Efficient differentiation of insulin-producing cells from skin-derived stem cells

In vitro preconditioning of insulin-producing cells with growth factors improves their survival and ability to release insulin

Glucose-induced oxidative stress in the diabetic pancreas directly affects viability and the consequent therapeutic outcome of transplanted stem cells. Pretreatment of stem cells with growth factors induces tolerance in them against various stresses (hypoxia, thermal or hyperglycaemic). This study investigated the effect of pretreatment on insulin-producing cells (IPCs) differentiated from adipose-derived mesenchymal stem cells (ADMSCs), with a combination of stromal cell-derived factor 1 alpha (SDF1 α) and basic fibroblast growth factor (bFGF) against hyperglycaemic stress (17 or 33 mM glucose). The results showed that IPCs pretreated with a combination of SDF1α and bFGF exhibited maximally alleviated apoptosis, senescence and cell damage with a concomitantly increased release of insulin, enhanced cell proliferation and greater upregulation of Insulin 1, Insulin 2, Ngn3, Pdx1 and Nkx6.2 when stressed with 33 mM glucose. These findings may offer an improved therapeutic outcome for the treatment of diabetes.

Vildagliptin Enhances Differentiation of Insulin Producing Cells from Adipose-Derived Mesenchymal Stem Cells

Objective

Type 1 diabetes is caused by destruction of beta cells of pancreas. Vildagliptin (VG), a dipeptidyl peptidase IV (DPP IV) inhibitor, is an anti-diabetic drug, which increases beta cell mass. In the present study, the effects of VG on generation of insulin-producing cells (IPCs) from adipose-derived mesenchymal stem cells (ASCs) is investigated.

Materials and Methods

In this experimental study, ASCs were isolated and after characterization were exposed to differentiation media with or without VG. The presence of IPCs was confirmed by morphological analysis and gene expression (Pdx-1, Glut-2 and Insulin). Newport Green staining was used to determine insulin-positive cells. Insulin secretion under different concentrations of glucose was measured using radioimmunoassay method.

Results

In the presence of VG the morphology of differentiated cells was similar to the pancreatic islet cells. Expression of Pdx-1, Glut-2 and Insulin genes in VG-treated cells was significantly higher than the cells exposed to induction media only. Insulin release from VG-treated ASCs showed a nearly 3.6 fold (P<0.05) increase when exposed to a high- glucose medium in comparison to untreated ASCs. The percentage of insulin-positive cells in the VG-treated cells was approximately 2.9-fold higher than the untreated ASCs.

Conclusion

The present study has demonstrated that VG elevates differentiation of ASCs into IPCs. Improvement of this protocol may be used in cell therapy in diabetic patients.

Photoprotection against UV-induced damage by skin-derived precursors in hairless mice

BACKGROUND

Skin photodamage is associated with UV-induced overproduction of reactive oxygen species (ROS) and the inactivation of NF-E2-related factor 2 (Nrf2). Skin-derived precursor cells (SKPs), a population of dermal stem cells, are considered to be involved in wound repair and skin regeneration through the activation of Nrf2. However, no reports concentrate on the treatment of skin photodamage with SKPs.

OBJECTIVE

To investigate the photoprotective role of SKPs against UV-induced damage in mice.

METHODS

Fifty Balb/c hairless mice were divided into five groups (n=10), namely, normal (no intervention), model, prevention, treatment, and control groups. The latter four groups were dorsally exposed to UVA+UVB irradiation over a 2-week period. Mice in the prevention group received weekly SKP injections for 2weeks the day before irradiation. Mice in the treatment and Hanks groups received a two-time injection of SKPs and Hanks, respectively, after irradiation. One week after final intervention, skin appearance, pathological alterations, and oxidative indicators were evaluated by enzyme-linked immunosorbent assay, immunohistochemical analysis, and western blotting.

RESULTS

After irradiation, lesions were observed on the dorsal skin of mice, including erythema, edema, scales, and wrinkles; however, these were significantly ameliorated by subcutaneous SKP injection. Hyperkeratosis, acanthosis, and spongiosis in the epidermis, as well as dermal papillae edema and inflammatory cell infiltration, were observed in both model and control groups; however, these conditions resolved with either pretreatment or posttreatment with SKPs. In addition, SKPs increased Nrf2, heme oxygenase-1, glutathione peroxidase, superoxide dismutase, catalase, and gluthathione expression, while decreasing levels of ROS, MDA, and H₂O₂.

