Human pluripotent stem cell-derived β cells: Truly immature islet β cells for type 1 diabetes therapy?

A century has passed since the Nobel Prize winning discovery of insulin, which still remains the mainstay treatment for type 1 diabetes mellitus (T1DM) to this day. True to the words of its discoverer Sir Frederick Banting, “insulin is not a cure for diabetes, it is a treatment”, millions of people with T1DM are dependent on daily insulin medications for life. Clinical donor islet transplantation has proven that T1DM is curable, however due to profound shortages of donor islets, it is not a mainstream treatment option for T1DM. Human pluripotent stem cell derived insulin-secreting cells, pervasively known as stem cell-derived β cells (SC-β cells), are a promising alternative source and have the potential to become a T1DM treatment through cell replacement therapy. Here we briefly review how islet β cells develop and mature in vivo and several types of reported SC-β cells produced using different ex vivo protocols in the last decade. Although some markers of maturation were expressed and glucose stimulated insulin secretion was shown, the SC-β cells have not been directly compared to their in vivo counterparts, generally have limited glucose response, and are not yet fully matured. Due to the presence of extra-pancreatic insulin-expressing cells, and ethical and technological issues, further clarification of the true nature of these SC-β cells is required.

Diagnostic role of multislice spiral computed tomography combined with clinical manifestations and laboratory tests in acute appendicitis subtypes

The study aimed to investigate the diagnostic role of multislice spiral CT (MSCT) combined with clinical manifestations and laboratory tests in acute appendicitis subtypes. Patients diagnosed with acute appendicitis were included for retrospective analysis and their clinical manifestations and MSCT signs were analyzed. The clinical manifestations of different subtypes of acute appendicitis, including simple appendicitis, suppurative appendicitis and gangrenous appendicitis, were compared. The clinical manifestations were anorexia in 51.1% of patients, nausea and vomiting in 62.0%, shifting right lower abdominal pain in 51.1%, elevated body temperature in 31.2%, right lower quadrant abdominal tenderness in 91.4%, rebound tenderness in 91.4%, increased white cell count in 89.1%, high neutrophil count in 88.2%, increased appendiceal diameter enlargement in 100%, surrounding exudate in 95.0%, fecal stones in 51.6%, appendiceal wall thickening in 94.6%, lymph node in 82.8% and intestinal stasis in 18.6%. There were statistically significant differences in body temperature and neutrophil percentage among the subtypes of appendicitis and they were lowest in simple appendicitis and highest in gangrenous appendicitis. There were statistically significant differences in appendix diameter and the surrounding exudate among the subtypes of appendicitis and they were lowest in simple appendicitis and highest in gangrenous appendicitis. Clinical manifestations and MSCT signs, especially body temperature, percentage of neutrophils and the surrounding exudate, might have significant diagnostic value in acute appendicitis.

Stem cell therapy for insulin-dependent diabetes: Are we still on the road?

In insulin-dependent diabetes, the islet β cells do not produce enough insulin and the patients must receive exogenous insulin to control blood sugar. However, there are still many deficiencies in exogenous insulin supplementation. Therefore, the replacement of destroyed functional β cells with insulin-secreting cells derived from functional stem cells is a good idea as a new therapeutic idea. This review introduces the development schedule of mouse and human embryonic islets. The differences between mouse and human pancreas embryo development were also listed. Accordingly to the different sources of stem cells, the important research achievements on the differentiation of insulin-secreting β cells of stem cells and the current research status of stem cell therapy for diabetes were reviewed. Stem cell replacement therapy is a promising treatment for diabetes, caused by defective insulin secretion, but there are still many problems to be solved, such as the biosafety and reliability of treatment, the emergence of tumors during treatment, untargeted differentiation and autoimmunity, etc. Therefore, further understanding of stem cell therapy for insulin is needed.

Functional maturation of immature β cells: A roadblock for stem cell therapy for type 1 diabetes

Type 1 diabetes mellitus (T1DM) is a chronic autoimmune disease caused by the specific destruction of pancreatic islet β cells and is characterized as the absolute insufficiency of insulin secretion. Current insulin replacement therapy supplies insulin in a non-physiological way and is associated with devastating complications. Experimental islet transplantation therapy has been proven to restore glucose homeostasis in people with severe T1DM. However, it is restricted by many factors such as severe shortage of donor sources, progressive loss of donor cells, high cost, etc. As pluripotent stem cells have the potential to give rise to all cells including islet β cells in the body, stem cell therapy for diabetes has attracted great attention in the academic community and the general public. Transplantation of islet β-like cells differentiated from human pluripotent stem cells (hPSCs) has the potential to be an excellent alternative to islet transplantation. In stem cell therapy, obtaining β cells with complete insulin secretion in vitro is crucial. However, after much research, it has been found that the β-like cells obtained by in vitro differentiation still have many defects, including lack of adult-type glucose stimulated insulin secretion, and multi-hormonal secretion, suggesting that in vitro culture does not allows for obtaining fully mature β-like cells for transplantation. A large number of studies have found that many transcription factors play important roles in the process of transforming immature to mature human islet β cells. Furthermore, PDX1, NKX6.1, SOX9, NGN3, PAX4, etc., are important in inducing hPSC differentiation in vitro. The absent or deficient expression of any of these key factors may lead to the islet development defect in vivo and the failure of stem cells to differentiate into genuine functional β-like cells in vitro. This article reviews β cell maturation in vivo and in vitro and the vital roles of key molecules in this process, in order to explore the current problems in stem cell therapy for diabetes.

