Background aims: Human cord blood (CB) is enriched in circulating endothelial colony forming cells (ECFCs) that display high proliferative potential and invivo vessel forming ability. Because Notch signaling is critical for embryonic blood vessel formation in utero, we hypothesized that Notch pathway activation may enhance cultured ECFC vasculogenic properties invivo. Methods: Invitro ECFC stimulation with an immobilized chimeric Notch ligand (Delta-like1<sup>ext-IgG</sup>) led to significant increases in the mRNA and protein levels of Notch regulated Hey2 and EphrinB2 that were blocked by treatment with γ-secretase inhibitor addition. However, Notch stimulated preconditioning invitro failed to enhance ECFC vasculogenesis invivo. In contrast, invivo co-implantation of ECFCs with OP9-Delta-like 1 stromal cells that constitutively expressed the Notch ligand delta-like 1 resulted in enhanced Notch activated ECFC-derived increased vessel density and enlarged vessel area invivo, an effect not induced by OP9 control stromal implantation. Results: This Notch activation was associated with diminished apoptosis in the exposed ECFC. Conclusions: We conclude that Notch pathway activation in ECFC invivo via co-implanted stromal cells expressing delta-like 1 promotes vasculogenesis and augments blood vessel formation via diminishing apoptosis of the implanted ECFC.
- Endothelial colony forming cells (ECFCs)
- Notch ligand delta-like 1 (Dll1)
- OP9-Delta-like 1 stromal cells (OP9-DL1)
ASJC Scopus subject areas
- Immunology and Allergy
- Cancer Research
- Cell Biology