In vitro differentiation of human adipose tissue-derived stem cells into cells with pancreatic phenotype by regenerating pancreas extract

Cell Therapies and Gene Therapy for Diabetes: Current Progress

The epidemic of diabetes continues to be an increasing problem, and there is a need for new therapeutic strategies. There are several promising drugs and molecules in synthetic medicinal chemistry that are developing for diabetes. In addition to this approach, extensive studies with gene and cell therapies are being conducted. Gene therapy is an existing approach in treating several diseases, such as cancer, autoimmune diseases, heart disease and diabetes. Several reports have also suggested that stem cells have the differentiation capability to functional pancreatic beta cell development in vitro and in vivo, with the utility to treat diabetes and prevent the progression of diabetes-related complications. In this current review, we have focused on the different types of cell therapies and vector-based gene therapy in treating or preventing diabetes.

Current Landscape of Various Techniques and Methods of Gene Therapy through CRISPR Cas9 along with its Pharmacological and Interventional Therapies in the Treatment of Type 2 Diabetes Mellitus

BACKGROUND

Type 2 diabetes mellitus (T2DM) is frequently referred to as a "lifestyle illness". In 2000, India (31.7 million) had the greatest global prevalence of diabetes mellitus, followed by China (20.8 million), the United States (17.7 million), and other countries. In recent years, the treatment of gene therapy (T2DM) has attracted intensive interest.

OBJECTIVE

We aimed to critically review the literature on the various techniques and methods, which may be a possible novel approach through the gene therapy CRISPR Cas9 and some other gene editing techniques for T2DM. Interventional and pharmacological approaches for the treatment of T2DM were also included to identify novel therapies for its treatment.

METHOD

An extensive literature survey was done on databases like PubMed, Elsevier, Science Direct and Springer.

CONCLUSION

It can be concluded from the study that recent advancements in gene-editing technologies, such as CRISPR Cas9, have opened new avenues for the development of novel therapeutic approaches for T2DM. CRISPR Cas9 is a powerful tool that enables precise and targeted modifications of the genome.

Trans-differentiation of mouse mesenchymal stem cells into pancreatic β-like cells by a traditional anti-diabetic medicinal herb Medicago sativa L

BACKGROUND AND AIM

Medicago sativa L. is a medicinal herb first cultivated in ancient Iran. Traditionally, it has been utilized for the treatment of several disorders. The plant has been in the human diet for at least 1500 years. Although the hypoglycaemic and anti-diabetic effects of the plant have been approved in traditional medicine, further investigations are needed to support the rational use of M. sativa by humans. This project aimed to evaluate the trans-differentiation potential of bone marrow mesenchymal stem cells (MSCs) to pancreatic β-like cells (insulin-producing cells; IPCs) under the influence of M. sativa extract.

EXPERIMENTAL PROCEDURE

Bone marrow MSCs isolated, characterized, and then treated by flower or leaf extract of M. sativa. Beta-cell characteristics of the differentiated cells were evaluated by several techniques, including specific staining, QPCR, immunofluorescence, and ELISA.

RESULTS

The results showed that the differentiated cells were able to express some specific pancreatic genes (PDX-1, insulin1, and insulin2) and proteins (insulin receptor beta, insulin, proinsulin, and C peptide). Furthermore, ELISA analysis indicated the ability of these cells in the production and secretion of insulin, after exposure to glucose.

CONCLUSION

Overall, both the flower and leaf extract of M. sativa had the potential of differentiation induction of MSCs into IPCs with the characteristics of pancreatic β-like cells. Therefore, M. sativa, as an herbal drug, may be beneficial for the treatment of diseases including diabetes.

Long Non-coding RNA Regulation of Mesenchymal Stem Cell Homeostasis and Differentiation: Advances, Challenges, and Perspectives

Given the self-renewal, multi-differentiation, immunoregulatory, and tissue maintenance properties, mesenchymal stem cells (MSCs) are promising candidates for stem cell-based therapies. Breakthroughs have been made in uncovering MSCs as key contributors to homeostasis and the regenerative repair of tissues and organs derived from three germ layers. MSC differentiation into specialized cell types is sophisticatedly regulated, and accumulating evidence suggests long non-coding RNAs (lncRNAs) as the master regulators of various biological processes including the maintenance of homeostasis and multi-differentiation functions through epigenetic, transcriptional, and post-translational mechanisms. LncRNAs are ubiquitous and generally referred to as non-coding transcripts longer than 200 bp. Most lncRNAs are evolutionary conserved and species-specific; however, the weak conservation of their sequences across species does not affect their diverse biological functions. Although numerous lncRNAs have been annotated and studied, they are nevertheless only the tip of the iceberg; the rest remain to be discovered. In this review, we characterize MSC functions in homeostasis and highlight recent advances on the functions and mechanisms of lncRNAs in regulating MSC homeostasis and differentiation. We also discuss the current challenges and perspectives for understanding the roles of lncRNAs in MSC functions in homeostasis, which could help develop promising targets for MSC-based therapies.

In vitro and in vivo effects of insulin-producing cells generated by xeno-antigen free 3D culture with RCP piece

To establish widespread cell therapy for type 1 diabetes mellitus, we aimed to develop an effective protocol for generating insulin-producing cells (IPCs) from adipose-derived stem cells (ADSCs). We established a 3D culture using a human recombinant peptide (RCP) petaloid μ-piece with xeno-antigen free reagents. Briefly, we employed our two-step protocol to differentiate ADSCs in 96-well dishes and cultured cells in xeno-antigen free reagents with 0.1 mg/mL RCP μ-piece for 7 days (step 1), followed by addition of histone deacetylase inhibitor for 14 days (step 2). Generated IPCs were strongly stained with dithizone, anti-insulin antibody at day 21, and microstructures resembling insulin secretory granules were detected by electron microscopy. Glucose stimulation index (maximum value, 4.9) and MAFA mRNA expression were significantly higher in 3D cultured cells compared with conventionally cultured cells (P < 0.01 and P < 0.05, respectively). The hyperglycaemic state of streptozotocin-induced diabetic nude mice converted to normoglycaemic state around 14 days after transplantation of 96 IPCs under kidney capsule or intra-mesentery. Histological evaluation revealed that insulin and C-peptide positive structures existed at day 120. Our established xeno-antigen free and RCP petaloid μ-piece 3D culture method for generating IPCs may be suitable for clinical application, due to the proven effectiveness in vitro and in vivo.