Claudin 4 in pancreatic β cells is involved in regulating the functional state of adult islets

The functional state (FS) of adult pancreatic islets is regulated by a large array of regulatory molecules including numerous transcription factors. Whether any islet structural molecules play such a role has not been well understood. Here, multiple technologies including bioinformatics analyses were used to explore such molecules. The tight junction family molecule claudin 4 (Cldn4) was the highest enriched amongst over 140 structural genes analysed. Cldn4 expression was ~75-fold higher in adult islets than in exocrine tissues and was mostly up-regulated during functional maturation of developing islet cells. Cldn4 was progressively down-regulated in functionally compromised, dedifferentiating insulin-secreting β cells and in db/db type 2 diabetic islets. Furthermore, the genetic deletion of Cldn4 impaired significantly the FS without apparently affecting pancreas morphology, islet architectural structure and cellular distribution, and secretion of enteroendocrine hormones. Thus, we suggest a previously unidentified role for Cldn4 in regulating the FS of islets, with implications in translational research for better diabetes therapies.

RNA-Seq Analysis of Islets to Characterise the Dedifferentiation in Type 2 Diabetes Model Mice db/db

Type 2 diabetes (T2D) is a global health issue and dedifferentiation plays underlying causes in the pathophysiology of T2D; however, there is a lack of understanding in the mechanism. Dedifferentiation results from the loss of function of pancreatic β-cells alongside a reduction in essential transcription factors under various physiological stressors. Our study aimed to establish db/db as an animal model for dedifferentiation by using RNA sequencing to compare the gene expression profile in islets isolated from wild-type, db/+ and db/db mice, and qPCR was performed to validate those significant genes. A reduction in both insulin secretion and the expression of Ins1, Ins2, Glut2, Pdx1 and MafA was indicative of dedifferentiation in db/db islets. A comparison of the db/+ and the wild-type islets indicated a reduction in insulin secretion perhaps related to the decreased Mt1. A significant reduction in both Rn45s and Mir6236 was identified in db/+ compared to wild-type islets, which may be indicative of pre-diabetic state. A further significant reduction in RasGRF1, Igf1R and Htt was also identified in dedifferentiated db/db islets. Molecular characterisation of the db/db islets was performed via Ingenuity analysis which identified highly significant genes that may represent new molecular markers of dedifferentiation.

An overview of type 2 diabetes and importance of vitamin D3-vitamin D receptor interaction in pancreatic β-cells

One significant health issue that plagues contemporary society is that of Type 2 diabetes (T2D). This disease is characterised by higher-than-average blood glucose levels as a result of a combination of insulin resistance and insufficient insulin secretions from the β-cells of pancreatic islets of Langerhans. Previous developmental research into the pancreas has identified how early precursor genes of pancreatic β-cells, such as Cpal, Ngn3, NeuroD, Ptf1a, and cMyc, play an essential role in the differentiation of these cells. Furthermore, β-cell molecular characterization has also revealed the specific role of β-cell-markers, such as Glut2, MafA, Ins1, Ins2, and Pdx1 in insulin expression. The expression of these genes appears to be suppressed in the T2D β-cells, along with the reappearance of the early endocrine marker genes. Glucose transporters transport glucose into β-cells, thereby controlling insulin release during hyperglycaemia. This stimulates glycolysis through rises in intracellular calcium (a process enhanced by vitamin D) (Norman et al., 1980), activating 2 of 4 proteinases. The rise in calcium activates half of pancreatic β-cell proinsulinases, thus releasing free insulin from granules. The synthesis of ATP from glucose by glycolysis, Krebs cycle and oxidative phosphorylation plays a role in insulin release. Some studies have found that the β-cells contain high levels of the vitamin D receptor; however, the role that this plays in maintaining the maturity of the β-cells remains unknown. Further research is required to develop a more in-depth understanding of the role VDR plays in β-cell function and the processes by which the beta cell function is preserved.

Transient Impairment of Islet Architectural Development in Pancreas-Specific Bmpr1a-Deleted Prenatal Mice Involves Reduced Expression of E-Cadherin

Bone morphogenetic protein (BMP) signaling plays critical roles on the development of a large array of embryonic organs and promotes the in vitro formation of pancreatic cystoid colonies containing insulin-producing cells. However, this signaling and its underlying mechanism on in vivo development of prenatal pancreas have not been clearly understood. To address these questions, we analyzed, with a variety of techniques, the prenatal mouse pancreas after Pdx1 (the pancreas and duodenum homeobox factor 1 gene)-driving deletion of the BMP receptor type 1a gene (Bmpr1a). In this study, we report that the Pdx1-driving deletion of Bmpr1a transiently disrupted only the assembly of architectural structure of prenatal islets. The differentiation of endocrine lineage cells and the development of pancreatic acinar tissue were comparable between Bmpr1a-deleted fetuses and -undeleted Controls throughout the period examined. Molecular studies revealed that among many proteins surveyed, the key cell-cell interaction molecule E-cadherin (E-cad) only was expressed significantly less at both messenger RNA (mRNA) and protein levels in Bmpr1a-deleted than Control fetal endocrine cells. We thus conclude that BMP signaling transiently regulates the expression of E-cad and the establishment of prenatal islet architecture.

