Cell-replacement therapy for diabetes: Generating functional insulin-producing tissue from adult human liver cells

Glucagon-producing α-cell transcriptional identity and reprogramming towards insulin production

β-Cell replacement by in situ reprogramming of non-β-cells is a promising diabetes therapy. Following the observation that near-total β-cell ablation in adult mice triggers the reprogramming of pancreatic α-, δ-, and γ-cells into insulin (INS)-producing cells, recent studies are delving deep into the mechanisms controlling adult α-cell identity. Systematic analyses of the α-cell transcriptome and epigenome have started to pinpoint features that could be crucial for maintaining α-cell identity. Using different transgenic and chemical approaches, significant advances have been made in reprogramming α-cells in vivo into INS-secreting cells in mice. The recent reprogramming of human α-cells in vitro is an important step forward that must now be complemented with a comprehensive molecular dissection of the mechanisms controlling α-cell identity.

Biochemical pancreatic β-cell lineage reprogramming: Various cell fate shifts

The incidence of pancreatic diseases has been continuously rising in recent years. Thus, research on pancreatic regeneration is becoming more popular. Chronic hyperglycemia is detrimental to pancreatic β-cells, leading to impairment of insulin secretion which is the main hallmark of pancreatic diseases. Obtaining plenty of functional pancreatic β-cells is the most crucial aspect when studying pancreatic biology and treating diabetes. According to the International Diabetes Federation, diabetes has become a global epidemic, with about 3 million people suffering from diabetes worldwide. Hyperglycemia can lead to many dangerous diseases, including amputation, blindness, neuropathy, stroke, and cardiovascular and kidney diseases. Insulin is widely used in the treatment of diabetes; however, innovative approaches are needed in the academic and preclinical stages. A new approach aims at synthesizing patient-specific functional pancreatic β-cells. The present article focuses on how cells from different tissues can be transformed into pancreatic β-cells.

Direct reprogramming of human fibroblasts into insulin-producing cells using transcription factors

Direct lineage reprogramming of one somatic cell into another without transitioning through a progenitor stage has emerged as a strategy to generate clinically relevant cell types. One cell type of interest is the pancreatic insulin-producing β cell whose loss and/or dysfunction leads to diabetes. To date it has been possible to create β-like cells from related endodermal cell types by forcing the expression of developmental transcription factors, but not from more distant cell lineages like fibroblasts. In light of the therapeutic benefits of choosing an accessible cell type as the cell of origin, in this study we set out to analyze the feasibility of transforming human skin fibroblasts into β-like cells. We describe how the timed-introduction of five developmental transcription factors (Neurog3, Pdx1, MafA, Pax4, and Nkx2-2) promotes conversion of fibroblasts toward a β-cell fate. Reprogrammed cells exhibit β-cell features including β-cell gene expression and glucose-responsive intracellular calcium mobilization. Moreover, reprogrammed cells display glucose-induced insulin secretion in vitro and in vivo. This work provides proof-of-concept of the capacity to make insulin-producing cells from human fibroblasts via transcription factor-mediated direct reprogramming.

Direct Reprogramming of Somatic Cells into Induced β-Cells: An Overview

The persistent shortage of insulin-producing islet mass or β-cells for transplantation in the ever-growing diabetic population worldwide is a matter of concern. To date, permanent cure to this medical complication is not available and soon after the establishment of lineage-specific reprogramming, direct β-cell reprogramming became a viable alternative for β-cell regeneration. Direct reprogramming is a straightforward and powerful technique that can provide an unlimited supply of cells by transdifferentiating terminally differentiated cells toward the desired cell type. This approach has been extensively used by multiple groups to reprogram non-β-cells toward insulin-producing β-cells. The β-cell identity has been achieved by various studies via ectopic expression of one or more pancreatic-specific transcription factors in somatic cells, bypassing the pluripotent state. This work highlights the importance of the direct reprogramming approaches (both integrative and non-integrative) in generating autologous β-cells for various applications. An in-depth understanding of the strategies and cell sources could prove beneficial for the efficient generation of integration-free functional insulin-producing β-cells for diabetic patients lacking endogenous β-cells.

Tissue engineering approaches and generation of insulin-producing cells to treat type 1 diabetes

Tissue engineering (TE) has become a new effective solution to a variety of medical problems, including diabetes. Mesenchymal stem cells (MSCs), which have the ability to differentiate into endodermal and mesodermal cells, appear to be appropriate for this function. The purpose of this review was to evaluate the outcomes of various researches on the insulin-producing cells (IPCs) generation from MSCs with TE approaches to increase efficacy of type 1 diabetes treatments. The search was performed in PubMed/Medline, Scopus and Embase databases until 2021. Studies revealed that MSCs could also differentiate into IPCs under certain conditions. Therefore, a wide range of protocols have been used for this differentiation, but their effectiveness is very different. Scaffolds can provide a microenvironment that enhances the MSCs to IPCs differentiation, improves their metabolic activity and up-regulate pancreatic-specific transcription factors. They also preserve IPCs architecture and enhance insulin production as well as protect against cell death. This systematic review offers a framework for prospective research based on data. In vitro and in vivo evidence suggests that scaffold-based TE can improve the viability and function of IPCs.

The role of DNA demethylation in liver to pancreas transdifferentiation

Background

Insulin producing cells generated by liver cell transdifferentiation, could serve as an attractive source for regenerative medicine. The present study assesses the relationship between DNA methylation pTFs induced liver to pancreas transdifferentiation.

Results

The transdifferentiation process is associated with DNA demethylation, mainly at gene regulatory sites, and with increased expression of these genes. Active inhibition of DNA methylation promotes the pancreatic transcription factor-induced transdifferentiation process, supporting a causal role for DNA demethylation in this process.

Conclusions

Transdifferentiation is associated with global DNA hypomethylation, and with increased expression of specific demethylated genes. A combination of epigenetic modulators may be used to increase chromatin accessibility of the pancreatic transcription factors, thus promoting the efficiency of the developmental process.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-03159-6.

Overcoming the Limitations of Stem Cell-Derived Beta Cells

Great advances in type 1 diabetes (T1D) and type 2 diabetes (T2D) treatment have been made to this day. However, modern diabetes therapy based on insulin injections and cadaveric islets transplantation has many disadvantages. That is why researchers are developing new methods to regenerate the pancreatic hormone-producing cells in vitro. The most promising approach is the generation of stem cell-derived beta cells that could provide an unlimited source of insulin-secreting cells. Recent studies provide methods to produce beta-like cell clusters that display glucose-stimulated insulin secretion—one of the key characteristics of the beta cell. However, in comparison with native beta cells, stem cell-derived beta cells do not undergo full functional maturation. In this paper we review the development and current state of various protocols, consider advantages, and propose ways to improve them. We examine molecular pathways, epigenetic modifications, intracellular components, and the microenvironment as a possible leverage to promote beta cell functional maturation. A possibility to create islet organoids from stem cell-derived components, as well as their encapsulation and further transplantation, is also examined. We try to combine modern research on beta cells and their crosstalk to create a holistic overview of developing insulin-secreting systems.

