Insulin - producing cells derived from stem cells: recent progress and future directions

Type 1 diabetes is characterized by the selective destruction of pancreatic beta-cells caused by an autoimmune attack. Type 2 diabetes is a more complex pathology which, in addition to beta-cell loss caused by apoptotic programs, includes beta-cell dedifferentiation and peripheric insulin resistance. beta-Cells are responsible for insulin production, storage and secretion in accordance to the demanding concentrations of glucose and fatty acids. The absence of insulin results in death and therefore diabetic patients require daily injections of the hormone for survival. However, they cannot avoid the appearance of secondary complications affecting the peripheral nerves as well as the eyes, kidneys and cardiovascular system. These afflictions are caused by the fact that external insulin injection does not mimic the tight control that pancreatic-derived insulin secretion exerts on the body's glycemia. Restoration of damaged beta-cells by transplantation from exogenous sources or by endocrine pancreas regeneration would be ideal therapeutic options. In this context, stem cells of both embryonic and adult origin (including beta-cell/islet progenitors) offer some interesting alternatives, taking into account the recent data indicating that these cells could be the building blocks from which insulin secreting cells could be generated in vitro under appropriate culture conditions. Although in many cases insulin-producing cells derived from stem cells have been shown to reverse experimentally induced diabetes in animal models, several concerns need to be solved before finding a definite medical application. These refer mainly to the obtainment of a cell population as similar as possible to pancreatic beta-cells, and to the problems related with the immune compatibility and tumor formation. This review will summarize the different approaches that have been used to obtain insulin-producing cells from embryonic and adult stem cells, and the main problems that hamper the clinical applications of this technology.

[Atypical pigmented penile macules]

Two patients with pigmented lesions of the penis are described. The lesions consisted of asymptomatic, multifocal, irregular macules, with variegated pigmentation. The main differential diagnostic problem was with mucocutaneous melanoma. Histologic examination of the lesions showed basal layer hyperpigmentation. No cytologic atypia of melanocytes was detectable. The diagnosis in both cases was melanotic macules. Because of their atypical clinical appearance, genital melanotic macules are often misinterpreted as mucocutaneous melanoma. However histopathologic study solves the problem because genital melanotic macules show no melanocytic proliferation nor melanocytic atypia.

Therapeutic potential of stem cells in diabetes

Stem cells possess the ability to self-renew by symmetric divisions and, under certain circumstances, differentiate to a committed lineage by asymmetric cell divisions. Depending on the origin, stem cells are classified as either embryonic or adult. Embryonic stem cells are obtained from the inner cell mass of the blastocyst, a structure that appears during embryonic development at day 6 in humans and day 3.5 in mice. Adult stem cells are present within tissues of adult organisms and are responsible for cell turnover or repopulation of tissues under normal or exceptional circumstances. Taken together, stem cells might represent a potential source of tissues for cell therapy protocols, and diabetes is a candidate disease that may benefit from cell replacement protocols. The pathology of type 1 diabetes is caused by the autoimmune destruction or malfunction of pancreatic beta cells, and consequently, a lack of insulin. The absence of insulin is life-threatening, thus requiring diabetic patients to take daily hormone injections from exogenous sources; however, insulin injections do not adequately mimic beta cell function. This results in the development of diabetic complications such as neuropathy, nephropathy, retinopathy and diverse cardiovascular disorders. This chapter intends to summarize the possibilities opened by embryonic and adult stem cells in regenerative medicine for the cure of diabetes.

From stem cells to insulin-producing cells: towards a bioartificial endocrine pancreas

The total absence or low production of insulin by beta-cells avoids a proper control of glycemia forcing diabetic people to daily insulin injection for survival. Islet transplantation represents a hallmark in the cure of diabetes and has been successfully applied to more than 400 patients, resulting in insulin independency for periods longer than 4 years. However, transplantation trials for diabetes have to face the scarcity of islets from cadaveric donors. Therefore, the finding of renewable sources of cells could circumvent this problem. In this respect, embryonic or adult stem cells are representing an interesting alternative. Stem cells display robust proliferation and the plasticity to differentiate to other cell types, including insulin-containing cells. The current therapeutical use in the future of bioengineered insulin-secreting cells derived from stem cells needs at present to fulfill several criteria. These criteria concern to the type of stem cell to be used as starting biomaterial (embryonic or adult), the in vitro differentiation protocol applied, the functional phenotype reached for the final cell product and the transplantation associated problems (likely immune rejection and tumor formation). This review will try to focus on these different aspects in order to emphasize in the key points to consider for designing unified strategies for diabetes cell therapy.

