The microRNA miR-132 is a key regulator of lymphatic vascular remodelling

Lymphangiogenesis (growth of new lymphatic vessels), and lymphatic remodelling more broadly, are important for disease progression in cancer, lymphedema and the pulmonary disease lymphangioleiomyomatosis. Multiple molecular pathways which signal for aspects of lymphangiogenesis are known but little is understood about their co-ordinate regulation in lymphatic endothelial cells (LECs). Small RNA molecules co-ordinately regulate complex biological processes, but knowledge about their involvement in lymphangiogenesis is limited. Here we used high-throughput small RNA sequencing of LECs to identify microRNAs (miRs) regulating lymphatic remodelling driven by the lymphangiogenic growth factors VEGF-C and VEGF-D. We identified miR-132 as up-regulated by both growth factors, and demonstrated that inhibiting miR-132 in LECs in vitro blocked cell proliferation and tube formation, key steps in lymphangiogenesis. We showed that miR-132 is expressed in human LECs in vivo in the lymphatics of human breast tumours expressing VEGF-D. Importantly, we demonstrated that inhibiting miR-132 in vivo blocked many aspects of lymphangiogenesis in mice. Finally, we identified mRNAs regulated by miR-132 in LECs, by sequencing after RNA-protein cross-linking and Argonaute immunoprecipitation, which demonstrated how miR-132 co-ordinately regulates signalling pathways in lymphangiogenesis. This study shows miR-132 is a critical regulator of lymphangiogenesis and a potential target for therapeutically manipulating lymphatic remodelling in disease. ### Competing Interest Statement MGA and SAS are shareholders in Opthea Pty. Ltd., a company developing inhibitors of angiogenesis.