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.
Almost 25 million Americans have diabetes, a disease which is characterized by high levels of blood sugar (glucose). Excessive glucose binds to tissues and cells and this binding reduces the activity of the heart muscle, heart valves, blood vessels, kidneys, and nerves. For this reason, patients with diabetes have much higher risks of cardiovascular and other diseases, as compared to non-diabetics. Surgery is required to replace diseased arteries with artificial implants, but these implants fail after 5-10 years because they are made of non-living materials which are not resistant to diabetes. ,mproved devices are needed for millions of GLDEHWLFvascular patients every year. To make better implants, we are developing biomaterials comprised of layers of tissue-like scaffolds or templates to which we add the patients? own cells. Although practically all current cardiovascular devices have been tested in healthy animals, our main concern is that implantation of tissue scaffolds and cells into diabetic patients will expose the implants to high glucose levels and damage the implants, similar to the way diabetes affects human tissues. Our ideas are based on numerous clinical studies which have shown that tissue implants have many more problems in diabetics as compared to non-diabetics. Thus we propose to study the effect of diabetes on tissue scaffolds and cells by using an animal model of diabetes in the rat. In an attempt to solve this problem, we also propose to treat the scaffolds with antioxidant chemicals that protect the scaffolds and make them resistant to diabetes. These studies have not been done before and will provide a guiding light for future development of implants for patients with diabetes.
