Regenerative Therapies For Diabetes Research Articles

346-LB: The Role of STAT3 Signaling toward a-to-ß Reprogramming within the Adult Pancreas

As diabetes mellitus results from the absolute or relative deficiency of insulin secretion from pancreatic β cells, the generation of surrogate β cells has attracted a lot of attention for the cure of diabetes. To date, insulin-producing cells have been generated from differentiated cell types in the pancreas, such as acinar cells and α cells, by inducing the exogenous expression of pancreas-specific transcription factors. However, it still remains unclear as to how surrogate β cells can be efficiently generated toward establishing future regenerative therapies for diabetes. STAT3 has been demonstrated to play a role in maintaining cellular identities in the pancreas, and we have reported that the activation of STAT3 signaling is required for acinar-to-ductal transition (Miyatsuka et al. Genes Dev. 2006), whereas the suppression of STAT3 signaling efficiently promotes acinar-to-β reprogramming (Miura M. et al. EBioMedicine. 2018). Therefore, we hypothesized that regulating STAT3 signaling may control the efficiency of α-to-β reprogramming. To address this, we generated transgenic mice that exogenously express Pdx1, Mafa and Ngn3 specifically in α cells, and deleted Stat3 in a tamoxifen inducible manner (Stat3KO; Gcg-CreERT2; Pdx1;Ngn3;Mafa mice: αStat3KO;PNM mice). Immunofluorescent imaging demonstrated that Stat3 deletion significantly increased the number of α-cell-derived insulin-producing cells in αStat3KO;PNM mice, compared with control mice (28.2±2.7 vs. 8.6±3.1%, p<0.05). Notably, 61.2±8.8% of α-cell-derived insulin-producing cells were negative for glucagon in αStat3KO;PNM mice, which was higher compared with controls (36.4±18.0 %). These results suggest that the suppression of STAT3 signaling efficiently promotes α-to-β reprogramming as well as acinar-to-β reprogramming in mice. Disclosure Y. Wakabayashi: None. T. Miyatsuka: None. L. Suzuki: None. M. Himuro: None. T. Katahira: None. M. Miura: None. H. Watada: Research Support; Self; Astellas Pharma Inc., Boehringer Ingelheim Pharmaceuticals, Inc., Daiichi Sankyo Company, Limited, Kissei Pharmaceutical Co., Ltd., Merck Sharp & Dohme Corp., Mitsubishi Tanabe Pharma Corporation, Novartis Pharmaceuticals Corporation, Novo Nordisk A/S, Pfizer Inc., Sanofi, Sumitomo Dainippon Pharma Co., Ltd., Takeda Pharmaceutical Company Limited, Teijin Pharma Limited. Speaker's Bureau; Self; Astellas Pharma Inc., Boehringer Ingelheim Pharmaceuticals, Inc., Daiichi Sankyo Company, Limited, Eli Lilly and Company, Merck Sharp & Dohme Corp., Mitsubishi Tanabe Pharma Corporation, Novo Nordisk A/S, Ono Pharmaceutical Co., Ltd., Sanofi, Takeda Pharmaceutical Company Limited, Terumo Medical Corporation. Other Relationship; Self; Boehringer Ingelheim Pharmaceuticals, Inc., Kowa Pharmaceutical Europe Co. Ltd., Merck Sharp & Dohme Corp., Mitsubishi Tanabe Pharma Corporation, Ono Pharmaceutical Co., Ltd., Sanwa Chemical Industry Co. Ltd., Takeda Pharmaceutical Company Limited.

Transgenic Expression of a Single Transcription Factor Pdx1 Induces Transdifferentiation of Pancreatic Acinar Cells to Endocrine Cells in Adult Mice.

A promising approach to new diabetes therapies is to generate β cells from other differentiated pancreatic cells in vivo. Because the acinar cells represent the most abundant cell type in the pancreas, an attractive possibility is to reprogram acinar cells into β cells. The transcription factor Pdx1 (Pancreas/duodenum homeobox protein 1) is essential for pancreatic development and cell lineage determination. Our objective is to examine whether exogenous expression of Pdx1 in acinar cells of adult mice might induce reprogramming of acinar cells into β cells. We established a transgenic mouse line in which Pdx1 and EGFP (enhanced green fluorescent protein) could be inducibly expressed in the acinar cells. After induction of Pdx1, we followed the acinar cells for their expression of exocrine and endocrine markers using cell-lineage tracing with EGFP. The acinar cell-specific expression of Pdx1 in adult mice reprogrammed the acinar cells as endocrine precursor cells, which migrated into the pancreatic islets and differentiated into insulin-, somatostatin-, or PP (pancreatic polypeptide)-producing endocrine cells, but not into glucagon-producing cells. When the mice undergoing such pancreatic reprogramming were treated with streptozotocin (STZ), the newly generated insulin-producing cells were able to ameliorate STZ-induced diabetes. This paradigm of in vivo reprogramming indicates that acinar cells hold promise as a source for new islet cells in regenerative therapies for diabetes.