CONCLUSIONS

These findings suggest that SKPs have a photoprotective role against UV-induced damage in mice, which may be associated with their ability to scavenge photo-oxidative insults and activate Nrf2.

Effects of Exendine-4 on The Differentiation of Insulin Producing Cells from Rat Adipose-Derived Mesenchymal Stem Cells

OBJECTIVE

To evaluate the effect of Exendine-4 (EX-4), a Glucagon-like peptide 1 (GLP-1) receptor agonist, on the differentiation of insulin-secreting cells (IPCs) from rat adipose-derived mesenchymal stem cells(ADMSCs).

MATERIALS AND METHODS

In this experimental study, ADMSCs were isolated from rat adi- pose tissue and exposed to induction media with or without EX-4. After induction, the existence of IPCs was confirmed by morphology analysis, expression pattern analysis of islet-specific genes (Pdx-1, Glut-2 and Insulin) and insulin synthesis and secretion.

RESULTS

IPCs induced in presence of EX-4 were morphologically similar to pancre- atic islet-like cells. Expression of Pdx-1, Glut-2 and Insulin genes in EX-4 treated cells was significantly higher than the cells exposed to differentiation media without EX-4. Compared to EX-4 untreated ADMSCs, insulin release from EX-4 treated ADMSCs showed a nearly 2.5 fold (P<0.05) increase when exposed to a high glucose (25 mM) medium. The percentage of insulin positive cells in the EX-4 treated group was ap- proximately 4-fold higher than in the EX-4 untreated ADMSCs.

CONCLUSION

The present study has demonstrated that EX-4 enhances the differen- tiation of ADMSCs into IPCs. Improvement of this method may help the formation of an unlimited source of cells for transplantation.

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

The aim of this study is to evaluate the collagen/hyaluronic acid (Col/HA) scaffold effect on the differentiation of insulin-producing cells (IPCs) from adipose-derived mesenchymal stem cells (ASCs). In this experimental study, ASCs were cultured and seeded in a Col/HA scaffold (3D culture) and then treated with induction media. After induction, the presence of IPCs was evaluated using gene expression (PDX-1, GLUT-2 and insulin) analysis and immunocytochemistry, while functional maturity was determined by measuring insulin release in response to low- and high-glucose media. The induced IPCs were morphologically similar to pancreatic islet-like cells. 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 the 2D culture of ASCs-derived IPCs, the insulin release from 3D ASCs-derived IPCs showed a nearly 4-fold (p < 0.05) increase when exposed to a high glucose (25 mmol) medium. The percentage of insulin-positive cells in the 3D experimental group showed an approximately 4-fold increase compared to the 2D experimental culture cells. The results of this study demonstrated that the COL/HA scaffold can enhance the differentiation of IPCs from rat ASCs.

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.

Therapeutic Implications of Newly Identified Stem Cell Populations From the Skin Dermis

Skin, the largest organ of the body, is a promising reservoir for adult stem cells. The epidermal stem cells and hair follicle stem cells have been well studied for their important roles in homeostasis, regeneration, and repair of the epidermis and appendages for decades. However, stem cells residing in dermis were not identified until the year 2001, when a variety of stem cell subpopulations have been isolated and identified from the dermis of mammalian skin such as neural crest stem cells, mesenchymal stem cell-like dermal stem cells, and dermal hematopoietic cells. These stem cell subpopulations exhibited capabilities of self-renewing, multipotent differentiating, and immunosuppressive properties. Hence, the dermis-derived stem cells showed extensive potential applications in regenerative medicine, especially for wound healing/tissue repair, neural repair, and hematopoietic recovery. Here we summarized current research on the stem cell subpopulations derived from the dermis and aimed to provide a comprehensive review on their isolation, specific markers, differentiation capacity, and the functional activities in homeostasis, regeneration, and tissue repair.

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.

