Establishment of a rapid and footprint-free protocol for differentiation of human embryonic stem cells into pancreatic endocrine cells with synthetic mRNAs encoding transcription factors

Oxygenated Scaffolds for Pancreatic Endocrine Differentiation from Induced Pluripotent Stem Cells

A 3D microenvironment is known to endorse pancreatic islet development from human induced pluripotent stem cells (iPSCs). However, oxygen supply becomes a limiting factor in a scaffold culture. In this study, oxygen-releasing biomaterials are fabricated and an oxygenated scaffold culture platform is developed to offer a better oxygen supply during 3D iPSC pancreatic differentiation. It is found that the oxygenation does not alter the scaffold's mechanical properties. The in situ oxygenation improves oxygen tension within the scaffolds. The unique 3D differentiation system enables the generation of islet organoids with enhanced expression of islet signature genes and proteins. Additionally, it is discovered that the oxygenation at the early stage of differentiation has more profound impacts on islet development from iPSCs. More C-peptide+ /MAFA+ β and glucagon+ /MAFB+ α cells formed in the iPSC-derived islet organoids generated under oxygenated conditions, suggesting enhanced maturation of the organoids. Furthermore, the oxygenated 3D cultures improve islet organoids' sensitivity to glucose for insulin secretion. It is herein demonstrated that the oxygenated scaffold culture empowers iPSC islet differentiation to generate clinically relevant tissues for diabetes research and treatment.

Therapeutic approaches for Type 1 Diabetes: Promising cell-based approaches to achieve ultimate success

Type 1 Diabetes mellitus (T1DM) is a chronic metabolic disorder characterized by pancreatic β-cells destruction. Despite substantial advances in T1DM treatment, lifelong exogenous insulin administration is the mainstay of treatments, and constant control of glucose levels is still a challenge. Endogenous insulin production by replacing insulin-producing cells is an alternative, but the lack of suitable donors is accounted as one of the main obstacles to its widespread application. The research and trials overview demonstrates that endogenous production of insulin has started to go beyond the deceased-derived to stem cells-derived insulin-producing cells. Several protocols have been developed over the past couple of years for generating insulin-producing cells (IPCs) from various stem cell types and reprogramming fully differentiated cells. A straightforward and quick method for achieving this goal is to investigate and apply the β-cell specific transcription factors as a direct strategy for IPCs generation. In this review, we emphasize the significance of transcription factors in IPCs development from different non-beta cell sources, and pertinent research underlies the marked progress in the methods for generating insulin-producing cells and application for Type 1 Diabetes treatment.

Exosome-derived miR-127-5p promotes embryonic-like stem cells differentiation into pacemaker cell through NKx2.5 down-regulation

Available evidence suggests the involvement of microRNAs (miRNAs) in the pathological process of several diseases. Nonetheless, molecular mechanism underlying biological effects of miRNAs such as pacemaker exosome-derived miR-127-5p in embryonic-like stem cells (ESCs) differentiation into pacemaker cell is yet to be clarified. Through real time quantitative polymerase chain reaction (qPCR) or western blotting (WB) techniques, levels of miRNAs, miR-127-5p, and NKx2.5 expressions were quantitatively measured. Cellular differentiation (CD) was probed with flow cytometric (FC) and WB techniques. Prediction of miR-127-5p association with NKx2.5 was studied through bioinformatics tools before verification with luciferase assays. Promotion of ESCs differentiation to pacemaker through miR-127-5p was measured with qPCR and WB techniques. Through the same assaying methods, up-regulation of pace-making genes (Shox2, HCN4, Cx45, Tbx3 and Tbx18) expression was observed in Nkx2.5 knockdown group. However, Nkx2.5 expression was down-regulated during differentiation of pacemaker-like cells into ESCs. Furthermore, techniques (such as qPCR, WB, immunofluorescent staining and FC) were employed to demonstrate that overexpressed miR-127-5p could suppress NKx2.5 expression. Through NKx2.5 targeting, ESCs could be differentiated into pacemaker-like cells with miR-127-5p possibly serving as a crucial positive regulator. On the account of our findings, further researches are needed to unearth the possible underlying mechanism and role of exosome-derived miRNAs in cell signaling.

