Growth and development of the islets of Langerhans: implications for the treatment of diabetes mellitus

β cell aging and age-related diabetes

Type 2 diabetes is characterized by insulin resistance and loss of β cell mass and function. Aging is considered as a major risk factor for development of type 2 diabetes. However, the roles of pancreatic β cell senescence and systemic aging in the pathogenesis of type 2 diabetes in elderly people remain poorly understood. In this review, we aimed to discuss the current findings and viewpoints focusing on β cell aging and the development of type 2 diabetes.

Effects of Huanglian-Renshen-Decoction, a Fixed Mixture of Traditional Chinese Medicine, on the Improvement of Glucose Metabolism by Maintenance of Pancreatic β Cell Identity in db/db Mice

Huanglian-Renshen-Decoction (HRD) is widely used to treat type 2 diabetes mellitus (T2DM) in China. However, the underlying mechanism is unclear. We aimed to investigate the mechanism by which HRD regulates the glucose level. Forty 7-8-week-old db/db (BSK) mice were randomly assigned to the following four groups: model, low dose HRD (LHRD), high dose HRD (HHRD), and saxagliptin (SAX). Additionally, 10 db/m mice were assigned to control group. The experimental mice were administered 3.03g/kg/d and 6.06g/kg/d of HRD in the LHRD and HHRD groups, respectively, and 10mg/kg/d saxagliptin in the SAX group for 8 weeks. The control and model groups were supplied with distilled water. After the intervention, the pancreas and blood were collected and tested. Compared with that of model group, the fasting blood glucose (FBG) was significantly decreased in all intervention groups (p < 0.05 or 0.01), whereas fasting serum insulin (FINS) was increased significantly in both HHRD and SAX groups. The immunofluorescence images showed that the mass of insulin⁺ cells was increased and that of glucagon⁺ cells was reduced obviously in experimental groups compared to those of the model group. In addition, the coexpression of insulin, glucagon, and PDX1 was decreased in HHRD group, and the level of caspase 12 in islet was decreased significantly in all intervention groups. However, little difference was found in the number and morphology of islet, and the expression of ki67, bcl2, bax, caspase 3, and cleaved-caspase 3 in the pancreas among groups. Interestingly, the cleaved-Notch1 level was increased and the Ngn3 level in islet was decreased significantly in HHRD group. The HRD showed dose-dependent effects on glucose metabolism improvement through maintenance of β cell identity via a mechanism that might involve the Notch1/Ngn3 signal pathway in db/db mice.

Direct differentiation of insulin-producing cells from human urine-derived stem cells

The loss of pancreatic β-cells is a cause of diabetes. Therefore, replacement of pancreatic β-cells is a logical strategy for the treatment of diabetes, and the generation of insulin-producing cells (IPCs) from stem cells has been widely investigated as an alternative source for pancreatic β-cells. Here, we isolated stem cells from human urine and investigated their differentiation potential into IPCs. We checked the expression of surface stem cell markers and stem cell transcription factors, and found that the isolated human urine-derived stem cells (hUDSCs) expressed the stem cell markers CD44, CD90, CD105 and stage-specific embryonic antigen (SSEA)-4. In addition, these cells expressed octamer binding transcription factor (Oct)4 and vimentin. hUDSCs could differentiate into adipocytes and osteocytes, as evidenced by Oil-red O staining and Alizarin Red S-staining of differentiated cells, respectively. When we directly differentiated hUDSCs into IPCs, the differentiated cells expressed mRNA for pancreatic transcription factors such as neurogenin (Ngn)3 and pancreatic and duodenal homeobox (Pdx)1. Differentiated IPCs expressed insulin and glucagon mRNA and protein, and these IPCs also secreted insulin in response to glucose stimulation. In conclusion, we found that hUDSCs can be directly differentiated into IPCs, which secrete insulin in response to glucose.