Pancreatic β-Cell Development and Regeneration

The pancreatic β-cells are essential for regulating glucose homeostasis through the coordinated release of the insulin hormone. Dysfunction of the highly specialized β-cells results in diabetes mellitus, a growing global health epidemic. In this review, we describe the development and function of β-cells the emerging concept of heterogeneity within insulin-producing cells, and the potential of other cell types to assume β-cell functionality via transdifferentiation. We also discuss emerging routes to design cells with minimal β-cell properties and human stem cell differentiation efforts that carry the promise to restore normoglycemia in patients suffering from diabetes.

Engineering Islets From Stem Cells: The Optimal Solution for the Treatment of Diabetes?

Diabetes is a metabolic disease characterized by insulin deficiency. Bioengineering of stem cells with the aim to restore insulin production and glucose regulation has the potential to cure diabetic patients. In this review, we focus on the recent developments for bioengineering of induced pluripotent stem cells (iPSCs), mesenchymal stem cells (MSCs), embryonic stem cells (ESCs), and pancreatic progenitor cells in view of generating insulin producing and glucose regulating cells for β-cell replacement therapies. Recent clinical trials using islet cells derived from stem cells have been initiated for the transplantation into diabetic patients, with crucial bottlenecks of tumorigenesis, post-transplant survival, genetic instability, and immunogenicity that should be further optimized. As a new approach given high expectations, bioengineered islets from stem cells occupies considerable potential for the future clinical application and addressing the treatment dilemma of diabetes.

[Generating pancreatic islets organoids: Langerhanoids]

The extension of islet transplantation to a wider number of Type 1 diabetic patients is compromised by the scarcity of donors, the reduced ex vivo survival of pancreatic islets and the use of immunosuppressive treatments. Islets of Langerhans isolated from brain-dead donors are currently the only cell source for transplantation. Thus, it is crucial to find an alternative and an abundant source of functional insulin secreting cells not only for clinical use but also for the development of research dedicated to the screening of drugs and to the development of new therapeutic targets. Several groups around the world, including ours, develop 3D culture models as Langerhanoids that closely mimick human pancreatic islets physiology. In this review, we describe recent advances to mimic the pancreatic niche (extracellular matrix, vascularization, microfluidics) allowing better functionality of Langerhanoids.

Conversion of Gastrointestinal Somatostatin-Expressing D Cells Into Insulin-Producing Beta-Like Cells Upon Pax4 Misexpression

Type 1 diabetes results from the autoimmune-mediated loss of insulin-producing beta-cells. Accordingly, important research efforts aim at regenerating these lost beta-cells by converting pre-existing endogenous cells. Following up on previous results demonstrating the conversion of pancreatic somatostatin delta-cells into beta-like cells upon Pax4 misexpression and acknowledging that somatostatin-expressing cells are highly represented in the gastrointestinal tract, one could wonder whether this Pax4-mediated conversion could also occur in the GI tract. We made use of transgenic mice misexpressing Pax4 in somatostatin cells (SSTCrePOE) to evaluate a putative Pax4-mediated D-to-beta-like cell conversion. Additionally, we implemented an ex vivo approach based on mice-derived gut organoids to assess the functionality of these neo-generated beta-like cells. Our results outlined the presence of insulin⁺ cells expressing several beta-cell markers in gastrointestinal tissues of SSTCrePOE animals. Further, using lineage tracing, we established that these cells arose from D cells. Lastly, functional tests on mice-derived gut organoids established the ability of neo-generated beta-like cells to release insulin upon stimulation. From this study, we conclude that the misexpression of Pax4 in D cells appears sufficient to convert these into functional beta-like cells, thus opening new research avenues in the context of diabetes research.

Alpha-to-beta cell trans-differentiation for treatment of diabetes

Diabetes mellitus is a significant cause of morbidity and mortality in the United States and worldwide. According to the CDC, in 2017, ∼34.2 million of the American population had diabetes. Also, in 2017, diabetes was the seventh leading cause of death and has become the number one biomedical financial burden in the United States. Insulin replacement therapy and medications that increase insulin secretion and improve insulin sensitivity are the main therapies used to treat diabetes. Unfortunately, there is currently no radical cure for the different types of diabetes. Loss of β cell mass is the end result that leads to both type 1 and type 2 diabetes. In the past decade, there has been an increased effort to develop therapeutic strategies to replace the lost β cell mass and restore insulin secretion. α cells have recently become an attractive target for replacing the lost β cell mass, which could eventually be a potential strategy to cure diabetes. This review highlights the advantages of using α cells as a source for generating new β cells, the various investigative approaches to convert α cells into insulin-producing cells, and the future prospects and problems of this promising diabetes therapeutic strategy.

REST Inhibits Direct Reprogramming of Pancreatic Exocrine to Endocrine Cells by Preventing PDX1-Mediated Activation of Endocrine Genes

The emerging appreciation of plasticity among pancreatic lineages has created interest in harnessing cellular reprogramming for β cell replacement therapy of diabetes. Current reprogramming methodologies are inefficient, largely because of a limited understanding of the underlying mechanisms. Using an in vitro reprogramming system, we reveal the transcriptional repressor RE-1 silencing transcription factor (REST) as a barrier for β cell gene expression in the reprogramming of pancreatic exocrine cells. We observe that REST-bound loci lie adjacent to the binding sites of multiple key β cell transcription factors, including PDX1. Accordingly, a loss of REST function combined with PDX1 expression results in the synergistic activation of endocrine genes. This is accompanied by increased histone acetylation and PDX1 binding at endocrine gene loci. Collectively, our data identify a mechanism for REST activity involving the prevention of PDX1-mediated activation of endocrine genes and uncover REST downregulation and the resulting chromatin alterations as key events in β cell reprogramming.

The Effect of Stem Cell Transplantation Therapy for Post Viral Chronic Liver Cell Failure on Associated Type II Diabetes Mellitus: A Pilot Study

BACKGROUND

It was observed that type II diabetes mellitus associated with chronic liver failure improved after stem cell transplantation. However, there were no adequate studies regarding this issue. The aim of this study was to evaluate the effect of stem cell transplantation on associated type II diabetes mellitus and on the liver function tests.

METHODS

This pilot study included 30 patients of post-hepatitis chronic liver failure who were classified into two groups: Group I included patients with chronic liver cell failure associated with type 2 diabetes. Group II included patients without type II diabetes. Autologous CD34+ and CD133+ stem cells were percutaneously infused into the portal vein. Responders (regarding the improvement of diabetes as well as improvement of liver condition) and non-responders were determined. Patients were followed up for one, three and six months after the intervention evaluating their three-hour glucose tolerance test, C- peptide (Fasting and postprandial), Child-Pugh score and performance score one month, three months, and six months after stem cell therapy.

RESULTS

Both synthetic and excretory functions of the liver were improved in 10 patients (66.66 %) of group I and in 12 patients (80 %) of group II. Significant improvement in the Oral Glucose Tolerance Test in the responders of both the groups was well defined from the 3rd month and this was comparable to changes in liver function tests and Child-Pugh score.

