Real-time analysis of the kinetics of angiogenesis and vascular permeability in an animal model of wound healing.

The use of engineered tissue for the treatment of a variety of acute to chronic wounds has become a clinical standard, and a better understanding of the cellular mechanisms of re-vascularization and barrier integrity could enhance clinical outcomes. Here, we focus on the characterization of the re-vascularization of acellular grafts such as Integra in an animal model to better understand the physiological properties of blood vessels growing in the collagen-glycosaminoglycan matrix vs. wound margins. While Integra has been extensively studied in pre-clinical models, the re-modeling mechanisms of the capillary bed under these matrices are not well understood. Therefore, our first objective was to quantify the kinetics of re-vascularization. The second objective was to assess changes in vascular permeability (VP) of the wound bed compared to normal adjacent skin. The third objective was to establish a non-invasive and quantitative assay for the measurement of VP to facilitate the rapid and reproducible characterization of vascular integrity. Using an excisional wound model in mice, we characterize the appearance, growth, and maturation of blood vessels in an Integra graft over 28 days after surgery. Initial appearance of blood vessels in the graft was observed at 7 days, with angiogenesis peaking between 7 and 14 days. The onset of VP coincided with the increase in re-vascularization of the wound bed and there was a sustained elevation of VP that declined to baseline by 28 days. We propose a non-invasive strategy to assess VP of the wound capillary bed will facilitate a better understanding of the cell and molecular basis of angiogenesis in wound healing.