Cell and matrix interactions in diabetic vascular tissue engineering models

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Diabetes is a major risk factor for vascular diseases that affects nearly all blood vessel types and calibers. In diabetes, elevated levels of blood glucose and lipids interact irreversibly with long-lived proteins, such as collagen and elastin from the blood vessel wall, via oxidation and crosslinking processes, resulting in formation of advanced glycation end products (AGEs); the consequence is vascular stiffening, the hallmark of diabetes. Furthermore, vascular cells respond to diabetes- related altered environment by activation and leading to pathological remodeling and to the onset and progression of vascular disease. Together, these severe cell and extracellular matrix (ECM) changes result in activation of inflammation, impaired healing, fibrosis, and ectopic calcification. The interaction of AGEs with their receptor, RAGE, stimulates the production of reactive oxygen species, leading to dysfunctional remodeling of the vascular wall (stiffening, fibrosis, and calcification). The goal of this project is to characterize the effect of diabetes on the adventitial fibroblasts and their involvement in vascular pathology. By using 3D models based on tissue engineering principles, we can control the type of cells seeded on a vascular matrix-based scaffold while providing the necessary biochemical and mechanical stimuli in a physiologic bioreactor. The tissue engineered construct can also be implanted in diabetic animal models, to explore the effect of ECM oxidation and AGE accumulation on the fate of adventitial fibroblasts. The effect of antioxidant and anti-inflammatory agents can also be monitored. Our hypothesis is that fibroblasts are activated by ROS and contribute to the dysfunctional remodeling of the vascular wall in response to diabetes-induced injuries. This hypothesis will be tested in the following two aims. In specific Aim 1 we will investigate the contribution of diabetic adventitial fibroblasts to the pathological vascular wall remodeling. Vascular ECM-based scaffolds (acellular arteries) will be seeded with human endothelial cells, smooth muscle cells, and fibroblasts and a) incubated in a physiologic vascular bioreactor for 2 months in diabetic media, b) implanted as transposition grafts in the abdominal aorta of normal and diabetic nude rats for 3 and 6 months. Grafts will be monitored for oxidative stress and inflammation. In specific Aim 2 we will explore the fate of diabetic adventitial fibroblasts in the presence of antioxidant and anti-inflammatory agents. Vascular ECM-based scaffolds seeded with human vascular cells will be a) incubated in a physiologic vascular bioreactor for 2 months in diabetic media and b) implanted as transposition grafts in the abdominal aorta of normal and diabetic nude rats for 3 and 6 months, in the presence of antioxidant polyphenolic compounds, metformin, an insulin- sensitizer drug, and immunomodulatory mesenchymal cells (in separate groups). Grafts will be monitored for oxidative stress and inflammation. Expectations: at the conclusion of this study, we would gain important information about the major diabetes-related alterations in the vascular wall initiated by the adventitial fibroblasts, potentially offering avenues for targeting these events.