Differentiation of human embryonic stem cells into insulin-producing clusters

Serum-free medium cultivation to improve efficacy in establishment of human embryonic stem cell lines

BACKGROUND

Serum-containing and serum-free media were used to derive human embryonic stem (HES) cells from donated oocytes and embryos.

METHODS AND RESULTS

Inner cell masses (ICM) were isolated by immunosurgery. The HES cells were found to be easily obtained and expanded in a serum-free medium. The efficacy in establishing human embryonic stem cell lines improved in a serum-free medium compared with that in serum-containing media. Four HES cell lines were derived from 13 isolated ICM on mouse embryonic fibroblast feeder layers. All four cell lines possess the same characteristics and differentiating potency: normal 46, XX or 46, XY karyotype; and expressing a series of surface markers such as APase, SSEA-3, SSEA-4, TRA-1-60, TRA-1-81, but not SSEA-1. They can form embryoid bodies in suspension culture and develop teratomas comprising derivatives of three embryonic germ layers when injected into severe combined immunodeficient mice.

CONCLUSION

These preliminary results suggest that serum-free cultivation may be superior to serum-containing cultivation for deriving human embryonic stem cells.

Gene expression signatures of seven individual human embryonic stem cell lines

Identification of molecular components that define a pluripotent human embryonic stem cell (hESC) provides the basis for understanding the molecular mechanisms regulating the maintenance of pluripotency and induction of differentiation. We compared the gene expression profiles of seven genetically independent hESC lines with those of nonlineage-differentiated cells derived from each line. A total of 8,464 transcripts were expressed in all hESC lines. More than 45% of them have no yet-known biological function, which indicates that a high number of unknown factors contribute to hESC pluripotency. Among these 8,464 transcripts, 280 genes were specific for hESCs and 219 genes were more than twofold differentially expressed in all hESC lines compared with nonlineage-differentiated cells. They represent genes implicated in the maintenance of pluripotency and those involved in early differentiation. The chromosomal distribution of these hESC-enriched genes showed over-representation in chromosome 19 and under-representation in chromosome 18. Although the overall gene expression profiles of the seven hESC lines were markedly similar, each line also had a subset of differentially expressed genes reflecting their genetic variation and possibly preferential differentiation potential. Limited overlap between gene expression profiles illustrates the importance of cross-validation of results between different ESC lines.

Gastrointestinal stem cells. I. Pancreatic stem cells

The transplantation of islets isolated from donor pancreas has renewed the interest in cell therapy for the treatment of diabetes. In addition, the capacity that stem cells have to differentiate into a wide variety of cell types makes their use ideal to generate beta-cells for transplantation therapies. Several studies have reported the generation of insulin-secreting cells from embryonic and adult stem cells that normalized blood glucose values when transplanted into diabetic animal models. Finally, although much work remains to be done, there is sufficient evidence to warrant continued efforts on stem cell research to cure diabetes.

Sequestration and Synthesis: The Source of Insulin in Cell Clusters Differentiated from Murine Embryonic Stem Cells

The source of insulin released from insulin-releasing cell clusters (IRCCs) differentiated from embryonic stem cells remains unclear. Rajagopal et al. have suggested that IRCCs do not synthesize but secrete insulin that had been absorbed from media during the multistep protocol. We report here further data relevant to this controversy. No radioisotopic labeling of insulin was observed when IRCCs were incubated in a medium containing 35S-cysteine. Less than 1% of the extra-cellular stoichiometric C-peptide equivalent to insulin was secreted during glucose stimulation. However, intracellular immunostaining and immunogold labeling were both positive for C-peptide. Finally, a mass balance calculation showed that simple equilibration of IRCCs by Fickian diffusion from media accounted for at most 4% of secreted insulin. These findings and further analysis of the results of others suggest that the mechanism of insulin secretion by IRCCs is a combination of sequestration and de novo synthesis.