Mesenchymal stem cells and immune disorders: from basic science to clinical transition

As a promising candidate seed cell type in regenerative medicine, mesenchymal stem cells (MSCs) have attracted considerable attention. The unique capacity of MSCs to exert a regulatory effect on immunity in an autologous/allergenic manner makes them an attractive therapeutic cell type for immune disorders. In this review, we discussed the current knowledge of and advances in MSCs, including its basic biological properties, i.e., multilineage differentiation, secretome, and immunomodulation. Specifically, on the basis of our previous work, we proposed three new concepts of MSCs, i.e., "subtotipotent stem cell" hypothesis, MSC system, and "Yin and Yang" balance of MSC regulation, which may bring new insights into our understanding of MSCs. Furthermore, we analyzed data from the Clinical Trials database ( http://clinicaltrials.gov ) on registered clinical trials using MSCs to treat a variety of immune diseases, such as graft-versus-host disease, systemic lupus erythematosus, and multiple sclerosis. In addition, we highlighted MSC clinical trials in China and discussed the challenges and future directions in the field of MSC clinical application.

Reduction of marginal mass required for successful islet transplantation in a diabetic rat model using adipose tissue-derived mesenchymal stromal cells

BACKGROUND AIMS

Adipose tissue-derived mesenchymal stromal cells (AT-MSCs), widely known as multipotent progenitors, release several cytokines that support cell survival and repair. There are in vitro and in vivo studies reporting the regenerative role of AT-MSCs possibly mediated by their protective effects on functional islet cells as well as their capacity to differentiate into insulin-producing cells (IPCs).

METHODS

On such a basis, our goal in the present study was to use three different models including direct and indirect co-cultures and islet-derived conditioned medium (CM) to differentiate AT-MSCs into IPCs and to illuminate the molecular mechanisms of the beneficial impact of AT-MSCs on pancreatic islet functionality. Furthermore, we combined in vitro co-culture of islets and AT-MSCs with in vivo assessment of islet graft function to assess whether co-transplantation of islets with AT-MSCs can reduce marginal mass required for successful islet transplantation and prolong graft function in a diabetic rat model.

RESULTS

Our findings demonstrated that AT-MSCs are suitable for creating a microenvironment favorable for the repair and longevity of the pancreas β cells through the improvement of islet survival and maintenance of cell morphology and insulin secretion due to their potent properties in differentiation. Most importantly, hybrid transplantation of islets with AT-MSCs significantly promoted survival, engraftment and insulin-producing function of the graft and reduced the islet mass required for reversal of diabetes.

CONCLUSIONS

This strategy might be of therapeutic potential solving the problem of donor islet material loss that currently limits the application of allogeneic islet transplantation as a more widespread therapy for type 1 diabetes.

Adipose stem cells for bone tissue repair

Adipose-derived stem/stromal cells (ASCs), together with adipocytes, vascular endothelial cells, and vascular smooth muscle cells, are contained in fat tissue. ASCs, like the human bone marrow stromal/stem cells (BMSCs), can differentiate into several lineages (adipose cells, fibroblast, chondrocytes, osteoblasts, neuronal cells, endothelial cells, myocytes, and cardiomyocytes). They have also been shown to be immunoprivileged, and genetically stable in long-term cultures. Nevertheless, unlike the BMSCs, ASCs can be easily harvested in large amounts with minimal invasive procedures. The combination of these properties suggests that these cells may be a useful tool in tissue engineering and regenerative medicine.

Effect of hypoxia on human adipose-derived mesenchymal stem cells and its potential clinical applications

Human adipose-derived mesenchymal stem cells (hASCs) are an ideal cell source for regenerative medicine due to their capabilities of multipotency and the readily accessibility of adipose tissue. They have been found residing in a relatively low oxygen tension microenvironment in the body, but the physiological condition has been overlooked in most studies. In light of the escalating need for culturing hASCs under their physiological condition, this review summarizes the most recent advances in the hypoxia effect on hASCs. We first highlight the advantages of using hASCs in regenerative medicine and discuss the influence of hypoxia on the phenotype and functionality of hASCs in terms of viability, stemness, proliferation, differentiation, soluble factor secretion, and biosafety. We provide a glimpse of the possible cellular mechanism that involved under hypoxia and discuss the potential clinical applications. We then highlight the existing challenges and discuss the future perspective on the use of hypoxic-treated hASCs.

Identification of reference genes for qPCR analysis during hASC long culture maintenance

Up to now quantitative PCR based assay is the most common method for characterizing or confirming gene expression patterns and comparing mRNA levels in different sample populations. Since this technique is relative easy and low cost compared to other methods of characterization, e.g. flow cytometry, we used it to typify human adipose-derived stem cells (hASCs). hASCs possess several characteristics that make them attractive for scientific research and clinical applications. Accurate normalization of gene expression relies on good selection of reference genes and the best way to choose them appropriately is to follow the common rule of the “Best 3”, at least three reference genes, three different validation software and three sample replicates. Analysis was performed on hASCs cultivated until the eleventh cell confluence using twelve candidate reference genes, initially selected from literature, whose stability was evaluated by the algorithms NormFinder, BestKeeper, RefFinder and IdealRef, a home-made version of GeNorm. The best gene panel (RPL13A, RPS18, GAPDH, B2M, PPIA and ACTB), determined in one patient by IdealRef calculation, was then investigated in other four donors. Although patients demonstrated a certain gene expression variability, we can assert that ACTB is the most unreliable gene whereas ribosomal proteins (RPL13A and RPS18) show minor inconstancy in their mRNA expression. This work underlines the importance of validating reference genes before conducting each experiment and proposes a free software as alternative to those existing.

