| Angiogenesis is a regulated process involving the proliferation, migration, and
remodeling of different cell types particularly mature endothelial and their progenitor
cells, nominated as endothelial progenitor cells (EPCs). Tie2/Tek is a tyrosine kinase
receptor expressed by endothelial cells that induces signal transduction pathways
involved in endothelial biology. To address the potential importance of the various
tyrosine residues of Tie2 in EPC development, we generated a series of Tie2 tyrosine
mutated (Y1106F, Y1100F, and Y1111F) EPCs and then assess the biological features
of these cells. Clonogenic, tubulogenic, proliferative, migratory, and functional
properties of these cells were analyzed. Next, GFP‐positive EPCs containing Tie2
tyrosine mutations were systemically transplanted into sublethaly irradiated mice to
analyze the potency of these cells for marrow reconstitution. We found that mutation
in the Tie2 tyrosine 1106 residue directed EPCs toward a mature endothelial
phenotype, which was associated with augmented tubulogenic and migratory
properties, and increased phosphorylation of the active site (tyrosine 992) as well
as increased vascular perfusion in the in vivo Matrigel plug assay. Moreover,
transplantation of 1106 Tie2 mutant EPCs failed to reconstitute the bone marrow
after myeloablation, whereas transplantation of EPCs with the 1100 or 1111 Tie2
tyrosine mutation resulted in bone marrow engraftment, leading to improved survival
of recipient mice. Our findings demonstrate that the tyrosine 1106 residue in Tie2
plays a key role to maintain the stemness features of EPCs |