Genetic Engineering of Human Embryonic Stem Cells with Lentiviral Vectors

Human embryonic stem (hES) cells present a valuable source of cells with a vast therapeutic potential. However, the low efficiency of directed differentiation of hES cells remains a major obstacle in their uses for regenerative medicine. While differentiation may be controlled by the genetic manipulation, effective and efficient gene transfer into hES cells has been an elusive goal. Here, we show stable and efficient genetic manipulations of hES cells using lentiviral vectors. This method resulted in the establishment of stable gene expression without loss of pluripotency in hES cells. In addition, lentiviral vectors were effective in conveying the expression of an U6 promoter-driven small interfering RNA (siRNA), which was effective in silencing its specific target. Taken together, our results suggest that lentiviral gene delivery holds great promise for hES cell research and application.

Differentiation of embryonic stem cells into insulin-producing cells promoted by Nkx2.2 gene transfer

AIM: To investigate the ability of a genetically altered embryonic stem (ES) cell line to generate insulin-producing cells in vitro following transfer of the Nkx2.2 gene.

METHODS: Hamster Nkx2.2 genes were transferred into mouse ES cells. Parental and Nkx2.2-transfected ES cells were initiated toward differentiation in embryoid body (EB) culture for 5 d and the resulting EBs were transferred to an attached culture system. Dithizone (DTZ), a zinc-chelating agent known to selectively stain pancreatic beta cells, was used to detect insulin-producing cells. The outgrowths were incubated in DTZ solution (final concentration, 100 μg/mL) for 15 min before being examined microscopically. Gene expression of the endocrine pancreatic markers was also analyzed by RT-PCR. In addition, insulin production was determined immunohistochemically and its secretion was examined using an ELISA.

RESULTS: DTZ-stained cellular clusters appeared after approximately 14 d in the culture of Nkx2.2-transfected ES cells (Nkx-ES cells), which was as much as 2 wk earlier, than those in the culture of parental ES cells (wt-ES). The frequency of DTZ-positive cells among total cultured cells on day 28 accounted for approximately 1.0% and 0.1% of the Nkx-ES- and wt-ES-derived EB outgrowths, respectively. The DTZ-positive cellular clusters were found to be immunoreactive to insulin, while the gene expressions of pancreatic-duodenal homeobox 1 (PDX1), proinsulin 1 and proinsulin 2 were observed in the cultures that contained DTZ-positive cellular clusters. Insulin secretion was also confirmed by ELISA, whereas glucose-dependent secretion was not demonstrated.

CONCLUSION: Nkx2.2-transfected ES cells showed an ability to differentiate into insulin-producing cells.

Transdifferentiation of Stem Cells in Pancreatic Cells: State of the Art

Among the different approaches for diabetes mellitus-pancreas and pancreatic islet transplantation-the use of stem cells represent a renewable alternative source of insulin-producing cells. Stem cells capable of differentiating into beta-like cells can be isolated namely from embryonic cells, bone marrow, and umbilical cord blood, but also from adult organs such as pancreas, liver, and spleen. Several studies have demonstrated that by manipulating culture conditions and using growth and transcription factors of beta-cell lineage (in particular pdx-1 and pax4), embryonic stem cells can differentiate in vitro after formation of embryoid bodies. Bone marrow stem cells can give rise to mesenchymal; endodermal-, and ectodermal-derived cells. In vivo it has been shown that after bone marrow transplantation, using a murine sex-mismatched model, insulin-producing cells expressing the Y chromosome can be detected in the donor pancreas, although not in a significantly number. Cells characterized by a group of markers (Nestin, CK-8, CK-18) and transcription factors (Isl-1, Pdx-1, Pax-4, Ngn-3) important for beta-cell differentiation have been detected in umbilical cord blood. The recent evidence of the possibility to transdifferentiate stem cells to beta cells encourages further studies in animal models to exhaustively determine the differentiation pathways of stem cells to insulin producing cells. These findings might open the way to a successful human investigation.