Insulin-secreting β cells require a post-genomic concept

Pancreatic insulin-secreting β cells are essential in maintaining normal glucose homeostasis accomplished by highly specialized transcription of insulin gene, of which occupies up to 40% their transcriptome. Deficiency of these cells causes diabetes mellitus, a global public health problem. Although tremendous endeavors have been made to generate insulin-secreting cells from human pluripotent stem cells (i.e., primitive cells capable of giving rise to all cell types in the body), a regenerative therapy to diabetes has not yet been established. Furthermore, the nomenclature of β cells has become inconsistent, confusing and controversial due to the lack of standardized positive controls of developmental stage-matched in vivo cells. In order to minimize this negative impact and facilitate critical research in this field, a post-genomic concept of pancreatic β cells might be helpful. In this review article, we will briefly describe how β cells were discovered and islet lineage is developed that may help understand the cause of nomenclatural controversy, suggest a post-genomic definition and finally provide a conclusive remark on future research of this pivotal cell.

Pigment epithelium-derived factor (PEDF) regulates metabolism and insulin secretion from a clonal rat pancreatic beta cell line BRIN-BD11 and mouse islets

Pigment epithelium-derived factor (PEDF) is a multifunctional glycoprotein, associated with lipid catabolism and insulin resistance. In the present study, PEDF increased chronic and acute insulin secretion in a clonal rat β-cell line BRIN-BD11, without alteration of glucose consumption. PEDF also stimulated insulin secretion from primary mouse islets. Seahorse flux analysis demonstrated that PEDF did not change mitochondrial respiration and glycolytic function. The cytosolic presence of the putative PEDF receptor - adipose triglyceride lipase (ATGL) - was identified, and ATGL associated stimulation of glycerol release was robustly enhanced by PEDF, while intracellular ATP levels increased. Addition of palmitate or ex vivo stimulation with inflammatory mediators induced β-cell dysfunction, effects not altered by the addition of PEDF. In conclusion, PEDF increased insulin secretion in BRIN-BD11 and islet cells, but had no impact on glucose metabolism. Thus elevated lipolysis and enhanced fatty acid availability may impact insulin secretion following PEDF receptor (ATGL) stimulation.

Multipotent pancreas progenitors: Inconclusive but pivotal topic

The establishment of multipotent pancreas progenitors (MPP) should have a significant impact not only on the ontology of the pancreas, but also for the translational research of glucose-responding endocrine β-cells. Deficiency of the latter may lead to the pandemic type 1 or type 2 diabetes mellitus, a metabolic disorder. An ideal treatment of which would potentially be the replacement of destroyed or failed β-cells, by restoring function of endogenous pancreatic endocrine cells or by transplantation of donor islets or in vitro generated insulin-secreting cells. Thus, considerable research efforts have been devoted to identify MPP candidates in the pre- and post-natal pancreas for the endogenous neogenesis or regeneration of endocrine insulin-secreting cells. In order to advance this inconclusive but critical field, we here review the emerging concepts, recent literature and newest developments of potential MPP and propose measures that would assist its forward progression.

Transcriptome of pancreas-specific Bmpr1a-deleted islets links to TPH1-5-HT axis

Bone morphogenetic protein (BMP) signaling is crucial for the development and function of numerous organs, but its role on the function of pancreatic islets is not completely clear. To explore this question, we applied the high throughput transcriptomic analyses on the islets isolated from mice with a pancreas-specific deletion of the gene, Bmpr1a, encoding the type 1a BMP receptor. Consistently, these pBmpr1aKO mice had impaired glucose homeostasis at 3 months, and were more severely affected at 12 months of age. These had lower fasting blood insulin concentrations, with reduced expression of several key regulators of β-cell function. Importantly, transcriptomic profiling of 3-month pBmpr1aKO islets and bioinformatic analyses revealed abnormal expression of 203 metabolic genes. Critically among these, the tryptophan hydroxylase 1 gene (Tph1), encoding the rate-limiting enzyme for the production of 5-hydroxytryptamine (5-HT) was the highest over-expressed one. 5-HT is an important regulator of insulin secretion from β cells. Treatment with excess 5-HT inhibited this secretion. Thus our transcriptomic analysis links two highly conserved molecular pathways the BMP signaling and the TPH1–5-HT axis on glucose homeostasis.

