Mesenchymal stem cells and differentiated insulin producing cells are new horizons for pancreatic regeneration in type I diabetes mellitus

BackgroundDiabetes mellitus has become the third human killer following cancer and cardiovascular disease. Millions of patients, often children, suffer from type 1 diabetes (T1D). Stem cells created hopes to regenerate damaged body tissues and restore their function.AimThis work aimed at clarifying and comparing the therapeutic potential of differentiated and non-differentiated mesenchymal stem cells (MSCs) as a new line of therapy for T1D.Methods40 Female albino rats divided into group I (control): 10 rats and group II (diabetic), III and IV, 10 rats in each, were injected with streptozotocin (50 mg/kg body weight). Group III (MSCs) were transplanted with bone marrow derived MSCs from male rats and group IV (IPCs) with differentiated insulin producing cells. Blood and pancreatic tissue samples were taken from all rats for biochemical and histological studies.ResultsMSCs reduced hyperglycemia in diabetic rats on day 15 while IPCs normalizes blood glucose level on day 7. Histological and morphometric analysis of pancreas of experimental diabetic rats showed improvement in MSCs-treated group but in IPCs-treated group, β-cells insulin immunoreactions were obviously returned to normal, with normal distribution of β-cells in the center and other cells at the periphery. Meanwhile, most of the pathological lesions were still detected in diabetic rats.ConclusionMSCs transplantation can reduce blood glucose level in recipient diabetic rats. IPCs initiate endogenous pancreatic regeneration by neogenesis of islets. IPCs are better than MSCs in regeneration of β-cells. So, IPCs therapy can be considered clinically to offer a hope for patients suffering from T1D.     

Differentiation of microfluidic-encapsulated trabecular meshwork mesenchymal stem cells into insulin producing cells and their impact on diabetic rats

Tissue and stem cell encapsulation andtransplantation were considered as promising tools in the treatment of patients with diabetes mellitus. The aim of this study was to evaluate the effect of microfluidic encapsulation on the differentiation of trabecular meshwork mesenchymal stem cells (TM-MSC), into insulin-producing cells (IPCs) both in vitro and in vivo. The presence of differentiated cells in microfibers (three dimensional [3D]) and tissue culture plates (TCPS; two dimensional [2D]) culture was evaluated by detecting mRNA and protein expression of pancreatic islet-specific markers as well as measuring insulin release of cells in response to glucose challenges. Finally, semi-differentiated cells in microfibers (3D) and 2D cultures were used to control the glucose level in diabetic rats. The results of this study showed that MSCs differentiated in alginate microfibers (fabricated by microfluidic device) express more Pdx-1 mRNA (1.938-fold, p-value: 0.0425) and Insulin mRNA (2.841-fold, p-value: 0.0001) compared with those cultured on TCPS. Furthermore, cell encapsulation in microfluidic derived microfibers decreased the level of blood glucose in diabetic rats. The approach used in this study showed the possibility of alginate microfibers as a matrix for differentiation of TM-MSCs (as a new source) into IPCs. In addition, it could minimize different steps in stem cell differentiation, handling, and encapsulation, which lead to loss of an unlimited number of cells.     

Induction of insulin‐producing cells from umbilical cord blood‐derived stromal cells by activation of the c‐Met/HGF axis

Efficient and effective therapies are required for diabetes mellitus. The use of adult stem cells for treating diabetes represents a major focus of current research. We have attempted to differentiate adult stem cells produced from umbilical cord blood‐derived stromal cells into insulin‐producing cells (IPCs). By activating the c‐Met/HGF axis through temporal hypoxia treatment and hepatocyte growth factor (HGF) supplementation, our protocol resulted in the differentiation of cells into functional pancreatic endocrine cells with increased viability. Glucose stimulation test results showed that significantly greater amounts of C‐peptide and insulin were released from the differentiated cells than from undifferentiated cells. These IPCs were capable of reversing the hyperglycemia of diabetic mice. In conclusion, targeting the c‐Met/HGF axis can be considered an effective and efficient means of obtaining IPCs from adult stem cells.     