Adipose Tissue-Derived Stem Cells in Regenerative Medicine

In regenerative medicine, adult stem cells are the most promising cell types for cell-based therapies. As a new source for multipotent stem cells, human adipose tissue has been introduced. These so called adipose tissue-derived stem cells (ADSCs) are considered to be ideal for application in regenerative therapies. Their main advantage over mesenchymal stem cells derived from other sources, e.g. from bone marrow, is that they can be easily and repeatable harvested using minimally invasive techniques with low morbidity. ADSCs are multipotent and can differentiate into various cell types of the tri-germ lineages, including e.g. osteocytes, adipocytes, neural cells, vascular endothelial cells, cardiomyocytes, pancreatic β-cells, and hepatocytes. Interestingly, ADSCs are characterized by immunosuppressive properties and low immunogenicity. Their secretion of trophic factors enforces the therapeutic and regenerative outcome in a wide range of applications. Taken together, these particular attributes of ADSCs make them highly relevant for clinical applications. Consequently, the therapeutic potential of ADSCs is enormous. Therefore, this review will provide a brief overview of the possible therapeutic applications of ADSCs with regard to their differentiation potential into the tri-germ lineages. Moreover, the relevant advancements made in the field, regulatory aspects as well as other challenges and obstacles will be highlighted.

In Vitro Differentiation of Human Umbilical Cord Blood CD133(+)Cells into Insulin Producing Cells in Co-Culture with Rat Pancreatic Mesenchymal Stem Cells

Objective

Pancreatic stroma plays an important role in the induction of pancreatic cells by the use of close range signaling. In this respect, we presume that pancreatic mesenchymal cells (PMCs) as a fundamental factor of the stromal niche may have an effective role in differentiation of umbilical cord blood cluster of differentiation 133⁺ (UCB-CD133⁺) cells into newly-formed β-cells in vitro.

Materials and Methods

This study is an experimental research. The UCB-CD133⁺cells were purified by magnetic activated cell sorting (MACS) and differentiated into insulin producing cells (IPCs) in co-culture, both directly and indirectly with rat PMCs. Immunocytochemistry and enzyme linked immune sorbent assay (ELISA) were used to determine expression and production of insulin and C-peptide at the protein level.

Results

Our results demonstrated that UCB-CD133⁺differentiated into IPCs. Cells in islet-like clusters with (out) co-cultured with rat pancreatic stromal cells produced insulin and C-peptide and released them into the culture medium at the end of the induction protocol. However they did not respond well to glucose challenges.

Conclusion

Rat PMCs possibly affect differentiation of UCB-CD133⁺cells into IPCs by increasing the number of immature β-cells.

Measurement of the biophysical properties of porcine adipose-derived stem cells by a microperfusion system

Adipose-derived stem cells (ADSCs), which are an accessible source of adult stem cells with capacities for self-renewal and differentiation into various cell types, have a promising potential in tissue engineering and regenerative medicine strategies. To meet the clinical demand for ADSCs, cryopreservation has been applied for long-term ADSC preservation. To optimize the addition, removal, freezing, and thawing of cryoprotective agents (CPAs) applied to ADSCs, we measured the transport properties of porcine ADSCs (pADSCs). The cell responses of pADSCs to hypertonic phosphate-buffered saline and common CPAs, dimethyl sulfoxide, ethylene glycol, and glycerol were measured by a microperfusion system at temperatures of 28, 18, 8, and -2°C. We determined the osmotically inactive cell volume (Vb), hydraulic conductivity (Lp), and CPA permeability (Ps) at various temperatures in a two-parameter model. Then, we quantitatively analyzed the effect of temperature on the transport properties of the pADSC membrane. Biophysical parameters were used to optimize CPA addition, removal, and freezing processes to minimize excessive shrinkage of pADSCs during cryopreservation. The biophysical properties of pADSCs have a great potential for effective optimization of cryopreservation procedures.

Characterization of human adipose tissue-derived stromal cells isolated from diabetic patient's distal limbs with critical ischemia

Adipose tissue is an abundant source of autologous adult stem cells that may bring new therapeutic perspectives on the treatment of diabetes and its complications. It is unclear whether adipose tissue-derived stromal cells (ASCs) of diabetic patients, constantly influenced by hyperglycaemia, have the same properties as non-diabetic controls. As an alternative source of ASCs, adipose tissue from distal limbs of diabetic patients with critical ischemia was isolated. ASCs were characterized in terms of cell surface markers, multilineage differentiation and the expression of vascular endothelial growth factor (VEGFA), chemokine-related genes and compared with non-diabetic controls. Flow cytometry analysis confirmed mesenchymal phenotypes in both diabetic and non-diabetic ASCs. Nevertheless, 40% of diabetic and 20% of non-diabetic ASC samples displayed high expressions of fibroblast marker, which inversely correlated with the expression of CD105. In diabetic patients, significantly decreased expression of VEGFA and chemokine receptor CXCR4 was found in fibroblast-positive ASCs, compared with their fibroblast-negative counterparts. Reduced osteogenic differentiation and the downregulation of chemokine CXCL12 were found in fibroblast-negative diabetic ASCs. Both diabetic and non-diabetic ASCs were differentiated into adipocytes and chondrocytes and did not reveal islet-like cell differentiation. According to this study, adipose tissue from distal limbs of diabetic patients is not satisfactory as an autologous ASC source. Hyperglycaemic milieu as well as other metabolic disorders linked to diabetes may have an influence on endogenous stem cell properties. The present study investigated the feasibility of autologous stem cell therapy in diabetic patients. ASCs isolated from the ischemic limb of diabetic patients were found to be less potent when compared phenotypically and functionally to control non-diabetic counterparts with no signs of limb ischemia. High expression of fibroblast markers associated with reduced expression of VEGFA as well as reduced osteogenic differentiation may have an impact on the effectiveness of autologous cell therapies in diabetic patients.

