Xenotransplantation of cultures of islet cells of human fetal pancreas into experimentally diabetic rats

Cultures of islet cells of fetal human pancreas were transplanted into the liver of alloxan diabetic rats. This xenotransplantation led to a long-term reduction of glycemia maintained during 8--18 weeks. Histological studies of the liver of recipients revealed the presence of the implanted islet cells.     

Cultures of islet cells obtained from the fetal bovine pancreas]

The pancreas from bovine fetuses of 27-35 cm crown-rump length were used as a source of islet cell cultures. Pancreatic tissue was treated by collagenase, filtered through the metal sieve and incubated in MEM for 24 h. Using this method, cultures similar to so-called pseudo-islets were obtained. Aldehyde-fuchsin staining and electron microscopy revealed a significant number of beta-cells within the pseudo-islets, the insulin-producing activity of which was confirmed by RIA.     

Ultrastructural studies of the ontogeny of fetal human and porcine endocrine pancreas, with special reference to colocalization of the four major islet hormones.

Most, if not all, endocrine cells seem capable of synthesizing and storing more than one hormone. Such cellular colocalization of hormones can be due either to the presence of two or more specific granules within the cells or to colocalization of the hormones within a single granule. The present study was performed to clarify the subcellular localization of insulin, glucagon, somatostatin, and pancreatic polypeptide within the endocrine cells of the human and porcine pancreas during fetal development, with special reference to possible colocalization of the hormones. The tissue specimens were processed for ultrastructural cytochemistry using Lowicryl as embedding medium. An immunogold labeling technique was used with two parallel, but not interacting, antibody chains. Sections from each specimen were double labeled in different combinations giving a complete covering of the four major islet hormones. During fetal life (50-90 days prenatally in porcine pancreas, 14 weeks gestation in the human pancreas) several hormones were demonstrated, not only in the same endocrine cells, but also in the same secretory granules (polyhormonal granules). Costorage of insulin, glucagon, somatostatin, and pancreatic polypeptide was demonstrated in granules in pancreatic endocrine fetal cells. At an early fetal stage, the endocrine cells contained either dense, round granules or pale, heteromorphous granules. With increasing age and maturation of the endocrine cells, structural differentiation of the secretory granules was found to be associated with a gradual disappearance of the polyhormonal granules. The first genuine monohormonal cell to appear in the porcine fetus was the pancreatic polypeptide cell (at 70 days gestation); it was followed by the somatostatin-producing endocrine cell. Mature insulin- and glucagon-producing cells were only demonstrated after birth. Thus, in the adult pancreatic endocrine cells, each specific endocrine cell type produced only one of the four classical hormones. The present investigation demonstrated that the endocrine cells of the fetal, but not the adult, pancreas are able to synthesize all the major islet hormones, and that these peptides are costored in the same granule. The data obtained support the concept of a common precursor stem cell for pancreatic hormone-producing cells.     

Selective processing of chromogranin A in the different islet cells in human pancreas.

We studied the immunoreactivity of 12 different region-specific antibodies to the chromogranin A (CgA) molecule in the four major neuroendocrine cell types of the human pancreas by using double immunofluorescence techniques. The antibodies raised to the N-terminal and midportions of CgA showed, on the whole, stronger immunoreactivity than did the C-terminal antibodies, with a few exceptions. Often the immunoreactivity was stronger in glucagon cells. Insulin cells expressed immunoreactivity to all region-specific antibodies, but glucagon cells were nonreactive to two antibodies. Somatostatin cells reacted only with the C-terminal antibodies (amino acid sequences CgA 411-424), while PP cells were stained with four CgA region-specific antibodies between amino acid sequences 63-195. The cause of these differences may be that the CgA molecule is cleaved, partly masked, or partly translated from CgA mRNA. Microwave treatment improved only the staining with the CgA 361-372 antibodies, which indicates that masking is not the sole or entire cause. Our findings may indicate that the CgA molecule is cleaved in different ways in the various pancreatic endocrine cell types, giving rise to a variety of biologically functional fragments.     

Alpha-1-antitrypsin immunoreactivity in islet cells of adult human pancreas

alpha-1-antitrypsin immunoreactivity was demonstrated by immunofluorescence technique in the peripheral islet cells of all ten normal adult human pancreata examined; normal adult human liver was negative. The specificity of the reactions was confirmed by applying various control tests including absorption of the specific antisera with purified alpha-1-antitrypsin, inhibition and blocking tests and by ensuring the monospecificity of the antisera used. The findings suggest that the pancreatic islet may be an additional source of alpha-1-antitrypsin.     

