLN7 expression was increased after Ang II treatment. Immunohistochemical staining and immunofluorescence staining further confirmed the high expression of FBLN7 in the media after Ang II infusion and colocalization of FBLN7 with the VSMC marker α-SMA (Figs. 2H and I). These results indicate a crucial role of FBLN7 in hypertension-induced vascular remodeling.

Fig. 2. The expression of FBLN7 is increased in vascular remodeling (Yao G Q, Zheng X H, et al., 2024).