J EXP MED

Petkova et al. identify a new Ptx3-positive immune-interacting subtype of lymphatic endothelial cells, iLECs, that drive oncogenic PI3K-driven lymphatic malformations. These cells produce chemokines that recruit pro-lymphangiogenic macrophages, which in turn promote pathological lymphatic vessel growth. Oncogenic mutations in PIK3CA, encoding p110 alpha-PI3K, are a common cause of venous and lymphatic malformations. Vessel type-specific disease pathogenesis is poorly understood, hampering development of efficient therapies. Here, we reveal a new immune-interacting subtype of Ptx3-positive dermal lymphatic capillary endothelial cells (iLECs) that recruit pro-lymphangiogenic macrophages to promote progressive lymphatic overgrowth. Mouse model of Pik3ca(H1047R)-driven vascular malformations showed that proliferation was induced in both venous and lymphatic ECs but sustained selectively in LECs of advanced lesions. Single-cell transcriptomics identified the iLEC population, residing at lymphatic capillary terminals of normal vasculature, that was expanded in Pik3ca(H1047R) mice. Expression of pro-inflammatory genes, including monocyte/macrophage chemokine Ccl2, in Pik3ca(H1047R)-iLECs was associated with recruitment of VEGF-C-producing macrophages. Macrophage depletion, CCL2 blockade, or anti-inflammatory COX-2 inhibition limited Pik3ca(H1047R)-driven lymphangiogenesis. Thus, targeting the paracrine crosstalk involving iLECs and macrophages provides a new therapeutic opportunity for lymphatic malformations. Identification of iLECs further indicates that peripheral lymphatic vessels not only respond to but also actively orchestrate inflammatory processes.