Date of Award
Doctor of Philosophy (PhD)
Dr. Dan Simionescu
Dr. Aggie Simionescu
Dr. Ying Mei
Dr. Jeko Madjarov
Diabetes has become one of the leading causes of lower-limb loss worldwide. Every 30 seconds, a person loses a limb due to diabetic-related vascular complications. About one-third of patients needing lower-limb bypass surgery have debilitated autologous vessels unsuitable for use, and no other good long-term options are available. These detrimental effects on the vasculature are caused mainly by the hyperglycemic and hyperlipidemic conditions derived from diabetes. Under these conditions, an increase in advanced glycation end products (AGEs) and reactive oxygen species leads to irreversible crosslinks of extracellular matrix proteins, accelerating vascular pathology through vascular stiffening, endothelial dysfunction, inflammation, atherosclerosis, fibrosis, and calcification.
For many years, scientists have attempted to develop tissue-engineered small-diameter vascular grafts (TEVGs) that can be used as off-the-shelf options for these patients. However, all these attempts have failed so far, leaving thousands of patients waiting. Preliminary studies performed in our lab demonstrated that treating decellularized porcine scaffolds with penta-galloyl glucose (PGG) prior to subdermal implantation in diabetic rats prevents diabetic-induced effects on the implant material, protects them from fast biodegradation, and provides anti-thrombogenic and enhanced mechanical properties. Furthermore, we have shown that our TEVGs can be repopulated with human endothelial cells and adventitial fibroblasts, which are necessary for the long-term integration and patency of the grafts.
Our long-term goal is to develop small-diameter TEVGs that provide an optimal off-the-shelf option for diabetic patients in need of lower-limb bypass surgery. To contribute to this goal, we investigated the performance of our decellularized vascular grafts treated with PGG and revitalized with human cells in perfusion models in vitro and in vivo in diabetic conditions. We hypothesized that our TEVGs would perform optimally as perfusion conduits in a diabetic environment by maintaining patency and preventing biodegradation and diabetes-related complications.
Decellularized porcine arteries were treated with PGG and seeded with adventitial fibroblasts. For in vitro studies, our TEVGs were placed in vascular bioreactors under normal and diabetic conditions for two weeks. We found that PGG treatment helps prevent detrimental effects on TEVGs under diabetic conditions. PGG treatment helped prevent calcification, impaired mechanical properties, expression of vascular pathology markers such as α-SMA, accumulation of AGEs, imbalance of matrix-metalloproteinases, and overexpression of some pro-inflammatory and apoptotic markers.
For the in vivo studies, our TEVGs were implanted as femoral-femoral bypass shunts in diabetic minipigs for 15 weeks. Results showed that PGG treatment provides protection against calcification, biodegradation of elastin, and accumulation of AGEs within the graft’s wall under diabetic conditions.
In summary, we found that PGG treatment of decellularized scaffolds provides significant therapeutic benefits to protect scaffolds and vascular cells against several diabetic-related complications. Additionally, our in vitro perfusion models could be considered an alternative to animal models in the early stages of research to study the effects of diabetic conditions on vascular cells and testing of potential therapeutics. Finally, to the best of our knowledge, our diabetic models are the first of their kind and could provide a robust link to clinical translation.
Carrillo Garcia, Juan Carlos, "In Vitro and in Vivo Diabetic Models for Assessment of Tissue Engineered Vascular Grafts" (2023). All Dissertations. 3433.
Author ORCID Identifier