Therapeutic efficacy of differentiated versus undifferentiated mesenchymal stem cells in experimental type I diabetes in rat

Selective MSCs differentiation protocol into pancreatic beta cells was conducted in the present study using exendin-4 and TGF-beta. Differentiated and undifferentiated MSCs were assessed in experimental type I diabetes in rats. Ninety female white albino rats were included in the study and divided equally (n=15/group) into 6 groups: healthy control, healthy control rats received acellular tissue culture medium, diabetic rats, diabetic rats received acellular tissue culture medium, diabetic rats received undifferentiated MSCs and diabetic rats received differentiated MSCs. Therapeutic efficacy of undifferentiated versus differentiated MSCs was evaluated via assessment of quantitative gene expressions of insulin1, insulin 2, Smad-2, Smad-3, PDX-1, PAX-4, neuroD. Blood glucose and insulin hormone levels were also assessed. Results showed that quantitative gene expressions of all studied genes showed significant decrease in diabetic rat groups. Use of undifferentiated and differentiated MSCs led to a significant elevation of expression levels of all genes with more superior effect with differentiated MSCs except smad-2 gene. As regards insulin hormone levels, use of either undifferentiated or differentiated MSCs led to a significant elevation of its levels with more therapeutic effect with differentiated MSCs. Blood glucose levels were significantly decreased with both undifferentiated and differentiated MSCs in comparison to diabetic groups but its levels were normalized 2 months after injection of differentiated MSCs. In conclusion, use of undifferentiated or differentiated MSCs exhibited significant therapeutic potentials in experimental type I diabetes in rats with more significant therapeutic effect with the use of differentiated MSCs.     

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.     

Improved differentiation of umbilical cord blood-derived mesenchymal stem cells into insulin-producing cells by PDX-1 mRNA transfection

Numerous studies have sought to identify diabetes mellitus treatment strategies with fewer side effects. Mesenchymal stem cell (MSC) therapy was previously considered as a promising therapy; however, it requires the cells to be trans-differentiated into cells of the pancreatic-endocrine lineage before transplantation. Previous studies have shown that PDX-1 expression can facilitate MSC differentiation into insulin-producing cells (IPCs), but the methods employed to date use viral or DNA-based tools to express PDX-1, with the associated risks of insertional mutation and immunogenicity. Thus, this study aimed to establish a new method to induce PDX-1 expression in MSCs by mRNA transfection. MSCs were isolated from human umbilical cord blood and expanded in vitro, with stemness confirmed by surface markers and multipotentiality. MSCs were transfected with PDX-1 mRNA by nucleofection and chemically induced to differentiate into IPCs (combinatorial group). This IPC differentiation was then compared with that of untransfected chemically induced cells (inducer group) and uninduced cells (control group). We found that PDX-1 mRNA transfection significantly improved the differentiation of MSCs into IPCs, with 8.3±2.5% IPCs in the combinatorial group, 3.21±2.11% in the inducer group and 0% in the control. Cells in the combinatorial group also strongly expressed several genes related to beta cells (Pdx-1, Ngn3, Nkx6.1 and insulin) and could produce C-peptide in the cytoplasm and insulin in the supernatant, which was dependent on the extracellular glucose concentration. These results indicate that PDX-1 mRNA may offer a promising approach to produce safe IPCs for clinical diabetes mellitus treatment.     

Insulin-Producing Cells Differentiated from Human Bone Marrow Mesenchymal Stem Cells In Vitro Ameliorate Streptozotocin-Induced Diabetic Hyperglycemia

Background

The two major obstacles in the successful transplantation of islets for diabetes treatment are inadequate supply of insulin-producing tissue and immune rejection. Induction of the differentiation of human bone marrow-derived mesenchymal stem cells (hMSCs) into insulin-producing cells (IPCs) for autologous transplantation may alleviate those limitations.