Making human pancreatic islet organoids: Progresses on the cell origins, biomaterials and three-dimensional technologies

Diabetes is one of the most socially challenging health concerns. Even though islet transplantation has shown promise for insulin-dependent diabetes, there is still no effective method for curing diabetes due to the severe shortage of transplantable donors. In recent years, organoid technology has attracted lots of attention as organoid can mirror the human organ in vivo to the maximum extent in vitro, thus bridging the gap between cellular- and tissue/organ-level biological models. Concurrently, human pancreatic islet organoids are expected to be a considerable source of islet transplantation. To construct human islet-like organoids, the seeding cells, biomaterials and three-dimensional structure are three key elements. Herein, this review summarizes current progresses about the cell origins, biomaterials and advanced technology being applied to make human islet organoids, and discusses the advantages, shortcomings, and future challenges of them as well. We hope this review can offer a cross-disciplinary perspective to build human islet organoids and provide insights for tissue engineering and regenerative medicine.

A simple method of hiPSCs differentiation into insulin-producing cells is improved with vitamin C and RepSox

Human induced pluripotent stem cells (hiPSCs) are considered a promising source of pancreatic β-cells for the treatment of diabetes. However, this approach is limited by issues such as low efficiency and high cost. Here, we have developed a new protocol to induce insulin-producing cells. To reduce costs, we decreased the number of reagents and replaced protein reagents with chemical compounds. In this method, we increased induction efficiency with ascorbic acid (vitamin C) and an ALK5 inhibitor, RepSox. In 2D culture, the majority of cells were immature β-cells with low glucose-stimulated insulin secretion. Transferring to 3D culture immediately after endocrine progenitor cell differentiation, however, improved glucose-stimulated insulin secretion. This simplified method will contribute to realizing transplantation therapy of β-cells using iPSCs.

Efficacy of Mesenchymal Stem Cell and Vitamin D in the Treatment of Diabetes Mellitus Induced in a Rat Model: Pancreatic Tissues

Treatment with mesenchyme stem cells (MSCs) plays a significant role in the therapies of many diseases such as diabetics. Vitamin D plays a significant role in the development of insulin and can increase the insulin action sensitivity of peripheral tissues. Moreover, there is limited research concerning the mechanism of the therapeutic action of MSCs with the combination of vitamin D (vit. D). Therefore, we evaluated the effect of MSC intervention in a diabetic animal model. Diabetes was induced by streptozotocin (STZ) injection at a dose of 50 mg/kg in adult male rats The diabetic rats were injected with MSCs derived from bone marrow (2 × 106 per rat), either alone or in combination with vit. D through the tail vein for four weeks. Serum insulin, glucose, C-peptide, glycosylated hemoglobin, and lipid profile levels were determined. Pancreatic oxidative stress, histology, and electron microscopy were evaluated, and the gene expression of cytokines was assessed by real-time polymerase chain reaction PCR. MSC treatment suppressed pancreatic inflammatory cytokine secretion and oxidative stress in diabetic rats, resulting in improved pancreatic histology and cellular structure, and the complication of hyperglycemia was observed. Engrafted MSCs were found inside degraded pancreatic regions and regulated inflammatory cytokines. Our results demonstrated that treatment with MSCs and vit. D in combination prevented pancreatic injury via antioxidant and immune regulation in diabetic rats, contributing to the prevention of pancreatic dysfunction, improvement of lipid metabolism, and regulation of cytokine gene expression compared with each one separately. All these mechanisms also improved the histological structure of the pancreas based on transmission electron microscopy. The combination of MSCs and vit. D appears to have contributed to a greater improvement in the diabetic pancreatic complication of rats than was observed by each one separately. Therefore, this association can be used as antidiabetic therapy.

Signaling Molecules Regulating Pancreatic Endocrine Development from Pluripotent Stem Cell Differentiation

Diabetes is one of the leading causes of death globally. Currently, the donor pancreas is the only source of human islets, placing extreme constraints on supply. Hence, it is imperative to develop renewable islets for diabetes research and treatment. To date, extensive efforts have been made to derive insulin-secreting cells from human pluripotent stem cells with substantial success. However, the in vitro generation of functional islet organoids remains a challenge due in part to our poor understanding of the signaling molecules indispensable for controlling differentiation pathways towards the self-assembly of functional islets from stem cells. Since this process relies on a variety of signaling molecules to guide the differentiation pathways, as well as the culture microenvironments that mimic in vivo physiological conditions, this review highlights extracellular matrix proteins, growth factors, signaling molecules, and microenvironments facilitating the generation of biologically functional pancreatic endocrine cells from human pluripotent stem cells. Signaling pathways involved in stepwise differentiation that guide the progression of stem cells into the endocrine lineage are also discussed. The development of protocols enabling the generation of islet organoids with hormone release capacities equivalent to native adult islets for clinical applications, disease modeling, and diabetes research are anticipated.