CONCLUSION

Successful stem cell therapy in chronic liver cell failure patients can improve but not cure the associating type 2 diabetes by improving insulin resistance.

Molecular mechanisms of transcription factor mediated cell reprogramming: conversion of liver to pancreas

Transdifferentiation is a type of cellular reprogramming involving the conversion of one differentiated cell type to another. This remarkable phenomenon holds enormous promise for the field of regenerative medicine. Over the last 20 years techniques used to reprogram cells to alternative identities have advanced dramatically. Cellular identity is determined by the transcriptional profile which comprises the subset of mRNAs, and therefore proteins, being expressed by a cell at a given point in time. A better understanding of the levers governing transcription factor activity benefits our ability to generate therapeutic cell types at will. One well-established example of transdifferentiation is the conversion of hepatocytes to pancreatic β-cells. This cell type conversion potentially represents a novel therapy in T1D treatment. The identification of key master regulator transcription factors (which distinguish one body part from another) during embryonic development has been central in developing transdifferentiation protocols. Pdx1 is one such example of a master regulator. Ectopic expression of vector-delivered transcription factors (particularly the triumvirate of Pdx1, Ngn3 and MafA) induces reprogramming through broad transcriptional remodelling. Increasingly, complimentary cell culture techniques, which recapitulate the developmental microenvironment, are employed to coax cells to adopt new identities by indirectly regulating transcription factor activity via intracellular signalling pathways. Both transcription factor-based reprogramming and directed differentiation approaches ultimately exploit transcription factors to influence cellular identity. Here, we explore the evolution of reprogramming and directed differentiation approaches within the context of hepatocyte to β-cell transdifferentiation focussing on how the introduction of new techniques has improved our ability to generate β-cells.

Phenotypic assessment of liver-derived cell cultures during in vitro expansion

Background: Liver cells represent an attractive source of cells for autologous regenerative medicine. The present study assesses the liver cells' stability during in vitro expansion, as a prerequisite for therapeutic use. Results: The human liver cell cultures in this study were propagated efficiently in vitro for at least 12 passages. No significant changes in morphology, intracellular ultrastructures and characteristic markers expression were found during in vitro expansion of cells from all analyzed donors. However, expanded cells derived from male donors of >60 years old, lost the Y chromosome. Conclusion: Liver-derived cell cultures adopt a proliferative, stable mesenchymal phenotype, through an epithelial to mesenchymal transition process. The molecular and phenotypic changes of the cells during propagation are uniform, despite the heterogeneity of the different donors. Loss of Y chromosome occurs after cells' propagation in elder male donors.

Improvement of the therapeutic capacity of insulin-producing cells trans-differentiated from human liver cells using engineered cell sheet

BACKGROUND

Although pancreatic islet transplantation therapy is ideal for diabetes patients, several hurdles have prevented it from becoming a standard treatment, including donor shortage and low engraftment efficacy. In this study, we prepared insulin-producing cells trans-differentiated from adult human liver cells as a new islet source. Also, cell sheet formation could improve differentiation efficiency and graft survival.

METHODS

Liver cells were expanded in vitro and trans-differentiated to IPCs using adenovirus vectors carrying human genes for PDX1, NEUROD1, and MAFA. IPCs were seeded on temperature-responsive culture dishes to form cell sheets. Differentiation efficiency was confirmed by ß cell-specific gene expression, insulin production, and immunohistochemistry. IPC suspension was injected by portal vein (PV), and IPC sheet was transplanted on the liver surface of the diabetic nude mouse. The therapeutic effect of IPC sheet was evaluated by comparing blood glucose control, weight gain, histological evaluation, and hepatotoxicity with IPC injection group. Also, cell biodistribution was assessed by in vivo/ex vivo fluorescence image tagging.

RESULTS

Insulin gene expression and protein production were significantly increased on IPC sheets compared with those in IPCs cultured on conventional culture dishes. Transplanted IPC sheets displayed significantly higher engraftment efficiency and fewer transplanted cells in other organs than injected IPCs, and also lower liver toxicity, improved blood glucose levels, and weight gain. Immunohistochemical analyses of liver tissue revealed positive staining for PDX1 and insulin at 1, 2, and 4 weeks after IPC transplantation.

CONCLUSIONS

In conclusion, cell sheet formation enhanced the differentiation function and maturation of IPCs in vitro. Additionally, parameters for clinical application such as distribution, therapeutic efficacy, and toxicity were favorable. The cell sheet technique may be used with IPCs derived from various cell sources in clinical applications.

The effect of liver donors' age, gender and metabolic state on pancreatic lineage activation

Autologous cells replacement therapy by liver to pancreas transdifferentiation (TD) allows diabetic patients to be also the donors of their own therapeutic tissue. Aim: To analyze whether the efficiency of the process is affected by liver donors' heterogeneity with regard to age, gender and the metabolic state. Materials & methods: TD of liver cells derived from nondiabetic and diabetic donors at different ages was characterized at molecular and cellular levels, in vitro. Results: Neither liver cells proliferation nor the propagated cells TD efficiency directly correlate with the age (3-60 years), gender or the metabolic state of the donors. Conclusion: Human liver cells derived from a wide array of ages and metabolic states can be used for autologous cells therapies for diabetics.

Spheroid Fabrication Using Concave Microwells Enhances the Differentiation Efficacy and Function of Insulin-Producing Cells via Cytoskeletal Changes

Pancreatic islet transplantation is the fundamental treatment for insulin-dependent diabetes; however, donor shortage is a major hurdle in its use as a standard treatment. Accordingly, differentiated insulin-producing cells (DIPCs) are being developed as a new islet source. Differentiation efficiency could be enhanced if the spheroid structure of the natural islets could be recapitulated. Here, we fabricated DIPC spheroids using concave microwells, which enabled large-scale production of spheroids of the desired size. We prepared DIPCs from human liver cells by trans-differentiation using transcription factor gene transduction. Islet-related gene expression and insulin secretion levels were higher in spheroids compared to those in single-cell DIPCs, whereas actin–myosin interactions significantly decreased. We verified actin–myosin-dependent insulin expression in single-cell DIPCs by using actin–myosin interaction inhibitors. Upon transplanting cells into the kidney capsule of diabetic mouse, blood glucose levels decreased to 200 mg/dL in spheroid-transplanted mice but not in single cell-transplanted mice. Spheroid-transplanted mice showed high engraftment efficiency in in vivo fluorescence imaging. These results demonstrated that spheroids fabricated using concave microwells enhanced the engraftment and functions of DIPCs via actin–myosin-mediated cytoskeletal changes. Our strategy potentially extends the clinical application of DIPCs for improved differentiation, glycemic control, and transplantation efficiency of islets.

