Progress Report: Conversions of Pancreatic Non-Endocrine Cells Into Insulin-Producing Cells By BMP-7 Stimulation
As the world’s largest and most comprehensive research center dedicated to curing diabetes, the Diabetes Research Institute (DRI) at the University of Miami Miller School of Medicine has already been able to reverse diabetes by transplanting insulin-producing islet cells in patients involved in clinical trials. This exquisite biological replacement approach has enabled many study participants to live free from insulin therapy – some for more than 10 years. However, the need for chronic anti-rejection drug therapy and the shortage of donor organs from which the islets are isolated have limited the treatment to only the most severe cases.
To build on this extraordinary progress, DRI researchers are addressing the three main research challenges for developing a biological cure. Among its major initiatives is the development of the DRI BioHub—a bioengineered mini-organ that mimics the native pancreas, containing insulin-producing cells that sense blood sugar levels and release the precise amount of insulin needed in real time, together with other vital components to keep the cells healthy and functioning long term. The research areas that comprise the BioHub are in various stages of development and testing with pre-clinical and clinical trials currently underway.
The three research challenge areas are:
- Site – developing an optimal environment within the body to house the DRI BioHub.
- Sustainability – retraining the immune system to prevent rejection of donor-supplied islet cells and reversing the autoimmune attack which caused diabetes in the first place.
- Supply – Identifying, developing and/or regenerating an unlimited supply of cells that produce insulin in response to glucose levels.
Funds raised during the #MultiplyCellSupply Match Challenge campaign will support the third area of research: Supply.
Using the Entire Pancreas
The pancreas is made up of endocrine and exocrine cells. The endocrine portion, which is less than two percent of the organ, is made up of islet cells that contain the insulin-producing beta cells along with other cell types that play a role in balancing blood glucose (sugar) levels. The exocrine portion of the pancreas, which is responsible for producing digestive enzymes, accounts for the remaining 98 percent of the pancreas. This compartment continues to work normally in those with diabetes. It has been known for a long time that one of the interesting features of the human non-endocrine pancreatic tissue (hNEPT) is its high plasticity to turn into other cell types or tissues. The conventional approach to reprogramming this type of pancreatic tissue entails genetic modification procedures, which are cumbersome and clinically risky. The DRI’s objective is to induce the non-genetic reprogramming of hNEPT into insulin-producing cells that can be used for transplantation and the restoration of natural insulin production to normalize blood sugar levels.
The DRI’s Juan Dominguez-Bendala, Ph.D., director of stem cell development for translational research, and Ricardo Pastori, Ph.D., director of molecular biology, and their teams have pioneered the use of a non-invasive means of reprogramming, which is expected to have a clearer path to clinical trials.
The team has successfully converted the NEPT of the pancreas into new, glucose-responsive islet-like clusters using a single agent, BMP-7, a member of the Bone Morphogenetic Protein family of growth factors. Initially discovered for their ability to induce bone formation, BMPs are now known to play crucial roles in all organ systems. BMP-7 is already approved by the Food and Drug Administration (FDA) for clinical use.
The team’s significant findings, which were published in the journal Diabetes, with a follow-up invited review in Trends in Endocrinology & Metabolism, demonstrated for the first time that non-endocrine cells can be reprogrammed to respond to blood glucose without the use of any genetic manipulation. The cells generated in this manner produced insulin levels between 50 and 250 times higher than previously published by other teams, which used genetically engineered viruses plus treatment with additional agents that are known to cause unpredictable genetic patterns in cells.
Their continued research has now enabled them to pinpoint the anatomical location of these stem cell-like cells, and explore their potential activation to generate new beta cells. Therefore, the promise of this technology also lies in its regenerative potential in targeting the native pancreas in vivo after researchers can restore self tolerance and halt autoimmunity (the Sustainability pillar of the DRI’s approach to developing a biological cure). Enabling the insulin-producing cells to regenerate within the patient’s body may eliminate the need to transplant donor cells altogether and address the challenge of foreign-tissue rejection.
The DRI’s process represents a safer and more efficient method to increase the limited supply of insulin-producing cells for transplant. The relative simplicity of the approach, coupled with its high efficiency, makes it a prime candidate for translation to people living with type 1 diabetes.