Immunogenicity of allogeneic mesenchymal stem cells transplanted via different routes in diabetic rats

Due to their hypoimmunogenicity and unique immunosuppressive properties, mesenchymal stem cells (MSCs) are considered one of the most promising adult stem cell types for cell therapy. Although many studies have shown that MSCs exert therapeutic effects on several acute and subacute conditions, their long-term effects are not confirmed in chronic diseases. Immunogenicity is a major limitation for cell replacement therapy, and it is not well understood in vivo. We evaluated the immunogenicity of allogeneic MSCs in vivo by transplanting MSCs into normal and diabetic rats via the tail vein or pancreas and found that MSCs exhibited low immunogenicity in normal recipients and even exerted some immunosuppressive effects in diabetic rats during the initial phase. However, during the later stage in the pancreas group, MSCs expressed insulin and MHC II, eliciting a strong immune response in the pancreas. Simultaneously, the peripheral blood mononuclear cells in the recipients in the pancreas group were activated, and alloantibodies developed in vivo. Conversely, in the tail vein group, MSCs remained immunoprivileged and displayed immunosuppressive effects in vivo. These data indicate that different transplanting routes and microenvironments can lead to divergent immunogenicity of MSCs.

Efficient and simple production of insulin-producing cells from embryonal carcinoma stem cells using mouse neonate pancreas extract, as a natural inducer

An attractive approach to replace the destroyed insulin-producing cells (IPCs) is the generation of functional β cells from stem cells. Embryonal carcinoma (EC) stem cells are pluripotent cells which can differentiate into all cell types. The present study was carried out to establish a simple nonselective inductive culture system for generation of IPCs from P19 EC cells by 1–2 weeks old mouse pancreas extract (MPE). Since, mouse pancreatic islets undergo further remodeling and maturation for 2–3 weeks after birth, we hypothesized that the mouse neonatal MPE contains essential factors to induce in vitro differentiation of pancreatic lineages. Pluripotency of P19 cells were first confirmed by expression analysis of stem cell markers, Oct3/4, Sox-2 and Nanog. In order to induce differentiation, the cells were cultured in a medium supplemented by different concentrations of MPE (50, 100, 200 and 300 µg/ml). The results showed that P19 cells could differentiate into IPCs and form dithizone-positive cell clusters. The generated P19-derived IPCs were immunoreactive to proinsulin, insulin and insulin receptor beta. The expression of pancreatic β cell genes including, PDX-1, INS1 and INS2 were also confirmed. The peak response at the 100 µg/ml MPE used for investigation of EP300 and CREB1 gene expression. When stimulated with glucose, these cells synthesized and secreted insulin. Network analysis of the key transcription factors (PDX-1, EP300, CREB1) during the generation of IPCs resulted in introduction of novel regulatory candidates such as MIR17, and VEZF1 transcription factors, as well as MORN1, DKFZp761P0212, and WAC proteins. Altogether, we demonstrated the possibility of generating IPCs from undifferentiated EC cells, with the characteristics of pancreatic β cells. The derivation of pancreatic cells from EC cells which are ES cell siblings would provide a valuable experimental tool in study of pancreatic development and function as well as rapid production of IPCs for transplantation.

Beyond islet transplantation in diabetes cell therapy: from embryonic stem cells to transdifferentiation of adult cells

Exogenous insulin is, at the moment, the therapy of choice of diabetes, but does not allow tight regulation of glucose leading to long-term complications. Recently, pancreatic islet transplantation to reconstitute insulin-producing β cells, has emerged as an alternative promising therapeutic approach. Unfortunately, the number of donor islets is too low compared with the high number of patients needing a transplantation leading to a search for renewable sources of high-quality β-cells. This review, summarizes more recent promising approaches to the generation of new β-cells from embryonic stem cells for transdifferentiation of adult cells, particularly a critical examination of the seminal work by Lumelsky et al.

Different isolation methods alter the gene expression profiling of adipose derived stem cells

Human adipose stem cells (ASCs) has been in the limelight since its discovery as a suitable source of mesenchymal stem cells (MSCs) in regenerative medicine. Currently, two major techniques are used to isolate ASCs, namely liposuction and tissue biopsy. These two methods are relatively risk-free but the question as to which method could give a more efficient output remains unclear. Thus, this study was carried out to compare and contrast the output generated in regards to growth kinetics, differentiation capabilities in vitro, and gene expression profiling. It was found that ASCs from both isolation methods were comparable in terms of growth kinetics and tri-lineage differentiation. Furthermore, ASCs from both populations were reported as CD44(+), CD73(+), CD90(+), CD166(+), CD34(-), CD45(-) and HLA-DR(-). However, in regards to gene expression, a group of overlapping genes as well as distinct genes were observed. Distinct gene expressions indicated that ASCs (liposuction) has endoderm lineage propensity whereas ASCs (biopsy) has a tendency towards mesoderm/ectoderm lineage. This information suggests involvement in different functional activity in accordance to isolation method. In conclusion, future studies to better understand these gene functions should be carried out in order to contribute in the applicability of each respective cells in regenerative therapy.

