Objective
Our long-term goal is to cure type 1 diabetes (T1D) through beta cell replacement therapy, which uses transplantation of donor-derived, insulin-producing pancreatic islets to restore the insulin-producing function that is lost in patients with T1D. In beta cell replacement therapy, current urgent needs are to find an alternative source of insulin-producing cells to address an existing islet donor shortage, and to find an optimal transplantation site instead of the conventional site of the liver. Stem cells are a potential alternative source for insulin-producing cells. The subcutaneous (under the skin) site is an attractive alternative site with many advantages over the liver, including a minimally invasive procedure and easy monitoring. Therefore, establishing a strategy for subcutaneous site transplantation will benefit both islet and stem cell-derived beta cell transplantations. However, transplantation strategies for T1D overall have encountered several major obstacles that lead to graft death, namely, shortage of oxygen due to low blood flow, host immune responses to the graft, and inflammation. Toward our long-term goal, our objective in the proposed project is to improve subcutaneous site transplantation of human islets as the current source for clinical islet transplantations and stem cell-derived, human islet-like organoids as future alternative source for beta cell replacement therapy. To address the obstacles listed above, we will test our newly developed technique – nanofibers that release key molecules (a source of oxygen, factors to encourage blood vessel growth, and molecules that limit immune reaction/inflammation) in a controlled manner to enhance graft survival of both human adult islets and human islet-like organoids – in a diabetic mouse model. We expect our results to advance a clinically applicable approach to ultimately cure T1D.
Background Rationale
Type 1 diabetes (T1D) is characterized by progressive loss of function of insulin-producing beta cells in the islets of the pancreas. Because insulin is the only hormone to reduce blood sugar in our body, this loss of insulin-producing beta cells leads to high blood sugar and can cause many complications, such as blindness, kidney failure, and cardiovascular disease. T1D is often found in young children due to autoimmune rejection of pancreatic islet beta cells. In the past decade, the number of juvenile patients with T1D has dramatically increased worldwide. In the U.S., the number of total patients with T1D has increased 60% from 2003 to 2013. Human islet transplantation significantly improves blood sugar control and prevents life-threatening severe hypoglycemia in patients with T1D. However, an ongoing shortage of human islets from deceased donors limits such therapeutic opportunities. Development of islet-like organoids derived from human stem cells is a promising alternative strategy. However, for any transplantation strategy, chronic immunosuppression, which is required to avoid rejection of transplanted cells, is associated with severe complications, such as increased risk of cancer and infections. Thus, there is a significant need for novel approaches to ensure long-lasting graft acceptance without immunosuppression or related complications. Important steps in addressing this need are improving graft survival and minimizing rejection risk in an easy-to-access transplantation site, such as under the skin (subcutaneous site). The subcutaneous site has many advantages over the liver, the current islet transplantation site: it avoids direct blood exposure, provides extensive space, and permits minimally invasive transplant procedures. However, it also has certain challenges, including poor oxygen supply due to low blood flow, as well as immune responses to the graft. Using tiny nanofibers, which are designed to release important molecular factors that support graft survival by enhancing oxygen supply, blood vessel growth, and immune protection, we aim to develop a novel approach for subcutaneous site islet transplantation that provides long-term efficacy in patients with T1D. Our proposed strategy will overcome critical shortcomings of the subcutaneous site, making the site a viable option for beta-cell replacement therapy, both for current practice using human donor islets as well as for the use of stem cell-derived islets. Our objective is to advance this technology toward preclinical evaluation by demonstrating the efficacy of the multi-molecule releasing nanofibers to support successful transplantation of human islets and stem cell-derived islets in diabetic mouse models. The expected findings will provide a novel platform for subcutaneous site transplantation of islets that will ultimately improve treatment of T1D.
Description of Project
Type 1 diabetes (T1D) occurs due to destruction of insulin-producing beta cells in the islets of the pancreas. Although pancreatic islets from deceased donors can be transplanted into patients for the treatment of T1D, there is an ongoing shortage of donors. To overcome this, development of islet-like organoids derived from human stem cells has rapidly progressed toward clinical use. For such stem cell-derived islets, the subcutaneous (under the skin) site is an attractive transplant site that allows a minimally invasive transplantation procedure and easy post-transplant monitoring. However, this strategy has encountered several major obstacles, including a shortage of oxygen due to few blood vessels in the subcutaneous site, acute to chronic inflammation caused by the transplantation procedure, as well as host immune reactions caused by the transplanted tissue, which can all reduce the survival and function of an islet graft. In this proposal, a strong collaborative team of researchers from three diverse fields, yet with complementary expertise, will aim to overcome these obstacles and advance this promising beta cell replacement strategy: the Komatsu Lab at City of Hope (islet-oxygen physiology and subcutaneous islet transplantations), the Steckl Lab at the University of Cincinnati (nanofiber engineering for molecular controlled release), and the Yoshihara Lab at The Lundquist Institute/University of California Los Angeles (immune-evasive stem cell technology). To address the major obstacles mentioned above, we will build a scaffold made of tiny but strong nanofibers that will allow key molecules to be sequentially delivered to the islet graft to enhance its survival. We will incorporate key components for engraftment – a source of oxygen, factors to encourage blood vessel growth, and molecules that limit inflammation/immune reaction – within a single ultra-fine nanofiber. Each component requires a distinct optimal dose and time of release to maximize engraftment of the transplanted cells, and to date, no one has been able to deliver them sequentially due to this technical complexity. We are confident that our unique technique can overcome this, and we will test our nanofiber scaffold in diabetic mouse models. Our paramount goal is to improve clinical transplantation of islets from deceased donors as well as stem cell-derived islet organoids in the subcutaneous site to cure T1D. Accordingly, in this proposal our team will develop a new method to enhance engraftment of human islets and stem cell-derived islet organoids using nanofiber scaffolds that sequentially release key factors to support successful engraftment.
Anticipated Outcome
We expect that both donated human pancreatic islets and human islet-like organoids will efficiently and functionally engraft in the subcutaneous site using our muti-molecule-releasing nanofiber membrane. Because our proposed project is intended to fill a gap between development of the multi-molecule-releasing nanofiber membrane and preclinical studies in large animals, we will test the ability of our multi-molecule-releasing nanofiber membrane to improve engraftment in small animal models (diabetic mice). We will assess successful engraftment by measuring the secretion of insulin-related hormones from the transplanted cells and observing cure of diabetes in the animal models. Once we successfully establish our novel strategy in animal models, we are confident about its future translation into human use, given that the nanofiber materials are safe for use in humans, and they can easily be made in large quantities for clinical use. Furthermore, the fine nanofibers enable us to load grafts with ample transplanted cells in a multi-layered structure within a small transplant area, which is critically important for a minimally invasive clinical transplant procedure for patients with T1D.
Relevance to T1D
We aim to establish effective beta cell replacement therapy (transplantation of insulin-producing cells) for patients living with type 1 diabetes (T1D). Current major challenges for beta cell replacement therapy include a less than-ideal transplant environment in the conventional liver site, and a shortage of insulin-producing cells from donated pancreases. Our proposed project is centered on an under-the-skin strategy that combines the use of our novel multi-molecule-releasing nanofiber membrane and stem cell-derived insulin-producing cells. We believe that this project will have a significant impact on transforming the current beta cell replacement strategy for T1D, because it addresses the current needs for an alternative transplantation site and an alternative insulin-producing cell source. In the long term this will have a significant impact on public health by dramatically improving quality of life for tens of millions of adults and children living with T1D worldwide.