Objective
The objective of this proposal is to generate the first of its kind vascularized pancreatic islets and to track the integration of these engineered islets with the blood vessel network once implanted into live animals. Pancreatic islets are clusters of insulin producing cells and significant progress has been made in generating these tissues in a dish from human induced pluripotent stem cells. These engineered islets hold incredible promise as potential cell replacement therapy. When implanted into the bodies of T1D patients, the successful integration of engineered islets with the host would enable the restoration of functional insulin production and blood sugar regulation, therefore eliminating the need for insulin treatment and blood glucose monitoring. However, a major challenge with implanted islets is that there is a high failure rate of integration and survival of implants largely due to a lack of blood supply. Currently, there is significant effort being made to improve the vascularization of engineered islets. However, there are still substantial technical challenges associated with this process. Our objective is to leverage a unique approach that we have developed to instruct stem cells to differentiate into pancreatic insulin producing cells and blood vessel cells simultaneously by mimicking the normal process by which these cell types arise during development. This will enable the generation of vascularized pancreatic islets that possess blood vessels that are tailored to their function. Our second objective is to implant these vascularized islets into the skin of live mice so that we will be able to understand the process by which the blood vessels of the engineered islets are able to connect with that of the host. To do this, we will utilize a specialized microscopy technique that allows us to see into the skin of live mice and watch the process by which islet blood vessels connect with that of the animal. It will also allow us to monitor the functionality of the islet blood vessels by visualizing the properties of blood flow within the implanted islets. By tracking the implanted islets over weeks to months, this will enable us to assess the long-term maintenance and integration of our engineered vascularized islets. This will set the stage for future studies whereby we will be able to test the insulin producing capacity of our vascularized islets in animal models of diabetes and their ability to modulate blood sugar levels long-term.
Background Rationale
Type 1 diabetes (T1D) is a debilitating chronic disease that results from the destruction of the insulin producing cells (β-cells) of the pancreas by one's own immune system. This leads to an inability to regulate blood sugar levels due to insulin deficiency and lifelong dependence on insulin therapy. A potential treatment for this disease with incredible promise is the transplantation of functional pancreatic islets into afflicted patients. This has been shown to be an effective approach through the successful transplantation of pancreatic islets from human donors. Although islet transplantation proves that β-cell replacement can restore blood sugar control, limited donor availability and poor graft survival limit its use. Given these challenges, there is growing interest in developing cell-based therapies for T1D using human induced pluripotent stem cells (hiPSC) to generate functional pancreatic islets for implantation. hiPSCs are cells that can be grown in a dish, that when provided with the correct combination of factors, can be instructed to become specific cell types. When grown under the correct conditions, these cells can self organize into three dimensional structures called organoids that approximate the structure and function of real tissues. However, a major barrier to islet organoid transplantation is poor engraftment and long-term survival, primarily due to a lack of blood vessels and as such, a lack of blood supply to these implanted islets. Most transplanted islet cells undergo extensive death within the first 2-3 days after implantation, well before host blood vessels can infiltrate the graft. As such, significant efforts have been made to improve the vascularization of implanted islets. A major limitation of current strategies is that the blood vessel components incorporated into engineered islets are not tailored to the unique structure and functional demands of islet cells. This is particularly important in light of recent advances in the field of vascular biology that have found that the organs in our body possess specialized blood vessels that are inherently tied to the health and function of the organ. Another major roadblock is the inability to visualize and follow the vascular integration of implanted islets, largely due to inaccessibility and technical limits of current imaging technology. In this proposal, we aim to overcome these barriers by engineering pancreatic islets with specialized blood vessels that are tailored to the structure and function of the islets. Furthermore, we will implant these engineered islets into the skin of mice and utilize a specialized imaging technique that will allow us to watch the process by which the blood vessels of the host animal connect with the vessels of the implanted islets.
Description of Project
Type 1 diabetes (T1D) is a chronic disease that occurs when the body’s immune system mistakenly attacks and destroys insulin-producing cells in the pancreas. Without insulin, the body cannot regulate blood sugar levels, so people with T1D must take insulin for the rest of their lives. Although insulin therapy manages the disease, it is not a cure and does not prevent long-term complications. One promising approach toward a lasting treatment is cell replacement therapy. This involves transplanting healthy insulin-producing cells into patients to restore natural insulin production. While transplants using donor islets (clusters of insulin-producing cells) have shown success, they are limited by donor shortages and immune rejection. To overcome these issues, scientists are developing lab-grown insulin-producing cells using human induced pluripotent stem cells—cells that can be made from a patient’s own tissue and turned into any cell type in the body, including pancreatic beta cells. However, a major challenge remains: once implanted, most of these lab-grown cells die quickly due to a lack of blood supply. Blood vessels are essential to deliver oxygen and nutrients, especially in the first few days after transplantation. Without proper vascularization, the transplanted cells cannot survive or function long term. This project aims to solve two key problems. Aim 1 focuses on creating pancreatic islet organoids (mini-organs) that include their own blood vessels. By mimicking how tissues develop in the body, we will grow both pancreatic and blood vessel cells together from human induced pluripotent stem cells. This co-development approach is expected to create a more natural and functional tissue. Then, we will test whether these organoids produce insulin and other key hormones and whether they closely resemble real human pancreatic tissue. Aim 2 will focus on tracking how these organoids connect with the host’s blood vessels after transplantation. Using a powerful live imaging technique in mice, we will observe the blood vessel growth process in real time and learn how to improve it for better long-term survival. Together, these advances could significantly improve the success of stem cell-based therapies for T1D and move the field closer to a functional cure.