Immunohistochemical demonstration of alpha-1-antitrypsin in the islet cells of human pancreas

Summary Using the unlabeled antibody peroxidase-antiperoxidase complex (PAP) technique at the light microscopic level, it has been shown that, in the dipnoan preoptico-hypophysial neurosecretory system, vasotocin and mesotocin are synthesized in separate neurons. In the preoptic nuclei, the perikarya of these two types of neurosecretory neurons are not located preferentially. The two types of neurosecretory perikarya give rise to separate vasotocinergic and mesotocinergic axons, respectively. The dipnoan median eminence and neural lobe contain separate vasotocinergic and mesotocinergic nerve fibres, the general distribution of which is described. In the pars distalis and the pars intermedia of the hypophysis, neurohypophysial hormone-containing nerve fibres have not been found.This investigation was supported by a grant from the Belgian Nationaal Fonds voor Geneeskundig Wetenschappelijk OnderzoekThe authors are greatly indebted to Prof. Dr. Hyder, Department of Zoology, University of Nairobi, Kenya for kindly supplying us with the fixed material used in this study     

On argyrophil reactions of endocrine cells in the human fetal pancreas

Summary The endocrine cells in the pancreas of five human fetuses with gestational ages of 18–20 weeks were examined by light and electron microscopy with special regard to argyrophil reactions. B-cells and typical A and D-cells were easily identified electron microscopically on the basis of their typical secretory granules. In the Grimelius argyrophil silver stain, a concentration of silver grains over the less electron dense peripheral mantle of the A-cell secretory granules was observed by electron microscopy. In the Hellerström and Hellman modification of the argyrophil Davenport alcoholic silver stain, silver grains were concentrated over the internal structures of the D-cell secretory granules. With this stain an accumulation of silver grains was also seen at the surface of the A-cell secretory granules. The argyrophil reaction of the A-granules was less pronounced than in the D-cells. In addition to B-cells and A- and D-cells, two other types of endocrine cell were observed by electron microscopy. These cells were argyrophil with the silver impregnation method of Grimelius. The electron microscopic findings at least partly explain the frequent overlapping between the two staining methods observed at the light microscope level.This study was supported by the Swedish Medical Research Council (Project No. 102)     

Polyhormonal aspect of the endocrine cells of the human fetal pancreas

Histological studies were performed on 30 pancreases obtained from normal human fetuses aged between the 9th and 38th week. For immunocytochemistry, the avidin-biotin-peroxidase method was used to identify and colocalise insulin, glucagon, somatostatin, pancreatic polypeptide and proliferating cell nuclear antigen. In the 9th week, cells containing all investigated peptides were present. During the fetal period, two populations of endocrine cells have been distinguished, Langerhans islets and freely dispersed cells. The free cells were polyhormonal, containing insulin, glucagon, somatostatin and pancreatic polypeptide, and were localised in the walls of pancreatic ducts throughout the whole gland. During the development of the islets we have observed four stages: (1) the scattered polyhormonal cell stage (9th–10th week), (2) the immature polyhormonal islet stage (11th–15th week), (3) the insulin monohormonal core islet stage (16th–29th week), in which zonular and mantle islets are observed, and (4) the polymorphic islet stage (from the 30th week onwards), which is characterised by the presence of monohormonal cells expressing glucagon or somatostatin. Bigeminal and polar islets also appeared during this last stage. The islets consisted of an insulin core surrounded by a thick (in the part developing from the dorsal primordium) or thin rim (part of the pancreas concerned with the ventral primordium) of intermingled mono- or dihormonal glucagon-positive or somatostatin-positive cells. The most externally located polyhormonal cells exhibited a reaction for glucagon, somatostatin and pancreatic polypeptide. Apart from the above-mentioned types of islets, all arrangements observed in earlier stages were present. Proliferating cell nuclear antigen-positive cells (single in the large islets and more numerous in the smaller ones) were predominantly observed in the outermost layer. Taken together our data indicate that, during the human prenatal development of the islet, endocrine cells are able to synthesise several different hormones. Maturation of these cells involved or depended on a change from a polyhormonal to a monohormonal state and is concerned with decreasing proliferative capacity. This supports the concept of a common precursor stem cell for the hormone-producing cells of the fetal human pancreas. Accepted: 1 June 1999     

Lack of glucose-induced functional maturation during long-term culture of human fetal islet cells

To investigate the long-term effects of glucose on the function of human fetal islets we cultured islet-like cell clusters (ICC) obtained from 12 human fetuses with a mean age of 16.1 weeks in media containing 2.8, 11.1 or 16.7 mM glucose. On the 8th day of culture, the ICC that had been maintained in 16.7 mM glucose contained 60% less insulin than the ICC cultured in 2.8 mM glucose. However, insulin release was similar in both groups, and was not affected by a 24-h incubation in high vs. low glucose. Also (pro) insulin biosynthesis was not significantly affected. During a 24-day culture period, the total release of insulin and glucagon was similar in all glucose concentrations. The ICC released about 75% of their insulin content but only 15% of their glucagon content during the last 48 h of the 24-day culture period, again regardless of glucose concentration in media. Insulin release was insensitive to acute glucose and leucine challenges in perifusion experiments after culture for 1, 5, 8 or 16 days in 11.1 mM glucose, whereas glucagon was always a potent stimulus. In conclusion, the function of cultured young human fetal islet cells is remarkably independent of glucose, even during prolonged exposure. Moreover, the primary role of glucagon in fetal life may be that of a paracrine stimulator of beta-cell function.     

