Pdx1 and controlled culture conditions induced differentiation of human amniotic fluid-derived stem cells to insulin-producing clusters

The efficiency of stem cell differentiation into functional beta cells for treating insulin-requiring diabetes: Recent advances and current challenges

In recent years, the potential of stem cells (SCs) to differentiate into various types of cells, including β-cells, has led to a significant boost in development. The efficiency of this differentiation process and the functionality of the cells post-transplantation are crucial factors for the success of stem cell therapy in diabetes. Herein, this article reviews the current advances and challenges faced by stem cell differentiation into functional β-cells for diabetes treatment. In vitro, researchers have sought to enhance the differentiation efficiency of functional β-cells by mimicking the normal pancreatic development process, using gene manipulation, pharmacological and culture conditions stimulation, three-dimensional (3D) and organoid culture, or sorting for functional β-cells based on mature islet cell markers. Furthermore, in vivo studies have also looked at suitable transplantation sites, the enhancement of the transplantation microenvironment, immune modulation, and vascular function reconstruction to improve the survival rate of functional β-cells, thereby enhancing the treatment of diabetes. Despite these advancements, developing stem cells to produce functional β-cells for efficacious diabetes treatment is a continuous research endeavor requiring significant multidisciplinary collaboration, for the stem-cell-derived beta cells to evolve into an effective cellular therapy.

Encapsulation of stem-cell derived β-cells: A promising approach for the treatment for type 1 diabetes mellitus

Type 1 diabetes mellitus is an auto-immune disease causing the T-cell mediated destruction of insulin-producing β-cells, resulting in chronic hyperglycemia. Current treatments such as insulin replacement therapy or the transplantation of pancreas or pancreatic islets present major disadvantages such as the constant need of drugs, as well as a shortage of donor organs. In this review, we discuss a sustainable solution to overcome these limitations combining the use of β-cells, derived from stem cells, and their encapsulation within a protective matrix. This article provides an exhaustive overview of currently investigated stem cell sources including embryonic, mesenchymal as well as induced pluripotent stem cells in combination with various up to date encapsulation methods allowing the formation of immuno-protective devices. In order to identify current limitations of this interdisciplinary therapeutic approach and to find sustainable solutions, it is essential to consider key aspects from all involved domains. This includes biological parameters such as the stem cell origin but also the different aspects of the encapsulation process, the used materials and their physico-chemical properties such as elasticity, porosity and permeability cut-off as well as the best implantation sites allowing efficient and self-autonomous control of glycemia by the transplanted encapsulated cells.

PDX1 is the cornerstone of pancreatic β-cell functions and identity

Diabetes has been a worldwide healthcare problem for many years. Current methods of treating diabetes are still largely directed at symptoms, aiming to control the manifestations of the pathology. This creates an overall need to find alternative measures that can impact on the causes of the disease, reverse diabetes, or make it more manageable. Understanding the role of key players in the pathogenesis of diabetes and the related β-cell functions is of great importance in combating diabetes. PDX1 is a master regulator in pancreas organogenesis, the maturation and identity preservation of β-cells, and of their role in normal insulin function. Mutations in the PDX1 gene are correlated with many pancreatic dysfunctions, including pancreatic agenesis (homozygous mutation) and MODY4 (heterozygous mutation), while in other types of diabetes, PDX1 expression is reduced. Therefore, alternative approaches to treat diabetes largely depend on knowledge of PDX1 regulation, its interaction with other transcription factors, and its role in obtaining β-cells through differentiation and transdifferentiation protocols. In this article, we review the basic functions of PDX1 and its regulation by genetic and epigenetic factors. Lastly, we summarize different variations of the differentiation protocols used to obtain β-cells from alternative cell sources, using PDX1 alone or in combination with various transcription factors and modified culture conditions. This review shows the unique position of PDX1 as a potential target in the genetic and cellular treatment of diabetes.

