Endothelial Rictor is crucial for midgestational development and sustained and extensive FGF2-induced neovascularization in the adult

Abstract

To explore the general requirement of endothelial mTORC2 during embryonic and adolescent development, we knocked out the essential mTORC2 component Rictor in the mouse endothelium in the embryo, during adolescence and in endothelial cells in vitro. During embryonic development, Rictor knockout resulted in growth retardation and lethality around embryonic day 12. We detected reduced peripheral vascularization and delayed ossification of developing fingers, toes and vertebrae during this confined midgestational period. Rictor knockout did not affect viability, weight gain, and vascular development during further adolescence. However during this period, Rictor knockout prevented skin capillaries to gain larger and heterogeneously sized diameters and remodeling into tortuous vessels in response to FGF2. Rictor knockout strongly reduced extensive FGF2-induced neovascularization and prevented hemorrhage in FGF2-loaded matrigel plugs. Rictor knockout also disabled the formation of capillary-like networks by FGF2-stimulated mouse aortic endothelial cells in vitro. Low RICTOR expression was detected in quiescent, confluent mouse aortic endothelial cells, whereas high doses of FGF2 induced high RICTOR expression that was associated with strong mTORC2-specific protein kinase Cα and AKT phosphorylation. We demonstrate that the endothelial FGF-RICTOR axis is not required during endothelial quiescence, but crucial for midgestational development and sustained and extensive neovascularization in the adult.

Adeno-Associated Viral Vector-Mediated mTOR Inhibition by Short Hairpin RNA Suppresses Laser-Induced Choroidal Neovascularization

“…A number of previous studies have documented that both mTORC1 and mTORC2 are involved in angiogenesis and pro-inflammatory processes, and that the inhibition of the mTOR pathway may have anti-inflammatory and anti-angiogenic effects 12, 14, 30, 40, 41, 42, 43. The rAAV-mTOR shRNA used in this study inhibits both mTOR complexes, leading to the profound suppression of inflammation and angiogenesis, confirmed by immunohistology utilizing CD11b, F4/80, and CD31.…”

“…mTORC2 contains RICTOR, PROCTOR1/2, and mLST8 as companion proteins and is closely related to the AKT pathway, because it phosphorylates AKT 11 . While mTORC1 signaling is relatively well understood, the functions of mTORC2 have not been widely investigated, and only recently has its critical roles in cytoskeletal organization, regulation of cell survival, and promotion of neovascularization been revealed 12, 13, 14. Furthermore, deregulation of the mTOR signaling pathway leads to the development of several human diseases, because it is directly related to abnormalities in cell proliferation and survival processes 7 …”

Common Angiogenic Signaling Pathways Induced by Monomeric C - reactive protein and FGF-2 through MAPK and PI3K

“…The morphogenesis effects of mCRP, FGF-2 or mCRP combined with FGF-2 was mainly attenuated after blocking MAPK and PI3K signaling pathways while these effects were partially inhibited after the blockade of γ-secretase activity. Additional studies are needed to determine whether our observations in regards with the potential risk of haemorrhage due to aggressive neovascularization induced by mCRP combined with FGF-2 through the use of mCRP combined with FGF-2-loaded matrigel plugs, for instance [65]. It would be also of a great interest to check whether the inhibition of common signaling pathway of mCRP and FGF-2 could retard the progression of instable plaques in vivo using animal models of atherosclerosis.…”

“…Sustained and extensive FGF-2-induced neovascularization has been reported to cause haemorrhage [65]. The combination of mCRP and FGF-2 displayed longer, thicker, and sparser sprouts when compared to the control cells and to mCRP and FGF-2 alone.…”

MicroRNA-142-3p Induces Atherosclerosis-Associated Endothelial Cell Apoptosis by Directly Targeting Rictor

“…Knockdown of Rictor inhibited activation of Akt and reduced ECs proliferation, migration, neovascularization [37,38] and promoted endothelial apoptosis [37,39], inflammation [39] and senescence [40]. To the contrary, fibroblast growth factor (FGF) [38], vascular endothelial growth factor (VEGF) [41] and 14, 15-epoxyeicosatrienoic acid [40] could provoke the expression of Rictor and phosphorylation of Akt, suppressing apoptosis and senescence of ECs. Ox-LDL induced apoptosis and oxidative stress in HAECs through inhibiting Akt/eNOS signaling pathway [42].…”