Objective
Our research addresses two critical aspects of stem cell-derived islet transplantation for Type 1 Diabetes (T1D) treatment. The first objective focuses on developing a robust safety mechanism. We will incorporate various safety switch configurations into luciferase-expressing human embryonic stem cells (hESCs), optimize small molecule dosage for efficient cell clearance both in vitro and in vivo, and ensure that genome editing does not impair differentiation into functional beta cells. The second objective aims to optimize the delivery and engraftment of engineered islets containing vascular niche components. We will determine the optimal dose and anatomical site for transplantation, investigate cellular and molecular mechanisms underlying niche-induced beta cell survival and function, and assess the ability of these engineered islets to rescue a T1D mouse model. Our preliminary data demonstrates improved survival and function of beta-like cells (BLCs) when implanted with niche components in immunodeficient mice. By addressing both safety and efficacy concerns, we aim to overcome significant hurdles in SC-islet transplantation, potentially advancing this promising therapeutic approach for T1D treatment.
Background Rationale
Type 1 diabetes (T1D) is an autoimmune disorder causing the destruction of insulin-producing beta cells, leading to loss of glucose homeostasis. It affects about 1.5 million people in the US and nearly 9 million worldwide. While cadaveric pancreatic islet transplantation has shown success in restoring glucose regulation, the limited donor availability necessitates alternative sources.
Human pluripotent stem cells (hPSCs) are a promising, sustainable source of beta cells for T1D therapy. Recent protocols have improved the generation of functional insulin-expressing hPSC-derived beta-like cells (BLCs). Early clinical trials with hESC-derived islets implanted into the portal vein of T1D patients have been promising, yet challenges remain.
One major issue is the significant loss of islet mass during the peri-transplant period, with over 60% loss observed in the first few days. This affects both cadaveric and SC-derived islets due to loss of endogenous vasculature and failure to establish immediate revascularization, resulting in hypoxia and cell death. Additionally, implanting SC-islets into the portal vein poses risks like tumorigenicity and difficulty in retrieving grafts.
To address these challenges, we propose improving transplant safety through advanced genome editing and enhancing efficacy via tissue engineering. We will also explore extra-hepatic transplantation sites for better graft retrieval and monitoring. This approach aims to develop safer, more effective beta cell replacement therapies for T1D patients, tackling key issues in regenerative medicine for diabetes.
Description of Project
The JDRF Postdoctoral Fellowship has long supported numerous meaningful research efforts dedicated to developing improved therapies for people with diabetes. The support offered by this fellowship is integral to helping the hundreds of millions of people worldwide afflicted with this chronic illness. Around 10% of all people with diabetes have type 1 diabetes (T1D), an autoimmune disease in which the destruction of insulin-producing beta cells within the pancreatic islets of Langerhans, results in the loss of control of blood sugar levels. A major focus for the treatment of T1D is beta cell replacement therapy to restore blood sugar control without the need of exogenous insulin. While this can be achieved through transplantation of cadaveric donor islets, their scarcity remains a significant limitation. In addition, despite recent advances, islet grafts often fail to survive and function long-term due to vascular loss and damage. Furthermore, this approach entails major safety risks, including the potential formation of tumors.
The goal of this project is to overcome these challenges through the transplantation of human pluripotent stem cell (hPSC)-derived islets together with key vascular niche cells, at the time of transplantation, while also making it safer. Our approach addresses donor shortage with the use of a renewable source of islets, and it improves revascularization of transplanted cells to ameliorate early graft failure. We also introduce a "safety switch" that renders cells susceptible to ablation using a non-toxic small molecule. Our ultimate goal is to improve the safety and efficacy of stem cell-derived beta-like cell transplantation, to advance T1D treatment.
Anticipated Outcome
Based on our initial findings and previous research, we anticipate several important results from this study. For the engineered islets with added supportive cells, we expect to see them survive for around 16 weeks and improve blood sugar control in diabetic animals. This should be evident by keeping non-fasting blood glucose levels low and maintaining healthy C-peptide levels for three months. We also predict better survival and functioning of the transplanted cells, with improved blood vessel formation and integration with the host’s circulation within two weeks. Depending on the transplant location (kidney capsule, intramuscular, or subcutaneous), we may need to adjust the ratio of beta-like cells to supportive cells.
For the safety aspect, our studies show that SM can selectively eliminate only the edited cells without affecting the others. Early data confirm this specific targeting for the V2-edited cells, though we need more experiments to confirm these results. Importantly, SM has a proven safety record, so we do not expect any toxicity issues.
Overall, these outcomes will significantly enhance the practical application of our engineered islet approach, addressing both effectiveness and safety in stem cell-derived beta cell therapy.
Relevance to T1D
In our proposal, we address two major hurdles to achieving widespread beta cell replacement therapy for Type 1 Diabetes (T1D): (1) The safety concerns associated with stem cell-derived transplants and (2) the limited long-term survival and function of transplanted islets. Our preliminary data demonstrate that integrating human pluripotent stem cell (hPSC)-derived insulin-producing beta-like cells (BLCs) with key vascular niche cells enhances BLC engraftment and function. We hypothesize that achieving complete independence from exogenous insulin requires both a robust safety mechanism and recapitulation of the native islet microenvironment.
To overcome these challenges, we will first develop a safety switch system in hPSCs to allow for selective elimination of transplanted cells if necessary, addressing potential tumorigenic risks. Concurrently, we will use these engineered hPSCs as a renewable source of islet cells for transplantation, incorporating vascular niche cells (endothelial cells and pericytes) to support revascularization upon transplant. This approach aims to combat islet cell death due to hypoxia and ischemia - a common cause of graft failure in T1D patients receiving islet transplants.
Our research will determine the optimal cell number and transplantation site for successful engraftment and function, directly addressing the issue of graft survival in T1D therapy. We will investigate the key components modulating vascular niche-induced improvements in beta cell engraftment and function, potentially uncovering new strategies to enhance islet transplant outcomes for T1D patients.
Finally, we will transplant the optimized engineered islets into diabetic mouse models to assess their ability to restore normoglycemia and demonstrate the efficacy of the safety switch system. This step is crucial in evaluating the potential of our approach to provide long-term blood glucose control for T1D patients without the need for exogenous insulin, while ensuring a high safety profile.
This comprehensive approach aims to significantly advance cell replacement therapy for T1D, potentially offering a more effective, sustainable, and safer treatment option for patients.