Methods

hMSCs were isolated and induced to differentiate into IPCs through a three-stage differentiation protocol in a defined media with high glucose, nicotinamide, and exendin-4. The physiological characteristics and functions of IPCs were then evaluated. Next, about 3 × 10⁶ differentiated cells were transplanted into the renal sub-capsular space of streptozotocin (STZ)-induced diabetic nude mice. Graft survival and function were assessed by immunohistochemistry, TUNEL staining and measurements of blood glucose levels in the mice.

Results

The differentiated IPCs were characterized by Dithizone (DTZ) positive staining, expression of pancreatic β-cell markers, and human insulin secretion in response to glucose stimulation. Moreover, 43% of the IPCs showed L-type Ca²⁺ channel activity and similar changes in intracellular Ca²⁺ in response to glucose stimulation as that seen in pancreatic β-cells in the process of glucose-stimulated insulin secretion. Transplantation of functional IPCs into the renal subcapsular space of STZ-induced diabetic nude mice ameliorated the hyperglycemia. Immunofluorescence staining revealed that transplanted IPCs sustainably expressed insulin, c-peptide, and PDX-1 without apparent apoptosis in vivo.

Conclusions

IPCs derived from hMSCs in vitro can ameliorate STZ-induced diabetic hyperglycemia, which indicates that these hMSCs may be a promising approach to overcome the limitations of islet transplantation.     

移植骨髓间充质干细胞治疗大鼠糖尿病的研究

目的 通过移植骨髓间充质干细胞（mesenchymal stem cell,MSC）的方法试治疗大鼠糖尿病。方法 贴壁生长的MSC与大鼠胰腺的细胞共培养以检测其向胰岛细胞分化的潜能。并将体外培养扩增的MSC移植入糖尿病大鼠体内,观测其能否改善糖尿病病情及其在大鼠体内微环境中的分化情况。结果 共培养法可使MSC分化为胰岛样细胞。对大鼠的MSC移植能明显缓解糖尿病病情。结论 MSC移植的方法对大鼠糖尿病有一定的治疗作用。     

Improving the efficacy of type 1 diabetes therapy by transplantation of immunoisolated insulin-producing cells

Type 1 diabetes occurs when pancreatic islet β-cells are damaged and are thus unable to secrete insulin. Pancreas- or islet-grafting therapy offers highly efficient treatment but is limited by inadequate donor islets or pancreases for transplantation. Stem-cell therapy holds tremendous potential and promises to enhance treatment efficiency by overcoming the limitations of traditional therapies. In this study, we evaluated the efficiency of preclinical diabetic treatment. Diabetes was induced in mice by injections of streptozotocin. Mesenchymal stem cells (MSCs) were derived from mouse bone marrow or human umbilical cord blood and subsequently differentiated into insulin-producing cells. These insulin-producing cells were encapsulated in an alginate membrane to form capsules. Finally, these capsules were grafted into diabetic mice by intraperitoneal injection. Treatment efficiency was evaluated by monitoring body weight and blood glucose levels. Immune reactions after transplantation were monitored by counting total white blood cells. Allografting or xenografting of encapsulated insulin-producing cells (IPCs) reduced blood glucose levels and increased body weight following transplantation. Encapsulation with alginate conferred immune isolation and prevented graft rejection. These results provide further evidence supporting the use of allogeneic or xenogeneic MSCs obtained from bone marrow or umbilical cord blood for treating type 1 diabetes.     

Adipose tissue-derived mesenchymal stromal cells efficiently differentiate into insulin-producing cells in pancreatic islet microenvironment both in vitro and in vivo