Generation and characterization of multipotent stem cells from established dermal cultures

Human multipotent skin derived precursor cells (SKPs) are traditionally sourced from dissociated dermal tissues; therefore, donor availability may become limiting. Here we demonstrate that both normal and diseased adult human dermal fibroblasts (DF) pre-cultured in conventional monolayers are capable of forming SKPs (termed m-SKPs). Moreover, we show that these m-SKPs can be passaged and that cryopreservation of original fibroblast monolayer cultures does not reduce m-SKP yield; however, extensive monolayer passaging does. Like SKPs generated from dissociated dermis, these m-SKPs expressed nestin, fibronectin and versican at the protein level. At the transcriptional level, m-SKPs derived from normal adult human DF, expressed neural crest stem cell markers such as p75NTR, embryonic stem cell markers such as Nanog and the mesenchymal stem cell marker Dermo-1. Furthermore, appropriate stimuli induced m-SKPs to differentiate down either mesenchymal or neural lineages resulting in lipid accumulation, calcification and S100β or β-III tubulin expression (with multiple processes). m-SKP yield was greater from neonatal foreskin cultures compared to those from adult DF cultures; however, the former showed a greater decrease in m-SKP forming capacity after extensive monolayer passaging. m-SKP yield was greater from adult DF cultures expressing more alpha-smooth muscle actin (αSMA). In turn, elevated αSMA expression correlated with cells originating from specimens isolated from biopsies containing more terminal hair follicles; however, αSMA expression was lost upon m-SKP formation. Others have shown that dissociated human hair follicle dermal papilla (DP) are a highly enriched source of SKPs. However, conversely and unexpectedly, monolayer cultured human hair follicle DP cells failed to form m-SKPs whereas those from the murine vibrissae follicles did. Collectively, these findings reveal the potential for using expanded DF cultures to produce SKPs, the heterogeneity of SKP forming potential of skin from distinct anatomical locations and ages, and question the progenitor status of human hair follicle DP cells.

Differentiation of human labia minora dermis-derived fibroblasts into insulin-producing cells

Recent evidence has suggested that human skin fibroblasts may represent a novel source of therapeutic stem cells. In this study, we report a 3-stage method to induce the differentiation of skin fibroblasts into insulin- producing cells (IPCs). In stage 1, we establish the isolation, expansion and characterization of mesenchymal stem cells from human labia minora dermis- derived fibroblasts (hLMDFs) (stage 1: MSC expansion). hLMDFs express the typical mesenchymal stem cell marker proteins and can differentiate into adipocytes, osteoblasts, chondrocytes or muscle cells. In stage 2, DMEM/F12 serum-free medium with ITS mix (insulin, transferrin, and selenite) is used to induce differentiation of hLMDFs into endoderm-like cells, as determined by the expression of the endoderm markers Sox17, Foxa2, and PDX1 (stage 2: mesenchymal-endoderm transition). In stage 3, cells in the mesenchymal- endoderm transition stage are treated with nicotinamide in order to further differentiate into self-assembled, 3-dimensional islet cell-like clusters that express multiple genes related to pancreatic β-cell development and function (stage 3: IPC). We also found that the transplantation of IPCs can normalize blood glucose levels and rescue glucose homeostasis in streptozotocin- induced diabetic mice. These results indicate that hLMDFs have the capacity to differentiate into functionally competent IPCs and represent a potential cell-based treatment for diabetes mellitus.

Regulation of mesenchymal stem cell differentiation and insulin secretion by differential expression of Pdx-1

In recent years, major effort has been made to differentiate embryonic stem cells, pancreatic ductal epithelial multipotent progenitor cells, and bone marrow stem cells into insulin secreting cells. Our previous work has also demonstrated the feasibility of inducing mesenchymal stem cells (MSC) to insulin secreting cells through overexpression of Pdx-1, a pancreas and islet-specific transcription factor that plays a major role in differentiation of islet β-cells during development (Yuan et al. in Mol Biol Rep 37:4023-4031, 2010). However, the levels of insulin secretion among these differentiated MSC were quite variable. The purpose of this study is to address the issue whether the insulin secretion level from the differentiated MSC lines are determined by the expression level of the Pdx-1 transgene. To do so, we have generated several differentiated MSC lines with stable transfection of the Pdx-1 gene. Using RT-PCR analysis and insulin secretion assay, we have analyzed Pdx-1 mRNA levels and insulin secretion from these stable MSC lines. Our results showed that Pdx-1 expression is absolutely required for the differentiation of MSC lines to insulin secreting cell lines. Furthermore, we demonstrated that the level of Pdx-1 expression is closely correlated with level of insulin mRNA and insulin secretion level in differentiated MSC stable cell lines. These findings suggest that the level of Pdx-1 expression plays a key role in induction of MSCs to insulin secreting cells.