Emerging routes to the generation of functional β-cells for diabetes mellitus cell therapy

Diabetes mellitus, which affects more than 463 million people globally, is caused by the autoimmune ablation or functional loss of insulin-producing β-cells, and prevalence is projected to continue rising over the next decades. Generating β-cells to mitigate the aberrant glucose homeostasis manifested in the disease has remained elusive. Substantial advances have been made in producing mature β-cells from human pluripotent stem cells that respond appropriately to dynamic changes in glucose concentrations in vitro and rapidly function in vivo following transplantation in mice. Other potential avenues to produce functional β-cells include: transdifferentiation of closely related cell types (for example, other pancreatic islet cells such as α-cells, or other cells derived from endoderm); the engineering of non-β-cells that are capable of modulating blood sugar; and the construction of synthetic 'cells' or particles mimicking functional aspects of β-cells. This Review focuses on the current status of generating β-cells via these diverse routes, highlighting the unique advantages and challenges of each approach. Given the remarkable progress in this field, scalable bioengineering processes are also discussed for the realization of the therapeutic potential of derived β-cells.

Protocol for Studying Reprogramming of Mouse Pancreatic Acinar Cells to β-like Cells

The potential of reprogrammed β cells derived from pancreatic exocrine cells to treat diabetes has been demonstrated in animal models. However, the precise mechanisms and regulators involved in this process are not clear. Here, we describe a method that allows mechanistic studies of this process in primary exocrine cultures using adenoviral expression vectors. This rapid 5-day protocol, provides the researcher with a highly controlled experimental system in which the effects of different compounds or genetic manipulations can be studied. For complete details on the use and execution of this protocol, please refer to Elhanani et al. (2020).

Functional β-Cell Differentiation of Small-Tail Han Sheep Pancreatic Mesenchymal Stem Cells and the Therapeutic Potential in Type 1 Diabetic Mice

OBJECTIVES

This study aims to investigate the characteristics of sheep pancreatic mesenchymal stem cells (PSCs) and therapeutic potential of differentiated β-like cells in streptozotocin-induced diabetic mice.

METHODS

Pancreatic mesenchymal stem cells were isolated from 3- to 4-month-old sheep embryos, and their biological characteristics were explored. The function and therapeutic potential of differentiated β-like insulin-producing cells were also investigated in vitro and in vivo. Differentiated cells were identified through dithizone staining and immunofluorescence staining. Insulin secretion was analyzed using an enzyme-linked immunosorbent assay kit. The preliminary therapeutic potential of induced β-like cells in diabetic mice was detected by blood glucose and body weight.

RESULTS

Primary PSCs were isolated and subcultured up to passage 36. Immunofluorescence staining presented PSC-expressed important markers such as Pdx1, Nkx6-1, Ngn3, and Nestin. Primary PSCs could be induced into functional pancreatic β-like islet cells with a 3-step protocol. The induced β-like islet cells could ameliorate blood glucose in diabetic mice.

CONCLUSIONS

The method proposed for generating pancreatic islet β cells provided a preliminary phenotypic investigation of induced cell treatment in diabetic mice, and also laid a foundation in the identification of pharmaceutical targets to treat insulin-dependent diabetes.

Islet-Like Structures Generated In Vitro from Adult Human Liver Stem Cells Revert Hyperglycemia in Diabetic SCID Mice

A potential therapeutic strategy for diabetes is the transplantation of induced-insulin secreting cells. Based on the common embryonic origin of liver and pancreas, we studied the potential of adult human liver stem-like cells (HLSC) to generate in vitro insulin-producing 3D spheroid structures (HLSC-ILS). HLSC-ILS were generated by a one-step protocol based on charge dependent aggregation of HLSC induced by protamine. 3D aggregation promoted the spontaneous differentiation into cells expressing insulin and several key markers of pancreatic β cells. HLSC-ILS showed endocrine granules similar to those seen in human β cells. In static and dynamic in vitro conditions, such structures produced C-peptide after stimulation with high glucose. HLSC-ILS significantly reduced hyperglycemia and restored a normo-glycemic profile when implanted in streptozotocin-diabetic SCID mice. Diabetic mice expressed human C-peptide and very low or undetectable levels of murine C-peptide. Hyperglycemia and a diabetic profile were restored after HLSC-ISL explant. The gene expression profile of in vitro generated HLSC-ILS showed a differentiation from HLSC profile and an endocrine commitment with the enhanced expression of several markers of β cell differentiation. The comparative analysis of gene expression profiles after 2 and 4 weeks of in vivo implantation showed a further β-cell differentiation, with a genetic profile still immature but closer to that of human islets. In conclusion, protamine-induced spheroid aggregation of HLSC triggers a spontaneous differentiation to an endocrine phenotype. Although the in vitro differentiated HLSC-ILS were immature, they responded to high glucose with insulin secretion and in vivo reversed hyperglycemia in diabetic SCID mice.

Current progress in stem cell therapy for type 1 diabetes mellitus

Type 1 diabetes mellitus (T1DM) is the most common chronic autoimmune disease in young patients and is characterized by the loss of pancreatic β cells; as a result, the body becomes insulin deficient and hyperglycemic. Administration or injection of exogenous insulin cannot mimic the endogenous insulin secreted by a healthy pancreas. Pancreas and islet transplantation have emerged as promising treatments for reconstructing the normal regulation of blood glucose in T1DM patients. However, a critical shortage of pancreases and islets derived from human organ donors, complications associated with transplantations, high cost, and limited procedural availability remain bottlenecks in the widespread application of these strategies. Attempts have been directed to accommodate the increasing population of patients with T1DM. Stem cell therapy holds great potential for curing patients with T1DM. With the advent of research on stem cell therapy for various diseases, breakthroughs in stem cell-based therapy for T1DM have been reported. However, many unsolved issues need to be addressed before stem cell therapy will be clinically feasible for diabetic patients. In this review, we discuss the current research advances in strategies to obtain insulin-producing cells (IPCs) from different precursor cells and in stem cell-based therapies for diabetes.

Direct Lineage Reprogramming: Harnessing Cell Plasticity between Liver and Pancreas

Direct lineage reprogramming of abundant and accessible cells into therapeutically useful cell types holds tremendous potential in regenerative medicine. To date, a number of different cell types have been generated by lineage reprogramming methods, including cells from the neural, cardiac, hepatic, and pancreatic lineages. The success of this strategy relies on developmental biology and the knowledge of cell-fate-defining transcriptional networks. Hepatocytes represent a prime target for β cell conversion for numerous reasons, including close developmental origin, accessibility, and regenerative potential. We present here an overview of pancreatic and hepatic development, with a particular focus on the mechanisms underlying the divergence between the two cell lineages. Additionally, we discuss to what extent this lineage relationship can be exploited in efforts to reprogram one cell type into the other and whether such an approach may provide a suitable strategy for regenerative therapies of diabetes.

Combination therapy with anti-CD20 mAb and IL-10 gene to reverse type 1 diabetes by attenuating pancreatitis and inhibiting apoptosis in NOD mice

AIMS

To assess the combination therapy of anti-CD20 mabs and adenovirus-mediated interleukin-10 (IL-10) gene delivery on the prevention of type 1 diabetes (T1D) in non-obese diabetes (NOD) mice.

