Objective
In this proposal, we aim to use a tissue engineering strategy to tackle the challenge of beta cell engraftment and survival after transplantation. We aim to establish a collaboration between our academic group and the company Vascugen, Inc. to develop a platform for generating human induced pluripotent stem cell (hiPSC)-derived islets containing beta cells and isogenic (from the same genetic background) vascular promoting cells from a single, commercially consented GMP hiPSC line. We also aim to determine which components of the vessels are being modulated by the vascular niche cells, including vessel characteristics and vascular function, and what molecules made by niche cells may be the messengers responsible for the improvement in beta cell survival and function.
Background Rationale
The role of vascular cells in normal islet function is not completely understood. A recent study using genetic methods suggested that loss of vascular cells in the adult mouse islet results in impaired insulin expression, total insulin content, and glucose clearing. In addition, changes in vascular niche cells within the islet have been associated with a number of pathological conditions in humans. For instance, perivascular cells, which decorate the blood vessels themselves and can modulate the permeability of the vessels, are enlarged in multiple models of insulin resistance, where the density of vessel coverage is markedly increased. Here, we will test the ability of human induced pluripotent stem cell-derived vascular promoting cells to promoting the development of new vessels at the site of transplant, accelerating and improving the process of early engraftment.
Description of Project
Diabetes affects over 37 million people in the United States, and its prevalence is rising. Type 1 diabetes (T1D) is characterized by the inability to properly maintain blood sugar levels, resulting from autoimmune destruction of the patient’s own insulin-producing beta cells within the islets of Langerhans in the pancreas. The holy grail of T1D treatment is the restoration of continuous, autonomous blood sugar control to patients with T1D without the need for the administration of outside insulin using injections or insulin pumps. Islet transplantation is one of the most promising therapies for patients with T1D. Despite recent advances, however, transplanted donor islets often fail to survive and function long-term. Loss of blood vessel cells upon islet isolation, damage to the remaining vessels, and failure to immediately establish new connections with the host’s blood vessel network upon transplantation results in hypoxia (the deprivation of oxygen) and significant islet cell death. Even short-term hypoxic conditions can have long-term effects on beta cells, including decreased insulin secretion in response to glucose. Moreover, the supply of functional islets for transplantation is severely limiting. Human embryonic stem cells (hESCs) have emerged as a promising alternative source for the development of replacement beta cells, but there remain several hurdles to overcome before they can be used for the more than 1.25 million people in the U.S. with T1D who could benefit. Notably, as with human islet transplantation, hESC-derived beta cell transplants also suffer from poor survival in mice and thus fail to function long-term. In the body, beta cells exist in a highly specialized microenvironment called the “niche,” characterized by close-range interactions with multiple other cell types. In our preliminary data, we have found that co-transplantation of certain kinds of niche cells called vascular cells, which make up our blood vessels, can rescue the otherwise significant early graft failure that plagues hESC-derived beta cell transplantation. Based on our extensive data in the dish and in mice, we anticipate that harnessing the pancreatic vascular niche to aid in the revascularization of human hESC-derived beta cells during transplantation will permit us to overcome the significant beta cell graft failure that currently poses a major challenge for cell replacement therapy for diabetes. A hurdle to translation with our current approach, however, is the use of primary human vascular niche cells that show variability from lot to lot, are derived from different individuals, and may not be consented for commercial use. Here, we propose a collaboration between our academic group and the company Vascugen to develop a platform for generating human induced pluripotent stem cell (hiPSC)-derived islets containing beta cells and isogenic (from the same genetic background) vascular-promoting cells from a single, commercially consented hiPSC line approved for use in humans. We anticipate that these studies will permit the generation of engineered, stem cell-derived islets that contain beta cells and the important vascular niche cells, all from one single, commercially consented hiPSC line and that thus can be suitable for future translation into humans.
Anticipated Outcome
Based on our preliminary data showing that co-transplantation of vascular niche cells with human embryonic stem cell-derived beta-like cells rescues early graft failure, we hypothesize that this co-transplantation method will allow for increased vascular density of induced beta-like cells, the accelerated formation of connections to host blood vessels, and long-term graft survival and glucose responsiveness. In other words, we anticipate that the commercially-consented version of the vascular cells that we will use will effectively recapitulate the previous effects we have seen, but in this case using a consistent, commercially available cell source from the same genetic background as the beta cells themselves.
Relevance to T1D
Failure of islet cells (either derived from cadaveric tissue or from human pluripotent stem cells) to properly survive and function after transplantation represents a major bottleneck to the realization of cell replacement therapy for patients with type I diabetes. Here, we aim to overcome this challenge by giving the implanted cells a boost by co-transplanting vascular cells that improve engraftment and function by increasing and accelerating blood vessel supply to the transplanted beta cells.