A synopsis of factors regulating beta cell development and beta cell mass

Modulation of transcription factors by small molecules in β-cell development and differentiation

Transcription factors regulate gene expression and play crucial roles in development and differentiation of pancreatic β-cell. The expression and/or activities of these transcription factors are reduced when β-cells are chronically exposed to hyperglycemia, which results in loss of β-cell function. Optimal expression of such transcription factors is required to maintain normal pancreatic development and β-cell function. Over many other methods of regenerating β-cells, using small molecules to activate transcription factors has gained insights, resulting in β-cells regeneration and survival. In this review, we discuss the broad spectrum of transcription factors regulating pancreatic β-cell development, differentiation and regulation of these factors in normal and pathological states. Also, we have presented set of potential pharmacological effects of natural and synthetic compounds on activities of transcription factor involved in pancreatic β-cell regeneration and survival. Exploring these compounds and their action on transcription factors responsible for pancreatic β-cell function and survival could be useful in providing new insights for development of small molecule modulators.

Stem cells differentiation into insulin-producing cells (IPCs): recent advances and current challenges

Type 1 diabetes mellitus (T1D) is a chronic disease characterized by an autoimmune destruction of insulin-producing β-pancreatic cells. Although many advances have been achieved in T1D treatment, current therapy strategies are often unable to maintain perfect control of glycemic levels. Several studies are searching for new and improved methodologies for expansion of β-cell cultures in vitro to increase the supply of these cells for pancreatic islets replacement therapy. A promising approach consists of differentiation of stem cells into insulin-producing cells (IPCs) in sufficient number and functional status to be transplanted. Differentiation protocols have been designed using consecutive cytokines or signaling modulator treatments, at specific dosages, to activate or inhibit the main signaling pathways that control the differentiation of induced pluripotent stem cells (iPSCs) into pancreatic β-cells. Here, we provide an overview of the current approaches and achievements in obtaining stem cell-derived β-cells and the numerous challenges, which still need to be overcome to achieve this goal. Clinical translation of stem cells-derived β-cells for efficient maintenance of long-term euglycemia remains a major issue. Therefore, research efforts have been directed to the final steps of in vitro differentiation, aiming at production of functional and mature β-cells and integration of interdisciplinary fields to generate efficient cell therapy strategies capable of reversing the clinical outcome of T1D.

Glucagon-receptor-antagonism-mediated β-cell regeneration as an effective anti-diabetic therapy

Type 1 diabetes mellitus (T1D) is a chronic disease with potentially severe complications, and β-cell deficiency underlies this disease. Despite active research, no therapy to date has been able to induce β-cell regeneration in humans. Here, we discover the β-cell regenerative effects of glucagon receptor antibody (anti-GcgR). Treatment with anti-GcgR in mouse models of β-cell deficiency leads to reversal of hyperglycemia, increase in plasma insulin levels, and restoration of β-cell mass. We demonstrate that both β-cell proliferation and α- to β-cell transdifferentiation contribute to anti-GcgR-induced β-cell regeneration. Interestingly, anti-GcgR-induced α-cell hyperplasia can be uncoupled from β-cell regeneration after antibody clearance from the body. Importantly, we are able to show that anti-GcgR-induced β-cell regeneration is also observed in non-human primates. Furthermore, anti-GcgR and anti-CD3 combination therapy reverses diabetes and increases β-cell mass in a mouse model of autoimmune diabetes.

Navigating the Genomic Landscape of Human Adipose Stem Cell-Derived β-Cells

Diabetes is a pandemic manifested through glucose dysregulation mediated by inadequate insulin secretion by beta cells. A beta cell replacement strategy would transform the treatment paradigm from pharmacologic glucose modulation to a genuine cure. Stem cells have emerged as a potential source for beta cell (β-cell) engineering. The detailed generation of functional β-cells from both embryonic and induced pluripotent stem cells has recently been described. Adult stem cells, including adipose derived, may also offer a therapeutic approach, but remain ill defined. In our study, we performed an in-depth assessment of insulin-producing beta cells generated from human adipose, irrespective of donor patient age, gender, and health status. Cellular transformation was confirmed using flow cytometry and single-cell imaging. Insulin secretion was observed with glucose stimulation and abrogated following palmitate exposure, a common free fatty acid implicated in human beta cell dysfunction. We used next-generation sequencing to explore gene expression changes before and after differentiation of patient-matched samples, which revealed more than 5,000 genes enriched. Adipose-derived beta cells displayed comparable gene expression to native β-cells. Pathway analysis demonstrated relevance to stem cell differentiation and pancreatic developmental processes, which are vital to cellular function, structural development, and regulation. We conclude that the functions associated with adipose derived beta cells are mediated through relevant changes in the transcriptome, which resemble those seen in native β-cell morphogenesis and maturation. Therefore, they may represent a viable option for the clinical translation of stem cell-based therapies in diabetes.