MAIN METHODS

In present study, we simultaneously blocked the B cell interactions and recovered the Th cell subset proportion by using through anti-CD20 Mab and adenovirus-mediated gene delivery of IL-10, respectively. After 9 consecutive days of combination therapy, various measurements, including hematoxylin-eosin staining (HE), terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labelling assay (TUNEL), immunohistochemistry, ELISA, PCR and western blot were applied to further assess the efficacy.

KEY FINDINGS

The results suggested that the combination intervention reduced the T1D-associated morbidity of NOD mice, promote insulin secretion, control blood glucose and ease pancreatitis. Moreover, the combination therapy might play a protective role in pancreatic β cells by suppressing the expression of TNF-α and Fas, blocking the Caspase-8 and Caspase-3 apoptotic pathways and activating the Bcl-2 anti-apoptotic pathway. Finally, the combination intervention may up-regulate the gene expression of CK-19 and PDX-1 and further accelerate the differentiation and proliferation of pancreatic β cells.

SIGNIFICANCE

Therefore, the combination intervention with anti-CD20 mabs and the IL-10 gene plays a role in the prevention of T1D to some extent in NOD mice.

Insulin-producing cells from mesenchymal stromal cells: Protection against cognitive impairment in diabetic rats depends upon implant site

Diabetes mellitus (DM) is a serious public health problem and can cause long-term damage to the brain, resulting in cognitive impairment in these patients. Insulin therapy for type 1 DM (DM1) can achieve overall blood glucose control, but glycemic variations can occur during injection intervals, which may contribute to some complications. Among the additional therapies available for DM1 treatment is the implantation of insulin-producing cells (IPCs) to attenuate hyperglycemia and even reverse diabetes. Here, we studied the strategy of implanting IPCs obtained from mesenchymal stromal cells (MSCs) from adipose tissue, comparing two different IPC implant sites, subcapsular renal (SR) and subcutaneous (SC), to investigate their putative protection against hippocampal damage, induced by STZ, in a rat DM1 model. Both implants improved hyperglycemia and reduced the serum content of advanced-glycated end products in diabetic rats, but serum insulin was not observed in the SC group. The SC-implanted group demonstrated ameliorated cognitive impairment (evaluated by novel object recognition) and modulation of hippocampal astroglial reactivity (evaluated by S100B and GFAP). Using GFP+ cell implants, the survival of cells at the implant sites was confirmed, as well as their migration to the pancreas and hippocampus. The presence of undifferentiated MSCs in our IPC preparation may explain the peripheral reduction in AGEs and subsequent cognitive impairment recovery, mediated by autophagic depuration and immunomodulation at the hippocampus, respectively. Together, these data reinforce the importance of MSCs for use in neuroprotective strategies, and highlight the logistic importance of the subcutaneous route for their administration.

Direct cell-fate conversion of somatic cells: Toward regenerative medicine and industries

Cells of multicellular organisms have diverse characteristics despite having the same genetic identity. The distinctive phenotype of each cell is determined by molecular mechanisms such as epigenetic changes that occur throughout the lifetime of an individual. Recently, technologies that enable modification of the fate of somatic cells have been developed, and the number of studies using these technologies has increased drastically in the last decade. Various cell types, including neuronal cells, cardiomyocytes, and hepatocytes, have been generated using these technologies. Although most direct reprogramming methods employ forced transduction of a defined sets of transcription factors to reprogram cells in a manner similar to induced pluripotent cell technology, many other strategies, such as methods utilizing chemical compounds and microRNAs to change the fate of somatic cells, have also been developed. In this review, we summarize transcription factor-based reprogramming and various other reprogramming methods. Additionally, we describe the various industrial applications of direct reprogramming technologies.

A change in the zinc ion concentration reflects the maturation of insulin-producing cells generated from adipose-derived mesenchymal stem cells

The generation of insulin-producing cells (IPCs) from pluripotent stem cells could be a breakthrough treatment for type 1 diabetes. However, development of new techniques is needed to exclude immature cells for clinical application. Dithizone staining is used to evaluate IPCs by detecting zinc. We hypothesised that zinc ion (Zn2+) dynamics reflect the IPC maturation status. Human adipose-derived stem cells were differentiated into IPCs by our two-step protocol using two-dimensional (2D) or 3D culture. The stimulation indexes of 2D -and 3D-cultured IPCs on day 21 were 1.21 and 3.64 (P < 0.05), respectively. The 3D-cultured IPCs were stained with dithizone during culture, and its intensity calculated by ImageJ reached the peak on day 17 (P < 0.05). Blood glucose levels of streptozotocin-induced diabetic nude mice were normalised (4/4,100%) after transplantation of 96 3D-cultured IPCs. Zn2+ concentration changes in the medium of 3D cultures had a negative value in the early period and a large positive value in the latter period. This study suggests that Zn2+ dynamics based on our observations and staining of zinc transporters have critical roles in the differentiation of IPCs, and that their measurement might be useful to evaluate IPC maturation as a non-destructive method.

Alterations in Beta Cell Identity in Type 1 and Type 2 Diabetes

PURPOSE OF REVIEW

To discuss the current understanding of "β cell identity" and factors underlying altered identity of pancreatic β cells in diabetes, especially in humans.

RECENT FINDINGS

Altered identity of β cells due to dedifferentiation and/or transdifferentiation has been proposed as a mechanism of loss of β cells in diabetes. In dedifferentiation, β cells do not undergo apoptosis; rather, they lose their identity and function. Dedifferentiation is well characterized by the decrease in expression of key β cell markers such as genes encoding major transcription factors, e.g., MafA, NeuroD1, Nkx6.1, and Foxo1, and an increase in atypical or "disallowed" genes for β cells such as lactate dehydrogenase, monocarboxylate transporter MCT1, or progenitor cell genes (Neurog3, Pax4, or Sox9). Moreover, altered identity of mature β cells in diabetes also involves transdifferentiation of β cells into other islet hormone producing cells. For example, overexpression of α cell specific transcription factor Arx or ablation of Pdx1 resulted in an increase of α cell numbers and a decrease in β cell numbers in rodents. The frequency of α-β double-positive cells was also prominent in human subjects with T2D. These altered identities of β cells likely serve as a compensatory response to enhance function/expand cell numbers and may also camouflage/protect cells from ongoing stress. However, it is equally likely that this may be a reflection of new cell formation as a frank regenerative response to ongoing tissue injury. Physiologically, all these responses are complementary. In diabetes, (1) endocrine identity recapitulates the less mature/less-differentiated fetal/neonatal cell type, possibly representing an adaptive mechanism; (2) residual β cells may be altered in their subtype proportions or other molecular features; (3) in humans, "altered identity" is a preferable term to dedifferentiation as their cellular fate (differentiated cells losing identity or progenitors becoming more differentiated) is unclear as yet.

Liver to Pancreas Transdifferentiation

PURPOSE OF THE REVIEW

Here, we review recent findings in the field of generating insulin-producing cells by pancreatic transcription factor (pTF)-induced liver transdifferentiation (TD). TD is the direct conversion of functional cell types from one lineage to another without passing through an intermediate stage of pluripotency. We address potential reasons for the restricted efficiency of TD and suggest modalities to overcome these challenges, to bring TD closer to its clinical implementation in autologous cell replacement therapy for insulin-dependent diabetes.