Background aimsDifferentiation or reprogramming of stem cells could be achieved by remodulating the microenvironment, which regulates the fate of cells by soluble factors and contacts. By providing an in vivo-like microenvironment, directional and functional differentiation of stem cells could be achieved in vitro. In this study, the differentiation of mesenchymal stromal cells (MSCs) derived from rat tissues (adipose, rAT; bone marrow, rBM) were analyzed by in vitro and in vivo co-culture experiments. The insulin-producing capacities of islets transplanted under the renal kidney capsule with rAT- and rBM-MSCs were compared and the reduction of hyperglycemia symptoms in rat models was examined.MethodsMSCs prelabeled with green fluorescence protein were co-cultured with islets directly. The insulin production of cells was determined by immunostaining and ELISA. Streptozotocin-induced diabetic rat models were created and MSCs were co-transplanted with the islets under the kidney capsule to confirm the in vitro results.ResultsMSCs were differentiated into insulin-producing cells after 38 days of co-culture, confirmed by insulin and C-peptide stainings. In vivo functional studies revealed that the co-culture of islets with MSCs provided higher differentiation efficiency. The weight gain measurement and glucose tolerance test in the rat group co-transplanted of rAT-MSCs and islets indicate a better recovery than islet-alone transplants and co-transplants of islets and rBM-MSCs.ConclusionsrAT-MSCs could be considered as the cell of choice for cell-based treatment of type 1 diabetes. Because the co-transplantation of islets with MSCs increases the number of insulin-producing cells, this method was suggested for clinical applications.     

In vitro trans-differentiation of rat mesenchymal cells into insulin-producing cells by rat pancreatic extract

Recent reports have suggested that mesenchymal cells derived from bone marrow may differentiate into not only mesenchymal lineage cells but also other lineage cells. There is possibility for insulin-producing cells (IPCs) to be differentiated from mesenchymal cells. We used self-functional repair stimuli of stem cells by partial injury. Rat pancreatic extract (RPE) from the regenerating pancreas (2 days after 60% pancreatectomy) was treated to rat mesenchymal cells. After the treatment of RPE, they made clusters like islet of Langerhans within a week and expressed four pancreatic endocrine hormones; insulin, glucagon, pancreatic polypeptide, and somatostatin. Moreover, IPCs released insulin in response to normal glucose challenge. Here we demonstrate that the treatment of RPE can differentiate rat mesenchymal cells into IPCs which can be a potential source for the therapy of diabetes.     

Pancreatic Insulin-Producing Cells Differentiated from Human Embryonic Stem Cells Correct Hyperglycemia in SCID/NOD Mice,an Animal Model of Diabetes

Background

Human pancreatic islet transplantation is a prospective curative treatment for diabetes. However, the lack of donor pancreases greatly limits this approach. One approach to overcome the limited supply of donor pancreases is to generate functional islets from human embryonic stem cells (hESCs), a cell line with unlimited proliferative capacity, through rapid directed differentiation. This study investigated whether pancreatic insulin-producing cells (IPCs) differentiated from hESCs could correct hyperglycemia in severe combined immunodeficient (SCID)/non-obese diabetic (NOD) mice, an animal model of diabetes.

Methods

We generated pancreatic IPCs from two hESC lines, YT1 and YT2, using an optimized four-stage differentiation protocol in a chemically defined culture system. Then, about 5–7×10⁶ differentiated cells were transplanted into the epididymal fat pad of SCID/NOD mice (n = 20). The control group were transplanted with undifferentiated hESCs (n = 6). Graft survival and function were assessed using immunohistochemistry, and measuring serum human C-peptide and blood glucose levels.

Results

The pancreatic IPCs were generated by the four-stage differentiation protocol using hESCs. About 17.1% of differentiated cells expressed insulin, as determined by flow cytometry. These cells secreted insulin/C-peptide following glucose stimulation, similarly to adult human islets. Most of these IPCs co-expressed mature β cell-specific markers, including human C-peptide, GLUT2, PDX1, insulin, and glucagon. After implantation into the epididymal fat pad of SCID/NOD mice, the hESC-derived pancreatic IPCs corrected hyperglycemia for ≥8 weeks. None of the animals transplanted with pancreatic IPCs developed tumors during the time. The mean survival of recipients was increased by implanted IPCs as compared to implanted undifferentiated hESCs (P<0.0001).

Conclusions

The results of this study confirmed that human terminally differentiated pancreatic IPCs derived from hESCs can correct hyperglycemia in SCID/NOD mice for ≥8 weeks.     