Treatment outcome in Turner syndrome

Short stature is an almost universal feature of Turner Syndrome (TS) with patients having a mean adult height up to 20 cm less than that of the general female population. As a result a significant focus of medical management in TS is on growth promoting strategies. The aim of this study was to assess factors influencing final height in those with TS and evaluate the response to various treatments. A retrospective study was performed in 2 Dublin centres. The age of commencement, cessation, dose and duration of treatment was calculated for growth hormone, oestrogen and oxandrolone, either alone or in combination. Additional factors known to influence growth in TS were also examined. The mean final height achieved was 147.31 cm (SD 4.77), the mean predicted height was 142.81 (SD 5.63). Height gain was 4.28 cm (SD 4.93). All patients received growth hormone. 75% of patients received oestrogen and 35% received oxandrolone. The maximal height gain of 6.71 cm (SD 2.43) in the triple therapy group. Parental height was found to have a significant correlation with final height (r=0.591). Spontaneous menarche in TS was associated with a poor adult height (r=-0.522), mean height 144.03 cm (SD 3.23) whereas those with induced menarche had a mean height of 148.43 cm (SD 4.67). Growth hormone therapy improves the mean final height in TS. However, the degree of height gain is influenced by confounding variables of parental height and age and tempo of puberty and treatment variables.

Bio-engineering inslulin-secreting cells from embryonic stem cells: a review of progress

According to the Edmonton protocol, human islet transplantation can result in insulin independency for periods longer than 3 years. However, this therapy for type 1 diabetes is limited by the scarcity of cadaveric donors. Owing to the ability of embryonic stem cells to expand in vitro and differentiate into a variety of cell types, research has focused on ways to manipulate these cells to overcome this problem. It has been demonstrated that mouse embryonic stem cells can differentiate into insulin-containing cells, restoring normoglycaemia in diabetic mice. To this end, mouse embryonic stem cells were transfected with a DNA construct that provides resistance to neomycin under the control of the regulatory regions of the human insulin gene. However, this protocol has a very low efficiency, needing improvements for this technology to be transferred to human stem cells. Optimum protocols will be instrumental in the production of an unlimited source of cells that synthesise, store and release insulin in a physiological manner. The review focuses on the alternative source of tissue offered by embryonic stem cells for regenerative medicine in diabetes and some key points that should be considered in order for a definitive protocol for in vitro differentiation to be established.

Evidence for a monomeric structure of nonribosomal Peptide synthetases

Nonribosomal peptide synthetases (NRPS) are multimodular biocatalysts that bacteria and fungi use to assemble many complex peptides with broad biological activities. The same modular enzymatic assembly line principles are found in fatty acid synthases (FAS), polyketide synthases (PKS), and most recently in hybrid NRPS/PKS multienzymes. FAS as well as PKS are known to function as homodimeric enzyme complexes, raising the question of whether NRPS may also act as homodimers. To test this hypothesis, biophysical methods (size exclusion chromatography, analytical equilibrium ultracentrifugation, and chemical crosslinking) and biochemical methods (two-affinity-tag-system and complementation studies with enzymes being inactivated in different catalytic domains) were applied to NRPS subunits from the gramicidin S (GrsA-ATE), tyrocidine (TycB(1)-CAT and TycB(2-3)-AT.CATE), and enterobactin (EntF-CATTe) biosynthetic systems. These methods had revealed the dimeric structure of FAS and PKS previously, but all three NRPS systems investigated are functionally active as monomers.

