Lats1/2 are essential for developmental vascular remodeling and biomechanical adaptation to shear stress

Abstract

Blood vessels in mammalian embryos develop from initial aggregates of endothelial cell (EC) progenitors, which coordinate the opening and stabilization of central vascular lumens, all while under progressively increasing flow and pressure from blood circulation. Mechanical cues exerted by shear stress from the blood flow remodel an initial vascular plexus into a ramifying array of large and small vessels. As plasma starts to fill vascular lumens, these forces trigger changes in EC gene expression and dynamic alterations in cell shape and cell adhesion, as cuboidal angioblasts elongate and flatten into ECs. Little is known about how embryonic ECs sense and transduce hemodynamic signals as vessels form in vivo. Here, we report a critical requirement for the Lats1 and Lats2 Hippo pathway kinases during this process. We show that when Lats1/2 are genetically deleted in ECs, embryos develop severe defects in blood vessel formation, which lead to embryonic lethality by E11.5. We find that initial vessel patterning and circulation initiate properly, however remodeling of the initial vascular plexus fails due to lumen collapse and altered blood flow. When Lats1/2 are knocked down using siRNA approaches in cultured ECs, cells fail to elongate and polarize, similar to ECs in the mutant embryos. In addition, VE-cadherin (VEcad) based junctions fail to mature under shear stress. These data show that Lats1/2 deficient cells no longer respond to laminar shear stress, both in vivo and in vitro. This work identifies the Hippo pathway kinases Lats1 and Lats2 as critical transducers of biomechanical cues during the early steps of blood vessel remodeling. This study will provide new targets for treatment of vascular diseases and new directions for efforts to generate vascularized tissues for replacement therapies. HighlightsO_LILats1 and Lats2 mRNA and protein are expressed in murine embryonic endothelial cells (ECs). C_LIO_LIDeletion of Lats1/2 in embryonic endothelium results in severe vascular defects and embryonic lethality. C_LIO_LILoss of Lats1/2 leads to failure of both vascular remodeling and EC elongation upon exposure to flow, in vivo and in vitro. C_LIO_LILats1/2 are required for cell-cell VE-cadherin adhesion maturation under flow. C_LIO_LILoss of Lats1/2 results in cytoskeletal disorganization in response to shear stress. C_LI