Basic Biology IV
The loss of pancreatic beta-cells in type 1 diabetes results in absence of insulin secreted by the pancreas, and consequently elevated blood sugar which leads to various long-term complications. Diabetic patients would benefit tremendously from availability of transplantable replacement beta-cells. Much of current research focuses on producing beta-cells from stem cells. Despite some progress, it is at present still not possible to generate functional beta-cells in culture. The beta-like cells generated with current protocols in vitro lack key features of normal beta-cells, most notably the ability to secrete insulin a regulated manner. However, when stem cell-derived beta-cell precursors are transplanted into mice, they acquire properties of functional beta-cells, indicating that the precursors have the potential to transition into a mature beta-cell state. By comprehensively comparing the molecular profiles of mature, functional beta-cells and malfunctioning insulin-producing cells generated in vitro, we have identified molecular cues that are not appropriately induced under current culture conditions. These studies have led to short list of candidate regulators of beta-cell maturation. We propose to manipulate these candidate factors in stem cell-derived beta-cell precursors in culture, with the goal of forcing them to adopt a mature phenotype. We will first characterize these cells in vitro and then test functionality in diabetic animal models.
Statement of Benefit to California:
Diabetes is a metabolic disorder that affects 8.3% of the U.S. population. Average medical expenditures among people with diabetes are 2.3 times higher than those of people without diabetes. The disease is characterized by either absolute insulin deficiency due to the autoimmune destruction of pancreatic insulin-producing beta-cells [Type 1 diabetes], or relative insulin deficiency due to defective insulin secretion or insulin sensitivity [Type 2 diabetes]. The resulting elevated blood glucose levels eventually lead to damage of the blood vessels followed by kidney failure, blindness, neuropathy, heart disease, and stroke. Despite current treatment regimens of several insulin injections per day, blood glucose levels still fluctuate significantly in diabetic patients, making diabetes the seventh leading cause of death in the United States. Alternative approaches to insulin injections include attempts to develop a cell therapy by producing transplantable beta-cells from stem cells. A cell therapy would lead to better blood glucose control and therefore ameliorate long-term complications. This proposal seeks to identify factors that force stem cell-derived beta-cells to functionally mature in culture with the goal to produce an unlimited source of transplantable beta-cells. Given the high prevalence of diabetes in California, we believe that the proposed research will have tremendous benefit to the State of California and its citizens.
This proposal seeks to define and characterize the key transcription factors necessary to promote maturation of human embryonic stem cell (hESC)-derived pancreatic progenitors to mature insulin-secreting beta cells. The applicant proposes three specific aims. The first aim will use beta cell-specific antibodies to sort insulin-secreting cells from hESC cultures. Aim two will define the minimum set of transcription factors necessary to induce beta cell maturation. The final aim will analyze the capacity of hESC-derived beta cells to secrete insulin as regulated by glucose levels, both in vitro and in vivo following transplantation into immune-compromised mice. Significance and Innovation - To date, there has been limited success in producing mature, glucose-regulated insulin-secreting pancreatic beta cells from human pluripotent stem cells in culture, and reviewers considered the generation of functional mature beta cells to be of high priority. -The project addresses a major problem in health care and a critical barrier to progress in the field. - Reviewers were impressed by the proposed depth of gene expression analysis at different stages of differentiation and the aim to use the resulting information to identify a regulatory network. Feasibility and Experimental Design - The experimental plan is logical, well developed and clearly presented. - Reviewers appreciated the systematic approach outlined in this proposal. - Sufficient preliminary data has been presented to justify the proposed experiments; reviewers applauded the applicant’s efforts in identifying genes that are under-expressed in vitro compared to levels achieved in vivo following transplantation. - The systematic testing of individual transcription factors as proposed appears feasible. - Since the greatest and most appropriate effect of the transcription factors may depend on temporal context, reviewers recommended that the applicant induce transcription factor expression at different time points during differentiation. - Some reviewers were not clear on the rationale behind the chosen number of transcription factors to pursue for additional characterization. Principal Investigator (PI) and Research Team - The investigator is highly accomplished and well published in high impact journals with a strong track record in transcription factors and in developmental biology of the endocrine pancreas. - The research environment and research staff are appropriate to carry out the proposed project. Core facilities for genomics and hESC culture significantly enhance the feasibility of the application. Responsiveness to the RFA - The proposed research was viewed as responsive to the RFA.