Proper migration of lymphatic endothelial cells requires survival and guidance cues from arterial mural cells

ABSTRACT The migration of lymphatic endothelial cells (LECs) is key for the development of the complex and vast lymphatic vascular network that pervades most of the tissues in an organism. In zebrafish, arterial intersegmental vessels together with chemokines have been shown to promote lymphatic cell migration from the horizontal myoseptum (HM). Here we found that LECs departure from HM coincides with the emergence of mural cells around the intersegmental arteries, raising the possibility that arterial mural cells promote LEC migration. Our live imaging and cell ablation experiments revealed that LECs migrate slower and fail to establish the lymphatic vascular network in the absence of arterial mural cells. We determined that mural cells are a source for the C-X-C motif chemokine 12 (Cxcl12a and Cxcl12b) and vascular endothelial growth factor C (Vegfc). We showed that ERK, a downstream component of Vegfc-Vegfr3 singling cascade, is activated in migrating LECs and that both chemokine and growth factor signalling is required for the robust migration. Furthermore, Vegfc-Vegfr3 has a pro-survival role in LECs during the migration. Together, the identification of mural cells a source for signals that guide LEC migration and survival will be important in the future design for rebuilding lymphatic vessels in the disease contexts.