Non-healing chronic diabetic ulcers are a major cause of morbidity and mortality in diabetic patients and are associated with inherent pathologies, including increased proteolysis, inflammatory dysregulation and impaired neovascularization, which prevent wound resolution. Insufficient neovascularization plays a major role in impaired diabetic wound healing. Mechanisms responsible for this impairment may be anti-angiogenic wound environment with excess protease activity, altered cell phenotype of diabetic endothelial cells, and an inability to recruit vascular cells (endothelial (ECs) and endothelial progenitor cells (EPCs)) to the wound. We tested the hypothesis that augmentation of local wound microenvironment using the proteolysis-resistant angiogenic peptide nanofibers will result in formation of stable provisional matrix. This matrix will support enhanced wound infiltration of vascular cells, early neovascularization and extracellular matrix deposition, attenuated inflammation, and improve diabetic wound healing via the synergism of these actions.

Using both in vitro cell culture experiments and in vivo diabetic (db/db) mouse excisional wound healing model with background matched non-diabetic controls, we demonstrated that the nanofibers create a permissive environment that support angiogenic processes of microvascular endothelial cells and fibroblasts. Our results also demonstrate that angiogenic potential of ECs is impaired in diabetic condition and that it can be restored to that of non diabetic ECs in the angiogenic microenvironment of the nanofibers. We found that diabetic wound treatment with the nanofibers resulted in formation of a stable and pro-angiogenic in situ tissue engineered provisional matrix. This matrix significantly attenuated the local inflammatory response at the wound site and significantly improved vascular cell infiltration, wound neovascularization, repair tissue strength, and accelerated epidermal and dermal restoration and healing.

The results of this study suggest that complex disruptions in the diabetic wound microenvironment may be compensated for by the appropriate design of the provisional matrix, which provides missing cues to the cells in the diabetic wound milieu and directs in situ responses toward improved healing. Our results also suggest that a comprehensive approach to control local wound microenvironment can significantly alleviate several inherent diabetic wound pathologies even in the absence of glycemic control. Indeed, in the current wound healing paradigm, inflammation plays a significant role in coordinating the wound healing outcome. The findings from this study suggest, however, that in the appropriate microenvironment, neovascularization can be the “driving force” for improved granulation tissue formation and wound healing. Since it is well established that the diabetic wounds are stalled in the inflammatory/proliferative phase, with increased inflammation and proteolysis of the wound tissue preventing wound resolution, the shift in paradigm towards correcting the wound microenvironment to reduce proteolysis and increase neovascularization may help redirect diabetic wounds from the chronic state towards acute wound healing progression. This preclinical translational research is therefore promising for future development of new therapies, which can potentially benefit a large population of patients suffering from chronic diabetic ulcers.