RECENT FINDINGS

Liver to pancreas TD is restricted to cells that are a priori predisposed to undergo the developmental process. In vivo, the predisposition of liver cells is affected by liver zonation and hepatic regeneration. The TD propensity of liver cells is related to permissive epigenome which could be extended to TD-resistant cells by specific soluble factors. An obligatory role for active Wnt signaling in continuously maintaining a "permissive" epigenome is suggested. Moreover, the restoration of the pancreatic niche and vasculature promotes the maturation of TD cells along the β cell function. Future studies on liver to pancreas TD should include the maturation of TD cells by 3D culture, the restoration of vasculature and the pancreatic niche, and the extension of TD propensity to TD-resistant cells by epigenetic modifications. Liver to pancreas TD is expected to result in the generation of custom-made "self" surrogate β cells for curing diabetes.

How, When, and Where Do Human β-Cells Regenerate?

PURPOSE OF REVIEW

Pancreatic β-cells play a critical role in whole-body glucose homeostasis by regulating the release of insulin in response to minute by minute alterations in metabolic demand. As such, β-cells are staunchly resilient but there are circumstances where they can become functionally compromised or physically lost due to pathophysiological changes which culminate in overt hyperglycemia and diabetes.

RECENT FINDINGS

In humans, β-cell mass appears to be largely defined in the postnatal period and this early replicative and generative phase is followed by a refractory state which persists throughout life. Despite this, efforts to identify physiological and pharmacological factors which might re-initiate β-cell replication (or cause the replenishment of β-cells by neogenesis or transdifferentiation) are beginning to bear fruit. Controlled manipulation of β-cell mass in humans still represents a holy grail for therapeutic intervention in diabetes, but progress is being made which may lead to ultimate success.

Reprogramming Cells to Make Insulin

Type 1 diabetes is a disease characterized by the destruction of insulin-secreting β-cells in the pancreas. Individuals are treated for this disease with lifelong insulin replacement. However, one attractive treatment possibility is to reprogram an individual’s endogenous cells to acquire the ability to secrete insulin, essentially replacing destroyed β-cells. Herein, we review the literature on the topic of reprogramming endodermal cells to produce insulin.

The role of the vasculature niche on insulin-producing cells generated by transdifferentiation of adult human liver cells

Background

Insulin-dependent diabetes is a multifactorial disorder that could be theoretically cured by functional pancreatic islets and insulin-producing cell (IPC) implantation. Regenerative medicine approaches include the potential for growing tissues and organs in the laboratory and transplanting them when the body cannot heal itself. However, several obstacles remain to be overcome in order to bring regenerative medicine approach for diabetes closer to its clinical implementation; the cells generated in vitro are typically of heterogenic and immature nature and the site of implantation should be readily vascularized for the implanted cells to survive in vivo. The present study addresses these two limitations by analyzing the effect of co-implanting IPCs with vasculature promoting cells in an accessible site such as subcutaneous. Secondly, it analyzes the effects of reconstituting the in vivo environment in vitro on the maturation and function of insulin-producing cells.

Methods

IPCs that are generated by the transdifferentiation of human liver cells are exposed to the paracrine effects of endothelial colony-forming cells (ECFCs) and human bone marrow mesenchymal stem cells (MSCs), which are the “building blocks” of the blood vessels. The role of the vasculature on IPC function is analyzed upon subcutaneous implantation in vivo in immune-deficient rodents. The paracrine effects of vasculature on IPC maturation are analyzed in culture.

Results

Co-implantation of MSCs and ECFCs with IPCs led to doubling the survival rates and a threefold increase in insulin production, in vivo. ECFC and MSC co-culture as well as conditioned media of co-cultures resulted in a significant increased expression of pancreatic-specific genes and an increase in glucose-regulated insulin secretion, compared with IPCs alone. Mechanistically, we demonstrate that ECFC and MSC co-culture increases the expression of CTGF and ACTIVINβα, which play a key role in pancreatic differentiation.

Conclusions

Vasculature is an important player in generating regenerative medicine approaches for diabetes. Vasculature displays a paracrine effect on the maturation of insulin-producing cells and their survival upon implantation. The reconstitution of the in vivo niche is expected to promote the liver-to-pancreas transdifferentiation and bringing this cell therapy approach closer to its clinical implementation.

Electronic supplementary material

The online version of this article (10.1186/s13287-019-1157-5) contains supplementary material, which is available to authorized users.

Applications of stem cells and bioprinting for potential treatment of diabetes

Currently, there does not exist a strategy that can reduce diabetes and scientists are working towards a cure and innovative approaches by employing stem cell-based therapies. On the other hand, bioprinting technology is a novel therapeutic approach that aims to replace the diseased or lost β-cells, insulin-secreting cells in the pancreas, which can potentially regenerate damaged organs such as the pancreas. Stem cells have the ability to differentiate into various cell lines including insulin-producing cells. However, there are still barriers that hamper the successful differentiation of stem cells into β-cells. In this review, we focus on the potential applications of stem cell research and bioprinting that may be targeted towards replacing the β-cells in the pancreas and may offer approaches towards treatment of diabetes. This review emphasizes on the applicability of employing both stem cells and other cells in 3D bioprinting to generate substitutes for diseased β-cells and recover lost pancreatic functions. The article then proceeds to discuss the overall research done in the field of stem cell-based bioprinting and provides future directions for improving the same for potential applications in diabetic research.

Phenotypic Plasticity: Driver of Cancer Initiation, Progression, and Therapy Resistance

Our traditional understanding of phenotypic plasticity in adult somatic cells comprises dedifferentiation and transdifferentiation in the context of tissue regeneration or wound healing. Although dedifferentiation is central to tissue repair and stemness, this process inherently carries the risk of cancer initiation. Consequently, recent research suggests phenotypic plasticity as a new paradigm for understanding cancer initiation, progression, and resistance to therapy. Here, we discuss how cells acquire plasticity and the role of plasticity in initiating cancer, cancer progression, and metastasis and in developing therapy resistance. We also highlight the epithelial-to-mesenchymal transition (EMT) and known molecular mechanisms underlying plasticity and we consider potential therapeutic avenues.

(Re)generating Human Beta Cells: Status, Pitfalls, and Perspectives

Diabetes mellitus results from disturbed glucose homeostasis due to an absolute (type 1) or relative (type 2) deficiency of insulin, a peptide hormone almost exclusively produced by the beta cells of the endocrine pancreas in a tightly regulated manner. Current therapy only delays disease progression through insulin injection and/or oral medications that increase insulin secretion or sensitivity, decrease hepatic glucose production, or promote glucosuria. These drugs have turned diabetes into a chronic disease as they do not solve the underlying beta cell defects or entirely prevent the long-term complications of hyperglycemia. Beta cell replacement through islet transplantation is a more physiological therapeutic alternative but is severely hampered by donor shortage and immune rejection. A curative strategy should combine newer approaches to immunomodulation with beta cell replacement. Success of this approach depends on the development of practical methods for generating beta cells, either in vitro or in situ through beta cell replication or beta cell differentiation. This review provides an overview of human beta cell generation.