Cell microencapsulation technologies for sustained drug delivery: Latest advances in efficacy and biosafety

The development of cell microencapsulation systems began several decades ago. However, today few systems have been tested in clinical trials. For this reason, in the last years, researchers have directed efforts towards trying to solve some of the key aspects that still limit efficacy and biosafety, the two major criteria that must be satisfied to reach the clinical practice. Regarding the efficacy, which is closely related to biocompatibility, substantial improvements have been made, such as the purification or chemical modification of the alginates that normally form the microspheres. Each of the components that make up the microcapsules has been carefully selected to avoid toxicities that can damage the encapsulated cells or generate an immune response leading to pericapsular fibrosis. As for the biosafety, researchers have developed biological circuits capable of actively responding to the needs of the patients to precisely and accurately release the demanded drug dose. Furthermore, the structure of the devices has been subject of study to adequately protect the encapsulated cells and prevent their spread in the body. The objective of this review is to describe the latest advances made by scientist to improve the efficacy and biosafety of cell microencapsulation systems for sustained drug delivery, also highlighting those points that still need to be optimized.

Generation of iPSC-derived insulin-producing cells from patients with type 1 and type 2 diabetes compared with healthy control

For alternative sources of β cells, patient-specific induced pluripotent stem cells (iPSCs) could be promising, as cells derived from the "self" allow autologous transplantation. However, only a few studies have investigated insulin-producing cells (IPCs) using iPSCs of patients with type 1 diabetes (T1D). In this study, we generated IPCs using iPSCs derived from patients with T1D and type 2 diabetes (T2D) and compared them with IPCs from a non-diabetic (ND) individual. To facilitate differentiation of human iPSCs into IPCs, we induced PDX-1 gene expression using Ad-PDX-1/VP16. IPCs derived from T1D- and T2D-specific iPSCs expressed islet-specific markers such as Pdx-1, MafA, Beta2/NeuroD, and insulin, similar to IPCs derived from ND-specific iPSCs. In addition, IPCs derived from T1D- and T2D-specific iPSCs showed comparable glucose-stimulated insulin secretion as IPCs derived from ND-specific iPSCs. These results suggest the potential for autologous transplantation using patient-specific iPSCs in patients with T1D and T2D. This study was clinically significant because the majority of people with diabetes have T2D and insulin secretion declines over time in T2D. To the best of our knowledge, this is the first study to generate and simultaneously compare IPCs from ND-, T1D-, and T2D-specific iPSCs.

hPL promotes osteogenic differentiation of stem cells in 3D scaffolds

Human platelet lysate (hPL) has been considered as the preferred supplement for the xeno-free stem cell culture for many years. However, the biological effect of hPL on the proliferation and differentiation of dental stem cells combined with the use of medical grade synthetic biomaterial is still under investigation. Thus, the optimal scaffold composition, cell type and specific growth conditions, yet need to be formulated. In this study, we aimed to investigate the regenerative potential of dental stem cells seeded on synthetic scaffolds and maintained in osteogenic media supplemented with either hPL or xeno-derived fetal bovine serum (FBS). Two types of dental stem cells were isolated from human impacted third molars and intact teeth; stem cells of apical papilla (SCAP) and periodontal ligament stem cells (PDLSCs). Cells were expanded in cell culture media supplemented with either hPL or FBS. Consequently, proliferative capacity, immunophenotypic characteristics and multilineage differentiation potential of the derived cells were evaluated on monolayer culture (2D) and on synthetic scaffolds fabricated from poly ’lactic-co-glycolic’ acid (PLGA) (3D). The functionality of the induced cells was examined by measuring the concentration of osteogenic markers ALP, OCN and OPN at different time points. Our results indicate that the isolated dental stem cells showed similar mesenchymal characteristics when cultured on hPL or FBS-containing culture media. Scanning electron microscopy (SEM) and H&E staining revealed the proper adherence of the derived cells on the 3D scaffold cultures. Moreover, the increase in the concentration of osteogenic markers proved that hPL was able to produce functional osteoblasts in both culture conditions (2D and 3D), in a way similar to FBS culture. These results reveal that hPL provides a suitable substitute to the animal-derived serum, for the growth and functionality of both SCAP and PDLSCs. Thus the use of hPL, in combination with PLGA scaffolds, can be useful in future clinical trials for dental regeneration.