Pancreatic stem cells remain unresolved

Diabetes mellitus is caused by absolute (type 1) or relative (type 2) deficiency of insulin-secreting islet β cells. An ideal treatment of diabetes would, therefore, be to replace the lost or deficient β cells, by transplantation of donated islets or differentiated endocrine cells or by regeneration of endogenous islet cells. Due to their ability of unlimited proliferation and differentiation into all functional lineages in our body, including β cells, embryonic stem cells and induced pluripotent stem cells are ideally placed as cell sources for a diabetic transplantation therapy. Unfortunately, the inability to generate functional differentiated islet cells from pluripotent stem cells and the poor availability of donor islets have severely restricted the broad clinical use of the replacement therapy. Therefore, endogenous sources that can be directed to becoming insulin-secreting cells are actively sought after. In particular, any cell types in the developing or adult pancreas that may act as pancreatic stem cells (PSC) would provide an alternative renewable source for endogenous regeneration. In this review, we will summarize the latest progress and knowledge of such PSC, and discuss ways that facilitate the future development of this often controversial, but crucial research.

Pancreatic stem cells: from possible to probable

Type 1 and some forms of type 2 diabetes mellitus are caused by deficiency of insulin-secretory islet β cells. An ideal treatment for these diseases would therefore be to replace β cells, either by transplanting donated islets or via endogenous regeneration (and controlling the autoimmunity in type 1 diabetes). Unfortunately, the poor availability of donor islets has severely restricted the broad clinical use of islet transplantation. The ability to differentiate embryonic stem cells into insulin-expressing cells initially showed great promise, but the generation of functional β cells has proven extremely difficult and far slower than originally hoped. Pancreatic stem cells (PSC) or transdifferentiation of other cell types in the pancreas may hence provide an alternative renewable source of surrogate β cells. However, the existence of PSC has been hotly debated for many years. In this review, we will discuss the latest development and future perspectives of PSC research, giving readers an overview of this controversial but important area.

Directed differentiation of embryonic stem cells allows exploration of novel transcription factor genes for pancreas development

Embryonic stem cells (ESCs) have been promised as a renewable source for regenerative medicine, including providing a replacement therapy in type 1 diabetes. However, they have not yet been differentiated into functional insulin-secreting β cells. This is due partially to the knowledge gap regarding the transcription factors (TFs) required for pancreas development. We hypothesize that, if directed differentiation in vitro recapitulates the developmental process in vivo, ESCs provide a powerful model to discover novel pancreatic TF genes. Guided by knowledge of their normal development and using RT-PCR and immunochemical analyses, we have established protocols for directed differentiation of mouse ESCs into pancreatic progenitors. Microarray analyses of these differentiating ESC cells at days 0, 4, 8 and 15 confirmed their sequential differentiation. By day 15, we found up-regulation of a group of pancreatic progenitor marker genes including Pdx1, Ptf1a, Nkx6.1, Pax4 and Pax6. Consistently, Pdx1-immunoreactive cells were detected on day 15. Most of these Pdx1(+) cells also expressed Nkx6.1. Bioinformatic analyses of sequential datasets allowed identification of over 20 novel TF genes potentially important for pancreas development. The dynamic expression of representative known and novel genes was confirmed by quantitative real time RT-PCR analysis. This strategy may be modified to study novel regulatory molecules for development of other tissue and organ systems.

In vitro reprogramming of rat bone marrow-derived mesenchymal stem cells into insulin-producing cells by genetically manipulating negative and positive regulators

Islet cell replacement therapy represents the most promising approach for the cure of type 1 diabetes if autoimmunity to β cells is under control. However, this potential is limited by a shortage of pancreas donors. To address the donor shortage problem, we determined whether bone marrow-derived mesenchymal stem cells (bmMSCs) can be directly reprogrammed to islet lineages by simultaneously forced suppression and over-expression of key regulator genes that play critical roles during pancreas development. Here, we report that rat bmMSCs were converted in vitro into insulin-producing cells by suppressing two-repressor genes repressor element-1 silencing transcription factor/neuronal restrictive silencing factor (Rest/Nrsf) and sonic hedgehog (Shh) and by over-expressing pancreas and duodenal transcription factor 1 (Pdx1). The reprogrammed bmMSCs expressed both genes and proteins specific for islet cells. These converted cells were capable of releasing insulin in a glucose-responsive manner. Our study suggests that bmMSCs may ultimately be reprogrammed to functional insulin-secreting cells.

TGF-beta induces telomerase-dependent pancreatic tumor cell cycle arrest

Recent studies suggest that transforming growth factor beta (TGF-beta) inhibits telomerase activity by repression of the telomerase reverse transcriptase (TERT) gene. In this report, we show that TGF-beta induces TERT repression-dependent apoptosis in pancreatic tumor, vascular smooth muscle, and cervical cancer cell cultures. TGF-beta activates Smad3 signaling, induces TERT gene repression and results in G1/S phase cell cycle arrest and apoptosis. TERT over-expression stimulates the G1/S phase transition and alienates TGF-beta-induced cell cycle arrest and apoptosis. Our data suggest that telomere maintenance is a limiting factor of the transition of the cell cycle. TGF-beta triggers cell cycle arrest and death by a mechanism involving telomerase deregulation of telomere maintenance.