Role of injured pancreatic extract promotes bone marrow-derived mesenchymal stem cells efficiently differentiate into insulin-producing cells

Mesenchymal stem cells (MSCs) can be successfully induced to differentiate into insulin-producing cells （IPCs) by a variety of small molecules and cytokines in vitro. However, problems remain, such as low transdifferentiation efficiency and poor maturity of trans-differentiated cells. The damaged pancreatic cells secreted a large amount of soluble proteins, which were able to promote pancreative islet regeneration and MSCs differentiation. In this study, we utilized the rat injured pancreatic tissue extract to modulate rat bone marrow-derived MSCs differentiation into IPCs by the traditional two-step induction. Our results showed that injured pancreatic tissue extract could effectively promote the trans-differentiation efficiency and maturity of IPCs by the traditional induction. Moreover, IPCs were able to release more insulin in a glucose-dependent manner and ameliorate better the diabetic conditions of streptozotocin (STZ)-treated rats. Our study provides a new strategy to induce an efficient and directional differentiation of MSCs into IPCs.

Mutual effect of subcutaneously transplanted human adipose-derived stem cells and pancreatic islets within fibrin gel

While subcutaneous tissue has been proposed as a potential site for pancreatic islet transplantation, concern remains that the microvasculature of subcutaneous tissue is too poor to support transplanted islets. In an effort to overcome this limitation, we evaluated whether fibrin gel with human adipose-derived stem cells (hADSCs) and rat pancreatic islets could cure diabetes mellitus when transplanted into the subcutaneous space of diabetic mice. Subcutaneously co-transplanted islets and hADSCs showed normalization of the diabetic recipient's blood glucose levels. The result was enhanced by co-treatment of fibroblast growth factor-2 (FGF2) in the fibrin gel. The hADSCs enhanced islet viability after transplantation by secreting various growth factors that can protect islets from hypoxic damage. Afterward, hADSCs could maintain islet viability by recruiting new microvasculature nearby the transplanted islets via overexpression of vascular endothelial growth factor (VEGF). The hADSCs did not directly differentiate into endothelial cells (no detection of biomarkers of human endothelial cells), but showed evidence of differentiation toward insulin-secreting cells (detection of human insulin). Mice receiving islet transplantation alone did not become normoglycemic. Collectively, co-transplantation of fibrin gel with islets and hADSCs will expand the indications for islet transplant therapy and the potential clinical application of cell-based therapy.

Adipose-Derived Stem Cells in Tissue Regeneration: A Review

In 2001, researchers at the University of California, Los Angeles, described the isolation of a new population of adult stem cells from liposuctioned adipose tissue. These stem cells, now known as adipose-derived stem cells or ADSCs, have gone on to become one of the most popular adult stem cells populations in the fields of stem cell research and regenerative medicine. As of today, thousands of research and clinical articles have been published using ASCs, describing their possible pluripotency in vitro, their uses in regenerative animal models, and their application to the clinic. This paper outlines the progress made in the ASC field since their initial description in 2001, describing their mesodermal, ectodermal, and endodermal potentials both in vitro and in vivo, their use in mediating inflammation and vascularization during tissue regeneration, and their potential for reprogramming into induced pluripotent cells.

Differentiation of human adipose-derived mesenchymal stem cell into insulin-producing cells: an in vitro study

Stem cells with the ability to differentiate into insulin-producing cells (IPCs) are becoming the most promising therapy for diabetes mellitus and reduce the major limitations of availability and allogeneic rejection of beta cell transplantations. Mesenchymal stem cells (MSCs) are pluripotent stromal cells with the ability to proliferate and differentiate into a variety of cell types including endocrine cells of the pancreas. This study sought to inspect the in vitro differentiation of human adipose-derived tissue stem cells into IPCs which could provide an abundant source of cells for the purpose of diabetic cell therapy in addition to avoid immunological rejection. Adipose-derived MSCs were obtained from liposuction aspirates and induced to differentiate into insulin-secreting cells under a three-stage protocol based on a combination of low-glucose DMEM medium, β-mercaptoethanol, and nicotinamide for pre-induction and high-glucose DMEM, β-mercaptoethanol, nicotinamide, and exendin-4 for induction stages of differentiation. Differentiation was evaluated by the analysis of morphology, dithizone staining, RT-PCR, and immunocytochemistry. Morphological changes including typical islet-like cell clusters were observed by phase-contrast microscope at the end of differentiation protocol. Based on dithizone staining, differentiated cells were positive and undifferentiated cells were not stained. Furthermore, RT-PCR results confirmed the expression of insulin, PDX1, Ngn3, PAX4, and GLUT2 in differentiated cells. Moreover, insulin production by the IPCs was confirmed by immunocytochemistry analysis. It is concluded that adipose-derived MSCs could differentiate into insulin-producing cells in vitro.

Differentiation of human adipose tissue-derived stem cells into aggregates of insulin-producing cells through the overexpression of pancreatic and duodenal homeobox gene-1

The pancreatic and duodenal homeobox gene 1 (Pdx-1) plays a key role in normal pancreas development and is required for maintaining the normal function of islets. In this study, we examined whether human adipose tissue-derived stem cells (hASCs) could differentiate into insulin-producing cells by exogenously expressed Pdx-1. hASCs were infected with recombinant adenovirus encoding the mouse Pdx-1 gene and differentiated under high-glucose conditions. Insulin transcript levels and the expression of key transcription factors required for pancreatic development including FoxA2, Nkx2.2, and NeuroD were significantly increased by exogenous Pdx-1 overexpression. The expression of Nkx6.1 was found only in Pdx-1-induced hASCs. In addition to transcripts for transcription factors involved in pancreatic development, transcripts for the GLP-1 receptor, glucokinase, and glucose transporter, which are required for maintaining the function of pancreatic β-cells, were observed only in Pdx-1-induced hASCs. Pdx-1-induced hASCs exhibited insulin secretion in response to glucose challenge in vitro. When Pdx-1-induced hASCs were transplanted into streptozotocin (STZ)-induced diabetic mice, they reduced blood glucose levels, although they did not restore normoglycemia. These results demonstrate that the expression of exogenous Pdx-1 is sufficient to induce pancreatic differentiation in vitro but does not induce the fully functional, mature insulin-producing cells that are required for restoring normoglycemia in vivo.