Current status of stem cell therapy, scaffolds for the treatment of diabetes mellitus

Diabetes mellitus (DM) remains the 7th leading cause of death in the world. Daily insulin injection is one component of a treatment plan for people with Diabetes mellitus type 1 (T1DM) that restores normal or near-normal blood sugar levels. However, Insulin treatment depends upon a variety of individual factors and leads to poor and drastic glycemic control. The need for an effective cell replacement strategy will be the aim of future clinical trials. Therefore, the aim of this systematic review is to outline the latest advances in scaffolding and stem cell therapy as a non-pharmacologic treatment for T1DM. It also emphasizes on some pancreas differentiation protocols and the clinical trials associated with stem cell therapy regarding T1DM in vitro and in vivo.

Combinations of Activin A or Nicotinamide with the Pancreatic Transcription Factor PDX1 Support Differentiation of Human Amnion Epithelial Cells Toward a Pancreatic Lineage

The differentiation of multipotent stem cells toward a pancreatic lineage provides us with an alternative cell-based therapeutic approach to type 1 diabetes and enables us to study pancreas development. The current study aims to study the effect of growth factors such as activin A or nicotinamide, alone and in combinations with the transcription factor, PDX1 (pancreatic and duodenal homeobox-1), on human amnion epithelial cells (hAECs) toward a pancreatic lineage. Ectopic expression of Pdx1 followed by treatment of hAECs with nicotinamide for 4 days resulted in strong induction of pancreatic endoderm and pancreatic progenitor genes, including NKX6.1 and NEUROD1. Pancreatic lineage cells expressing PDX1, SOX17, and RFX6 are derived from Pdx1-transduced hAECs treated with activin A or nicotinamide, but not cells treated with activin A or nicotinamide alone. Our study provides a novel culture protocol for generating pancreas-committed cells from hAECs and reveals an interplay between Pdx1 and activin A/nicotinamide signaling in early pancreatic fate determination.

Encapsulated Islet Transplantation: Where Do We Stand?

Transplantation of pancreatic islets encapsulated within immuno-protective microcapsules is a strategy that has the potential to overcome graft rejection without the need for toxic immunosuppressive medication. However, despite promising preclinical studies, clinical trials using encapsulated islets have lacked long-term efficacy, and although generally considered clinically safe, have not been encouraging overall. One of the major factors limiting the long-term function of encapsulated islets is the host's immunological reaction to the transplanted graft which is often manifested as pericapsular fibrotic overgrowth (PFO). PFO forms a barrier on the capsule surface that prevents the ingress of oxygen and nutrients leading to islet cell starvation, hypoxia and death. The mechanism of PFO formation is still not elucidated fully and studies using a pig model have tried to understand the host immune response to empty alginate microcapsules. In this review, the varied strategies to overcome or reduce PFO are discussed, including alginate purification, altering microcapsule geometry, modifying alginate chemical composition, co-encapsulation with immunomodulatory cells, administration of pharmacological agents, and alternative transplantation sites. Nanoencapsulation technologies, such as conformal and layer-by-layer coating technologies, as well as nanofiber, thin-film nanoporous devices, and silicone based NanoGland devices are also addressed. Finally, this review outlines recent progress in imaging technologies to track encapsulated cells, as well as promising perspectives concerning the production of insulin-producing cells from stem cells for encapsulation.

Highly potent stem cells from full-term amniotic fluid: A realistic perspective

Amniotic fluid (AF) is now known to harbor highly potent stem cells, making it an excellent source for cell therapy. However, most of the stem cells isolated are from AF of mid-term pregnancies in which the collection procedure involves an invasive technique termed amniocentesis. This has limited the access in getting the fluid as the technique imposes certain level of risks to the mother as well as to the fetus. Alternatively, getting AF from full-term pregnancies or during deliveries would be a better resolution. Unfortunately, very few studies have isolated stem cells from AF at this stage of gestation, the fluid that is merely discarded. The question remains whether full-term AF harbors stem cells of similar potency as of the stem cells of mid-term AF. Here, we aim to review the prospect of having this type of stem cells by first looking at the origin and contents of AF particularly during different gestation period. We will then discuss the possibility that the AF, at full term, contains a population of highly potent stem cells. These stem cells are distinct from, and probably more potent than the AF mesenchymal stem cells (AF-MSCs) isolated from full-term AF. By comparing the studies on stem cells isolated from mid-term versus full-term AF from various species, we intend to address the prospect of having highly potent amniotic fluid stem cells from AF of full-term pregnancies in human and animals.

