PB0808 - Localized Endothelial Colony-Forming Cell-derived von Willebrand Factor (VWF) influences In Vivo Angiogenesis in VWF‐deficient Mice

Monday, June 26, 2023

18:30 – 19:30 ET

Room: Exhibition

Co-Author(s)

EO

Edwin K. Ocran

Graduate Student
Queen's University, Department of Medicine
Kingston, Ontario, Canada

Co-Author(s)

EB

Erin Burnett

Veterinary Technician
Queen's University, Pathology and Molecular Medicine
Kingston, Ontario, Canada

Presenting Author(s)

Mackenzie Bowman, PhD (she/her/hers)

Research Associate, Assistant Professor (Adjunct)
Department of Medicine, Queen's University
Kingston, Ontario, Canada

Co-Author(s)

Orla Rawley, PhD (she/her/hers)

Post-Doctoral Fellow
Queen's University, Pathology and Molecular Medicine
Kingston, Ontario, Canada
DM

Donald Maurice

Professor
Queen's University, Department of Biomedical and Molecular Sciences
Kingston, Ontario, Canada
David Lillicrap, MD

Professor
Department of Pathology and Molecular Medicine, Queen's University
Kingston, Ontario, Canada
Paula James, MD

Professor
Department of Medicine, Queen's University, Kingston, ON, Canada
Kingston, Ontario, Canada

Background: The established negative regulatory role of von Willebrand Factor (VWF) in angiogenesis provides support for the hypothesis that VWF abnormalities contribute to the pathogenic mechanisms resulting in angiodysplasia.

Aims: To evaluate the effect of localized VWF produced by endothelial colony-forming cells (ECFCs) on in vivo angiogenesis in a VWF‐deficient mouse model.

Methods: 10 to 12-week C57Bl/6 VWF-/- mice of both sexes were used (N=15 per experiment). Matrigel with recombinant fibroblast growth factor (FGF) basic (146 aa) and recombinant human vascular endothelial growth factor (VEGF165) was supplemented with normal human ECFCs and injected subcutaneously in the right back flank of mice. Similar injections without ECFCs were made in the left back flank as a control. A second similar experiment was performed using human Type 3 von Willebrand disease (VWD) ECFCs, which lack VWF. After seven days, plugs were processed for hematoxylin and eosin (H&E) and immunohistochemical (IHC) staining.

Results: Compared to plugs that had normal ECFCs, those without ECFCs (controls) were dark red in colour, indicating the presence of erythrocytes. These plugs showed increased capillary formation on H&E and on IHC staining as evidenced by higher signals of CD31 which stains murine endothelial cells (Figure 1).

In contrast, no clear differences were observed both grossly and histologically between plugs that received Type 3 VWD ECFCs and corresponding controls (Figure 1A). The mild decrease in vascularization seen in ECFC-supplemented plugs on IHC quantitation was not significant. NG2 staining for pericytes, a marker of vessel maturity, however, was significantly lower in these plugs (Figure 1B).

Conclusion(s): Supplementation of plugs with normal ECFCs reduced vessel formation, potentially due to the inhibitory role of VWF in angiogenesis. The addition of Type 3 VWD ECFCs resulted in more immature vessels, perhaps driven by the lack of VWF.