Fine-scale mapping of a locus for severe bipolar mood disorder on chromosome 18p11.3 in the Costa Rican population

We have searched for genes predisposing to bipolar disorder (BP) by studying individuals with the most extreme form of the affected phenotype, BP-I, ascertained from the genetically isolated population of the Central Valley of Costa Rica (CVCR). The results of a previous linkage analysis on two extended CVCR BP-I pedigrees, CR001 and CR004, and of linkage disequilibrium (LD) analyses of a CVCR population sample of BP-I patients implicated a candidate region on 18p11.3. We further investigated this region by creating a physical map and developing 4 new microsatellite and 26 single-nucleotide polymorphism markers for typing in the pedigree and population samples. We report the results of fine-scale association analyses in the population sample, as well as evaluation of haplotypes in pedigree CR001. Our results suggest a candidate region containing six genes but also highlight the complexities of LD mapping of common disorders.

Genome screening for linkage disequilibrium in a Costa Rican sample of patients with bipolar-I disorder: a follow-up study on chromosome 18

Linkage disequilibrium (LD) methods offer great promise for mapping complex traits, but have thus far been applied sparingly. In this paper we describe an LD mapping study of severe bipolar disorder (BP-I) in the genetically isolated population of the Central Valley of Costa Rica. This study provides the first complete screen of a chromosome for a complex trait using LD mapping and presents the first application of a new LD mapping statistic (ancestral haplotype reconstruction (AHR)) that evaluates haplotype sharing among affected individuals. The results of this chromosome-wide analysis are instructive for genome-wide LD mapping in isolated populations. Furthermore, the analysis continues to support a possible BP-I locus on 18pter, suggested by previous analyses in this population. Evidence for a possible BP-I locus on 18q12.2 is also described.

Glucose down-regulates the expression of the peroxisome proliferator-activated receptor-alpha gene in the pancreatic beta -cell

To better understand the action of glucose on fatty acid metabolism in the beta-cell and the link between chronically elevated glucose or fatty acids and beta-cell decompensation in adipogenic diabetes, we investigated whether glucose regulates peroxisomal proliferator-activated receptor (PPAR) gene expression in the beta-cell. Islets or INS(832/13) beta-cells exposed to high glucose show a 60-80% reduction in PPARalpha mRNA expression. Oleate, either in the absence or presence of glucose, has no effect. The action of glucose is dose-dependent in the 6-20 mm range and maximal after 6 h. Glucose also causes quantitatively similar reductions in PPARalpha protein and DNA binding activity of this transcription factor. The effect of glucose is blocked by the glucokinase inhibitor mannoheptulose, is partially mimicked by 2-deoxyglucose, and is not blocked by the 3-O-methyl or the 6-deoxy analogues of the sugar that are not phosphorylated. Chronic elevated glucose reduces the expression levels of the PPAR target genes, uncoupling protein 2 and acyl-CoA oxidase, which are involved in fat oxidation and lipid detoxification. A 3-day exposure of INS-1 cells to elevated glucose results in a permanent rise in malonyl-CoA, the inhibition of fat oxidation, and the promotion of fatty acid esterification processes and causes elevated insulin secretion at low glucose. The results suggest that a reduction in PPARalpha gene expression together with a rise in malonyl-CoA plays a role in the coordinated adaptation of beta-cell glucose and lipid metabolism to hyperglycemia and may be implicated in the mechanism of beta-cell "glucolipotoxicity."

Mapping of the locus for cholestasis-lymphedema syndrome (Aagenaes syndrome) to a 6.6-cM interval on chromosome 15q

Patients with cholestasis-lymphedema syndrome (CLS) suffer severe neonatal cholestasis that usually lessens during early childhood and becomes episodic; they also develop chronic severe lymphedema. The genetic cause of CLS is unknown. We performed a genome screen, using DNA from eight Norwegian patients with CLS and from seven unaffected relatives, all from an extended pedigree. Regions potentially shared identical by descent in patients were further characterized in a larger set of Norwegian patients. The patients manifest extensive allele and haplotype sharing over the 6.6-cM D15S979-D15S652 region: 30 (83.3%) of 36 chromosomes of affected individuals carry a six-marker haplotype not found on any of the 32 nontransmitted parental chromosomes. All Norwegian patients with CLS are likely homozygous for the same disease mutation, inherited from a shared ancestor.

