Role of endothelial Lats1 and Lats2 in endothelial response to flow

Mechanical cues exerted by shear stress from blood flow remodel an initial vascular plexus into a ramifying array of large and small vessels. Hemodynamic forces trigger changes in endothelial cell (EC) gene expression and dynamic alterations in cell shape and adhesion. The objective of this study is to elucidate the role of the Lats1 and Lats2 (Lats1/2) Hippo pathway kinases in EC transducing of hemodynamic signals as vessels form. Lats1/2 were genetically deleted in murine ECs (LatsiECDKO) and developing vessels were evaluated using immunofluorescence. Primary Human Pulmonary Artery ECs were used to model endothelial response to blood flow and Lats1/2 depletion was achieved via siRNA treatment. EC junctions, cytoskeletal rearrangements, cell shape and polarization were assessed using immunofluorescence. mRNA expression analyses and western blotting were performed to understand changes in the response to shear stress in cultured ECs. We report a critical requirement for Lats1/2 in adapting to blood flow during vascular development. When Lats1/2 are genetically deleted in ECs, embryos develop severe defects in blood vessel formation, which lead to embryonic lethality by E11.5. Vessel patterning and circulation initiate properly; however remodeling of the initial vascular plexus fails due to lumen collapse. Lats1/2 depletion in cultured ECs leads to failed polarization, elongation, and VE-cadherin (VEcad) junctional maturation under flow. Finally, YAP/TAZ co-depletion in Lats1/2 depleted conditions leads to a partial rescue of phenotypes in vivo and in vitro. Our results suggest that Lats1/2 deficient cells no longer respond to laminar shear stress, in vivo and in vitro. This work identifies Lats1 and Lats2 as critical transducers of biomechanical cues during early blood vessel remodeling. This study provides new targets for treating vascular diseases and new directions for efforts to generate vascularized tissues for replacement therapies.