大鼠骨骼肌卫星细胞诱导分化为胰岛素生成细胞的研究

目的探讨大鼠骨骼肌卫星细胞（MDSCs）定向诱导分化为胰岛素生成细胞（IPCs）,为1型糖尿病的干细胞治疗提供一种新的研究思路。 方法通过二次酶消化法和差速贴壁培养法分离、培养大鼠MDSCs,利用不同的诱导培养液使MDSCs定向分化为IPCs,并对诱导后细胞进行形态观察,通过双硫腙染色和免疫组化染色对MDSCs-IPCs形态进行鉴定,采用Q-PCR和Western Blot方法检测MDSCs-IPCs中C-peptide和Insulin的表达,通过胰岛素释放实验检测MDSCs-IPCs的生物学功能,β细胞和MDSCs-IPCs两组间比较采用t检验。 结果MDSCs在接种4 h后开始贴壁部分细胞伸出小的突起,48 h后绝大多数细胞贴壁呈梭形、胞浆丰富、折光度高。随着培养时间的延长,细胞的梭形形状更为明显且生长迅速。免疫组化结果显示细胞表达Desmin、α-Sarcomeric Actinin、MyoD1、Myf5和PAX7。成胰诱导后MDSCs形成胰岛样的圆形细胞团,双硫腙染色呈猩红色,Insulin免疫组化染色阳性。Q-PCR结果显示MDSCs-IPCs中C-peptide和Insulin mRNA表达量分别是β细胞的0.73倍（P > 0.05）和0.79倍（P > 0.05）。胰岛素释放实验显示,5.6 mmol/L和16.7 nmlol/L葡萄糖刺激培养2 h后,β细胞和MDSCs-IPCs分泌胰岛素量分别为[（20.3±4.2）mU/L]、[（16.1±3.7）mU/L]、[（60.5±9.3）mU/L]和[（40.9±7.3）mU/L],葡萄糖可调节MDSCs-IPCs胰岛素的分泌。 结论MDSCs易于分离培养、增殖能力强,体外可诱导分化为有功能的IPCs,适合作为再生医学的种子细胞。     

Mesenchymal stem cells: biology and clinical potential in type 1 diabetes therapy

Mesenchymal stem cells (MSCs) can be derived from adult bone marrow, fat and several foetal tissues. In vitro , MSCs have the capacity to differentiate into multiple mesodermal and non-mesodermal cell lineages. Besides, MSCs possess immunosuppressive effects by modulating the immune function of the major cell populations involved in alloantigen recognition and elimination. The intriguing biology of MSCs makes them strong candidates for cell-based therapy against various human diseases. Type 1 diabetes is caused by a cell-mediated autoimmune destruction of pancreatic β-cells. While insulin replacement remains the cornerstone treatment for type 1 diabetes, the transplantation of pancreatic islets of Langerhans provides a cure for this disorder. And yet, islet transplantation is limited by the lack of donor pancreas. Generation of insulin-producing cells (IPCs) from MSCs represents an attractive alternative. On the one hand, MSCs from pancreas, bone marrow, adipose tissue, umbilical cord blood and cord tissue have the potential to differentiate into IPCs by genetic modification and/or defined culture conditions In vitro . On the other hand, MSCs are able to serve as a cellular vehicle for the expression of human insulin gene. Moreover, protein transduction technology could offer a novel approach for generating IPCs from stem cells including MSCs. In this review, we first summarize the current knowledge on the biological characterization of MSCs. Next, we consider MSCs as surrogate β-cell source for islet transplantation, and present some basic requirements for these replacement cells. Finally, MSCs-mediated therapeutic neovascularization in type 1 diabetes is discussed.     