Pancreatic islets and their roles in metabolic programming

Experimental and epidemiologic data have confirmed that undernutrition or overnutrition during critical periods of life can result in metabolic dysfunction, leading to the development of obesity, hypertension, and type 2 diabetes, later in life. These studies have contributed to the concept of the developmental origins of health and disease (DOHaD), which involves metabolic programming patterns. Beyond the earlier phases of development, puberty can be an additional period of plasticity, during which any insult can lead to changes in metabolism. Impaired brain development, associated with imbalanced autonomous nervous system activity due to metabolic programming, is pivotal to the creation of pathophysiology. Excess glucocorticoid exposure, due to hypothalamic-pituitary-adrenal axis deregulation, is also involved in malprogramming in early life. Additionally, the pancreatic islets appear to play a decisive role in the setup and maintenance of these metabolic dysfunctions as key targets of metabolic programming, and epigenetic mechanisms may underlie these changes. Moreover, studies have indicated the possibility that deprogramming renders the islets able to recover their functioning after malprogramming. In this review, we discuss the key roles of the pancreatic islets as targets of malprogramming; however, we also discuss their roles as important targets for the treatment and prevention of metabolic diseases.

Solid-pseudopapillary tumor of the pancreas: clinical features, pathological characteristics, and origin

OBJECTIVE

[corrected] To study clinically pathological features and origin of solid-pseudopapillary tumor of pancreas (SPT).

PATIENTS AND METHODS

Clinical and pathological data of 82 cases with SPT were retrospectively studied. SAS6.12 statistics package was used for analysis. P < 0.05 was regarded as statistically significant difference.

RESULTS

The SPT patients included 70 females and 12 males, with a median age of 31 years old. The mean tumor size was 6.71 ± 4.42 cm. Vascular or organs was invaded in nine cases. The clinical and pathological characteristics show no significant difference between male and female patients. In the non-encapsulate group (22 cases), the tumor was larger (P = 0.0015), exogenous growth pattern (P = 0.0194), and would probably involve major vascular or organs (P = 1.697E-06). The typical features of SPT include pseudopapillary pattern with fibro vascular stalks by uniform poorly cohesive polygonal cells. The tumor cell expresses a variety of immune markers in heterogeneity. Under electron microscope, there are some electron dense granules, about 8-1.2 µm in diameter, with membrane similar to the zymogen granules in SPT cell cytoplasm.

CONCLUSIONS

SPT with incomplete capsule often presents malignant behaviors. SPT shows multi-heterogeneity, which is caused by the disorder in the development of pancreatic stem cell.

Endothelial cell co-culture mediates maturation of human embryonic stem cell to pancreatic insulin producing cells in a directed differentiation approach

Embryonic stem cells (ESC) have two main characteristics: they can be indefinitely propagated in vitro in an undifferentiated state and they are pluripotent, thus having the potential to differentiate into multiple lineages. Such properties make ESCs extremely attractive for cell based therapy and regenerative treatment applications. However for its full potential to be realized the cells have to be differentiated into mature and functional phenotypes, which is a daunting task. A promising approach in inducing cellular differentiation is to closely mimic the path of organogenesis in the in vitro setting. Pancreatic development is known to occur in specific stages, starting with endoderm, which can develop into several organs, including liver and pancreas. Endoderm induction can be achieved by modulation of the nodal pathway through addition of Activin A in combination with several growth factors. Definitive endoderm cells then undergo pancreatic commitment by inhibition of sonic hedgehog inhibition, which can be achieved in vitro by addition of cyclopamine. Pancreatic maturation is mediated by several parallel events including inhibition of notch signaling; aggregation of pancreatic progenitors into 3-dimentional clusters; induction of vascularization; to name a few. By far the most successful in vitro maturation of ESC derived pancreatic progenitor cells have been achieved through inhibition of notch signaling by DAPT supplementation. Although successful, this results in low yield of the mature phenotype with reduced functionality. A less studied area is the effect of endothelial cell signaling in pancreatic maturation, which is increasingly being appreciated as an important contributing factor in in-vivo pancreatic islet maturation. The current study explores such effect of endothelial cell signaling in maturation of human ESC derived pancreatic progenitor cells into insulin producing islet-like cells. We report a multi-stage directed differentiation protocol where the human ESCs are first induced towards endoderm by Activin A along with inhibition of PI3K pathway. Pancreatic specification of endoderm cells is achieved by inhibition of sonic hedgehog signaling by Cyclopamine along with retinoid induction by addition of Retinoic Acid. The final stage of maturation is induced by endothelial cell signaling achieved by a co-culture configuration. While several endothelial cells have been tested in the co-culture, herein we present our data with rat heart microvascular endothelial Cells (RHMVEC), primarily for the ease of analysis.