Abnormal glucose metabolism in heterozygous mutant mice for a type I receptor required for BMP signaling

BMPRIA and its high-affinity ligand BMP4 have recently been shown to be expressed in the beta-cells of the pancreas. Here, we report the abnormalities of heterozygous mice for Bmpr1a in glucose metabolism during the course of intraperitoneal glucose tolerance test. The heterozygous mice had increased blood glucose levels throughout the first 2.5 h after the administration of glucose. Analysis of glucose-stimulated insulin secretion (GSIS) indicates that insulin secretion in the heterozygous mice is compromised, and induction of secreted insulin by stimulation is substantially lower compared with the wild-type controls. No apparent abnormalities in pancreas, thyroid, and liver were seen upon histological examination. Real-time PCR results of selected genes showed an increase in the mRNA level of Ins1 and Ins2 in the heterozygous group. These results indicate that the glucose-sensing pathway in these heterozygous mice is altered because of the heterozygosity in Bmpr1a. Together, our data suggest that BMP signaling through BMPRIA plays an important role in glucose metabolism and possibly working through the GSIS pathway.

Activin inhibits telomerase activity in cancer

Activin is a pleiotropic cytokine with broad tissue distributions. Recent studies demonstrate that activin-A inhibits cancer cell proliferation with unknown mechanisms. In this report, we demonstrate that recombinant activin-A induces telomerase inhibition in cancer cells. In breast and cervical cancer cells, activin-A resulted in telomerase activity in a concentration-dependent manner. Significant inhibition was observed at 10 ng/ml of activin-A, with a near complete inhibition at 80 ng/ml. Consistently, activin-A induced repression of the telomerase reverse transcriptase (hTERT) gene, with the hTERT gene to be suppressed by 60-80% within 24h. In addition, activin-A induced a concomitant increase in Smad3 signaling and decrease of the hTERT gene promoter activity in a concentration-dependent fashion. These data suggest that activin-A triggered telomerase inhibition by down-regulating hTERT gene expression is involved in activin-A-induced inhibition of cancer cell proliferation.

Laminin-1 and epidermal growth factor family members co-stimulate fetal pancreas cell proliferation and colony formation

The epidermal growth factor (EGF) family is implicated in the development and function of multiple cells and organs, including the pancreas. We used a serum-free, low-cell density culture system to investigate the effect of EGFs on fetal pancreas cells. By RT-PCR, the EGF receptors ErbB 1-3 were detected in the developing mouse pancreas between embryonic day (E) 13.5 and E17.5, whereas ErbB4 was not detected until E17.5. The presence but not absence of the basement membrane glycoprotein laminin-1, betacellulin, and to a lesser extent EGF, transforming growth factor alpha, heparin binding EGF, and epiregulin induced E15.5 pancreatic cells to proliferate and form cystoid and solid colonies. These results demonstrate that laminin-1 and EGF signaling pathways interact to promote pancreas development.

Convergence of bone morphogenetic protein and laminin-1 signaling pathways promotes proliferation and colony formation by fetal mouse pancreatic cells

We previously reported that bone morphogenetic proteins (BMPs), members of the transforming growth factor superfamily, together with the basement membrane glycoprotein laminin-1 (Ln-1), promote proliferation of fetal pancreatic cells and formation of colonies containing peripheral insulin-positive cells. Here, we further investigate the cross-talk between BMP and Ln-1 signals. By RT-PCR, receptors for BMP (BMPR) (excepting BMPR-1B) and Ln-1 were expressed in the fetal pancreas between E13.5 and E17.5. Specific blocking antibodies to BMP-4 and -6 and selective BMP antagonists partially inhibited colony formation by fetal pancreas cells. Colony formation induced by BMP-6 and Ln-1 was completely abolished in a dose-dependent manner by blocking Ln-1 binding to its alpha(6) integrin and alpha-dystroglycan receptors or by blocking the Ln-1 signaling molecules, phosphatidyl-inositol-3-kinase (P13K) and MAP kinase kinase-1. These results demonstrate a convergence of BMP and Ln-1 signaling through P13K and MAP kinase pathways to induce proliferation and colony formation in E15.5 fetal mouse pancreatic cells.

A mutation in SART3 gene in a Chinese pedigree with disseminated superficial actinic porokeratosis

BACKGROUND

Disseminated superficial actinic porokeratosis (DSAP) is an uncommon autosomal dominant chronic disorder of keratinization, characterized by multiple superficial keratotic lesions surrounded by a slightly raised keratotic border. Thus far, although two loci for DSAP have been identified, and the genetic basis and pathogenesis of this disorder have not been elucidated.

OBJECTIVES

To determine the locus of DSAP and identify the candidate gene(s) of the disease.

METHODS

Genome-wide scan and linkage analysis were performed in a six-generation Chinese family with DSAP. The coding exons of the candidate genes were sequenced to analyse and detect the nucleotide variations.

RESULTS

Linkage analysis showed that the maximum two-point lod score of 5.56 was obtained with the marker D12S79 at a recombination fraction theta of 0.00. Haplotype analysis defined the critical region for DSAP between D12S330 and D12S1612 on 12q24.1-24.2. By sequence analysis, we found a Val591Met mutation in SART3 in all affected individuals of the family.

CONCLUSION

SART3 is a candidate gene for DSAP, and is possibly involved in the pathogenesis of DSAP.