Stem-cell therapy for hepatobiliary pancreatic disease

The transplantation of pancreatic beta cells or hepatocytes represents a potential therapeutic approach for type I diabetes and inherited liver diseases, respectively. Furthermore, acquired liver diseases, particularly acute hepatic failure due to toxic or viral injury, have been treated in limited clinical trials with fetal and adult hepatocytes. However, a major limitation is the insufficient amount of beta cells and hepatocytes available for grafts. Alternative sources of these cells have yet to be determined. During the past few years, progress has been made in the development of new strategies to produce mature beta cells and hepatocytes. In this review, we outline the current state of scientific understanding and controversy regarding the properties of embryonic and adult stem cells in the field of hepatobiliary and pancreatic diseases. Our objective is to provide a framework of understanding for the challenges behind translating fundamental stem cell biology into clinical therapies.

Characterization and culture of human embryonic stem cells

Human embryonic stem cells have been defined as self-renewing cells that can give rise to many types of cells of the body. How and whether these cells can be manipulated to replace cells in diseased tissues, used to screen drugs and toxins, or studied to better understand normal development, however, depends on knowing more about their fundamental properties. Many different human embryonic stem cell lines--which are pluripotent, proliferate indefinitely in vitro and maintain a normal, euploid karyotype over extended culture--have now been derived, but whether these cell lines are in fact equivalent remains unclear. It will therefore be important to define robust criteria for the assessment of both existing and newly derived cell lines and for the validation of new culture conditions.

Perfusion cultures of human embryonic stem cells

Human embryonic stem cells (hESC) are self-renewing pluripotent cells capable of differentiating into cells representative of all three embryonic germ layers. Hence, they hold great potential for regenerative medicine. However, significant cell numbers are required to fulfill their potential therapeutic applications. In this study, perfusion with supplemented conditioned media (SCM), produced by mouse embryonic fibroblasts (MEF), was adopted to improve cell densities of hESC cultures. Perfusion enhanced hESC numbers by 70% compared to static conditions, on both organ culture dish (OCD) and petri dish cultures. All cultures maintained healthy expression of the pluripotent marker, Oct-4 transcription factor. In vivo, perfused hESC formed teratomas in severe combined immunodeficiency (SCID) mice models that represent the three embryonic germ layers. When SCM was produced with lower concentrations of MEF, hESC densities and Oct-4 levels were reduced. Hence, perfusion with SCM is a potential feeding method for scale-up production of hESC.

In search of endocrine progenitor/stem cells in the human pancreas

Motives to isolate endocrine precursor cells vary between clinical and basic research needs. In our case, the object has been to identify cell populations that could be used for cell replacement in situations of beta-cell deficiency, such as type 1 diabetes. Initially, as was the case with most laboratories oriented toward translational islet research, experimentation was geared more toward cell replication than to the identification and isolation of putative endocrine cell precursors.

Embryonic stem cells and islet replacement in diabetes mellitus

Transplantation of functional islets of Langerhans may emerge as a useful therapy for some patients with type 1 diabetes mellitus (DM), but donor islet shortages motivate the search for new sources of transplantable islets. Pluripotent embryonic stem (ES) cells are expandable in culture and have the potential to give rise to all cell types in the body. The recent isolation of pluripotent ES cells from humans has generated excitement over the possibility of engineering glucose-responsive islet replacement tissue from these cells in large quantities. In this study, we review the recent advances in generating insulin-producing cells (IPC) from mouse and human ES (hES) cells.

Induction of Stable Mixed Chimerism by Embryonic Stem Cells Requires Functional Fas/FasL Engagement

BACKGROUND

Recent data show the efficacy of embryonic stem cells (ESC) to engraft in allogeneic recipients without host pretreatment. This property is due to their low expression of major histocompatibility complex (MHC) class I antigens and lack of MHC class II expression. Here, we tested the hypothesis that the constitutive FasL expression by ESC is a requirement for their stable engraftment in allogeneic recipients.

METHODS

MRL and MRL-lpr/lpr mice (H-2k) were infused allogeneic 129SvJ RW-4 (H-2b) ESC without host preconditioning. The development of mixed chimerism was monitored over 100 days by flow cytometry.

RESULTS

Mixed chimerism was detectable by day 7. The amount of donor cells detected varied between 3-5.5% and were lymphoid, but nonmyeloid. Only 50% of lpr/lpr mice engrafted and lost donor cells by day 28 post-ESC infusion. In contrast, >80% wild type mice engrafted and maintained mixed chimerism up to day 100.