The Wnt/β-catenin pathway determines the predisposition and efficiency of liver-to-pancreas reprogramming

Transdifferentiation (TD) is the direct reprogramming of adult cells into cells of alternate fate and function. We have previously shown that liver cells can be transdifferentiated into beta-like, insulin-producing cells through ectopic expression of pancreatic transcription factors (pTFs). However, the efficiency of the process was consistently limited to <15% of the human liver cells treated in culture. The data in the current study suggest that liver-to-pancreas TD is restricted to a specific population of liver cells that is predisposed to undergo reprogramming. We isolated TD-predisposed subpopulation of liver cells from >15 human donors using a lineage tracing system based on the Wnt response element, part of the pericentral-specific promoter of glutamine synthetase. The cells, that were propagated separately, consistently exhibited efficient fate switch and insulin production and secretion in >60% of the cells upon pTF expression. The rest of the cells, which originated from 85% of the culture, resisted TD. Both populations expressed the ectopic pTFs with similar efficiencies, followed by similar repression of hepatic genes. Our data suggest that the TD-predisposed cells originate from a distinct population of liver cells that are enriched for Wnt signaling, which is obligatory for efficient TD. In TD-resistant populations, Wnt induction is insufficient to induce TD. An additional step of chromatin opening enables TD of these cells.

CONCLUSION

Liver-to-pancreas TD occurs in defined predisposed cells. These cells' predisposition is maintained by Wnt signaling that endows the cells with the plasticity needed to alter their transcriptional program and developmental fate when triggered by ectopic pTFs. These results may have clinical implications by drastically increasing the efficacy of TD in future clinical uses. (Hepatology 2018).

Magnetic nanoparticles loaded with functional RNA nanoparticles

RNA is now widely acknowledged not only as a multifunctional biopolymer but also as a dynamic material for constructing nanostructures with various biological functions. Programmable RNA nanoparticles (NPs) allow precise control over their formulation and activation of multiple functionalities, with the potential to self-assemble in biological systems. These attributes make them attractive for drug delivery and therapeutic applications. In the present study, we demonstrate the ability of iron oxide magnetic nanoparticles (MNPs) to deliver different types of RNA NPs functionalized with dicer substrate RNAs inside human cells. Our results show that use of functionalized RNA NPs result in statistically higher transfection efficiency compared to the use of RNA duplexes. Furthermore, we show that the nucleic acids in the MNP/RNA NP complexes are protected from nuclease degradation and that they can achieve knockdown of target protein expression, which is amplified by magnetic stimulus. The current work represents the very first report indicating that iron oxide nanoparticles may efficiently protect and deliver programmable RNA NPs to human cells.

Treatment with specific soluble factors promotes the functional maturation of transcription factor-mediated, pancreatic transdifferentiated cells

Pancreatic lineage-specific transcription factors (TFs) display instructive roles in converting adult cells to endocrine pancreatic cells through a process known as transdifferentiation. However, little is known about potential factors capable of accelerating transdifferentiation following transduction to achieve the functional maturation of transdifferentiated cells. In this study, we demonstrated, using adult liver-derived progenitor cells, that soluble factors utilized in pancreatic differentiation protocols of pluripotent stem cells promote functional maturation of TFs-mediated transdifferentiated cells. Treatment with an N2 supplement in combination with three soluble factors (glucagon-like peptide-1 [GLP-1] receptor agonist, notch inhibitor, and transforming growth factor-β [TGF-β] inhibitor) enhanced liver-to-pancreas transdifferentiation based on the following findings: i) the incidence of c-peptide-positive cells increased by approximately 1.2-fold after the aforementioned treatment; ii) the c-peptide expression level in the treated cells increased by approximately 12-fold as compared with the level in the untreated cells; iii) the treated cells secreted insulin in a glucose-dependent manner, whereas the untreated cells did not; and iv) transplantation of treated-transdifferentiated cells into streptozotocin-induced immunodeficient diabetic mice led to the amelioration of hyperglycemia. These results suggest that treatment with specific soluble factors promotes the functional maturation of transdifferentiated cells. Our findings could facilitate the development of new modalities for cell-replacement therapy for patients with diabetes.

Reprogramming, oscillations and transdifferentiation in epigenetic landscapes

Waddington’s epigenetic landscape provides a phenomenological understanding of the cell differentiation pathways from the pluripotent to mature lineage-committed cell lines. In light of recent successes in the reverse programming process there has been significant interest in quantifying the underlying landscape picture through the mathematics of gene regulatory networks. We investigate the role of time delays arising from multi-step chemical reactions and epigenetic rearrangement on the cell differentiation landscape for a realistic two-gene regulatory network, consisting of self-promoting and mutually inhibiting genes. Our work provides the first theoretical basis of the transdifferentiation process in the presence of delays, where one differentiated cell type can transition to another directly without passing through the undifferentiated state. Additionally, the interplay of time-delayed feedback and a time dependent chemical drive leads to long-lived oscillatory states in appropriate parameter regimes. This work emphasizes the important role played by time-delayed feedback loops in gene regulatory circuits and provides a framework for the characterization of epigenetic landscapes.

Partial pancreatic transdifferentiation of primary human hepatocytes in the livers of a humanised mouse model

BACKGROUND

Gene therapy is one treatment that may ultimately cure type 1 diabetes. We have previously shown that the introduction of furin-cleavable human insulin (INS-FUR) to the livers in several animal models of diabetes resulted in the reversal of diabetes and partial pancreatic transdifferentiation of liver cells. The present study investigated whether streptozotocin-diabetes could be reversed in FRG mice in which chimeric mouse-human livers can readily be established and, in addition, whether pancreatic transdifferentiation occurred in the engrafted human hepatocytes.

METHODS

Engraftment of human hepatocytes was confirmed by measuring human albumin levels. Following delivery of the empty vector or the INS-FUR vector to diabetic FRG mice, mice were monitored for weight and blood glucose levels. Intraperitoneal glucose tolerance tests (IPGTTs) were performed. Expression levels of pancreatic hormones and transcription factors were determined by a reverse transcriptase-polymerase chain reaction (RT-PCR) and immunohistochemistry.

RESULTS

Diabetes was reversed for a period of 60 days (experimental endpoint) after transduction with INS-FUR. IPGTTs of the insulin-transduced animals were not significantly different from nondiabetic animals. Immunofluorescence microscopy revealed the expression of human albumin and insulin in transduced liver samples. Quantitative RT-PCR showed expression of human and mouse endocrine hormones and β-cell transcription factors, indicating partial pancreatic transdifferentiation of mouse and human hepatocytes. Nonfasting human C-peptide levels were significantly higher than mouse levels, suggesting that transdifferentiated human hepatocytes made a significant contribution to the reversal of diabetes.