Lipopolysaccharide inhibits long term potentiation in the rat dentate gyrus by activating caspase-1

Lipopolysaccharide, a component of the cell wall of Gram-negative bacteria, may be responsible for at least some of the pathophysiological sequelae of bacterial infections, probably by inducing an increase in interleukin-1beta (IL-1beta) concentration. We report that intraperitoneal injection of lipopolysaccharide increased hippocampal caspase-1 activity and IL-1beta concentration; these changes were associated with increased activity of the stress-activated kinase c-Jun NH(2)-terminal kinase, decreased glutamate release, and impaired long term potentiation. The degenerative changes in hippocampus and entorhinal cortical neurones were consistent with apoptosis because translocation of cytochrome c and poly(ADP-ribose) polymerase cleavage were increased. Inhibition of caspase-1 blocked these changes, suggesting that IL-1beta mediated the lipopolysaccharide-induced changes.

Nutrient toxicity in pancreatic beta-cell dysfunction

Nutrients, such as glucose and fatty acids, have a dual effect on pancreatic beta-cell function. Acute administration of high glucose concentrations to pancreatic beta-cells stimulates insulin secretion. In addition, short term exposure of this cell type to dietary fatty acids potentiates glucose-induced insulin release. On the other hand, long-term exposure to these nutrients causes impaired insulin secretion, characterized by elevated exocytosis at low concentrations of glucose and no response when glucose increases in the extracellular medium. In addition, other phenotypic changes are observed in these conditions. One major step in linking these phenotypic changes to the diabetic pathology has been the recognition of both glucose and fatty acids as key modulators of beta-cell gene expression. This could explain the adaptative response of the cell to sustained nutrient concentration. Once this phase is exhausted, the beta-cell becomes progressively unresponsive to glucose and this alteration is accompanied by the irreversible induction of apoptotic programs. The aim of this review is to present actual data concerning the development of the toxicity to the main nutrients glucose and fatty acids in the pancreatic beta-cell and to find a possible link to the development of type 2 diabetes.

Immunohistochemical analyses of focal adhesion kinase expression in benign and malignant human breast and colon tissues: correlation with preinvasive and invasive phenotypes

The focal adhesion kinase (FAK) is a protein tyrosine kinase linked to signaling events between cells and the extracellular matrix. Studies at the Western blot level have demonstrated up-regulation of FAK expression in invasive breast and colon cancers. To assess p125FAK expression at the cellular level, we developed monoclonal antibodies that specifically detected FAK in formalin-fixed, paraffin-embedded tissue sections and analyzed the levels of FAK expression in human breast and colon tissues. Monoclonal antibody 4.47 demonstrated FAK-specific focal adhesion staining by immunofluorescence assays on BT-474 breast cancer cells and detected a Mr 125,000 protein by both Western blotting and immunoprecipitation analyses. Using immunohistochemical techniques, the expression of p125FAK was analyzed in 36 normal and 43 preinvasive or invasive human breast and colon tissues from individual patients. FAK was weakly expressed in most benign breast epithelium but was up-regulated at moderate or strong levels in 14 of 18 invasive breast carcinomas. In seven samples of ductal carcinoma-in situ, FAK was overexpressed. Borderline-to-weak expression of FAK was detected in the normal colonic epithelium. In the invasive colon cancers, FAK was overexpressed at moderate or strong levels in 13 of 15 tumors. Furthermore, FAK expression was up-regulated in areas of dysplastic, premalignant colon epithelium. These results provide the first evidence at the cellular level that FAK expression is variably overexpressed in breast and colon cancer and suggest that up-regulation occurs at an early stage of tumorigenesis.

