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Impaired wound healing is a major source of morbidity in diabetic patients. Poor outcome has, in part, been related to increased inflammation, poor angiogenesis, and deficiencies in extracellular matrix components. Despite the enormous impact of these chronic wounds, effective therapies are lacking. Here, we showed that the topical application of recombinant matricellular protein angiopoietin-like 4 (ANGPTL4) accelerated wound reepithelialization in diabetic mice, in part, by improving angiogenesis. ANGPTL4 expression is markedly elevated upon normal wound injury. In contrast, ANGPTL4 expression remains low throughout the healing period in diabetic wounds. Exogenous ANGPTL4 modulated several regulatory networks involved in cell migration, angiogenesis, and inflammation, as evidenced by an altered gene expression signature. ANGPTL4 influenced the expression profile of endothelial-specific CD31 in diabetic wounds, returning its profile to that observed in wild-type wounds. We showed ANGPTL4-induced nitric oxide production through an integrin/JAK/STAT3-mediated upregulation of inducible nitric oxide synthase (iNOS) expression in wound epithelia, thus revealing a hitherto unknown mechanism by which ANGPTL4 regulated angiogenesis via keratinocyte-to-endothelial-cell communication. These data show that the replacement of ANGPTL4 may be an effective adjunctive or new therapeutic avenue for treating poor healing wounds. The present finding also confirms that therapeutic angiogenesis remains an attractive treatment modality for diabetic wound healing. Accepted version

Tumor development and progression to malignancy is increasingly viewed as a consequence of disrupted homeostatic interactions between epithelial cells and the underlying stromal elements. In squamous cell carcinoma of the skin, genomic and histological abnormalities have been observed in keratinocytes and stroma bordering multifocal neoplastic lesions, suggesting a regional carcinogenic signal that promotes aberrant cellular behavior within the tumor microenvironment. This has been termed field cancerization. Cancer associated fibroblasts (CAFs) are the major cell type in the tumor stroma and are known producers of extracellular pro-tumor signaling molecules. While growth factors and cytokines are candidate molecules for targeted therapy, reactive oxygen species (ROS) are gaining attention for their roles in heterotypic paracrine signaling in cancer. The importance of ROS in field cancerization remains poorly understood. Histological analysis of on sections of patient tumor biopsies revealed that ROS was elevated in the tumor stroma. CAFs explanted from patient tumors also released high levels of hydrogen peroxide into the extracellular space. Interestingly, normal fibroblasts exposed to CAF-conditioned medium displayed increased ROS production, an observation that could be reversed by the antioxidant N-acetyl cysteine. Exposure to hydrogen peroxide also resulted in elevated ROS production in normal fibroblasts. Taken together, these findings suggest that CAFs are a potent source of ROS in the tumor microenvironment and can induce a field effect that transforms adjacent normal fibroblasts into a CAF-like state. Transformed fibroblasts in turn produce ROS to spread oxidative stress in the microenvironment, potentially exacerbating field cancerization. Therefore, antioxidant-based therapies targeting the tumor microenvironment may be important adjuvant treatments to current anticancer chemotherapy or targeted therapy.