CONCLUSIONS

These data show that human hepatocytes can be induced to undergo partial pancreatic transdifferentiation in vivo, indicating that the technology holds promise for the treatment of type 1 diabetes.

Generation of Insulin-Expressing Cells in Mouse Small Intestine by Pdx1, MafA, and BETA2/NeuroD

BACKGROUND

To develop surrogate insulin-producing cells for diabetes therapy, adult stem cells have been identified in various tissues and studied for their conversion into β-cells. Pancreatic progenitor cells are derived from the endodermal epithelium and formed in a manner similar to gut progenitor cells. Here, we generated insulin-producing cells from the intestinal epithelial cells that induced many of the specific pancreatic transcription factors using adenoviral vectors carrying three genes: PMB (pancreatic and duodenal homeobox 1 [Pdx1], V-maf musculoaponeurotic fibrosarcoma oncogene homolog A [MafA], and BETA2/NeuroD).

METHODS

By direct injection into the intestine through the cranial mesenteric artery, adenoviruses (Ad) were successfully delivered to the entire intestine. After virus injection, we could confirm that the small intestine of the mouse was appropriately infected with the Ad-Pdx1 and triple Ad-PMB.

RESULTS

Four weeks after the injection, insulin mRNA was expressed in the small intestine, and the insulin gene expression was induced in Ad-Pdx1 and Ad-PMB compared to control Ad-green fluorescent protein. In addition, the conversion of intestinal cells into insulin-expressing cells was detected in parts of the crypts and villi located in the small intestine.

CONCLUSION

These data indicated that PMB facilitate the differentiation of mouse intestinal cells into insulin-expressing cells. In conclusion, the small intestine is an accessible and abundant source of surrogate insulin-producing cells.

Regenerative medicine and cell-based approaches to restore pancreatic function

The pancreas is a complex organ with exocrine and endocrine components. Many pathologies impair exocrine function, including chronic pancreatitis, cystic fibrosis and pancreatic ductal adenocarcinoma. Conversely, when the endocrine pancreas fails to secrete sufficient insulin, patients develop diabetes mellitus. Pathology in either the endocrine or exocrine pancreas results in devastating economic and personal consequences. The current standard therapy for treating patients with type 1 diabetes mellitus is daily exogenous insulin injections, but cell sources of insulin provide superior glycaemic regulation and research is now focused on the goal of regenerating or replacing β cells. Stem-cell-based models might be useful to study exocrine pancreatic disorders, and mesenchymal stem cells or secreted factors might delay disease progression. Although the standards that bioengineered cells must meet before being considered as a viable therapy are not yet established, any potential therapy must be acceptably safe and functionally superior to current therapies. Here, we describe progress and challenges in cell-based methods to restore pancreatic function, with a focus on optimizing the site for cell delivery and decreasing requirements for immunosuppression through encapsulation. We also discuss the tools and strategies being used to generate exocrine pancreas and insulin-producing β-cell surrogates in situ and highlight obstacles to clinical application.

Effect of small molecules on cell reprogramming

The essential idea of regenerative medicine is to fix or replace tissues or organs with alive and patient-specific implants. Pluripotent stem cells are able to indefinitely self-renew and differentiate into all cell types of the body which makes them a potent substantial player in regenerative medicine. The easily accessible source of induced pluripotent stem cells may allow obtaining and cultivating tissues in vitro. Reprogramming refers to regression of mature cells to its initial pluripotent state. One of the approaches affecting pluripotency is the usage of low molecular mass compounds that can modulate enzymes and receptors leading to the formation of pluripotent stem cells (iPSCs). It would be great to assess the general character of such compounds and reveal their new derivatives or modifications to increase the cell reprogramming efficiency. Many improvements in the methods of pluripotency induction have been made by various groups in order to limit the immunogenicity and tumorigenesis, increase the efficiency and accelerate the kinetics. Understanding the epigenetic changes during the cellular reprogramming process will extend the comprehension of stem cell biology and lead to potential therapeutic approaches. There are compounds which have been already proven to be or for now only putative inducers of the pluripotent state that may substitute for the classic reprogramming factors (Oct3/4, Sox2, Klf4, c-Myc) in order to improve the time and efficiency of pluripotency induction. The effect of small molecules on gene expression is dosage-dependent and their application concentration needs to be strictly determined. In this review we analysed the role of small molecules in modulations leading to pluripotency induction, thereby contributing to our understanding of stem cell biology and uncovering the major mechanisms involved in that process.

Lineage conversion of mouse fibroblasts to pancreatic α-cells

α-cells, which synthesize glucagon, also support β-cell survival and have the capacity to transdifferentiate into β-cells. However, the role of α-cells in pathological conditions and their putative clinical applications remain elusive due in large part to the lack of mature α-cells. Here, we present a new technique to generate functional α-like cells. α-like cells (iAlpha cells) were generated from mouse fibroblasts by transduction of transcription factors, including Hhex, Foxa3, Gata4, Pdx1 and Pax4, which induce α-cell-specific gene expression and glucagon secretion in response to KCl and Arg stimulation. The cell functions in vivo and in vitro were evaluated. Lineage-specific and functional-related gene expression was tested by realtime PCR, insulin tolerance test (ITT), glucose tolerance test (GTT), Ki67 and glucagon immunohistochemistry analysis were done in iAlpha cells transplanted nude mice. iAlpha cells possess α-cell function in vitro and alter blood glucose levels in vivo. Transplantation of iAlpha cells into nude mice resulted in insulin resistance and increased β-cell proliferation. Taken together, we present a novel strategy to generate functional α-like cells for the purposes of disease modeling and regenerative medicine.

From Human Mesenchymal Stem Cells to Insulin-Producing Cells: Comparison between Bone Marrow- and Adipose Tissue-Derived Cells

The aim of this study is to compare human bone marrow-derived mesenchymal stem cells (BM-MSCs) and adipose tissue-derived mesenchymal stem cells (AT-MSCs), for their differentiation potentials to form insulin-producing cells. BM-MSCs were obtained during elective orthotopic surgery and AT-MSCs from fatty aspirates during elective cosmetics procedures. Following their expansion, cells were characterized by phenotyping, trilineage differentiation ability, and basal gene expression of pluripotency genes and for their metabolic characteristics. Cells were differentiated according to a Trichostatin-A based protocol. The differentiated cells were evaluated by immunocytochemistry staining for insulin and c-peptide. In addition the expression of relevant pancreatic endocrine genes was determined. The release of insulin and c-peptide in response to a glucose challenge was also quantitated. There were some differences in basal gene expression and metabolic characteristics. After differentiation the proportion of the resulting insulin-producing cells (IPCs), was comparable among both cell sources. Again, there were no differences neither in the levels of gene expression nor in the amounts of insulin and c-peptide release as a function of glucose challenge. The properties, availability, and abundance of AT-MSCs render them well-suited for applications in regenerative medicine. Conclusion. BM-MSCs and AT-MSCs are comparable regarding their differential potential to form IPCs. The availability and properties of AT-MSCs render them well-suited for applications in regenerative medicine.