Reduced immunogenicity of pancreatic progenitor cells derived from first-trimester human fetal pancreas

The relatively low immunogenic and tumorigenic nature of fetal stem cells makes them attractive candidates for transplantation. Pancreatic progenitor cells (PPCs) derived from human fetal pancreas that are amenable to growth and differentiation into transplantable insulin-producing islet-like cell clusters (ICCs) have been reported recently; however, the immunological nature of these cells has yet to be characterized. We thus investigated and compared the immunogenicity of pancreatic progenitor cells and islet-like cell clusters from first- and second-trimester human fetal pancreas. Polymerase chain reaction demonstrated that pancreatic progenitor cells and islet-like cell clusters express immune-related genes of major histocompatibility complex, MHC-I and MHC-II, complement component 3 (C3), chemokine ligand (CCL19), and tumor necrosis factor super family (TNFSF10), but no expression of the co-stimulatory genes, CD80 and CD86. Interestingly, pancreatic progenitor cells showed a differential expression of MHC-I and MHC-II with advancing gestational age with a greater expression in pancreatic progenitor cells from the second trimester. Pre-incubation of the second-trimester cells with interferon-γ (IFN-γ) increased MHC molecule expression. Functional alloreactivity of pancreatic progenitor cells was investigated via mixed lymphocyte reactions (MLRs). Relative to first-trimester pancreatic progenitor cells, second-trimester pancreatic progenitor cells induced a greater extent of proliferation of peripheral blood mononuclear cells (PBMCs) and resulted in more IFN-γ production in phytohaemagllutinin-stimulated peripheral blood mononuclear cells following co-culture. Results of the study indicated that first-trimester pancreatic progenitor cells and islet-like cell clusters have a distinctively lower immunogenicity relative to second-trimester pancreatic progenitor cells, even after a pro-inflammatory cytokine challenge.     

Pancreatic hormones are expressed on the surfaces of human and rat islet cells through exocytotic sites

Human and rat insulin cells show insulin immunoreactivity, and glucagon cells show glucagon immunoreactivity on their membrane surfaces, respectively. The reaction occurs in the form of small dots on the islet cell surface and colocalizes with the chromogranin family of secretory granule markers. Electron microscopy reveals the labeling to occur at sites of exocytotic granule release, involving the surfaces of extruded granule cores. The surfaces of islet cells were labeled both by polyclonal and monoclonal antibodies, excluding that receptor-interacting, anti-idiotypic hormone antibodies were responsible for the staining. Human insulin cells were surface-labeled by monoclonal antibodies recognizing the mature secretory products, insulin and C-peptide but not with monoclonal antibodies specific for proinsulin. Thus, routing of unprocessed preproinsulin to the cell surface may not account for these results. It is concluded that the staining reflects interactions between the appropriate antibodies and exocytotic sites of hormone release.     

The eel pancreas contains opiate-like but not corticotropin-like materials

Eel pancreatic acetone powder was extracted with an acetone-water-HCL mixture. An acid acetone powder was formed by addition of a copious volume of cold acetone to the extract. The powder was subsequently subjected to gel filtration on Sephadex G25. Opiate receptor binding activity was present mainly in fractions retarded on Sephadex G25 (MW less than 5,000) although some activity was present in the unretarded fraction (MW greater than 5,000). Steroidogenic activity was absent from all fractions.     

The ghrelin cell: a novel developmentally regulated islet cell in the human pancreas