Bifocal solid pseudopapillary tumor of the pancreas: a report of one case

AIM: To analyze the pathological characteristics and origin of bifocal solid pseudopapillary tumor (SPT) of the pancreas.

METHODS: The clinical data of a patient with bifocal SPT of the pancreas, who underwent pancreatoduodenectomy and distal pancreatectomy with splenectomy at our hospital, were retrospectively analyzed. The expression of multiple differentiation markers was detected by immunohistochemistry to evaluate the origin of the tumor.

RESULTS: The postoperative course was uneventful. The postoperative blood glucose levels ranged from 5.5 to 8.9 mmol/L. The patient restored food intake five days after operation. No postoperative complications occurred. Pathological examination showed different combination ratios of solid and cystic components between the tumors arising from both foci. However, the morphology of neoplastic cells was similar between them. Both of them were diagnosed as SPT of the pancreas. The SPT cells were highly positive for some differentiation markers such as vimentin (VIM), S100, alpha-1 antitrypsin (AAT), cyclin D1, PR, and nestin proteins.

CONCLUSION: Bifocal SPT of the pancreas shows heterogeneous differentiation. SPT may be originated from pancreatic embryonic stem cells and results from immature differentiation of pluripotential stem cells during pancreas genesis.

Stem cell therapy to treat diabetes mellitus

Transplantation of pancreatic islets offers a direct treatment for type 1 diabetes and in some cases, insulin-dependent type 2 diabetes. However, its widespread use is hampered by a shortage of donor organs. Many extant studies have focused on deriving beta-cell progenitors from pancreas and pluripotent stem cells. Efforts to generate beta-cells in vitro will help elucidate the mechanisms of beta-cell formation and thus provide a versatile in vivo system to evaluate the therapeutic potential of these cells to treat diabetes. Various successful experiments using beta-cells in animal models have generated extensive interest in using human embryonic stem cells to restore normoglycemia in diabetic patients. While new techniques are continually unveiled, the success of beta-cell generation rests upon successful manipulation of culture conditions and the induction of key regulatory genes implicated in pancreas development. In this review, we compare successfully conducted protocols, highlight essential steps and identify some of the remarkable shortfalls common to these methods. In addition, we discuss recent advancements in the derivation of patient-specific pluripotent stem cells that may facilitate the use of autologous beta-cells in stem cell therapy.

The potential for stem cell therapy in diabetes

Both type 1 and type 2 diabetes are characterized by a marked deficit in beta-cell mass causing insufficient insulin secretion. Beta-cell replacement strategies may eventually provide a cure for diabetes. Current therapeutic approaches include pancreas and islet transplantation, but the chronic shortage of donor organs restricts this treatment option to a small proportion of affected patients. Moreover, recent evidence shows a progressive decline in beta-cell function after islet transplantation so that most patients have to revert to insulin treatment within a few years. In this article recent progress in the generation, culture and targeted differentiation of human embryonic stem (ES) cells is reviewed, and some of the issues surrounding their use as a source of beta-cells are discussed.

Role of bone marrow mesenchymal stem cells in pancreas self-restoration and pathological regeneration

AIM: To investigate the role of bone marrow mesenchymal stem cells (MSC) in pancreatic self-restoration and pathological regeneration.