Distinct distribution of laminin and its integrin receptors in the pancreas

Tissue function is regulated by the extracellular microenvironment including cell basement membranes, in which laminins are a major component. Previously, we found that laminin-1 promotes differentiation and survival of pancreatic islet cells. Here we characterize the expression pattern of laminins and their integrin receptors in adult pancreas. Although they are expressed in the basement membrane of acinar cells and duct epithelium, no laminin chains examined were detected extracellularly in the pancreatic islets. In contrast to laminin beta(1)- and gamma(1)-chains, the alpha(1)-chain, unique to laminin-1, was not detected. Laminin-10 (alpha(5)beta(1)gamma(1)) was expressed in acinar tissue, whereas laminins-2 (alpha(2)beta(1)gamma(1)) and -10 were expressed in the blood vessels. The laminin connector molecule, nidogen-1, had a distribution similar to that of laminin beta(1) and gamma(1), whereas fibulin-1 and -2, which compete with nidogen-1, were mostly confined to blood vessels. Integrin subunits alpha(6) and alpha(3) were detected in acinar cells and duct epithelial cells, but alpha(6) was absent in islet cells. Integrin alpha(6)beta(4) was detected only in duct cells, alpha(6)beta(1) in both acinar and ductal cells, and alpha(3)beta(1) in acinar, duct, and islet cells. These findings are a basis for further investigation of the role of extracellular matrix molecules and their receptors in pancreas function.

Extracellular signals and pancreatic beta-cell development: a brief review

Cell lineage development is a finely tuned process of proliferation and differentiation, survival and apoptosis, that is regulated by numerous extracellular signals. Here we review some of the extracellular signals--including insoluble cell-cell and extracellular matrix-cell interactions, as well as soluble factors--that appear critical for pancreatic beta-cell development. Knowledge of how these signals control the development of pancreatic endocrine stem/precursor cells into fully functional insulin-secreting beta cells is a platform for the restoration of beta-cell function and the cure therapy of type 1 diabetes.

Male germ cell transplantation: promise and problems

Male germ cell transplantation is a novel technique in which donor male stem germ cells are surgically transferred to the seminiferous tubules of a recipient testis by direct injection or via the rete testis or efferent duct. All germ cells that are destined to become stem spermatogonia are defined as male stem germ cells, including primordial germ cells from the gonadal ridges, and gonocytes and stem spermatogonia from the testis, all of which are transplantable and capable of undergoing normal spermatogenesis. Xenotransplantation of male germ cells from one species into the testis of another species, including human testicular cells in the mouse, has so far proved to be unsuccessful. However, the immunodeficient mouse testis can support rat spermatogenesis and produce apparently normal rat spermatozoa. The underlying mechanisms remain elusive. The present mini-review will focus on the importance of stem spermatogonial transplantation for testicular stem cell biology and discuss the likelihood of immune rejection after transplantation, which may limit the success of all male germ cell transplantation.

Bone morphogenetic proteins promote development of fetal pancreas epithelial colonies containing insulin-positive cells

Extracellular signals that guide pancreas cell development are not well characterized. In an in vitro culture system of dissociated pancreas cells from the E15.5 mouse fetus we show that, in the presence of the extracellular matrix protein laminin-1, bone morphogenetic proteins (BMPs-4, -5 and -6)promote the development of cystic epithelial colonies. Transforming growth factor β1 (TGF-β1) and activin A antagonise this effect of BMP-6 and inhibit colony formation. Histological analysis revealed that the colonies are composed of E-cadherin-positive epithelial cells, which in localised areas are insulin positive. The colonies also contain occasional glucagon-positive cells, but no somatostatin- or α-amylase-positive cells. These findings indicate that members of the TGF-β superfamily regulate pancreas epithelial cell development and can promote the formation of islet-like structures in vitro.

[Clinical observation of compound salvia injection in treating mid-severe infantile hypoxic-ischemic encephalopathy]

OBJECTIVE

To observe the changes of endothelin-1 (ET-1), nitrogen oxide (NO) and creatine phosphokinase BB isozyme (CK-BB) in blood and cerebrospinal fluid (CSF) in patients of infantile hypoxic-ishemic encephalopathy (HIE), and explore the efficacy of compound Salvia injection (CSI) in treating mid-severe HIE.

METHODS

Sixty mid-severe infantile HIE patients were divided randomly into the treated and the control group. To the treated group CSI was added on the basis of conventional treatment, and to the control group the conventional treatment was given alone. The blood and CSF content of ET-1, NO and CK-BB at acute and convalescent stage in the two groups were determined and the therapeutic effects were compared between the two groups.

RESULTS

The markedly effective rate and effective rate of the treated group was 80.0% and 93.3% respectively, while that of the control group was 66.7% and 83.3% respectively, the therapeutic effect in the treated group were obviously superior to that in the control group, the difference was significant (P < 0.05).

CONCLUSION

ET-1, NO and CK-BB participated the pathological process of HIE. CSI was markedly effective in treating mid and severe HIE infants.