Enhanced differentiation of human amniotic fluid-derived stem cells into insulin-producing cells in vitro

AIMS/INTRODUCTION

To investigate the ability of human amniotic fluid stem cells (hAFSCs) to differentiate into insulin-producing cells.

MATERIALS AND METHODS

hAFSCs were induced to differentiate into pancreatic cells by a multistep protocol. The expressions of pancreas-related genes and proteins, including pancreatic and duodenal homeobox-1, insulin, and glucose transporter 2, were detected by polymerase chain reaction and immunofluorescence. Insulin secreted from differentiated cells was tested by enzyme-linked immunosorbent assay.

RESULTS

hAFSCs were successfully isolated from amniotic fluid that expressed the pluripotent markers of embryonic stem cells, such as Oct3/4, and mesenchymal stem cells, such as integrin β-1 and ecto-5'-nucleotidase. Here, we first obtained the hAFSCs that expressed pluripotent marker stage-specific embryonic antigen 1. Real-time polymerase chain reaction analysis showed that pancreatic and duodenal homeobox-1, paired box gene 4 and paired box gene 6 were expressed in the early phase of induction, and then stably expressed in the differentiated cells. The pancreas-related genes, such as insulin, glucokinase, glucose transporter 2 and Nkx6.1, were expressed in the differentiated cells. Immunofluorescence showed that these differentiated cells co-expressed insulin, C-peptide, and pancreatic and duodenal homeobox-1. Insulin was released in response to glucose stimulation in a manner similar to that of adult human islets.

CONCLUSIONS

The present study showed that hAFSCs, under selective culture conditions, could differentiate into islet-like insulin-producing cells, which might be used as a potential source for transplantation in patients with type 1 diabetes mellitus.

The combined effect of PDX1, epidermal growth factor and poly-L-ornithine on human amnion epithelial cells' differentiation

Background

It has been suggested that the ectopic expression of PDX1, a dominant pancreatic transcription factor, plays a critical role in the developmental programming of the pancreas even from cells of unrelated tissues such as keratinocytes and amniotic fluid stem cells. In this study we have chosen to drive pancreatic development in human amnion epithelial cells by inducing endogenous PDX1 expression. Further, we have investigated the role of Epidermal Growth Factor (EGF) and Poly-L-Ornithine (PLO) on this differentiation process.

Results

Human amnion epithelial cells expressed high levels of endogenous PDX1 upon transduction with an adenoviral vector expressing murine Pdx1. Other markers of various stages of pancreatic differentiation such as NKX6.1, SOX17, RFX6, FOXA2, CFTR, NEUROD1, PAX4 and PPY were also expressed upon Pdx1 transduction.

Although initial expression of pancreatic progenitor markers was higher in culture conditions lacking EGF, for a sustained and increased expression EGF was required. Culture on PLO further increased the positive impact of EGF.

Conclusion

Pancreatic marker expression subsequent to mPdx1 transduction suggests that this approach may facilitate the in vitro differentiation of hAECs into cells of the endocrine pancreas. This result may have important implications in diabetes therapy.

Electronic supplementary material

The online version of this article (doi:10.1186/s12861-016-0108-y) contains supplementary material, which is available to authorized users.

Three-dimensional differentiation of bone marrow-derived mesenchymal stem cells into insulin-producing cells

Fibrin glue (FG) is used in a variety of clinical applications and in the laboratory for localized and sustained release of factors potentially important for tissue engineering. The aim of this study was to evaluate FG scaffold effect on differentiation of insulin-producing cells (IPCs) from bone marrow-derived mesenchymal stem cells (BM-MSCs). In this experimental study BM-MSCs were cultured and the cells characterized by analysis of cell surface markers using flow cytometry. BM-MSCs were seeded in FG scaffold (3D culture) and then treated with induction media. After induction, the presence of IPCs was demonstrated using gene expression profiles for pancreatic cell differentiation markers (PDX-1, GLUT-2 and insulin) and insulin detection in cytoplasm. Release of insulin by these cells was confirmed by radioimmunoassay. Expression of the islet-associated genes PDX-1, GLUT-2 and Insulin genes in 3D cultured cells was markedly higher than the 2D cultured cells exposure differentiation media. Compared to 2D culture of BM-MSCs-derived IPCs, the insulin release from 3D BM-MSCs-derived IPCs showed a nearly 3 fold (p<0.05) increase when exposed to a high glucose (25 mM) medium. Percentage of insulin positive cells in 3D experimental group showed an approximately 3.5-fold increase in compared to 2D experimental culture cells. The results of this study demonstrated that FG scaffold can enhance the differentiation of IPCs from rats BM-MSCs.