Hepatogenic differentiation of mesenchymal stem cells in a rat model of thioacetamide-induced liver cirrhosis

Implantation of bone-marrow-derived MSCs (mesenchymal stem cells) has emerged as a potential treatment modality for liver failure, but in vivo differentiation of MSCs into functioning hepatocytes and its therapeutic effects have not yet been determined. We investigated MSC differentiation process in a rat model of TAA (thioacetamide)-induced liver cirrhosis. Male Sprague-Dawley rats were administered 0.04% TAA-containing water for 8 weeks, MSCs were injected into the spleen for transsplenic migration into the liver, and liver tissues were examined over 3 weeks. Ingestion of TAA for 8 weeks induced micronodular liver cirrhosis in 93% of rats. Injected MSCs were diffusely engrafted in the liver parenchyma, differentiated into CK19 (cytokeratin 19)- and thy1-positive oval cells and later into albumin-producing hepatocyte-like cells. MSC engraftment rate per slice was measured as 1.0-1.6%. MSC injection resulted in apoptosis of hepatic stellate cells and resultant resolution of fibrosis, but did not cause apoptosis of hepatocytes. Injection of MSCs treated with HGF (hepatocyte growth factor) in vitro for 2 weeks, which became CD90-negative and CK18-positive, resulted in chronological advancement of hepatogenic cellular differentiation by 2 weeks and decrease in anti-fibrotic activity. Early differentiation of MSCs to progenitor oval cells and hepatocytes results in various therapeutic effects, including repair of damaged hepatocytes, intracellular glycogen restoration and resolution of fibrosis. Thus, these results support that the in vivo hepatogenic differentiation of MSCs is related to the beneficial effects of MSCs rather than the differentiated hepatocytes themselves.     

Amelioration of streptozotocin-induced diabetes in mice with cells derived from human marrow stromal cells

Background

Pluri-potent bone marrow stromal cells (MSCs) provide an attractive opportunity to generate unlimited glucose-responsive insulin-producing cells for the treatment of diabetes. We explored the potential for human MSCs (hMSCs) to be differentiated into glucose-responsive cells through a non-viral genetic reprogramming approach.

Methods and Findings

Two hMSC lines were transfected with three genes: PDX-1, NeuroD1 and Ngn3 without subsequent selection, followed by differentiation induction in vitro and transplantation into diabetic mice. Human MSCs expressed mRNAs of the archetypal stem cell markers: Sox2, Oct4, Nanog and CD34, and the endocrine cell markers: PDX-1, NeuroD1, Ngn3, and Nkx6.1. Following gene transfection and differentiation induction, hMSCs expressed insulin in vitro, but were not glucose regulated. After transplantation, hMSCs differentiated further and ∼12.5% of the grafted cells expressed insulin. The graft bearing kidneys contained mRNA of insulin and other key genes required for the functions of beta cells. Mice transplanted with manipulated hMSCs showed reduced blood glucose levels (from 18.9+/−0.75 to 7.63+/−1.63 mM). 13 of the 16 mice became normoglycaemic (6.9+/−0.64 mM), despite the failure to detect the expression of SUR1, a K⁺-ATP channel component required for regulation of insulin secretion.

Conclusions

Our data confirm that hMSCs can be induced to express insulin sufficient to reduce blood glucose in a diabetic mouse model. Our triple gene approach has created cells that seem less glucose responsive in vitro but which become more efficient after transplantation. The maturation process requires further study, particularly the in vivo factors influencing the differentiation, in order to scale up for clinical purposes.     

Differentiation of insulin-producing cells from human neural progenitor cells

BackgroundSuccess in islet-transplantation-based therapies for type 1 diabetes, coupled with a worldwide shortage of transplant-ready islets, has motivated efforts to develop renewable sources of islet-replacement tissue. Islets and neurons share features, including common developmental programs, and in some species brain neurons are the principal source of systemic insulin.Methods and FindingsHere we show that brain-derived human neural progenitor cells, exposed to a series of signals that regulate in vivo pancreatic islet development, form clusters of glucose-responsive insulin-producing cells (IPCs). During in vitro differentiation of neural progenitor cells with this novel method, genes encoding essential known in vivo regulators of pancreatic islet development were expressed. Following transplantation into immunocompromised mice, IPCs released insulin C-peptide upon glucose challenge, remained differentiated, and did not form detectable tumors.ConclusionProduction of IPCs solely through extracellular factor modulation in the absence of genetic manipulations may promote strategies to derive transplantable islet-replacement tissues from human neural progenitor cells and other types of multipotent human stem cells.