Proliferation and differentiation potential of cryopreserved human skin-derived precursors

OBJECTIVES

Skin-derived precursors are recognized to be a potentially autologous and accessible source of neural precursor cells for drug screening or cell-based treatments, in many neurological disorders. Thus, it is necessary to investigate appropriate methods for cryopreservation of such human skin-derived precursors (hSKPs). The aim of this study was to evaluate different cryopreservation techniques for retention of hSKPs to discover an optimized protocol.

MATERIALS AND METHODS

We cryopreserved hSKPs treated with 0%, 10%, 20%, 30% and 40% foetal bovine serum (FBS) and three concentrations of dimethylsulphoxide (DMSO) 5%, 10% and 15%, with two different storage periods in liquid nitrogen (2 days: short-term storage; and 2 months: long-term storage). Then, we assessed survival and proliferation levels of the cells after freeze-thaw processes, by viability measurement and colony-forming assay. For detecting hSKPs, we used immunocytochemistry and RT-PCR assessments.

RESULTS

Our findings indicated that hSKPs cryopreserved in 5% DMSO without FBS, had better survival and proliferation potentials compared to other working formulations. With various concentrations of cryoprotectants over different time periods, hSKPs retained their differentiation potentiality and were able to differentiate into neurons (NFM and βΙΙΙ tubulin-positive), glial cells (GFAP-positive) and smooth muscle cells (SMA-positive).

CONCLUSIONS

  Results revealed that in only 5% DMSO, hSKPs could be cryopreserved for long-term storage with considerable survival and proliferation levels, without losing multipotency.

The PI3K-Akt pathway inhibits senescence and promotes self-renewal of human skin-derived precursors in vitro

Skin-derived precursors (SKPs) are embryonic neural crest- or somite-derived multipotent progenitor cells with properties of dermal stem cells. Although a large number of studies deal with their differentiation ability and potential applications in tissue damage repair, only a few studies have concentrated on the regulation of SKP self-renewal. Here, we found that after separation from their physiological microenvironment, human foreskin-derived SKPs (hSKPs) quickly senesced and lost their self-renewal ability. We observed a sharp decrease in Akt activity during this process, suggesting a possible role of the PI3K-Akt pathway in hSKP maintenance in vitro. Blocking this pathway with several inhibitors inhibited hSKP proliferation and sphere formation and increased hSKP senescence. In contrast, activating this pathway with PDGF-AA and a PTEN inhibitor, bpV(pic), promoted proliferation, improved sphere formation, and alleviated senescence of hSKPs, without altering their differentiation potential. Data also implied that this effect was associated with altered actions of FoxO3 and GSK-3β. Our results suggest an important role of the PI3K-Akt pathway in the senescence and self-renewal of hSKPs. These findings also provide a better understanding of the cellular mechanisms underlying hSKP self-renewal and stem cell senescence to allow more efficient expansion of hSKPs for regenerative medical applications.

Induction of pancreatic β-cell-like cells from CD44+/CD105+ human amniotic fluids via epigenetic regulation of the pancreatic and duodenal homeobox factor 1 promoter

Pancreatic and duodenal homeobox factor 1 (PDX-1) maintains β-cell function and differentiation via direct regulation of multiple islet cell genes. However, the molecular mechanisms involved in this process remain unknown. Here, we show that PDX-1 plays an important role in the induction of CD44+/CD105+ human amniotic fluid cells (HuAFCs) into functional pancreatic β-cell-like cells in vitro. CD44+/CD105+ HuAFCs were transfected with either siRNA targeting PDX-1 (siRNA-PDX-1) or mock plasmid (siRNA-MOCK). Following induction, siRNA-MOCK-transfected cells differentiated into β-cell-like cells that expressed multiple islet cell markers and produced insulin and C-peptide in a glucose-regulated manner. However, siRNA-PDX-1-transfected cells did not fully differentiate into β-cell-like cells. Further, we observed epigenetic changes at the PDX-1 gene locus in induced CD44(+)/CD105(+) HuAFCs. Therefore, CD44+/CD105+ HuAFCs could be a source of human pancreatic β-cell-like cells with potential uses in cell replacement therapy for diabetes.

