Objective
If the limitations of current protocols for maintaining transplanted islet viability and function can be overcome, then they can be translated to clinic as treatment for patients. The major factors responsible for the inferior efficacy are poor vascularization and relative hypoxia of the transplanted islets. Therefore, we postulate that the health and function of transplanted islets can be dramatically improved by achieving two major objectives:
1 – Rapidly vascularizing the graft using an Arteriovenous (AV) bundle, which is ubiquitous in the body and has been shown to provide a strong and reliable vascularization of the graft. Vascularization and integration with the host will support improved nutrient delivery and glucose responsiveness of the transplanted islets, and meet their anatomical, physiological, and metabolic requirements.
2 – Recreating the natural environment where islets normally reside. To do so, the graft will be supplemented with acellular extracellular matrix (ECM) that is from human pancreas with a proprietary method developed at Wake Forest. The same ECM will also provide pro-angiogenic factors for further promoting rapid graft vascularization and integration with the recipient.
This combination approach will result in a device or a system that will maintain islet health and function, while promoting revascularization and integration with the recipient. Eventually, it can be scaled up for reproducible and consistent biomanufacturing of physiological pancreatic tissues.
Background Rationale
There is no cure for T1D, as the causative agent(s) remains unknown. Although exogenous insulin therapy is effective at preventing acute metabolic decompensation and is life-saving for T1DM, less than 40% of diabetic patients achieve recommended therapeutic goals. Overall, a large number of diabetic patients are inadequately controlled, complete and steady remission of hyperglycemia is rare, treatment may be complicated by hypoglycemia, and most patients with diabetes mellitus will develop one or more end organ complications during their lifetime. In the last couple of decades, the use of islet transplantation to provide a replacement for the lost insulin-producing cells has proven to be an effective therapy, resulting in restoration of insulin secretion and glucose homeostasis and preventing complications associated with T1D. However, critical limitations such as poor vascularization, and relative hypoxia of the transplanted islets have hindered the translation of islet replacement therapy to the clinic. We have shown that supplementing islets with factors from native-like ECM have individually shown to enhance the health and function of islets. Our team has also developed a clinically validated vascularization device, which could be ideal for islet delivery. Therefore, we are proposing a vascularization strategy that synergistically combines their positive effects and has the ability to engineer them into a bigger clinically-relevant tissue, which would be ideal for large scale manufacturing of pancreatic tissues. Importantly, this strategy can simultaneously address multiple limitations by providing (i) rapid graft vascularization and integration with the host, (ii) improved nutrient and oxygen transfer, (iii) biochemical factors for maintaining islet health and function as well as provide pro-angiogenic factors for promoting rapid graft vascularization by adding ECM. Thus, this biofabricated platform is uniquely suited for engineering high-density pancreatic constructs that can provide islets with factors for maintaining health and function as well as dramatically improving efficacy by promoting rapid graft vascularization and integration with the recipient.
Description of Project
Diabetes is a debilitating disease affecting millions of Americans and leading to billions of dollars in healthcare costs. In Type 1 Diabetes (T1D), the body’s own immune system attacks and destroys islets, which are tiny clusters of cells in the pancreas that produce the hormone insulin. Islet transplantation is a means of restoring physiological function, which would offer an alternative to a complete pancreas transplant or artificial pancreas and has high potential to treat these patients. However, the widespread application of islet transplantation as a treatment for T1D is hindered by the lack of long-term efficacy, mainly due to poor vascularization and relative hypoxia of the transplanted islets. This research addresses this major hurdle by testing a strategy that combines a clinically validated vascularization device with native-like extracellular matrix (ECM) of islets. The vascularization device uses an Arteriovenous (AV) bundle, which is ubiquitous in the body and has been shown to provide a strong and reliable vascularization of the graft. Here, human pancreas ECM will be produced using a method that preserves the ECM components that islets need to function. The ECM will support islet health and also provide pro-angiogenic factors to further promote rapid graft vascularization and integration with the recipient. Our research proposal hypothesizes that this combinatorial approach will improve the viability and overall function of islets, when implanted in a rat model. The final product of this research will be a construct capable of nutritionally supporting a therapeutic dosage of islets that can provide durable glycemic control, while also allowing for ease of implantation and retrieval. These techniques are being combined for the first time to provide long-term survival and function, ease of application, and ultimately, a cost-effective treatment and standard of care for diabetic patients
Anticipated Outcome
Based on strong preliminary data from our groups and others, we are confident that our research strategy will be successful. When ECM technology is considered, an extensive body of data show incontrovertibly that ECM-based supporting scaffolds enhance cell viability, function and lifespan, and represent an ideal delivery tool for cell therapy. Our group at Wake Forest was the first in reporting on the production of ECM scaffolds from the pig and human pancreas. These scaffolds sustain islet function in vitro, are able to modulate the immune response, and guide the differentiation of stem cells into pancreas specific lineages. The vascularization device containing the Arteriovenous (AV) bundle, will result in a strong and reliable vascularization of the graft, in order to provide the islets with a nutrient and oxygen rich culture environment, for maintaining their health and proper function. The vascularization device will be validated in vivo in pre-clinical rat models. We anticipate being able to engineer grafts that will demonstrate maintenance of islet health and function by promoting rapid graft vascularization and integration with the recipient.
Relevance to T1D
In T1D, the pancreas is unable to produce sufficient quantities of insulin, the hormone that regulates blood glucose levels. Insulin is produced by cells that are embedded in the pancreas, called beta cells. For reasons that remain unknown, these cells are attacked by the immune system of the patient and eventually destroyed. Insulin therapy represents the gold standard in the treatment of uncomplicated diabetes. However, as highlighted earlier, less than 40% of diabetic patients achieve the recommended therapeutic goals and a large number of patients are inadequately controlled. Thus, most T1D patients will develop complications sometime during their lifetime because standard insulin injection therapy is not effective in the prevention of the long-term complications of this disease. In the past decade, the use of islet transplantation to provide a replacement for the lost insulin-producing cells has proven to be an effective therapy. Yet, this technology has not kept its promise so far and as it lacks long-term efficacy and durability. Our research proposal aims at enhancing the viability and function of transplanted islet by promoting graft vascularization and integration with the recipient. Herein, we propose a combinatorial strategy. First, we propose to recreate islet’s natural environment, as thirty years of tissue engineering and regenerative medicine investigations have incontrovertibly shown that cells do not do well once they are removed from their natural environment – otherwise said, to do well, cells need a supporting scaffolding material which consists of the extracellular matrix (ECM) of the organ of origin, that represents the innate 3D framework where cells reside in normal, physiological circumstances. Second, we will use a clinically validated vascularization device that uses an Arteriovenous (AV) bundle, which is ubiquitous in the body and has been shown to provide a strong and reliable vascularization of the graft that would allow for adequate oxygen and nutrient supply. This combinatorial approach is intended to improve the viability and glucose responsiveness of the islets by accelerating the speed of, and degree of vascularization once implanted. For all the above, our research proposal is extremely relevant to T1D as it aims to provide an improved bioengineered device for islet transplantation and advancing what may be referred to as the most promising next generation treatment for T1D.