A minimalist approach to gene mapping: locating the gene for acheiropodia, by homozygosity analysis

Acheiropodia is an autosomal recessive disease that results in hemimelia (lack of formation of the distal extremities). We performed a complete genome screen of seven members of an extended pedigree that included three siblings with acheiropodia. Homozygosity mapping was used to identify regions most likely to harbor the gene for acheiropodia in this pedigree. In these two key regions (14p and 7q), further genotyping of one additional affected member of this pedigree plus seven additional unaffected siblings provided evidence, through linkage analysis, that the 7q36 region contains the acheiropodia gene. In this region, a maximum two-point LOD score of 3.81 (4.2 with multipoint analysis) was achieved, and a homozygous haplotype spanning a region of 11.7 cM was seen in all affected in this pedigree. Finally, genotypic analysis of two additional cases of acheiropodia with no known relation to the other samples revealed homozygous sharing of a portion of the same haplotype on 7q36, which reduces the chromosomal location of the acheiropodia gene to an 8.6-cM region. Localization of this gene, at the screening level, by use of data from only three affected subjects, provides an example of how certain genes may be mapped by use of a minimal number of affected cases.

Engineering pancreatic islets

Pancreatic islets are neuroendocrine organs that control blood glucose homeostasis. The precise interplay of a heterogeneous group of cell populations (beta, alpha, delta and PP cells) results in the fine-tuned release of counterbalanced hormones (insulin, glucagon, somatostatin and pancreatic polypeptide respectively). Under the premises of detailed knowledge of the physiological basis underlying this behaviour, two lines of investigation might be inferred: generating computational and operational models to explain and predict this behaviour and engineering islet cells to reconstruct pancreatic endocrine function. Whilst the former is being fuelled by new computational strategies, giving biophysicists the possibility of modelling a system in which new "emergent" properties appear, the latter is benefiting from the useful tools and strategic knowledge achieved by molecular, cell and developmental biologists. This includes using tumour cell lines, engineering islet cell precursors, knowledge of the mechanisms of differentiation, regeneration and growth and, finally, therapeutic cloning of human tissues. Gaining deep physiological understanding of the basis governing these processes is instrumental for engineering new pancreatic islets.

Insulin-secreting cells derived from embryonic stem cells normalize glycemia in streptozotocin-induced diabetic mice

Embryonic stem (ES) cells display the ability to differentiate in vitro into a variety of cell lineages. Using a cell-trapping system, we have obtained an insulin-secreting cell clone from undifferentiated ES cells. The construction used allows the expression of a neomycin selection system under the control of the regulatory regions of the human insulin gene. The chimeric gene also contained a hygromycin resistance gene (pGK-hygro) to select transfected cells. A resulting clone (IB/3x-99) containing 16.5 ng/microg protein of total insulin displays regulated hormone secretion in vitro in the presence of various secretagogues. Clusters obtained from this clone were implanted (1 x 10(6) cells) in the spleen of streptozotocin-induced diabetic animals. Transplanted animals correct hyperglycemia within 1 week and restore body weight in 4 weeks. Whereas an intraperitoneal glucose tolerance test showed a slower recovery in transplanted versus control mice, blood glucose normalization after a challenge meal was similar. This approach opens new possibilities for tissue transplantation in the treatment of type 1 and type 2 diabetes and offers an alternative to gene therapy.

Palmitate and oleate induce the immediate-early response genes c-fos and nur-77 in the pancreatic beta-cell line INS-1