CONCLUSIONS

These data suggest a critical role for Fas-FasL engagement in ESC engraftment. We conclude that ESC may induce clonal deletion of alloreactive T cells by Fas-induced apoptosis in recipient T cells, protecting them from rejection. The data provide a rationale for improved protocols for the achievement of robust ESC-induced mixed chimerism.

Embryonic stem cells: prospects for developmental biology and cell therapy

Stem cells represent natural units of embryonic development and tissue regeneration. Embryonic stem (ES) cells, in particular, possess a nearly unlimited self-renewal capacity and developmental potential to differentiate into virtually any cell type of an organism. Mouse ES cells, which are established as permanent cell lines from early embryos, can be regarded as a versatile biological system that has led to major advances in cell and developmental biology. Human ES cell lines, which have recently been derived, may additionally serve as an unlimited source of cells for regenerative medicine. Before therapeutic applications can be realized, important problems must be resolved. Ethical issues surround the derivation of human ES cells from in vitro fertilized blastocysts. Current techniques for directed differentiation into somatic cell populations remain inefficient and yield heterogeneous cell populations. Transplanted ES cell progeny may not function normally in organs, might retain tumorigenic potential, and could be rejected immunologically. The number of human ES cell lines available for research may also be insufficient to adequately determine their therapeutic potential. Recent molecular and cellular advances with mouse ES cells, however, portend the successful use of these cells in therapeutics. This review therefore focuses both on mouse and human ES cells with respect to in vitro propagation and differentiation as well as their use in basic cell and developmental biology and toxicology and presents prospects for human ES cells in tissue regeneration and transplantation.

Differentiation of insulin-producing cells from human neural progenitor cells

BACKGROUND

Success 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 FINDINGS

Here 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.

CONCLUSION

Production 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.

Effect of human umbilical cord blood cells on glycemia and insulitis in type 1 diabetic mice

Several studies have shown that transplantation of embryonic stem cells into diabetic animals either improved or normalized blood glucose levels. In this study, we examined the dose-dependent effect of early (prediabetic stage) intravenous administration of human umbilical cord blood (HUCB) mononuclear cells on blood glucose levels, survival, and insulitis in nonobese diabetic (NOD) mice with autoimmune type 1 diabetes. The results show that mice treated with HUCB cells significantly lowered their blood glucose levels and increased their lifespan, as compared with untreated mice. Also, a significant reduction in insulitis was observed in treated than in untreated mice. The mice that received the highest dosage (200 x 10(6)) of cells had greater reduction in blood glucose levels and the degree of insulitis than the mice that received lower dosage (100-150 x 10(6)) of cells. Prolonged lifespan in the former group of mice seems to be related to better control of blood glucose levels. Thus, administration of HUCB cells in the prediabetic stage without any immunosuppression improves type 1 diabetes by protecting the islets from insulitis in NOD mice.

Human embryonic stem cells: possibilities for human cell transplantation

Human embryonic stem (ES) cells serve as a potentially unlimited renewable source for cell transplantation targeted to treat several diseases. One advantage of embryonic stem (ES) cells over other stem cells under research is their apparently indefinite self-renewal capacity if cultured appropriately, and their ready differentiation into various cell phenotypes of all three germ layers. To date, a number of studies have reported the derivation of specific functional derivatives from human ES cells in vitro. While there have been clinical trials of human embryonal carcinoma (EC) cell-derived neurons in humans there has been no attempt as yet using human ES cell derivatives. However, the latter have been transplanted into recipient animals. In some cases ES-derived cells were shown to undergo further maturation, displayed integration with host tissue and even ameliorated the disease condition in the animal model. Recently, it has been reported that human ES cells can be genetically manipulated. Such procedures could be used to direct differentiation to a specific cell type or to reduce graft rejections by the modification of immune responses. This review highlights some of the recent advances in the field and the challenges that lie ahead before clinical trials using ES-derived cells can be contemplated.

