Chen, Alex F.
Pro-angiogenic microRNA let-7f regulation of wound healing in diabetes
General Research Subject: Type 1 Diabetes
Type of Grant: Basic Science
Project Start Date: July 1, 2011
Project End Date: June 30, 2014
Refractory wounds in diabetic patients represent a significant clinical problem that results in amputation. Endothelial progenitors cells (EPC) actively participate in wound repair through angiogenesis after homing to the wounding site. However, EPC angiogenic functions are impaired in diabetes due to oxidative stress, a limiting factor of clinical EPC cell therapy for wound healing. Remarkably, the mechanisms underlying diabetic EPC dysfunction are poorly understood. Our preliminary studies demonstrate that reduced pro-angiogenic microRNA let-7f and elevated anti-angiogenic molecule thrombospondin-2 (TSP-2) in EPCs contributed to their dysfunction in streptozotocin (STZ)-induced type 1 diabetic mice. Overexpression of let-7f suppressed p66shc, a ShcA protein that promotes oxidative stress, resulting in diminished mitochondrial reactive oxygen species (ROS) in diabetic EPCs. Yet how let-7f regulates EPC function and wound repair in diabetes are unknown. Thus, the objective of this proposal is to determine the mechanisms of let-7f regulation of EPC function and wound repair. We hypothesize that let-7f promotes EPC angiogenesis by directly targeting TSP-2 with subsequent p66shc reduction, resulting in decreased oxidative stress and accelerated wound repair in STZ mice. We will test our hypothesis by performing three specific aims encompassing in vitro and in vivo studies utilizing TSP-2 and p66shc deficient mice. The proposed study is significant, because it will elucidate for the first time, the mechanisms underlying microRNA regulation of EPC angiogenesis, which may provide a basis for the use of diabetic EPCs modified with pro-angiogenic microRNAs prior to EPC cell therapy of refractory wounds that affect millions of Americans with diabetes.
What area of diabetes research does your project cover? What role will this particular project play in preventing, treating and/or curing diabetes?
Non-healing wounds in diabetic patients represent a challenging clinical problem that often results in amputation. Endothelial progenitors cells (EPC), the precursor of mature endothelial cells covering the inner wall of blood vessels, actively participate in wound repair by moving to the wounding site to form new blood vessels. However, EPC functions are impaired in diabetes with unknown causes. Our pilot studies found that a beneficial small RNA, microRNA let-7f, was reduced and a detrimental molecule, thrombospondin-2 (TSP-2) was increased in diabetic EPCs, both of which contribute to impaired EPC function in diabetes. Increase of let-7f or decrease of p66shc, a protein that produces harmful free radicals, resulted in improved EPC function. Yet little is known about how let-7f regulates EPC function in diabetic wound repair. The objective of this proposal is to determine the mechanisms of let-7f regulation of EPC function and wound repair. We hypothesize that let-7f improves EPC function by directly binding to TSP-2 thus reducing p66shc, resulting in decreased free radicals and accelerated wound repair in diabetes. We will test this possibility by carrying out three specific aims which include cell culture and animal wound studies using TSP-2 and p66shc deficient mice. The proposed study is significant, because it will determine for the first time, the mechanisms underlying microRNA regulation of EPC function for new vessel formation, which may provide a basis for the use of diabetic EPCs modified with beneficial microRNA for EPC cell therapy of refractory wounds that affect millions of Americans with diabetes.
If a person with diabetes were to ask you how your project will help them in the future, how would you respond?
Many diabetic patients suffer from non-healing wounds, a situation that often results in amputation. To date, there is no good way to treat these wounds because of the complicated disorders in diabetes. A type of adult stem cells called endothelial progenitor cells (EPCs), which can be isolated and expanded from human blood, help to form new vessel that is critical for wound healing. They are hopeful candidates for cell therapy on wounds. Unfortunately, EPCs isolated from diabetic patients are severely damaged. Therefore, we attempt to understand why these cells become dysfunctional. We now have some clue that certain small molecules, such as microRNAs, are responsible for EPCs functional loss in diabetes. This project will allow us to study microRNA regulation of EPC function, and to determine if EPCs with microRNA manipulation is helpful when these cells are used for cell therapy for treating diabetic wounds. This study will bring new hope to the current treatment on non-healing wounds in diabetic patients.
Why is it important for you, personally, to become involved in diabetes research? What role will this award play in your research efforts?
My research focuses on the regulation of oxidative stress in endothelial cell function, especially in wound healing. Diabetes is one of the most detrimental factors to wound healing. My research team has been making efforts to investigate the underlying mechanisms and potential therapeutic targets for refractory wound healing in diabetes. This project is a logical step forward from our previous work. The research award of ADA provides a critical means for me to reach the first step of my long-term goal in this field.
In what direction do you see the future of diabetes research going?
Major advances in molecular targeting techniques (in areas such as antisense oligonucleotides, silencing RNA, antibodies, and small molecules), and tissue engineering (such as bone marrow–derived cell therapy, human skin engineering, cellular matrices) could be integrated to provide cellular and matrix basis in order to improve wound healing. Hopefully these coordinated efforts will be applied to patients with diabetic wounds in the future.
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