Environment-Sensing Aryl Hydrocarbon Receptor Inhibits the Chondrogenic Fate of Modulated Smooth Muscle Cells in Atherosclerotic Lesions.

Smooth muscle cells (SMC) play a critical role in atherosclerosis. The Aryl hydrocarbon receptor (AHR) is an environment-sensing transcription factor that contributes to vascular development, and has been implicated in coronary artery disease (CAD) risk. We hypothesized that AHR can affect atherosclerosis by regulating phenotypic modulation of SMC. We combined RNA-Seq, ChIP-Seq, ATAC-Seq and in-vitro assays in human coronary artery SMC (HCASMC), with single-cell RNA-Seq (scRNA-Seq), histology, and RNAscope in an SMC-specific lineage-tracing Ahr knockout mouse model of atherosclerosis to better understand the role of AHR in vascular disease. Genomic studies coupled with functional assays in cultured HCASMC revealed that AHR modulates HCASMC phenotype and suppresses ossification in these cells. Lineage tracing and activity tracing studies in the mouse aortic sinus showed that the Ahr pathway is active in modulated SMC in the atherosclerotic lesion cap. Furthermore, scRNA-Seq studies of the SMC-specific Ahr knockout mice showed a significant increase in the proportion of modulated SMC expressing chondrocyte markers such as Col2a1 and Alpl, which localized to the lesion neointima. These cells, which we term “chondromyocytes” (CMC), were also identified in the neointima of human coronary arteries. In histological analyses, these changes manifested as larger lesion size, increased lineage-traced SMC participation in the lesion, decreased lineage-traced SMC in the lesion cap, and increased alkaline phosphatase activity in lesions in the Ahr knockout compared to wild-type mice. We propose that AHR is likely protective based on these data and inference from human genetic analyses. Overall, we conclude that AHR promotes maintenance of lesion cap integrity and diminishes the disease related SMC-to-CMC transition in atherosclerotic tissues.

平滑肌细胞（SMC）在动脉粥样硬化中起着关键作用。芳香烃受体（AHR）是一种环境感应转录因子，有助于血管发育，并与冠状动脉疾病（CAD）风险有关。我们假设AHR可通过调节SMC的表型调节来影响动脉粥样硬化。 我们在人冠状动脉平滑肌细胞（HCASMC）中结合了RNA - Seq、ChIP - Seq、ATAC - Seq和体外实验，并在一个平滑肌细胞特异性谱系追踪的Ahr基因敲除动脉粥样硬化小鼠模型中进行了单细胞RNA - Seq（scRNA - Seq）、组织学和RNAscope研究，以更好地理解AHR在血管疾病中的作用。 对培养的HCASMC进行的基因组研究以及功能实验表明，AHR调节HCASMC表型并抑制这些细胞的骨化。在小鼠主动脉窦进行的谱系追踪和活性追踪研究表明，Ahr通路在动脉粥样硬化病变帽中的调节型SMC中具有活性。此外，对平滑肌细胞特异性Ahr基因敲除小鼠的scRNA - Seq研究显示，表达软骨细胞标志物（如Col2a1和Alpl）的调节型SMC比例显著增加，这些细胞位于病变新生内膜。我们将这些细胞称为“软骨肌细胞”（CMC），在人冠状动脉的新生内膜中也发现了它们。在组织学分析中，与野生型小鼠相比，Ahr基因敲除小鼠表现出病变尺寸更大、谱系追踪的SMC在病变中的参与增加、谱系追踪的SMC在病变帽中的数量减少以及病变中的碱性磷酸酶活性增加。根据这些数据以及来自人类遗传学分析的推断，我们认为AHR可能具有保护作用。 总体而言，我们得出结论：AHR促进动脉粥样硬化组织中病变帽完整性的维持，并减少与疾病相关的SMC向CMC的转变。