Stem cells as a tool to improve outcomes of islet transplantation

The publication of the promising results of the Edmonton protocol in 2000 generated optimism for islet transplantation as a potential cure for Type 1 Diabetes Mellitus. Unfortunately, follow-up data revealed that less than 10% of patients achieved long-term insulin independence. More recent data from other large trials like the Collaborative Islet Transplant Registry show incremental improvement with 44% of islet transplant recipients maintaining insulin independence at three years of follow-up. Multiple underlying issues have been identified that contribute to islet graft failure, and newer research has attempted to address these problems. Stem cells have been utilized not only as a functional replacement for β cells, but also as companion or supportive cells to address a variety of different obstacles that prevent ideal graft viability and function. In this paper, we outline the manners in which stem cells have been applied to address barriers to the achievement of long-term insulin independence following islet transplantation.

Promoting long-term survival of insulin-producing cell grafts that differentiate from adipose tissue-derived stem cells to cure type 1 diabetes

BACKGROUND

Insulin-producing cell clusters (IPCCs) have recently been generated in vitro from adipose tissue-derived stem cells (ASCs) to circumvent islet shortage. However, it is unknown how long they can survive upon transplantation, whether they are eventually rejected by recipients, and how their long-term survival can be induced to permanently cure type 1 diabetes. IPCC graft survival is critical for their clinical application and this issue must be systematically addressed prior to their in-depth clinical trials.

METHODOLOGY/PRINCIPAL FINDINGS

Here we found that IPCC grafts that differentiated from murine ASCs in vitro, unlike their freshly isolated islet counterparts, did not survive long-term in syngeneic mice, suggesting that ASC-derived IPCCs have intrinsic survival disadvantage over freshly isolated islets. Indeed, β cells retrieved from IPCC syngrafts underwent faster apoptosis than their islet counterparts. However, blocking both Fas and TNF receptor death pathways inhibited their apoptosis and restored their long-term survival in syngeneic recipients. Furthermore, blocking CD40-CD154 costimulation and Fas/TNF signaling induced long-term IPCC allograft survival in overwhelming majority of recipients. Importantly, Fas-deficient IPCC allografts exhibited certain immune privilege and enjoyed long-term survival in diabetic NOD mice in the presence of CD28/CD40 joint blockade while their islet counterparts failed to do so.

CONCLUSIONS/SIGNIFICANCE

Long-term survival of ASC-derived IPCC syngeneic grafts requires blocking Fas and TNF death pathways, whereas blocking both death pathways and CD28/CD40 costimulation is needed for long-term IPCC allograft survival in diabetic NOD mice. Our studies have important clinical implications for treating type 1 diabetes via ASC-derived IPCC transplantation.

The potential of adipose stem cells in regenerative medicine

Adipose stem cells (ASCs) are an attractive and abundant stem cell source with therapeutic applicability in diverse fields for the repair and regeneration of acute and chronically damaged tissues. Importantly, unlike the human bone marrow stromal/stem stem cells (BMSCs) that are present at low frequency in the bone marrow, ASCs can be retrieved in high number from either liposuction aspirates or subcutaneous adipose tissue fragments and can easily be expanded in vitro. ASCs display properties similar to that observed in BMSCs and, upon induction, undergo at least osteogenic, chondrogenic, adipogenic and neurogenic, differentiation in vitro. Furthermore, ASCs have been shown to be immunoprivileged, prevent severe graft-versus-host disease in vitro and in vivo and to be genetically stable in long-term culture. They have also proven applicability in other functions, such as providing hematopoietic support and gene transfer. Due to these characteristics, ASCs have rapidly advanced into clinical trials for treatment of a broad range of conditions. As cell therapies are becoming more frequent, clinical laboratories following good manufacturing practices are needed. At the same time as laboratory processes become more extensive, the need for control in the processing laboratory grows consequently involving a greater risk of complications and possibly adverse events for the recipient. Therefore, the safety, reproducibility and quality of the stem cells must thoroughly be examined prior to extensive use in clinical applications. In this review, some of the aspects of examination on ASCs in vitro and the utilization of ASCs in clinical studies are discussed.

Insulin-producing cells from human pancreatic islet-derived progenitor cells following transplantation in mice

Stem/progenitor cells hold promise for alleviating/curing type 1 diabetes due to the capacity to differentiate into functional insulin-producing cells. The current study aims to assess the differentiation potential of human pancreatic IPCs (islet-derived progenitor cells). IPCs were derived from four human donors and subjected to more than 2000-fold expansion before turning into ICCs (islet-like cell clusters). The ICCs expressed ISL-1 Glut2, PDX-1, ngn3, insulin, glucagon and somatostatin at the mRNA level and stained positive for insulin and glucagon by immunofluorescence. Following glucose challenge in vitro, C-peptide was detected in the sonicated ICCs, instead of in the conditioned medium. To examine the function of the cells in vivo, IPCs or ICCs were transplanted under the renal capsule of immunodeficient mice. One month later, 19 of 28 mice transplanted with ICCs and 4 of 14 mice with IPCs produced human C-peptide detectable in blood, indicating that the in vivo environment further facilitated the maturation of ICCs. However, among the hormone-positive mice, only 9 of 19 mice with ICCs and two of four mice with IPCs were able to secrete C-peptide in response to glucose.