Purification and characterization of primordial germ cells in male rat fetuses

The primordial germ cells in the testes of male rat fetuses at 15.5 days post coitum were purified by equilibrium centrifugation on a discontinuous Percoll gradient column after dissociation by trypsin-EDTA treatment and characterized before and after purification. Gonadal dimorphism first becomes evident at 14.5 days post coitum but the "stripey" appearance can not be observed in every fetal testis. Complete dissociation of the testes was essential for successful purification of the primordial germ cells. Using the isolation technique described here, over 50% of the primordial germ cells (around 10,000) could be harvested from each fetal testis with about 95% viability as determined by trypan blue exclusion and 90% purity, as determined by alkaline phosphatase histochemistry. Prior to and following purification, the primordial germ cells were characterized by their large size and round or oval nuclei. Their nucleoli were large and located centrally or eccentrically in the nucleus. The mitochondria were large, and round or oval, and there were a great number of ribosomes and polysomes dispersed in the cytoplasm. All these characteristics were similar to that of type A spermatogonia in postnatal testes. These morphological aspects correlate the observation that the primordial germ cells may be able to undergo normal spermatogenesis in an adult recipient testis.

Regulation of laminin 1-induced pancreatic beta-cell differentiation by alpha6 integrin and alpha-dystroglycan

BACKGROUND

The ability to manipulate the development of pancreatic insulin-producing beta cells has implications for the treatment of type 1 diabetes. Previously, we found that laminin-1, a basement membrane trimeric glycoprotein, promotes beta-cell differentiation. We have investigated the mechanism of this effect, using agents that block the receptors for laminin-1, alpha6 integrin, and alpha-dystroglycan (alpha-DG).

MATERIALS AND METHODS

Dissociated cells from 13.5-day postcoitum (dpc) fetal mouse pancreas were cultured for 4 days with laminin-1, with and without monoclonal antibodies and other agents known to block integrins or alpha-DG. Fetuses fixed in Bouin's solution or fetal pancreas cells fixed in 4% paraformaldehyde were processed for routine histology and for immunohistology to detect hormone expression and bromodeoxyuridine (BrdU) uptake.

RESULTS

Blocking the binding of laminin-1 to alpha6 integrin with a monoclonal antibody, GoH3, abolished cell proliferation (BrdU uptake) and doubled the number of beta cells. Inhibition of molecules involved in alpha6 integrin signaling (phosphotidylinositol 3-kinase, F-actin, or mitogen-activated protein kinase) had a similar effect. Nevertheless, beta cells appeared to develop normally in alpha6 integrin-deficient fetuses. Blocking the binding of laminin-1 to alpha-DG with a monoclonal antibody, IIH6, dramatically decreased the number of beta cells. Heparin, also known to inhibit laminin-1 binding to alpha-DG, had a similar effect. In the presence of heparin, the increase in beta cells in response to blocking alpha integrin with GoH3 was abolished.

CONCLUSIONS

These findings reveal an interplay between alpha6 integrin and alpha-DG to regulate laminin-1-induced beta-cell development. Laminin-I had a dominant effect via alpha-DG to promote cell survival and beta-cell differentiation, which was modestly inhibited by alpha6 signaling.

Laminin-1 promotes differentiation of fetal mouse pancreatic beta-cells

Extracellular factors that regulate the growth and differentiation of cell lineages in the pancreatic primordia are poorly understood. Identification of these factors for pancreatic islet beta-cells could open new avenues for the treatment of insulin-dependent diabetes. We developed a low cell density serum-free culture system for dissociated pancreatic cells from the 13.5-day mouse fetus and investigated the effects of extracellular matrix proteins on differentiation of islet cells. After 4 days in culture, total cell number decreased by two-thirds, but insulin-positive beta-cell number increased 10-fold. Both of collagens I and IV inhibited cell survival (by >50%), whereas fibronectin had no effect. In the presence of soluble laminin-1, however, the number of beta-cells increased linearly by 60-fold without an increase in the total cell number; glucagon-positive cell number was unchanged, and somatostatin and pancreatic polypeptide-positive cells were not detected. The effect of laminin-1 was completely blocked by a monoclonal rat anti-laminin-1 antibody. In the presence of laminin-1, the thymidine analogue, BrdU, was incorporated into only 2.5% of cells, which were mainly insulin-negative at days 1-3. Laminin-1 appeared, therefore, to induce differentiation of beta-cells from precursor cells in day-13.5 fetal pancreas. Laminin-1 was shown to be expressed in the epithelial basement membrane of the 13.5- to 17.5-day fetal pancreas. These findings provide the first evidence of a role for laminin-1 to promote differentiation of pancreatic beta-cells.

Male germ cell transplantation: present achievements and future prospects

Germ cells are unique, since their surviving descendants can undergo meiosis and differentiate into gametes, which transmit genetic material from one generation to another. We now know that male germ cells, whether they be primordial germ cells in gonadal ridges, gonocytes, or stem spermatogonia, are transplantable. The donor cells can be transferred by direct microinjection into the seminiferous tubules, rete testis or efferent ducts, depending on the recipient species. Following transplantation, the donor cells undergo spermatogenesis in the host's seminiferous tubules in rats and mice, and have even sired offspring in mice. Interspecific germ cell transfer is possible if the recipient's immune system is defective; nude or SCID mice can even produce rat spermatozoa. However, the major obstacle restricting widespread use of this new technology is its extremely low success rate. This article discusses some ideas for improving the success rate of the transfer technique, and considers several potential applications.