Stem cells in the treatment of diabetes

Clinical islet transplantation trials based on cadaveric allogenic islets have demonstrated that it is indeed possible to restore near-physiological insulin secretion capacity in a type 1 diabetic patient through transplantation of insulin-producing cells. In order to develop this form of therapy to become available for the vast majority of patients with diabetes, new sources of transplantable insulin-producing cells need to be identified. Stem cells provide the best potential to achieve this goal. Controversial results have been presented concerning the existence and nature of pancreatic islet stem or precursor cells. An increasing body of evidence suggests that the pancreatic and hepatic cell types (hepatocytes, islet, acinar and ductal cells) have remarkable plasticity and can de- and trans-differentiate into each other under appropriate conditions. Elucidation of the molecular mechanisms regulating these processes could lead to clinically applicable ways of either inducing pancreatic islet regeneration in situ or to expanding the insulin-producing cells in vitro for transplantation. The emergence of human embryonic stem cells has led to an active area of research aiming to achieve targeted differentiation of these cells into a safely transplantable beta-like cell. After initial excitement, it appears that much basic research is still required before this goal could be achieved.

The promise of human embryonic stem cells

Pluripotency refers to the ability of a cell to give rise to cells that originate from all three germ layers. Among the available human pluripotent cells, human embryonic stem cells (hESCs) are considered to have the greatest probability for practical clinical application because of their simple propagation and stability in culture. Since their first derivation, issues concerning hESC maintenance and self-renewal have been widely addressed. The first part of this review presents the accumulated knowledge concerning the self-renewal of hESCs and discusses recent genetic profile data, which seem to shed light on hESC self-renewal and pluripotency mechanism. The second part deals with the regenerative potential of hESCs. Available lineage-specific differentiations of hESCs are presented, with detailed data on the ability of hESCs to differentiate into trophoblast cells, an observation that might broaden the definition of their developmental potential. Specific focus is given to vascular cell differentiation, including endothelial and smooth muscle cells. Transplantation limitations as well as current steps taken toward resolution conclude the review.

Gene Therapy Progress and Prospects: Gene therapy for diabetes mellitus

Diabetes mellitus has long been targeted, as yet unsuccessfully, as being curable with gene therapy. The main hurdles have not only been vector-related toxicity but also the lack of physiological regulation of the expressed insulin. Recent advances in understanding the developmental biology of beta-cells and the transcriptional cascade that drives it have enabled both in vivo and ex vivo gene therapy combined with cell therapy to be used in animal models of diabetes with success. The associated developments in the stem cell biology and immunology have opened up further opportunities for gene therapy to be applied to target autoimmune diabetes.

Stem-cell therapy for diabetes mellitus

CONTEXT

Curative therapy for diabetes mellitus mainly implies replacement of functional insulin-producing pancreatic beta cells, with pancreas or islet-cell transplants. However, shortage of donor organs spurs research into alternative means of generating beta cells from islet expansion, encapsulated islet xenografts, human islet cell-lines, and stem cells. Stem-cell therapy here implies the replacement of diseased or lost cells from progeny of pluripotent or multipotent cells. Both embryonic stem cells (derived from the inner cell mass of a blastocyst) and adult stem cells (found in the postnatal organism) have been used to generate surrogate beta cells or otherwise restore beta-cell functioning.

STARTING POINT

Recently, Andreas Lechner and colleagues failed to see transdifferentiation into pancreatic beta cells after transplantation of bone-marrow cells into mice (Diabetes 2004; 53: 616-23). Last year, Jayaraj Rajagopal and colleagues failed to derive beta cells from embryonic stem cells (Science 2003; 299: 363). However, others have seen such effects. WHERE NEXT? As in every emerging field in biology, early reports seem confusing and conflicting. Embryonic and adult stem cells are potential sources for beta-cell replacement and merit further scientific investigation. Discrepancies between different results need to be reconciled. Fundamental processes in determining the differentiation pathways of stem cells remain to be elucidated, so that rigorous and reliable differentiation protocols can be established. Encouraging studies in rodent models may ultimately set the stage for large-animal studies and translational investigation.