A CXCL12 morphogen gradient uncovers lung endothelial heterogeneity and promotes distal vascular growth

Abstract

In adults, there is a growing amount of data uncovering the cellular diversity of the pulmonary circulation and mechanisms governing vascular repair after injury, however, molecular and cellular mechanisms contributing to the morphogenesis and growth of the pulmonary vasculature during embryonic development are less clear. Importantly, deficits in vascular development lead to a large number of lung diseases in children, indicating a need to uncover fetal programs that promote pulmonary vascular growth. To address this, we used a transgenic mouse reporter for expression of Cxcl12, an arterial hallmark gene, and performed single-cell RNA sequencing on isolated Cxcl12-DsRed+ endothelium to assess cellular heterogeneity within pulmonary endothelium. Combining cell annotation, gene ontology analysis, and spatial transcriptomics allowed us to segregate the developing artery into spatially and functionally distinct novel subpopulations. In addition, expression of Cxcl12 suggests a morphogen gradient from arteries to capillaries, suggesting directed cell migration for pulmonary vascular development. Disruption of this gradient led to abnormal branching and pulmonary vascular hypoplasia. These data provide evidence for arterial endothelial functional heterogeneity and reveal conserved signaling mechanisms essential for pulmonary vascular development.

Molecular Changes Implicate Angiogenesis and Arterial Remodeling in Systemic Sclerosis–Associated and Idiopathic Pulmonary Hypertension

“…Phalanx cells were marked by enrichment of fatty acid-binding proteins RBP7 (retinol-binding protein 7), FABP4 (fatty acid binding protein 4), and taurine transporter SLC6A6 and the absence of canonical tip markers (PGF and APLN; Figure 2A). Phalanx cells shared a similar gene expression profile with tip cells and exhibited high expression level of genes associated with vascular development (CXCL12 [C-X-C motif chemokine 12], 48,49 HSPG2, 50 and SOX18 51 ), endothelial barrier integrity (PLVAP 52 and COL15A1 53 ), and Notch signaling (NOTCH4 and HEY1; Figures 1B, 1C, and 2A). Although some of these gene markers were shared by arterial and venous populations, phalanx cells were distinguished from these populations by the absence of other markers for arterial (DKK2 and GJA5) and venous ECs (NR2F2 54 and ACKR1; Figure 2A).…”