Isolation of genes involved in pancreas regeneration by subtractive hybridization

The deterioration of β cells in the pancreas is a crucial factor in the progression of diabetes mellitus; therefore, the recovery of β cells is of vital importance for effective diabetic therapeutic strategies. Partially pancreatectomized rats have been used for the investigation of pancreatic regeneration. Because it was determined that tissue extract from the partially-dissected pancreas induces pancreatic differentiation in embryonic stem cells, paracrine factors were thought to be involved in the regeneration. In this study, we screened for genes that had higher mRNA levels 2 days after 60%-pancreatectomy. The genes were isolated using subtractive hybridization and DNA sequencing. Twelve genes (adipsin, Aplp2, Clu, Col1a2, Glul, Krt8, Lgmn, LOC299907, LOC502894, Pla2g1b, Reg3α and Xbp1) were identified, and RT-PCR and real-time PCR analyses were performed to validate their expression levels. Among the genes identified, three genes (Glul, Lgmn and Reg3a) were selected for further analyses. Assays revealed that Glul and Reg3α enhance cell growth. Glul, Lgmn and Reg3α change the expression level of islet marker genes, where NEUROD, NKX2.2, PAX4 and PAX6 are up-regulated and somatostatin is down-regulated. Thus, we believe that Glul, Lgmn and Reg3a can serve as novel targets in diabetes mellitus genetic therapy.

Islet-like cell aggregates generated from human adipose tissue derived stem cells ameliorate experimental diabetes in mice

Background

Type 1 Diabetes Mellitus is caused by auto immune destruction of insulin producing beta cells in the pancreas. Currently available treatments include transplantation of isolated islets from donor pancreas to the patient. However, this method is limited by inadequate means of immuno-suppression to prevent islet rejection and importantly, limited supply of islets for transplantation. Autologous adult stem cells are now considered for cell replacement therapy in diabetes as it has the potential to generate neo-islets which are genetically part of the treated individual. Adopting methods of islet encapsulation in immuno-isolatory devices would eliminate the need for immuno-suppressants.

Methodology/Principal Findings

In the present study we explore the potential of human adipose tissue derived adult stem cells (h-ASCs) to differentiate into functional islet like cell aggregates (ICAs). Our stage specific differentiation protocol permit the conversion of mesodermic h-ASCs to definitive endoderm (Hnf3β, TCF2 and Sox17) and to PDX1, Ngn3, NeuroD, Pax4 positive pancreatic endoderm which further matures in vitro to secrete insulin. These ICAs are shown to produce human C-peptide in a glucose dependent manner exhibiting in-vitro functionality. Transplantation of mature ICAs, packed in immuno-isolatory biocompatible capsules to STZ induced diabetic mice restored near normoglycemia within 3–4 weeks. The detection of human C-peptide, 1155±165 pM in blood serum of experimental mice demonstrate the efficacy of our differentiation approach.

Conclusions

h-ASC is an ideal population of personal stem cells for cell replacement therapy, given that they are abundant, easily available and autologous in origin. Our findings present evidence that h-ASCs could be induced to differentiate into physiologically competent functional islet like cell aggregates, which may provide as a source of alternative islets for cell replacement therapy in type 1 diabetes.

Embryonic stem cell factors undifferentiated transcription factor-1 (UFT-1) and reduced expression protein-1 (REX-1) are widely expressed in human skin and may be involved in cutaneous differentiation but not in stem cell fate determination

Undifferentiated transcription factor-1 (UTF-1) and reduced expression protein-1 (REX-1) are used as markers for the undifferentiated state of pluripotent stem cells. Because no highly specific cytochemical marker for epidermal stem cells has yet been identified, we investigated the expression pattern of these markers in human epidermis and skin tumours by immunohistochemistry and in keratinocyte cell cultures. Both presumed stem cell markers were widely expressed in the epidermis and skin appendages. Distinct expression was found in the matrix cells of the hair shaft. Differentiation of human primary keratinocytes (KC) in vitro strongly downregulated UTF-1 and REX-1 expression. In addition, REX-1 was upregulated in squamous cell carcinomas, indicating a possible role of this transcription factor in malignant tumour formation. Our data point to a role for these proteins not only in maintaining KC stem cell populations, but also in proliferation and differentiation of matrix cells of the shaft and also suprabasal KC.

Combined transplantation of pancreatic islets and adipose tissue-derived stem cells enhances the survival and insulin function of islet grafts in diabetic mice

BACKGROUND

Overcoming significant loss of transplanted islet mass is important for successful islet transplantation. Adipose tissue-derived stem cells (ADSCs) seem to have angiogenic potential and antiinflammatory properties. We hypothesized that the inclusion of ADSCs with islet transplantation should enhance the survival and insulin function of the islet graft.

METHODS

Syngeneic ADSCs and allogeneic islets were transplanted simultaneously under the kidney capsules of diabetic C57BL/6J mice. Rejection of the graft was examined by measurement of blood glucose level. Revascularization and inflammatory cell infiltration were examined by immunohistochemistry.

RESULTS

Transplantation of 400 islets only achieved normoglycemia with graft survival of 13.6±1.67 days (mean±standard deviation), whereas that of 100 or 200 allogeneic islets never reversed diabetes. Transplantation of 200 islets with 2×10(5) ADSCs reversed diabetes and significantly prolonged graft survival (13.0±5.48 days). Results of glucose tolerance tests performed on day 7 were significantly better in islets-ADSCs than islets-alone recipients. Immunohistochemical analysis confirmed the presence of insulin-stained islet grafts with well-preserved structure in islets-ADSCs transplant group. Significant revascularization (larger number of von Willebrand factor-positive cells) and marked inhibition of inflammatory cell infiltration, including CD4+ and CD8+ T cells and macrophages, were noted in the islets-ADSCs transplant group than islets-alone transplant group.