To better understand the link between fatty acid signaling and the pleiotropic effects of fatty acids in the pancreatic beta-cell, we investigated whether fatty acids regulate immediate-early response genes (IEGs) coding for transcription factors implicated in cell proliferation, differentiation, and apoptosis. Palmitate and oleate, but not long-chain polyunsaturated fatty acids, caused a pronounced accumulation of c-fos and nur-77 mRNAs in beta-cells (INS cells) to an extent similar to that produced by the protein kinase C (PKC) activator phorbol myristate acetate (PMA). The effect was dose dependent and occurred at concentrations between 0.1 and 0.5 mmol/l in the presence of 0.5% albumin. The action of the fatty acid occurred at the transcriptional level, and the mRNA accumulation displayed a bell-shaped kinetics with a maximal effect at 1 h. 2-Bromopalmitate was ineffective, indicating that fatty acids must be metabolized to cause their effect. Neither fatty acid was able to induce c-fos and nur-77 in PKC-downregulated cells or cells incubated in the presence of the Ca2+ channel blocker nifedipine or the Ca2+ chelator EGTA, suggesting involvement of the PKC and Ca2+ signaling pathways. Palmitate and oleate also increased c-fos protein expression and DNA binding activity of the transcription factor AP-1. Oleate, but not palmitate, increased [3H]thymidine incorporation in INS cells. Finally, both palmitate and oleate caused c-fos and nur-77 mRNA accumulation in isolated rat islets. It is suggested that IEG induction by the most abundant circulating fatty acids plays a role in the adaptive process of the beta-cell to hyperlipidemia. These results have implications for our understanding of obesity-associated diabetes and the link between fatty acids and tumorigenesis.

Lipid rather than glucose metabolism is implicated in altered insulin secretion caused by oleate in INS-1 cells

A comprehensive metabolic study was carried out to understand how chronic exposure of pancreatic beta-cells to fatty acids causes high basal secretion and impairs glucose-induced insulin release. INS-1 beta-cells were exposed to 0.4 mM oleate for 3 days and subsequently incubated at 5 or 25 mM glucose, after which various parameters were measured. Chronic oleate promoted triglyceride deposition, increased fatty acid oxidation and esterification, and reduced malonyl-CoA at low glucose in association with elevated basal O(2) consumption and redox state. Oleate caused a modest (25%) reduction in glucose oxidation but did not affect glucose usage, the glucose 6-phosphate and citrate contents, and the activity of pyruvate dehydrogenase of INS-1 cells. Thus changes in glucose metabolism and a Randle-glucose/fatty acid cycle do not explain the altered secretory properties of beta-cells exposed to fatty acids. The main response of INS-1 cells to chronic oleate, which is to increase the oxidation and esterification of fatty acids, may contribute to cause high basal insulin secretion via increased production of reducing equivalents and/or the generation of complex lipid messenger molecule(s).

Glucose and glucoincretin peptides synergize to induce c-fos, c-jun, junB, zif-268, and nur-77 gene expression in pancreatic beta(INS-1) cells

To link glucose signaling to its long-term pleiotropic effects in the pancreatic beta-cell, we have investigated whether glucose regulates immediate-early response genes (IEGs) coding for transcription factors implicated in cell proliferation and differentiation. Glucose causes a coordinated transcriptional activation of the IEGs c-fos, c-jun, JunB, zif-268, and nur-77 in the pancreatic beta-cell line INS-1. This activation is entirely dependent on the presence of the cell-permeant cAMP analog chlorophenylthio-cAMP, which has only a modest effect by itself. The accumulation of c-fos, JunB, and nur-77 mRNA occurs at physiological concentrations of glucose (3 to 11 mM), requires a 1-2 h period, and is mimicked by other nutrient stimuli including mannose, leucine plus glutamine, and pyruvate. Glucose is synergistic with the glucoincretin peptides GLP-1 and PACAP-38, whereas these neurohormonal agents have no effect at low (3 mM) glucose. Mechanistically, the synergy between glucose and the glucoincretins is not based on cAMP alone as glucose does not further increase intracellular cAMP in response to GLP-1 and PACAP-38. A role for Ca2+ signaling is inferred, since the L-type Ca2+ channel blocker nifedipine markedly reduces the induction of c-fos and nur-77 by glucose and GLP-1. The induction of IEGs by glucose and chlorophenylthio-cAMP or GLP-1 and the inhibitory effect of nifedipine are also observed in the betaHC9 cell line. The results indicate that GLP-1 and PACAP-38 act as competence factors for the action of glucose on c-fos, JunB, and nur-77. It is suggested that the synergistic effect of glucose and glucoincretins on IEG expression plays an important role in the adaptive processes of the beta-cell to hyperglycemia.