Transdifferentiation of pancreatic cells by loss of contact-mediated signaling

BackgroundReplacement of dysfunctional β-cells in the islets of Langerhans by transdifferentiation of pancreatic acinar cells has been proposed as a regenerative therapy for diabetes. Adult acinar cells spontaneously revert to a multipotent state upon tissue dissociation in vitro and can be stimulated to redifferentiate into β-cells. Despite accumulating evidence that contact-mediated signals are involved, the mechanisms regulating acinar-to-islet cell transdifferentiation remain poorly understood.ResultsIn this study, we propose that the crosstalk between two contact-mediated signaling mechanisms, lateral inhibition and lateral stabilization, controls cell fate stability and transdifferentiation of pancreatic cells. Analysis of a mathematical model combining gene regulation with contact-mediated signaling reveals the multistability of acinar and islet cell fates. Inhibition of one or both modes of signaling results in transdifferentiation from the acinar to the islet cell fate, either by dedifferentiation to a multipotent state or by direct lineage switching.ConclusionsThis study provides a theoretical framework to understand the role of contact-mediated signaling in pancreatic cell fate control that may help to improve acinar-to-islet cell transdifferentiation strategies for β-cell neogenesis.

Determinants of pancreatic β‐cell regeneration

Recent studies have revealed a surprising plasticity of pancreatic beta-cell mass. beta-cell mass is now recognized to increase and decrease in response to physiological demand, for example during pregnancy and in insulin-resistant states. Moreover, we and others have shown that mice recover spontaneously from diabetes induced by killing of 70-80% of beta-cells, by beta-cell regeneration. The major cellular source for new beta-cells following specific ablation, as well as during normal homeostatic maintenance of adult beta-cells, is proliferation of differentiated beta-cells. More recently, it was shown that one form of severe pancreatic injury, ligation of the main pancreatic duct, activates a population of embryonic-type endocrine progenitor cells, which can differentiate into new beta-cells. The molecular triggers for enhanced beta-cell proliferation during recovery from diabetes and for activation of embryonic-type endocrine progenitors remain unknown and represent key challenges for future research. Taken together, recent data suggest that regenerative therapy for diabetes may be a realistic goal.

β-cell proliferation is the major source of new pancreatic β cells

New insulin-producing β cells are produced throughout adult life and could potentially be exploited in regenerative therapies for diabetes. Although pancreatic progenitor cell differentiation has been proposed to drive de novo β-cell generation, this Viewpoint argues that new β cells arise from the proliferation of pre-existing β cells.

Prospective isolation of multipotent pancreatic progenitors using flow-cytometric cell sorting.

During pancreatic development, neogenesis, and regeneration, stem cells might act as a central player to generate endocrine, acinar, and duct cells. Although these cells are well known as pancreatic stem cells (PSCs), indisputable proof of their existence has not been reported. Identification of phenotypic markers for PSCs leads to their prospective isolation and precise characterization to clear whether stem cells exist in the pancreas. By combining flow cytometry and clonal analysis, we show here that a possible pancreatic stem or progenitor cell candidate that resides in the developing and adult mouse pancreas expresses the receptor for the hepatocyte growth factor (HGF) c-Met, but does not express hematopoietic and vascular endothelial antigens such as CD45, TER119, c-Kit, and Flk-1. These cells formed clonal colonies in vitro and differentiated into multiple pancreatic lineage cells from single cells. Some of them could largely expand with self-renewing cell divisions in culture, and, following cell transplantation, they differentiated into pancreatic endocrine and acinar cells in vivo. Furthermore, they produced cells expressing multiple markers of nonpancreatic organs including liver, stomach, and intestine in vitro. Our data strongly suggest that c-Met/HGF signaling plays an important role in stem/progenitor cell function in both developing and adult pancreas. By using this antigen, PSCs could be isolated prospectively, enabling a detailed investigation of stem cell markers and application toward regenerative therapies for diabetes.