Biologic platform for beta cell therapy in diabetes

Research output: Book/ReportBook

Abstract

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Type 1 diabetes is a major health problem that reduces quality of life and increases risks for serious acute and chronic complications, despite insulin treatment. The disease is caused by massive destruction of insulin-producing beta cells involving an autoimmune reactivity. Therapeutic strategies should restore a functionally adequate beta cell mass and establish conditions that preserve its long-term survival and function. The implanted or regenerated beta cells are expected to achieve a tight metabolic control and should therefore exhibit the physiologic properties of the normal beta cell population. They should also be protected against loss or dysfunction, as might be induced by autoimmune reactivation, rejection, or toxicity of chronically elevated glucose or lipid levels. A beta cell therapy is thus needed that is based on knowledge of the biology and pathology of beta cells (Chapter 1). In this perspective, we developed a long-term program that would establish a biologic platform for beta cell therapy in diabetes. The successive steps are described in five chapters.

We first developed methods for purification of rat beta cells and their in vitro analysis. This novel in vitro model allowed to functionally dissect the endocrine pancreas (Chapter 2). By studying beta cells in absence and presence of other cell types, the glucose response was reconstructed at the single cell level. A synergy was demonstrated between glucose-induced signaling and a cyclic AMP signal that integrates (neuro)hormonal influences. It was however noticed that individual cells differ in their glucose sensitivity. This led us to propose that the beta cell population is functionally heterogeneous. The physiologic relevance of this concept was demonstrated. Its pathophysiologic implications are discussed and related to the histopathologic findings in type 1 diabetic patients.

The availability of purified beta cells was also useful for investigating the regulation of beta cell survival (Chapter 3). These studies demonstrated that beta cells possess defense mechanisms against cell death. Glucose was shown to counteract acute oxidative damage leading to necrosis. In addition, it protects -at physiologic concentrations- beta cells against apoptosis by maintaining their glucose-responsive phenotype. Prolonged exposure to low or high glucose levels, or to beta cell stimulating or inhibiting drugs causes shifts in phenotypes with subsequent changes in cell survival and/or function. Chronic excess of glucose or lipids was also found to induce functional and/or structural changes in human beta cells. The close anatomic association of human beta cells and duct cells led us to investigate whether it could influence beta cell mass. Using purified human duct cells we showed that this cell type can exhibit inflammatory and immune properties that can contribute to beta cell destruction. In preparations from young donors, a duct cell associated neogenesis of immature beta cells was identified. Taken together, the data suggest that different beta cell phenotypes are necessary to compose a functional beta cell mass for treatment, be it transplantation or endogenous regeneration. The phenotypes of naturally occurring beta cells will also serve as template for insulin-expressing cells that are generated from embryonic or somatic stem cells, from transdifferentiating cells or from other beta cells.

The ability to compose and distinguish beta cell preparations of different composition was used to examine the role of graft composition on its outcome in rodent models (Chapter 4). Effects were identified both on the metabolic capacity of implants and on the immunogenicity of donor tissue. In isogenic diabetic recipients, purified beta cell aggregates corrected hyperglycemia but metabolic control progressively decreased with time. Inclusion of alfa cells achieved long-term correction of diabetes, also when allografted and, importantly, without the need for continuous immune suppressive therapy. Local release of glucagon may mediate this beneficial effect through improving survival and function of neighboring beta cells. On the other hand, presence of non-endocrine pancreatic cells abolished graft function, both in allogenic and isogenic recipients.

On basis of our observations in rodents, we initiated a clinical trial in which cultured human beta cell grafts were prepared according to selected composition (Chapter 5). An international network was formed to integrate complementary expertise for driving the trials. A central Beta Cell Bank receives donor pancreases through intermediate of the Eurotransplant Foundation, and isolates and characterizes diverse pancreatic cell preparations for the transplant trial and its associated research projects. The tasks and activities of this central core are discussed. This report on 15 years experience can be useful for starting similar activities in other countries. A multicenter team conducts the trial. A first study showed that standardized beta cell grafts corrected diabetes in patients who were on maintenance immune suppressive therapy for a prior kidney implant. Surprisingly, administration of antithymocyte globulins (ATG) at the time of the kidney transplant preceded success of the later islet cell transplant while this was not the case for other induction therapies. Immune data suggested presence of an operational state of immune tolerance. The second protocol was conducted in 24 non-uremic patients with ATG administered at the time of a first beta cell implant, and a second implant given 3 months later under maintenance therapy of MMF and Tacrolimus. A correlation was demonstrated between the beta cell mass in the graft and metabolic control. Conditions for reaching insulin-independence were defined. Side effects were lower than those reported in other trials. At posttransplant year 1, insulin-independent graft recipients exhibited a functional beta cell mass that corresponded to 26 % of that in matched normal controls. These data, together with the standardized procedure for graft preparation and characterization, set standards for multicenter trials and identify components for further improvement.

Since 2002, our multicenter program is carried out under the flag of the JDRF Center for Beta Cell Therapy in Diabetes, an international consortium of clinical and research centers with central Beta Cell Bank and Coordination Core in Brussels (Chapter 6). The Center develops methods and trials for preservation and restoration of a functional beta cell mass in type1 diabetes. One trial aims replacement through beta cell transplantation in type 1 diabetic patients with early stage complications, the other protection by anti-CD3-antibody treatment in recently diagnosed patients. Rationale and experimental design of both trials are based on observations in associated laboratories, and conducted by a multidisciplinary team. A clinical Biology laboratory, the Belgian Diabetes Registry and Eurotransplant Foundation serve as reference centers to the trials. Further research and development is carried out at the R&D platform in which 21 European teams collaborate on complementary projects aiming the programming of cells for beta cell therapy. A major aim is to (re)generate insulin-producing cells in therapeutic quantities. Projects are undertaken to derive a functional beta cell mass from embryonic stem cells, from transdifferentiating endodermal cells and from beta cell(progenitor)s. Nature's biologic program to develop and preserve a functional beta cell mass throughout life is taken as platform for directing our strategies towards laboratory production of a therapeutic beta cell mass. It provides efficacy and safety standards that have been validated by nature.
Original languagePortuguese
PublisherBial Porto
Number of pages144
ISBN (Print)978-989-95520-3-6
Publication statusPublished - 2008

Keywords

  • Bial Award

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