OBJECTIVES: Ghrelin, an endogenous ligand of the growth hormone secretagogue receptor (GHS-R), was recently identified in the stomach. Ghrelin is produced in a population of endocrine cells in the gastric mucosa, but expression in intestine, hypothalamus and testis has also been reported. Recent data indicate that ghrelin affects insulin secretion and plays a direct role in metabolic regulation and energy balance. On the basis of these findings, we decided to examine whether ghrelin is expressed in human pancreas. Specimens from fetal to adult human pancreas and stomach were studied by immunocytochemistry, for ghrelin and islet hormones, and in situ hybridisation, for ghrelin mRNA. RESULTS: We identified ghrelin expression in a separate population of islet cells in human fetal, neonatal, and adult pancreas. Pancreatic ghrelin cells were numerous from midgestation to early postnatally (10% of all endocrine cells). The cells were few, but regularly seen in adults as single cells at the islet periphery, in exocrine tissue, in ducts, and in pancreatic ganglia. Ghrelin cells did not express any of the known islet hormones. In fetuses, at midgestation, ghrelin cells in the pancreas clearly outnumbered those in the stomach. CONCLUSIONS: Ghrelin is expressed in a quite prominent endocrine cell population in human fetal pancreas, and ghrelin expression in the pancreas precedes by far that in the stomach. Pancreatic ghrelin cells remain in adult islets at lower numbers. Ghrelin is not co-expressed with any known islet hormone, and the ghrelin cells may therefore constitute a new islet cell type.     

Effects of steroid hormones in fetal bovine serum on plating ang cloning of human cells in vitro.

Fetal bovine sera from each of three different commercial sources were tested for their ability to support cloning of human fibroblastoid cells in vitro. Cloning efficiencies varied according to serum source. Serum (10 samples) from company A did not support growth, while sera (10 samples) from companies B and C provided adequate to excellent conditions for cloning and growth. Cells from neonatal foreskin or embryonic lung responded to each serum similarly. Bovine serum albumin type H7 from company C supported cell growth in media without serum. Sera containing 1.0 ng per ml or more of progesterone inhibited growth, whereas sera containing less than 1.0 ng per ml supported cloning and growth. In the low progesterone sera, the concentration of 17-beta-estradiol exceeded 100 pg per ml. Growth supporting sera could be made non-supportive by adding 0.1 mug per ml of progesterone. The addition to non-supporative sera of 0.1 mug per ml of 17-beta-estradiol or hydrocortisone made these sera supportive of cell growth. Addition of estrogen or hydrocortisone to a culture medium that inhibits growth, with subsequent reversal of the inhibitory effect, implies that these hormones competitively regulate growth of responsive cells in vitro.     

Isolation and identification of islet amyloid polypeptide in normal human pancreas

To identify islet amyloid polypeptide (IAPP) present in normal human pancreas, we isolated the peptide from a soluble peptide fraction of amyloid deposit-free pancreata of two non-diabetic patients by using reverse-phase high performance liquid chromatography coupled with a radioimmunoassay specific for human IAPP. IAPP(1-37) and IAPP(17-37) were isolated and their complete amino acid sequences were determined up to the C-terminus. Identification of IAPP in normal human pancreas suggests the possible biological function of IAPP as a novel pancreatic hormone in humans.     

The role of calcium in insulin release from the human fetal pancreas

Previous experiments have established that the human fetal pancreas is relatively unresponsive to glucose as regards insulin release, but will secrete this hormone when exposed to agents which increase levels of cAMP or which activate protein kinase C. The current experiments were designed to establish which role another major stimulus, calcium, had in the release of insulin from this organ. For this purpose, cultured explants of human fetal pancreas were exposed to stimuli either in static or dynamic stimulation. The data show that insulin release is enhanced in the presence of 10 mM Ca2+, as well as the calcium ionophores A23187 and ionomycin, the latter agent being effective only if extracellular Ca2+ was present. A biphasic response was seen for Ca2+ but only a second phase response for A23187. Voltage-dependent calcium channels were shown to be present by the ability of the calcium channel blocker, verapamil, to inhibit insulin release caused by an agent that depolarizes membranes, potassium. The essential role of extracellular calcium in the insulinogenic effect of agents which increase cAMP levels--theophylline--and which activate protein kinase C--12-O-tetradecanoylphorbol-13-acetate--was demonstrated by showing (a) partial inhibition of insulin secretion by calcium channel blockers, (b) no enhancement of insulin release in the absence of extracellular calcium and (c) greater enhancement of insulin release in the presence of the calcium channel activator BAY-K-8644, which caused no stimulation by itself. These data put into better perspective our understanding of the mechanisms involved in insulin release from the human fetal pancreas.(ABSTRACT TRUNCATED AT 250 WORDS)     

Immunocytochemical studies of the evolution of islet hormones.

By using both immunofluorescence and peroxidase-anti-peroxidase procedures to detect cells producing the four islet hormones, supplemented by biochemical, biological, and radioimmunological assays of tissue extracts, it has been shown that insulin seems to be the most original hormone, apparently occurring already in invertebrates in cells of open type in the alimentary tract mucosa. Insulin cells also predominate in the first islet organ, namely that of the cyclostomes. The order of appearance in the endocrine pancreas during the subsequent evolution is: somatostatin; glucagon; and the pancreatic polypeptide. Even in lower vertebrates pancreatic polypeptide cells occur in those parts of the pancreas situated in close proximity to the gut.