METHODS: Sixty Sprague-Dawley (SD) rats were randomly assigned into 5 groups (n = 12). Group A acted as the normal negative control without any treatment, and group B received labeled autologous bone marrow MSC only. Group C was induced mild acute pancreatitis by subcutaneous injection of caerulein 20 mg/(kg·h) 4 times, and group D was induced severe acute pancreatitis by intraperitoneal injection of L-arginine (2 g/kg) twice. Group E was the stem cell mobilized group treated by injection of granulocyte-colony stimulating factor (G-CSF) into rats for 3 d at a dose of 40 mg/(kg·d) 3 d before the induction of SAP. MSC were stained with Hoechst33258 and transplanted into their original cavity. Two and eight weeks after transplantation, the rats were sacrificed, and pancreatic tissues were harvested. Samples were snap-frozen and sectioned on a cryostat. The presence of labeled MSC in the cryostat prepared was examined directly by fluorescent microscopy. The positive sections were selected for further immunofluorescence assay. Anti-Cytokeratin(CK)19, anti-glucagon and anti-insulin immunofluorescence staining were performed on the pancreatic sections to determine whether incorporated MSC differentiated into mature pancreatic cells.

RESULTS: Frozen section of pancreas in group A didn't appear yellow-green fluorescence. The labeled MSC were detected in normal pancreatic tissues in group B and in injured pancreatic tissues in group C, D and E, especially in group E, which lasted 8 wk. The results of immunofluorescence analysis were as follows: All tests were negative in controls, including spontaneous fluorescence control, fluorescence antibody control and inhibitory control. No positive cells with CK19, insulin and glucagons were visualized in group A and D (died rats). Positive cells with CK19, which differentiated from the labeled MSC, were found in normal pancreas in group B and injured pancreatic models in group C, E and D (survival rats). No positive cells with insulin and glucagons were observed 2 wk after modeling, while the positive cells appeared 8 wk after modeling in group C, D and E.

CONCLUSION: The bone marrow MSC participate in pancreatic self-restoration and pathological regeneration.

Production of transgenic tilapia with Brockmann bodies secreting [desThrB30] human insulin

BACKGROUND

Tilapia are commercially important tropical fish which, like many teleosts, have anatomically discrete islet organs called Brockmann bodies. When transplanted into diabetic nude mice, tilapia islets provide long-term normoglycemia and mammalian-like glucose tolerance profiles.

METHODS

Using site-directed mutagenesis and linker ligation we have "humanized" the tilapia insulin gene so that it codes for [desThrB30] human insulin while maintaining the tilapia regulatory sequences. Following microinjection into fertilized eggs, we screened DNA isolated from whole fry shortly after hatching by PCR. Positive fish were grown to sexual maturity and mated to wild-types and positive Fl's were further characterized.

RESULTS

Human insulin was detected in both serum and in the clusters of beta cells scattered throughout the Brockmann bodies. Surrounding non-beta cells as well as other tissues were negative indicating beta cell specific expression. Purification and sequencing of both A-and B-chains verified that the insulin was properly processed and humanized.

CONCLUSIONS

After extensive characterization, transgenic tilapia could become a suitable, inexpensive source of islet tissue that can be easily mass-produced for clinical islet xenotransplantation. Because tilapia islets are exceedingly resistant to hypoxia by mammalian standards, transgenic tilapia islets should be ideal for xenotransplantation using immunoisolation techniques.

Glucagon-like peptide 1 agonists and the development and growth of pancreatic beta-cells

Glucagon-like peptide 1 (GLP-1) is an intestine-derived insulinotropic hormone that stimulates glucose-dependent insulin production and secretion from pancreatic beta-cells. Other recognized actions of GLP-1 are to suppress glucagon secretion and hepatic glucose output, delay gastric emptying, reduce food intake, and promote glucose disposal in peripheral tissues. All of these actions are potentially beneficial for the treatment of type 2 diabetes mellitus. Several GLP-1 agonists are in clinical trials for the treatment of diabetes. More recently, GLP-1 agonists have been shown to stimulate the growth and differentiation of pancreatic beta-cells, as well as to exert cytoprotective, antiapoptotic effects on beta-cells. Recent evidence indicates that GLP-1 agonists act on receptors on pancreas-derived stem/progenitor cells to prompt their differentiation into beta-cells. These new findings suggest an approach to create beta-cells in vitro by expanding stem/progenitor cells and then to convert them into beta-cells by treatment with GLP-1. Thus GLP-1 may be a means by which to create beta-cells ex vivo for transplantation into patients with insulinopenic type 1 diabetes and severe forms of type 2 diabetes.