CONCLUSIONS

Our results indicated that cotransplantation of ADSCs with islet graft promoted survival and insulin function of the graft and reduced the islet mass required for reversal of diabetes. This innovative protocol may allow "one donor to one recipient" islet transplantation.

Bone marrow-derived mesenchymal stromal cells support rat pancreatic islet survival and insulin secretory function in vitro

BACKGROUND AIMS

Recent evidence has suggested that transplanted bone marrow (BM)-derived mesenchymal stromal cells (MSC) are able to engraft and repair non-hematopoietic tissues successfully, including central nervous system, renal, pulmonary and skin tissue, and may possibly contribute to tissue regeneration. We examined the cytoprotective effect of BM MSC on co-cultured, isolated pancreatic islets.

METHODS

Pancreatic islets and MSC isolated from Lewis rats were divided into four experimental groups: (a) islets cultured alone (islet control); (b) islets cultured in direct contact with MSC (IM-C); (c) islets co-cultured with MSC in a Transwell system, which allows indirect cell contact through diffusible media components (IM-I); and (d) MSC cultured alone (MSC control). The survival and function of islets were measured morphologically and by analyzing insulin secretion in response to glucose challenge. Cytokine profiles were determined using a cytokine array and enzyme-linked immunosorbent assays.

RESULTS

Islets contact-cultured with MSC (IM-C) showed sustained survival and retention of glucose-induced insulin secretory function. In addition, the levels of monocyte chemoattractant protein-1 (MCP-1) and tumor necrosis factor-α (TNF-α) were decreased, and tissue inhibitor of metalloproteinases-1 (TIMP-1) and vascular endothelial growth factor (VEGF) levels were increased at 4 weeks in both the IM-C and IM-I groups.

CONCLUSIONS

These results indicate that contact co-culture is a major factor that contributes to islet survival, maintenance of cell morphology and insulin function. There might also be a synergic effect resulting from the regulation of inflammatory cytokine production. We propose that BM MSC are suitable for generating a microenvironment favorable for the repair and longevity of pancreatic islets.

Human adipose-derived stem cells: potential clinical applications in surgery

Regenerative medicine is emerging as a rapidly evolving field of research and therapeutics. Stem cells hold great promise for future translational research and clinical applications in many fields. Much research has focused on mesenchymal stem cells isolated from bone marrow in vitro and in vivo; however, bone marrow procurement causes considerable discomfort to the patient and yields a relatively small number of harvested cells. By contrast, adipose tissue represents an abundant and easily accessible source of adult stem cells, termed adipose-derived stem cells (ADSCs), with the ability to equally differentiate along multiple lineage pathways. These stem cells have angiogenic properties, possibly because of their secretion of cytokines. They may also play a role in healing acute and chronic tissue damage. Subsequently, they have a wide range of potential clinical implications. This article reviews the potential preclinical and clinical applications of mesenchymal stem cells, especially ADSCs, in surgery.

Bone marrow-derived mesenchymal stem cells co-cultured with pancreatic islets display β cell plasticity

The direct co-culturing effect of rat bone-marrow-derived mesenchymal stem cells (rBM-MSCs) on the pancreatic-islets (PIs) was studied to obtain functional islet cells. MSCs were isolated from rat bone marrow and cultivated under standard conditions. Following their characterization, the rBM-MSCs were directly (with cell-islet contact) co-cultured with recovered PIs together with the single cell cultures of those cell cultures as a control. The effect of direct co-cultures of rBM-MSCs with the PIs of normal rats was investigated using immunophenotypical and functional methods. The change in the amount of insulin secretion was evaluated as an indicator for differentiation of rBM-MSCs. One approache for in vitro differentiation to achieve reprogramming for differentiation into suitable cell types by changing the microenvironment of the cells to provide signals that might activate metabolic pathways is to use co-cultures with the microenvironment of the specific cells of the desired cell type, tissue/organ extracts, extracellular matrix compounds or biologically absorbable materials. Differentiated rBM-MSCs were found to be immunopositive for the specific insulin-producing cell marker, insulin, but not in undifferentiated rBM-MSCs. The functionality tests by ELISA confirmed that insulin secretion of co-cultured MSCs with islets was higher than that of islets. These evidences indicated that PIs could be regarded as critical components of the stem cell niche, such that MSCs can be differentiated into insulin-producing cells (IPCs). Moreover, direct cell-to-cell contact might provide additional and independent support. This approach would circumvent the need for PI-stem cell co-culture and could potentially facilitate the production of functional IPCs for future clinical applications.

Treatment of type 1 diabetes with adipose tissue-derived stem cells expressing pancreatic duodenal homeobox 1

Due to the limited supply of donor pancreas, it is imperative that we identify alternative cell sources that can be used to treat diabetes mellitus (DM). Multipotent adipose tissue-derived stem cells (ADSC) can be abundantly and safely isolated for autologous transplantation and therefore are an ideal candidate. Here, we report the derivation of insulin-producing cells from human or rat ADSC by transduction with the pancreatic duodenal homeobox 1 (Pdx1) gene. RT-PCR analyses showed that native ADSC expressed insulin, glucagon, and NeuroD genes that were up-regulated following Pdx1 transduction. ELISA analyses showed that the transduced cells secreted increasing amount of insulin in response to increasing concentration of glucose. Transplantation of these cells under the renal capsule of streptozotocin-induced diabetic rats resulted in lowered blood glucose, higher glucose tolerance, smoother fur, and less cataract. Histological examination showed that the transplanted cells formed tissue-like structures and expressed insulin. Thus, ADSC-expressing Pdx1 appear to be suitable for treatment of DM.