Encompassing View of Spatial and Single-Cell RNA Sequencing Renews the Role of the Microvasculature in Human Atherosclerosis

The manuscript by Bleckwehl et al. proposes a paradigm shift in our understanding and analyses of atherosclerotic plaque formation through the integration of single-cell RNA sequencing (scRNA-seq) and spatial transcriptomics, unveiling the vital role of microvessels to disease progression. Further, it sheds new lights on the spatiotemporal cross interaction and transcription of a variety of cell types including vascular cells and immune cells by employing high resolution approaches where patients with human atherosclerotic plaques are precisely mapped over a healthy situation.

The study identifies two subsets of endothelial cells, “endothelial_1” and “endothelial_2” where the first is found in the adventitia and the second is localized towards the luminal aspect. Both populations also have shown differential patterns: Endothelial_2 cells upregulate genes responsible for Endothelial to Mesenchymal transition (ex. TGFB2, FOXC2) during atherosclerosis. On the other hand, Endothelial_1 enriched cells, located in the vasa vasorum, are recruited for peripheral lymphocyte infiltration especially through ACKR1, and consequently implying enhanced immune cell infiltration. This knowledge highlights the role of endothelial cell diversity in influencing the immune microenvironment in atherosclerotic plaques.

A significant strength of the study lies in its integration of spatial transcriptomics, revealing localized cell-cell communication networks. For instance, the interaction between ACKR1+ endothelial cells and CD4+ T cells in the adventitia suggests that the microvasculature actively orchestrates immune cell dynamics. The computational and experimental validation of these interactions adds robustness to the findings. Notably, the recruitment of immune cells, including CD4+ T cells and macrophages, aligns with observed spatial gradients of inflammation and extracellular matrix remodelling.

The study further addresses the diversity of macrophage populations. In detail, the authors characterise macrophage populations of inflammatory and lipid-associated types including SPP1+ subtypes which are found in the more advanced plaques. These cells may have close interactions with fibromyocytes and vascular smooth muscle cells which partake in the remodelling of the extracellular matrix and stabilising the plaque. The close positioning of macrophages to lipid-rich regions and their participation in lipid transporter molecules such as TREM2 and CD36 have highlighted even more the relevant role of the macrophages in lipid metabolism and disease.
Despite the novelty and rigour of the manuscript, some limitations can be identified. The study includes a cross-sectional analysis precluding a more longitudinal approach to changes in the cells over time. Additionally, this study opens avenues to expand the findings of this study in the context of coronary arteries. More sophisticated functional imaging is needed to establish the cardiomyocyte specific role of the identified pathways, and its applicability to other vascular beds warrants further investigation.

In aggregate, this comprehensive work re-defines the role of the microvasculature in atherosclerosis, shedding light on cell-specific and spatially distinct mechanisms that collectively drive disease progression. These findings may have significant implications for therapeutic strategies targeting the microvasculature and immune cell interactions in atherosclerosis.