Anticipated Outcome
Following the completion of these studies, we anticipate that we will have generated the first of its kind engineered pancreatic islets that contain specialized blood vessels that mimic the properties of blood vessels normally found in the pancreas. We predict that our unique strategy in applying the physiological signals that the body utilizes to form the pancreas and its associated blood vessels during development, we will be successful in generating pancreatic islets with integrated blood vessels that are tailored to the structure and function of these insulin producing cells. Furthermore, we anticipate that our strategy will lead to improved survival and function of transplanted islet organoids. By including blood vessels in the organoids before transplantation, the implanted cells are expected to survive longer and function more effectively, overcoming a major hurdle in current cell replacement therapies for T1D. By applying advanced imaging techniques, we also anticipate that we will gain a detailed understanding of how transplanted islet organoids integrate with the host vasculature. This will provide valuable insight into the timeline and quality of vascular maturation, which is critical for long-term graft success. The ability to track vascular changes in real-time in live animals will open new possibilities for optimizing and regulating graft integration in future therapies. Overall, we anticipate that these studies will overcome one of the key limitations in current stem cell-based therapies for Type 1 diabetes, i.e. the poor survival of transplanted insulin-producing cells. If successful, the outcomes will lay the foundation for more durable, effective, and scalable cell replacement treatments, ultimately moving us closer to a functional cure for T1D.
Relevance to T1D
Type 1 diabetes is a chronic autoimmune disease where the body’s immune system destroys the insulin-producing cells in the pancreas. Without these cells, people with T1D are unable to regulate blood sugar and must rely on lifelong insulin therapy. Even with careful management, many people experience serious complications over time, such as kidney damage, nerve problems, and cardiovascular disease. A long-term goal in T1D research is to replace the lost insulin-producing cells—not just treat the disease, but cure it. One approach that has shown promise is transplanting clusters of insulin-producing cells (called islets) into patients. These transplants can restore natural insulin production. However, this therapy is limited by two major challenges, a shortage of donor islet cells, and poor survival of the transplanted cells, which often die within days of being implanted due to a lack of connection with the body’s blood supply. To solve the problem of donor shortage, scientists can now create insulin-producing cells from a patient’s own blood or skin cells by turning them into induced pluripotent stem cells (hiPSCs) and then guiding them to become pancreatic islet cells. These lab-grown “islet organoids” can potentially provide a renewable, personalized source of insulin-producing cells for people with T1D. However, these stem cell-derived islet organoids still suffer from the same issue as donor cells whereby they do not survive well after transplantation, mostly because they don’t connect quickly enough to the patient’s blood vessels. Without a functioning blood supply, the cells can’t get the oxygen and nutrients they need and die before they can take over insulin production. This research project aims to make stem cell-based therapies for T1D more successful by solving two key problems:
Firstly, we will generate islet organoids with their own blood vessels. We aim to create more advanced islet organoids that already contain their own internal blood vessels before transplantation. This is important because in the natural development of the pancreas, insulin-producing cells grow alongside blood vessels, which play a critical role in supporting their function. Using a method developed in our lab, we will co-grow the cell types that form both the insulin-producing islets and the surrounding vascular (blood vessel) structures. These vascularized islet organoids are designed to mimic the real pancreas more closely, increasing their chance of survival and function after transplantation. Secondly, we will track how blood vessels grow after transplantation in real-time. Even with better-designed organoids, we still need to understand how they behave after transplantation. We will use a specialized imaging system that lets us watch blood vessels grow and change inside live animals over time. With this technology, we will track how the implanted islet organoids connect with the host’s blood vessels to observe how these connections develop and mature. In summary, this project directly tackles a major barrier to curing T1D with stem cell therapies: the lack of proper blood supply to transplanted cells. By developing islet organoids that include their own blood vessels and by tracking how these vessels mature after implantation, we aim to dramatically improve the survival, integration, and insulin-producing ability of transplanted cells. If successful, this research could bring us significantly closer to a curative, cell-based therapy for people living with Type 1 diabetes.