In vitro and in vivo germ line potential of stem cells derived from newborn mouse skin

We previously reported that fetal porcine skin-derived stem cells were capable of differentiation into oocyte-like cells (OLCs). Here we report that newborn mice skin-derived stem cells are also capable of differentiating into early OLCs. Using stem cells from mice that are transgenic for Oct4 germline distal enhancer-GFP, germ cells resulting from their differentiation are expected to be GFP(+). After differentiation, some GFP(+) OLCs reached 40-45 µM and expressed oocyte markers. Flow cytometric analysis revealed that ∼ 0.3% of the freshly isolated skin cells were GFP(+). The GFP-positive cells increased to ∼ 7% after differentiation, suggesting that the GFP(+) cells could be of in vivo origin, but are more likely induced upon being cultured in vitro. To study the in vivo germ cell potential of skin-derived cells, they were aggregated with newborn ovarian cells, and transplanted under the kidney capsule of ovariectomized mice. GFP(+) oocytes were identified within a subpopulation of follicles in the resulting growth. Our finding that early oocytes can be differentiated from mice skin-derived cells in defined medium may offer a new in vitro model to study germ cell formation and oogenesis.

The multi-potentiality of skin-derived stem cells in pigs

Multipotent skin-derived stem cells represent neural-crest derived precursors which have neural and mesodermal potency and can generate neurons, glias, smooth muscle cells, and adipocytes. Transcriptional profiling studies show that both intrinsic programs and extrinsic signaling pathways mediate their neural and mesodermal potency. In addition, recent progress implies that skin-derived stem cells may have a broader developmental potency than previously expected, of which is their potential to generate germline cells in vitro. In this review, we discuss the transcriptional profiling of multipotency and neural crest-derived characteristics of skin-derived stem cells, and argue for their potential germ-line competency in the view of nuclear and cellular reprogramming.

Differentiation of human multipotent dermal fibroblasts into islet-like cell clusters

Background

We have previously obtained a clonal population of cells from human foreskin that is able to differentiate into mesodermal, ectodermal and endodermal progenies. It is of great interest to know whether these cells could be further differentiated into functional insulin-producing cells.

Results

Sixty-one single-cell-derived dermal fibroblast clones were established from human foreskin by limiting dilution culture. Of these, two clones could be differentiated into neuron-, adipocyte- or hepatocyte-like cells under certain culture conditions. In addition, those two clones were able to differentiate into islet-like clusters under pancreatic induction. Insulin, glucagon and somatostatin were detectable at the mRNA and protein levels after induction. Moreover, the islet-like clusters could release insulin in response to glucose in vitro.

Conclusions

This is the first study to demonstrate that dermal fibroblasts can differentiate into insulin-producing cells without genetic manipulation. This may offer a safer cell source for future stem cell-based therapies.

Skeletal myogenic potential of mouse skin-derived precursors

Cell transplantation-based therapy could be an effective way for the treatment of many diseases. Among numerous somatic stem cells isolated and purified, skin-derived precursors (SKPs) are abundant autologous cells, providing a large reservoir of cells for therapeutic transplantation. Previous studies showed that SKPs could be differentiated into neural and mesodermal progeny in vitro. In the present study, we attempted to differentiate SKPs to muscle progenitors in vitro. After treatment with a combination of growth factors, SKPs were differentiated into cells expressing markers of muscle progenitors, including Pax7. Furthermore, some of these cells expressed desmin, TnT, Mstn, and Myog, suggesting their differentiation into the muscular lineage. After single point injection, the differentiation of SKPs from green fluorescent protein positive donors into muscle precursors was also demonstrated in vivo. Additionally, donor SKPs migrated to the niche of muscle progenitors, participated in the regeneration of recipient muscles, and expressed markers of muscle progenitors, including Pax7, M-cadherin, and MyoD. After recovery of donor cells from recipient muscles at 3 weeks postinjection, some of the injected SKPs were converted to myogenic precursors, based on the expression of specific markers (Pax7 and MyoD). Some of these donor cells also expressed muscle makers (desmin, TnT, and Myog). At 20 weeks postinjection, the injected SKPs were localized to recipient muscles without decreases in their population size. In summary, these findings indicated that SKPs could develop into muscle progenitors and differentiated muscle cells in vitro and in vivo, thus providing valuable autologous cells for the treatment of muscle diseases.