The Fine Points of the DRI’s Findings
1.BMPs have critical roles in many biological processes, including stem cell activation across many organ systems. The DRI team hypothesized that exposure of human non-endocrine pancreatic tissue (hNEPT) to BMP-7 may lead to endocrine cell conversion.
2.hNEPT were obtained from the DRI’s cGMP cell processing lab as a byproduct of human islet isolation. Cells were exposed to BMP-7 (in the experimental group) or regular medium (in the control group) for 12 days. Throughout the course of the experiment, BMP-7 induced the formation of abundant islet-like clusters. These were virtually undetectable in the control group.
3.BMP-7 induced changes that were consistent with robust endocrine cell conversion, evidenced by average increases of 40-fold in insulin, 92-fold in glucagon, 14-fold in pancreatic polypeptide (PPY), 28-fold in somatostatin (SST) and 29-fold in the key beta cell developmental gene PDX1. BMP-7-treated cells had insulin levels within the range of the human islet cell preparations we transplant into patients in clinical trails.
4.Insulin+ cells in hNEPT after BMP-7 treatment were approximately 30 percent of the whole culture. Glucagon and other important islet hormones were also observed.
5.BMP-7-induced clusters of insulin-producing cells were glucose responsive. The average C-peptide release in the experimental group had a stimulation index of 2.4 (i.e., they ramp up insulin production by 2.4x when exposed to high sugar). This is also within the range reported for human islets. Additional assays showed that BMP-7-treated hNEPT responded dynamically to glucose.
6.To assess function in a living experimental model, the DRI team transplanted BMP-7-treated hNEPT into a group of diabetic mice, and untreated hNEPT into a control group. No human insulin could be detected in the plasma of mice receiving untreated hNEPT, either prior to or after glucose stimulation. In contrast, all mice transplanted with BMP-7-treated cells exhibited long-term robust human insulin secretion and glucose responsiveness.
7.Newly formed beta-like cells arise mostly from PDX1+ cells. To determine the origin of the insulin-producing cells that arise after BMP-7 stimulation, we tagged every specific cell type present at the beginning of the culture (e.g., ductal, acinar, residual beta cells) and then determined if the resulting beta cells had the tag corresponding to any given original sub-population. The DRI’s results suggest that BMP-7-induced insulin-expressing cells arise mainly from exocrine resident stem/progenitor cells, rather than from acinar, ductal or pre-existing beta cells. In particular, the DRI researchers concluded that those stem cells are characterized by the expression of PDX1 and the BMP-7 receptor ALK3, but not of insulin or other “mature” markers of the ductal and acinar tissue.
8.BMP-7 induces the formation of C-peptide+ cells through the engagement of the ALK3 receptor, which is present in PDX1+ expressing cells. Our findings are consistent with numerous reports that identify ALK3 as the mediator of BMP-7 function in several models of regeneration, including adult liver regrowth, epidermal cell differentiation and kidney regeneration/fibrosis reversal.
The DRI team’s data are consistent with the hypothesis that BMP-7 simulates a sub-population of cells within the exocrine compartment with progenitor/stem cell characteristics. Such conclusions are aligned with an extensive body of work (including the DRI’s own findings) supporting the hypothesis that the pancreatic exocrine compartment harbors beta cell progenitors.
Thanks to the funds raised during the #MultiplyCellSupply Match Challenge, DRI researchers will continue to advance this promising area of research. The team will work to further characterize these stem cell populations within the pancreas that have given rise to the new islet-like clusters, as well as work to induce beta cell regeneration in vivo.
To the DRI researchers’ knowledge, there is no other published report on the efficient conversion of human pancreatic exocrine tissue to endocrine cell types using a non-genetic method. Exposure to BMP-7 was sufficient to elicit this conversion and yield abundant insulin-secreting clusters that are glucose-responsive both in vitro (outside an organism, as in a petri dish), and in vivo (in a living organism such as a mouse). Total insulin levels of BMP-7-treated hNEPT are within the range reported for human islets and >50-fold higher than those most recently reported by another team working on exocrine tissue conversion using eight different agents (four of which are viruses).
BMP-7 is an FDA-approved clinical product routinely used for bone fusion in spinal surgery, and it is in multiple clinical trials for osteoarthritis. BMP-7 and other BMP agonists with BMP-7-like activity are also in the pipeline for the treatment of kidney and lung fibrosis.
Even though the #MultiplyCellSupply campaign has ended, you can still support this work!