Behaviour of spermatogonia following recovery from busulfan treatment in the rat

This study describes the morphological behaviour of spermatogonia following recovery from two doses of busulfan treatment in the rat. Twenty days after the second intraperitoneal injection of busulfan, the testes lost most of their spermatogenic cells and there were fewer dispersed singly surviving spermatogonia. These surviving cells were in close contact with the basal portions of adjacent Sertoli cells and the shrunken basal lamina, and were the source for repopulating the depleted seminiferous epithelium. During the initial stage of repopulation (48 days later), surviving spermatogonia underwent a phase of active proliferation: type A spermatogonia underwent symmetric and asymmetric divisions; type B spermatogonia underwent asynchronous differentiation. At day 96, normal spermatogenesis was fully recovered in many seminiferous tubules, represented by 80% of the rats regaining various degrees of fertility at day 120. These data provide an additional model for the study of self-renewal of stem spermatogonia and suggest that the asymmetric division of type A spermatogonia and their close contact with both the basal lamina and the Sertoli cells may be involved in regulating the number of stem spermatogonia and the delicate process of normal spermatogenesis.

Different fate of primordial germ cells and gonocytes following transplantation

We have previously demonstrated that both donor primordial germ cells (PGCs) and gonocytes are capable of establishing spermatogenesis in the lumen of the seminiferous tubules of an adult host following transplantation in rats. Here we show that the PGCs, either in crude suspensions or after purification, undergo spermatogenesis only in the intraluminal compartment of the host's seminiferous tubules, while 4-5 days postpartum gonocytes also interdigitate with the host's seminiferous epithelium. The donor seminiferous epithelium was always in synchrony with the cycles of the host's spermatogenesis. It seems that the pattern of spermatogenesis of donor germ cells following transplantation in terms of its spacial location and the connection with the host's seminiferous epithelium depends on their developmental stages at transfer.

Ultrastructural characteristics of primordial germ cells and their amoeboid movement to the gonadal ridges in the tammar wallaby

The primordial germ cells (PGCs) of tammar wallaby fetuses are large cells with large nuclei. The cytoplasm of the PGCs contains characteristic spherical mitochondria and abundant ribosomes that make the cyoplasm appear dense. No permanent junctional complexes between PGCs and somatic cells were observed, and there were few cytoplasmic inclusions. The majority of migrating PGCs were observed outside the gonad in the dorsal mesentery and in the tissues adjacent to the gonad. The migrating PGCs have many finger-like, blunt pseudopodia, within which microfilament bundles are observed. The numerous dumbell-like PGCs with polarised cytoplasm suggest that the PGCs of this marsupial move to the gonadal ridges by amoeboid movement, but once the PGCs reach the gonadal ridge, they assume their more characteristic ovoid shape.

Male germ cell transplantation in rats: apparent synchronization of spermatogenesis between host and donor seminiferous epithelia

Primordial germ cells (PGC) and gonocytes from male Sprague-Dawley rat fetuses and neonates were transplanted via the rete testis into the lumen of the seminiferous tubules of recipient adult Long Evans rats. The donor germ cells apparently differentiated into mini-tubules or irregular segments of seminiferous epithelium within the lumen of the host seminiferous tubules, and exhibited qualitatively normal spermatogenesis in 10 out of 16 recipients. The stage of spermatogenesis of the intraluminal epithelium was synchronized closely with that of the adjacent seminiferous tubule epithelium, suggesting that the spermatogenic cycle is regulated locally by the intraluminal microenvironment. Male germ cell transplantation provides an interesting new tool for investigating the control of spermatogenesis.

Postnatal differentiation and development of the rat epididymis: a stereological study

Postnatal development and differentiation of the rat epididymis was studied in the rat from 15 to 120 days of life using stereological techniques. Both the relative volume (volume density) and absolute volume of the epithelial, interstitial, and luminal compartments in the initial segment, caput, corpus, and cauda epididymides were determined. In all segments the volume density of the epithelial compartment increased between days 15 and 30 before falling to adult values at 45 days in the initial segment (0.476 +/- 0.031), at 60 days in the caput (0.258 +/- 0.028) and at 90 days in the corpus (0.245 +/- 0.007) and cauda (0.140 +/- 0.004). The relative volume of the interstitium decreased, whilst that of the lumen increased over the same period with adult values being achieved earlier in the proximal segments than in the distal segments. In contrast to volume fraction the absolute volume of all compartments in all segments increased from day 15 to day 90. Between 90 and 120 days the absolute volumes of compartments in the initial segment and caput showed little volume change. All compartments in the corpus and cauda showed significant increases in volume over the same period. A similar pattern of development was observed with respect to the surface area of both the luminal and basement membrane aspects of the epithelium; surface area per unit volume (surface density) in all segments reached adult values at approximately 60 days, whilst the increase in absolute area of the surfaces ceased at 90 days in the initial segment and caput and continued to 120 days in the corpus and cauda.(ABSTRACT TRUNCATED AT 250 WORDS)