Single-cell RNA sequencing of medial vascular smooth muscle cells of normal aorta from healthy mouse

Vascular smooth muscle cell (VSMC) subpopulations relevant to vascular disease and injury repair have been depicted in healthy vessels and atherosclerosis profiles. However, whether VSMC subpopulation associated with vascular homeostasis exists in the healthy artery and how are their nature and fate in vascular remodeling remains elusive. Here, using single-cell RNA-sequencing (scRNA-seq) to detect VSMC functional heterogeneity in an unbiased manner, we showed that VSMC subpopulations in healthy artery presented transcriptome diversity and that there was significant heterogeneity in differentiation state and development within each subpopulation. Notably, we detected an independent subpopulation of VSMCs that highly expressed regulator of G protein signaling 5 (Rgs5), upregulated the genes associated with inhibition of cell proliferation and construction of cytoskeleton compared with the general subpopulation, and mainly enriched in descending aorta. Additionally, the proportion of Rgs5+ VSMCs was markedly decreased or almost disappeared in the vascular tissues of neointimal formation, abdominal aortic aneurysm and atherosclerosis. Specific spatiotemporal characterization of Rgs5+ VSMC subpopulation suggested that this subpopulation was implicated in vascular homeostasis. Together, our analyses identify homeostasis-relevant transcriptional signatures of VSMC subpopulations in healthy artery, which may explain the regional vascular resistance to atherosclerosis at some extent. Detection of VSMC functional heterogeneity in medial cell layer of normal mouse aortic tissue by single-cell RNA sequencing.与血管疾病及损伤修复相关的血管平滑肌细胞（vascular smooth muscle cell, VSMC）亚群，已在健康血管与动脉粥样硬化的转录组特征中得到阐明。然而，与血管稳态相关的VSMC亚群是否存在于健康动脉中，以及其在血管重塑过程中的本质与命运如何，目前仍不明确。本研究采用无偏分析策略，借助单细胞RNA测序（single-cell RNA-sequencing, scRNA-seq）探究VSMC的功能异质性，结果显示健康动脉中的VSMC亚群存在转录组多样性，且各亚群内部的分化状态与发育进程均存在显著异质性。值得注意的是，我们检测到一类独立的VSMC亚群：该亚群高表达G蛋白信号调节因子5（regulator of G protein signaling 5, Rgs5），与普通亚群相比，其上调了与细胞增殖抑制及细胞骨架构建相关的基因，且主要富集于降主动脉中。此外，在新内膜形成、腹主动脉瘤及动脉粥样硬化的血管组织中，Rgs5阳性VSMC的占比显著降低，甚至几乎消失。对Rgs5阳性VSMC亚群的特异性时空特征分析表明，该亚群参与维持血管稳态。综上，本研究明确了健康动脉中与稳态相关的VSMC亚群转录特征，这在一定程度上可解释区域血管对动脉粥样硬化的抵抗性。本研究通过单细胞RNA测序，检测了正常小鼠主动脉中膜层的VSMC功能异质性。