Promotion of Lymphangiogenesis by Targeted Delivery of VEGF-C Improves Diabetic Wound Healing.

Chronic wounds represent a major therapeutic challenge. Lymphatic vessel function is impaired in chronic ulcers but the role of lymphangiogenesis in wound healing has remained unclear. We found that lymphatic vessels are largely absent from chronic human wounds as evaluated in patient biopsies. Excisional wound healing studies were conducted using transgenic mice with or without an increased number of cutaneous lymphatic vessels, as well as antibody-mediated inhibition of lymphangiogenesis. We found that a lack of lymphatic vessels mediated a proinflammatory wound microenvironment and delayed wound closure, and that the VEGF-C/VEGFR3 signaling axis is required for wound lymphangiogenesis. Treatment of diabetic mice (db/db mice) with the F8-VEGF-C fusion protein that targets the alternatively spliced extra domain A (EDA) of fibronectin, expressed in remodeling tissue, promoted wound healing, and potently induced wound lymphangiogenesis. The treatment also reduced tissue inflammation and exerted beneficial effects on the wound microenvironment, including myofibroblast density and collagen deposition. These findings indicate that activating the lymphatic vasculature might represent a new therapeutic strategy for treating chronic non-healing wounds.

Non-invasive longitudinal imaging of VEGF-induced microvascular alterations in skin wounds.

Background: Microcirculation is essential for skin homeostasis and repair. A variety of growth factors have been identified as important regulators of wound healing. However, direct observation and longitudinal monitoring of skin remodeling in an unperturbed in vivo environment remains challenging. Methods: We report on non-invasive longitudinal imaging of the wound healing process in transgenic mice overexpressing vascular endothelial growth factor A (VEGF-A) in keratinocytes by means of large-scale optoacoustic microscopy (LSOM). This rapid, label-free, high throughput intravital microscopy method averts the use of dorsal skin-fold chambers, allowing for fully non-invasive repeated imaging of intact wounds with capillary resolution over field-of-view spanning several centimeters. Results: We observed VEGF-driven enhancement of dermal vascularization in ears, dorsal skin and healing wounds and quantified the hemoglobin content, fill fraction, vessel diameter and tortuosity. The in vivo findings were further corroborated by detailed side-by-side classical histological whole-mount vascular stainings and pan-endothelial CD31 immunofluorescence. Conclusion: The new approach is suitable for supplementing or replacing the cumbersome histological procedures in a broad range of skin regeneration and tissue engineering applications.