An Efficient and Footprint-Free Protocol for the Transdifferentiation of Hepatocytes Into Insulin-Producing Cells With IVT mRNAs

Background

Direct transdifferentiation of adult somatic cells into insulin-producing cells (IPCs) is a promising approach for cell-based therapies for type 1 diabetes mellitus. Liver cells are an ideal source for generating IPCs because they have regenerative ability and a developmental process similar to that of the pancreas. Pancreas versus liver fate is regulated by TALE homeoprotein (TGIF2) during development. Here, we wanted to investigate whether TGIF2 could enhance the efficiency of transdifferentiation of hepatocytes into IPCs induced by three pancreatic transcription factors (pTFs), i.e., Pdx1, NeuroD, and Mafa, which are crucial for pancreatic development in the embryo.

Methods

The in vitro transcribed (IVT) mRNAs of TGIF2 and the three pTFs were synthesized in vitro and sequentially supplemented in hepatocytes. On day 6, the expression of transcription factors was assessed by quantitative real-time polymerase chain reaction (qRT-PCR), and insulin expression was detected by immunofluorescence. Glucose-stimulated insulin secretion was assessed by enzyme-linked immunosorbent assay (ELISA). The key genes controlling cell polarity and the Wnt/PCP signaling pathway were assayed by qRT-PCR, and the level of JNK protein phosphorylation, which regulates the Wnt/PCP signaling pathway, was detected by western blotting.

Results

IVT mRNAs could be efficiently transfected into hepatocytes. Quantitative real-time polymerase chain reaction results revealed that compared with ectopic expression of the three pTFs alone, ectopic expression of the three pTFs plus TGIF2 could strongly reduce hepatic gene expression and subsequently improve the induction of a set of pancreatic genes. Immunofluorescence analysis showed that TGIF2 expression could double the transdifferentiation yield; 30% of the cells were insulin positive if induced by TGIF2 plus the 3 pTFs, while only 15% of the cells were insulin positive if induced by the three pTFs alone. ELISA analysis confirmed that glucose-stimulated insulin secretion was less efficient after transfection with the three pTFs alone. The differentiated cells derived from the addition of TGIF2 mRNA could form islet-like clusters. By contrast, the cells differentiated with the three pTFs did not form clusters under the same conditions. Tgif2 induced transdifferentiation more efficiently by remodeling the expression of genes in the Wnt/PCP pathway. Overexpression of TGIF2 in hepatocytes could activate the expression of key genes controlling cell polarity and genes in the Wnt/PCP signaling pathway, increasing the level of JNK protein phosphorylation.

Conclusions

Our study established a novel footprint-free protocol for efficient transdifferentiation of hepatocytes into IPCs using IVT mRNAs of TGIF2 and 3 pTFs, which paved the way toward a clinical application.

Directed Differentiation of Pluripotent Stem Cells by Transcription Factors

Embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) have been used as promising tools for regenerative medicine, disease modeling, and drug screening. Traditional and common strategies for pluripotent stem cell (PSC) differentiation toward disease-relevant cell types depend on sequential treatment of signaling molecules identified based on knowledge of developmental biology. However, these strategies suffer from low purity, inefficiency, and time-consuming culture conditions. A growing body of recent research has shown efficient cell fate reprogramming by forced expression of single or multiple transcription factors. Here, we review transcription factor-directed differentiation methods of PSCs toward neural, muscle, liver, and pancreatic endocrine cells. Potential applications and limitations are also discussed in order to establish future directions of this technique for therapeutic purposes.

Stem cells as a potential therapy for diabetes mellitus: a call-to-action in Latin America

Latin America is a fast-growing region that currently faces unique challenges in the treatment of all forms of diabetes mellitus. The burden of this disease will be even greater in the coming years due, in part, to the large proportion of young adults living in urban areas and engaging in unhealthy lifestyles. Unfortunately, the national health systems in Latin-American countries are unprepared and urgently need to reorganize their health care services to achieve diabetic therapeutic goals. Stem cell research is attracting increasing attention as a promising and fast-growing field in Latin America. As future healthcare systems will include the development of regenerative medicine through stem cell research, Latin America is urged to issue a call-to-action on stem cell research. Increased efforts are required in studies focused on stem cells for the treatment of diabetes. In this review, we aim to inform physicians, researchers, patients and funding sources about the advances in stem cell research for possible future applications in diabetes mellitus. Emerging studies are demonstrating the potential of stem cells for β cell differentiation and pancreatic regeneration. The major economic burden implicated in patients with diabetes complications suggests that stem cell research may relieve diabetic complications. Closer attention should be paid to stem cell research in the future as an alternative treatment for diabetes mellitus.