53 - Freie Mitteilung
Inflammation & transplantation
16. Mai 2019, 10:15 - 11:45, Szenario 1, 5. OG


Fibrin-based transient delivery of engineered VEGF and PDGF-BB proteins ensures robust and stable angiogenesis in the skin of diabetic mice
P. Valente, A. Certelli, A. Uccelli, A. Grosso, N. Di Maggio, T. Wolff, L. Gürke, R. Gianni-Barrera, A. Banfi, Presenter: P. Valente (Basel)

Here we aimed at establishing the angiogenic and arteriogenic potential of an optimized fibrin-based co-delivery of VEGF and PDGF-BB in a pre-clinical animal model of diabetic Skin.
10-week old diabetic mice (BKS.Cg-Dock7m+/+Leprdb/J) received intracutaneous injections (in the dermal layer) of fibrin hydrogels (20 µl) containing VEGF alone (100 µg/ml) or together with PDGF-BB (10 µg/ml), or no factors as negative control (6 injections/animal; n=6-9/condition and time-point). Tissues were harvested at 7- and 28-day time-points after intravascular perfusion of fixative (1% paraformaldehyde), frozen and cryosectioned. Vascular growth was imaged by immunofluorescence staining and confocal microscopy. The amount and size of induced vessels were quantified with the Olympus Cell Sense software.
By 7 days fibrin was almost consumed. Both VEGF alone (V) or with PDGF-BB (VP) induced a comparable increase in vascular density (Vessel Length Density, VLD: V=24,1+-0,9 mm/mm^2; VP=25.9+-0,9 mm/mm^2; control=11,9+-0,9 mm/mm^2; p<0.0001). The total amount of induced vessels (vessel density multiplied by the total area of angiogenic effect) was also similar in V and VP tissues. However, V-induced new vessels were significantly larger than those induced by VP (V=11,7+-0,77 µm; VP=8,9+-0,72 µm; control= 5,6+-0,34 µm; p<0.05 V vs VP), confirming the ability of PDGF-BB to prevent aberrant vascular enlargement by high-dose VEGF. After 28 days fibrin was no longer detectable in any condition. Vessels induced by VEGF alone showed partial regression compared to 7 days (VLD V=19,1+-1,5 mm/mm^2), which was prevented by addition of PDGF-BB (VP=23,6+-1,1 mm/mm^2). Definitively remodeled vessels showed similar capillary-size diameters in all conditions by 28 days (V=4+-0,15 µm; VP= 3,9+-0,12 µm; control= 4,2+-0,12 µm; p n.s.), suggesting a preferential regression of the more aberrant structures induced by high-dose VEGF alone.
These results establish the feasibility of fibrin-based delivery of angiogenic factors in the skin of diabetic mice. Co-delivery of PDGF-BB both prevented aberrant angiogenesis and ensured persistence of new vessels despite transient factor delivery. Although spontaneous angiogenesis is impaired in diabetic mice, high-dose delivery of fibrin-bound VEGF and PDGF-BB was effective to induce robust growth of stable and physiological vascular networks.
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