In vitro cultivation of human fetal pancreatic ductal stem cells and their differentiation into insulin-producing cells

AIM: To isolate, culture and identify the human fetal pancreatic ductal stem cells in vitro, and to observe the potency of these multipotential cells differentiation into insulin-producing cells.

METHODS: The human fetal pancreas was digested by 1 g/L collagease type IV and then 2.5 g/L trypsin was used to isolate the pancreatic ductal stem cells, followed by culture in serum-free, glucose-free DMEM media with some additional chemical substrates in vitro (according to the different stage). The cells were induced by glucose-free (control), 5 mmol/L, 17.8 mmol/L and 25 mmol/L glucose, respectively. The cell types of differentiated cells were identified using immunocytochemical staining.

RESULTS: The shape of human fetal pancreatic ductal stem cells cultured in vitro was firstly fusiform in the first 2 wk, and became monolayer and cobblestone pattern after another 3 to 4 wk. After induced and differentiated by the glucose of different concentrations for another 1 to 2 wk, the cells formed the pancreatic islet-like structures. The identification and potency of these cells were then identified by using the pancreatic ductal stem cell marker, cytokeratin-19 (CK-19), pancreatic β cell marker, insulin and pancreatic α cell marker, glucagons with immunocytochemical staining. At the end of the second week, 95.2% of the cells were positive for CK-19 immunoreactivity. Up to 22.7% of the cells induced by glucose were positive for insulin immunoreactivity, and less than 3.8% of the cells were positive for glucagon immunoreactivity in pancreatic islet-like structures. The positive ratio of immunoreactive staining was dependent on the concentration of glucose, and it was observed that the 17.8 mmol/L glucose stimulated effectively to produce insulin- and glucagons-producing cells.

CONCLUSION: The human fetal pancreatic ductal stem cells are capable of proliferation in vitro. These cells have multidifferentiation potential and can be induced by glucose and differentiated into insulin-producing cells in vitro.

Replacement by a lacZ reporter gene assigns mouse connexin36, 45 and 43 to distinct cell types in pancreatic islets

Transcripts of three connexin isoforms (Cx36, Cx43 and Cx45) have been reported in rodent pancreatic islets, but the precise distribution of the cognate proteins is still unknown. We determined expression of Cx36 in a cell-autonomous manner using mice with a targeted replacement of the Cx36 coding region by a lacZ reporter gene. For cell-autonomous monitoring of Cx43 expression, we used the Cre/loxP system: Mice carrying the Cx43 coding region flanked by loxP sites (floxed) also carried an embedded lacZ gene that is activated after Cre-mediated recombination in cells with transcriptional activity of the Cx43 gene. Deletion of the Cx43 coding region in beta-cells did not result in the activation of the embedded lacZ reporter gene. Instead, Cx43 expression was found in endothelial cells of the islets of Langerhans in mice with endothelium-specific deletion. Ubiquitous deletion of Cx43 led to a similar endothelial lacZ expression, but again, activity of the reporter gene was not detected in beta-cells. Mice with targeted replacement of the Cx45 coding region by lacZ showed a vascular expression similar to Cx43. The data show that native insulin-producing cells express a connexin isoform (Cx36) which differs from those (Cx43 and Cx45) expressed by vascular islet cells.

Are islet cells the gatekeepers of the pancreas?

The pancreas is one of the body's most complex tissues composed of a mixture of endocrine and exocrine cell components. Although, islets comprise 1-2% of the pancreatic volume, there is some evidence that they control the function and the integrity of the pancreas and play the role of a gatekeeper. This review intends to highlight the importance of islet cells, not only for glucose metabolism, but also for their significant role in drug metabolism and diseases, especially in pancreatic cancer.