Endothelial VEGFR2 insufficiency promotes the transition of lymphatic to hematopoietic transcriptional programs

Vascular endothelial growth factor receptor-2 (VEGFR2) is a key target for regulating the endothelial cell lineage and angiogenesis. It is also expressed by lymphatic endothelial cells (LECs) while its participation in lymphangiogenesis remains inadequately characterized. We demonstrate in this study that VEGFR2 is highly expressed in dermal initial lymphatic vessels and valves. The induced deletion of pan-endothelial Vegfr2 at the neonatal stage produced a potent suppression of dermal lymphatic growth, characterized by a thinner lymphatic diameter, a decreased number of LECs and lymphatic valves. Mechanistically, VEGFR2 insufficiency led to a dramatic decrease in lymphatic VEGFR3, a key regulator mediating signals for lymphatic growth and remodeling. RNA sequencing analysis revealed that GO terms enriched for downregulated genes included biological processes related to EC development while pathways related to hematopoiesis and immune responses were upregulated in the skin of Vegfr2 mutants compared with littermate controls. This was further confirmed by RNA-seq analysis of dermal tissues 48 h after endothelial Vegfr2 deletion. Consistently, targeting Vegfr2 in PROX1⁺ cells produced an inhibitory effect on dermal lymphatic growth and recapitulated a similar altered transcriptomic signature. The alteration of lymphatic gene expression was further validated by siRNA-mediated Vegfr2 knockdown in primary LECs, showing a transcriptional trend toward a hematopoietic fate. Findings from this study imply that VEGFR2 is required for the maintenance of endothelial identity, and its insufficiency triggers a transcriptional reprogramming that diminishes VEGFR3-mediated lymphangiogenesis.