Tracing the cellular basis of islet specification in mouse pancreas

Pancreatic islets play an essential role in regulating blood glucose level. Although the molecular pathways underlying islet cell differentiation are beginning to be resolved, the cellular basis of islet morphogenesis and fate allocation remain unclear. By combining unbiased and targeted lineage tracing, we address the events leading to islet formation in the mouse. From the statistical analysis of clones induced at multiple embryonic timepoints, here we show that, during the secondary transition, islet formation involves the aggregation of multiple equipotent endocrine progenitors that transition from a phase of stochastic amplification by cell division into a phase of sublineage restriction and limited islet fission. Together, these results explain quantitatively the heterogeneous size distribution and degree of polyclonality of maturing islets, as well as dispersion of progenitors within and between islets. Further, our results show that, during the secondary transition, α- and β-cells are generated in a contemporary manner. Together, these findings provide insight into the cellular basis of islet development.

The cellular basis of islet morphogenesis and fate allocation remain unclear. Here, the authors use a R26-CreER-R26R-Confetti mouse line to follow quantitatively the clonal dynamics of islet formation showing how, during the secondary transition, islet progenitors amplify through rounds of stochastic cell division before becoming restricted to α and β cell sublineages.

SMAD7 enhances adult β-cell proliferation without significantly affecting β-cell function in mice

The interplay between the transforming growth factor β (TGF-β) signaling proteins, SMAD family member 2 (SMAD2) and 3 (SMAD3), and the TGF-β-inhibiting SMAD, SMAD7, seems to play a vital role in proper pancreatic endocrine development and also in normal β-cell function in adult pancreatic islets. Here, we generated conditional SMAD7 knockout mice by crossing insulin1^Cre mice with SMAD7^fx/fx mice. We also created a β cell-specific SMAD7-overexpressing mouse line by crossing insulin1^Dre mice with HPRT-SMAD7/RosaGFP mice. We analyzed β-cell function in adult islets when SMAD7 was either absent or overexpressed in β cells. Loss of SMAD7 in β cells inhibited proliferation, and SMAD7 overexpression enhanced cell proliferation. However, alterations in basic glucose homeostasis were not detectable following either SMAD7 deletion or overexpression in β cells. Our results show that both the absence and overexpression of SMAD7 affect TGF-β signaling and modulates β-cell proliferation but does not appear to alter β-cell function. Reversible SMAD7 overexpression may represent an attractive therapeutic option to enhance β-cell proliferation without negative effects on β-cell function.

Insulin-Producing Cell Transplantation Platform for Veterinary Practice

Diabetes mellitus (DM) remains a global concern in both human and veterinary medicine. Type I DM requires prolonged and consistent exogenous insulin administration to address hyperglycemia, which can increase the risk of diabetes complications such as retinopathy, nephropathy, neuropathy, and heart disorders. Cell-based therapies have been successful in human medicine using the Edmonton protocol. These therapies help maintain the production of endogenous insulin and stabilize blood glucose levels and may possibly be adapted to veterinary clinical practice. The limited number of cadaveric pancreas donors and the long-term use of immunosuppressive agents are the main obstacles for this protocol. Over the past decade, the development of potential therapies for DM has mainly focused on the generation of effective insulin-producing cells (IPCs) from various sources of stem cells that can be transplanted into the body. Another successful application of stem cells in type I DM therapies is transplanting generated IPCs. Encapsulation can be an alternative strategy to protect IPCs from rejection by the body due to their immunoisolation properties. This review summarizes current concepts of IPCs and encapsulation technology for veterinary clinical application and proposes a potential stem-cell-based platform for veterinary diabetic regenerative therapy.

In Depth Quantification of Extracellular Matrix Proteins from Human Pancreas

Extracellular matrix (ECM) is an important component of the pancreatic microenvironment which regulates β cell proliferation, differentiation, and insulin secretion. Protocols have recently been developed for the decellularization of the human pancreas to generate functional scaffolds and hydrogels. In this work, we characterized human pancreatic ECM composition before and after decellularization using isobaric dimethylated leucine (DiLeu) labeling for relative quantification of ECM proteins. A novel correction factor was employed in the study to eliminate the bias introduced during sample preparation. In comparison to the commonly employed sample preparation methods (urea and FASP) for proteomic analysis, a recently developed surfactant and chaotropic agent assisted sequential extraction/on pellet digestion (SCAD) protocol has provided an improved strategy for ECM protein extraction of human pancreatic ECM matrix. The quantitative proteomic results revealed the preservation of matrisome proteins while most of the cellular proteins were removed. This method was compared with a well-established label-free quantification (LFQ) approach which rendered similar expressions of different categories of proteins (collagens, ECM glycoproteins, proteoglycans, etc.). The distinct expression of ECM proteins was quantified comparing adult and fetal pancreas ECM, shedding light on the correlation between matrix composition and postnatal β cell maturation. Despite the distinct profiles of different subcategories in the native pancreas, the distribution of matrisome proteins exhibited similar trends after the decellularization process. Our method generated a large data set of matrisome proteins from a single tissue type. These results provide valuable insight into the possibilities of constructing a bioengineered pancreas. It may also facilitate better understanding of the potential roles that matrisome proteins play in postnatal β cell maturation.