Amniotic fluid stem cells prevent β-cell injury

BACKGROUND AIMS

The contribution of amniotic fluid stem cells (AFSC) to tissue protection and regeneration in models of acute and chronic kidney injuries and lung failure has been shown in recent years. In the present study, we used a chemically induced mouse model of type 1 diabetes to determine whether AFSC could play a role in modulating β-cell injury and restoring β-cell function.

METHODS

Streptozotocin-induced diabetic mice were given intracardial injection of AFSC; morphological and physiological parameters and gene expression profile for the insulin pathway were evaluated after cell transplantation.

RESULTS

AFSC injection resulted in protection from β-cell damage and increased β-cell regeneration in a subset of mice as indicated by glucose and insulin levels, increased islet mass and preservation of islet structure. Moreover, β-cell preservation/regeneration correlated with activation of the insulin receptor/Pi3K/Akt signaling pathway and vascular endothelial growth factor-A expression involved in maintaining β-cell mass and function.

CONCLUSIONS

Our results suggest a therapeutic role for AFSC in preserving and promoting endogenous β-cell functionality and proliferation. The protective role of AFSC is evident when stem cell transplantation is performed before severe hyperglycemia occurs, which suggests the importance of early intervention. The present study demonstrates the possible benefits of the application of a non-genetically engineered stem cell population derived from amniotic fluid for the treatment of type 1 diabetes mellitus and gives new insight on the mechanism by which the beneficial effect is achieved.

Transplantation of islet-like cell clusters derived from human dental pulp stem cells restores normoglycemia in diabetic mice

BACKGROUND AIMS

The success of islet transplantation for diabetes depends on the availability of an adequate number of allogeneic or autologous islets. Postnatal stem cells are now considered for the generation of physiologically competent, insulin-producing cells. Our group showed earlier that it is possible to generate functional islets from human dental pulp stem cells by using a serum-free cocktail in a three-step protocol.

METHODS

We compared the yield of generated islet-like cell clusters (ICCs) from stem cells from pulps of human exfoliated deciduous teeth (SHED) and dental pulp stem cells from permanent teeth (DPSCs). ICCs derived from SHED were packed in immuno-isolatory biocompatible macro-capsules and transplanted into streptozotocin (STZ)-induced diabetic mice. Non-diabetic and diabetic controls were transplanted with macro-capsules with or without islets.

RESULTS

SHED were superior to DPSCs. STZ diabetic mice alone and mice transplanted with empty macro-capsules exhibited hyperglycemia throughout the experiment, whereas mice transplanted with macro-capsules containing ICCs were restored to normoglycemia within 3-4 weeks, which persisted for >60 days.

CONCLUSIONS

Our results demonstrate for the first time that ICCs derived from SHED reverse STZ diabetes in mice without immunosuppression and offer an autologous and non-controversial source of human tissue that could be used for stem cell therapy in diabetes.

Porcine pancreas extracellular matrix as a platform for endocrine pancreas bioengineering

Emergent technologies of regenerative medicine have the potential to overcome the limitations of organ transplantation by supplying tissues and organs bioengineered in the laboratory. Pancreas bioengineering requires a scaffold that approximates the biochemical, spatial and vascular relationships of the native extracellular matrix (ECM). We describe the generation of a whole organ, three-dimensional pancreas scaffold using acellular porcine pancreas. Imaging studies confirm that our protocol effectively removes cellular material while preserving ECM proteins and the native vascular tree. The scaffold was seeded with human stem cells and porcine pancreatic islets, demonstrating that the decellularized pancreas can support cellular adhesion and maintenance of cell functions. These findings advance the field of regenerative medicine towards the development of a fully functional, bioengineered pancreas capable of establishing and sustaining euglycemia and may be used for transplantation to cure diabetes mellitus.