Retrospective Analysis Reveals the Early Origin and Development of Pulmonary Perivascular Cells

The pulmonary vasculature develops in close association with the airways and this network expands through the interactions between endothelial cells and the surrounding mesenchymal cells, the pericytes. Emerging evidence suggests that pericytes play a significant role in various lung diseases, such as congenital diaphragmatic hernia and chronic obstructive pulmonary disease. However, characterizing pericytes remains challenging, impeding our understanding of their exact role in lung development and disease. Therefore, we used a novel cell tracing technology based on a bacterial DNA cytosine methyltransferase (Dcm) fused to RNA polymerase II (DCM-TM) to methylate active genes. The doxycycline inducible Dcm-PolII fusion protein was activated at specific time points during gestation, while the epigenetically labeled genes were analyzed at later time points. This retrospective cell tracing was coupled to single-cell RNA sequencing to track the development of mouse pulmonary pericytes at the single cell level. This revealed the paths to differentiation of perivascular progenitors into pericytes and vascular smooth muscle cells. Temporal analysis uncovered dynamic gene expression profiles during pericyte differentiation, highlighting pathways crucial for pulmonary vascular development. Further analysis showed intricate signaling interactions between pericyte progenitors and mature pericytes, and we validated MCAM as a bona fide pulmonary pericyte marker. Our findings challenge conventional views on pericyte origin and underscore the importance of accurate pericyte identification in developmental and disease contexts. Overall, this study enhances our understanding of pulmonary pericyte ontogeny and differentiation, offering insights into their potential as therapeutic targets in pericyte-associated lung diseases.