Akt1 Activity Regulates Vessel Maturation in a Tissue Engineering Model of Angiogenesis

Abstract

Akt kinase is a central signal transduction node that integrates extracellular cues that regulate cell migratory, proliferative, and morphological functions during angiogenesis. However, how Akt activity is modulated and contributes to subsequent vessel maturation is unclear. In this study we investigated the role of Akt1 in vessel maturation using human dermal microvascular endothelial cells (HDMVECs) expressing constitutively active and hemiphosphorylated Akt1 epi-alleles with graded kinase activity. HDMVECs expressing Akt1 epi-alleles were analyzed in vivo in a tissue engineering setting using a model of angiogenesis comprising cell-seeded poly-L-lactic acid scaffolds implanted subcutaneously into NOD/SCID murine hosts. The resultant intraimplant microvasculature was quantified for vascular parameters, including vessel diameter, perfusion, vascular density, and pericyte coverage. We found that constitutive Akt1 kinase activity in implanted HDMVECs correlated with loss of neovasculature function. Further, we found that the presence of coimplanted vascular smooth muscle cells (vSMCs) in the implants failed to promote blood vessel growth and maturation in a graded, Akt1 kinase activity-dependent manner. These results indicate that constitutive Akt1 activity disrupts the normal blood vessel growth and maturation. Therefore, we suggest that a downregulation of Akt1 activity is necessary for vSMC-induced maturation of newly formed blood vessels to occur.

AMIGO2, a novel membrane anchor of PDK1, controls cell survival and angiogenesis via Akt activation

“…Inhibition of Akt by siRNA revealed decreased ovarian tumor growth, angiogenesis, EC tube formation, and morphogenesis (Xia et al, 2006;Kitamura et al, 2008). However, recent studies show that inhibition of Akt did not affect capillary-like network formation, and expression of constitutively active Akt led to nonfunctional vasculature formation in ECs after co-culture with vascular smooth muscle cells (Hellesøy et al, 2014;Hellesøy and Lorens, 2015). In addition, partial inhibition of PI3K signaling activates the Erk1/2 (MAPK) pathway by suppressing Akt1 activity and promotes arteriogenesis, though expression of constitutively active Akt promotes venous specification (Hong et al, 2006;Ren et al, 2010).…”

Cellular context–mediated Akt dynamics regulates MAP kinase signaling thresholds during angiogenesis

“…We expressed constitutively active myristolated Akt1 (myrAkt1) and phosphorylation-site alanine-substitution mutants (myrAkt1(T308A), myrAkt1(S473A)) in primary human dermal microvascular endothelial cells (HDMVECs) and human umbilical vein endothelial cells (HUVECs). The phosphorylation profiles of the Akt1 mutant constructs have been described previously ( Hellesoy et al. , 2014 ).…”