Expression of stem cell markers and transcription factors during the remodeling of the rat pancreas after duct ligation

Comprehensive summary: the role of PBX1 in development and cancers

PBX1 is a transcription factor that can promote the occurrence of various tumors and play a reg-ulatory role in tumor growth, metastasis, invasion, and drug resistance. Furthermore, a variant generated by fusion of E2A and PBX1, E2A-PBX1, has been found in 25% of patients with childhood acute lymphoblastic leukemia. Thus, PBX1 is a potential therapeutic target for many cancers. Here, we describe the structure of PBX1 and E2A-PBX1 as well as the molecular mecha-nisms whereby these proteins promote tumorigenesis to provide future research directions for developing new treatments. We show that PBX1 and E2A-PBX1 induce the development of highly malignant and difficult-to-treat solid and blood tumors. The development of specific drugs against their targets may be a good therapeutic strategy for PBX1-related cancers. Furthermore, we strongly recommend E2A-PBX1 as one of the genes for prenatal screening to reduce the incidence of childhood hematological malignancies.

Protective effects of Coenzyme Q10 against acute pancreatitis

Acute pancreatitis (AP) refers to inflammation in the pancreas, which may lead to death in severe cases. Coenzyme Q10 (Q10), generally known to generate energy, plays an important role as an anti-oxidant and anti-inflammatory effector. Here, we showed the effect of Q10 on inflammatory response in murine AP model. For this study, we induced AP by injection of cerulein intraperitoneally or pancreatic duct ligation (PDL) in mice. The level of cytokines and digestive enzymes were measured in pancreas, and blood. All pancreatic tissues were excised for investigation such as histological changes, infiltration of immune cells. Administration of Q10 attenuated the severity of AP and its associated pulmonary complication as shown by reduction of acinar cell death, parenchymal edema, inflammatory cell infiltration and alveolar thickening in both cerulein-induced AP and PDL-induced AP. Moreover, reduction of the cytokines such as interleukin (IL)-1β, IL-6 and tumor necrosis factor (TNF)-α were observed in pancreas and pancreatic acinar cells by Q10. Furthermore, Q10 reduced the infiltration of immune cells such as monocytes and neutrophils and augmentation of chemokines such as CC chemokine-2 (CCL2) and C-X-C chemokine-2 (CXCL2) in pancreas of AP mice. In addition, Q10 deactivates the phosphorylation of extracellular signal-regulated kinase (ERK) and c-jun NH₂-terminal kinase (JNK) in pancreas. In conclusion, these observations suggest that Q10 could attenuate the pancreatic damage and its associated pulmonary complications via inhibition of inflammatory cytokines and inflammatory cell infiltration and that the deactivation of ERK and JNK by Q10 might contribute to the attenuation of AP.

Long-term c-Kit overexpression in beta cells compromises their function in ageing mice

AIMS/HYPOTHESIS

c-Kit signalling regulates intracellular pathways that enhance beta cell proliferation, insulin secretion and islet vascularisation in mice up to 28 weeks of age and on short-term high-fat diet. However, long-term c-Kit activation in ageing mouse islets has yet to be examined. This study utilises beta cell-specific c-Kit-overexpressing transgenic (c-KitβTg) ageing mice (~60 weeks) to determine the effect of its activation on beta cell dysfunction and insulin secretion.

METHODS

Wild-type and c-KitβTg mice, aged 60 weeks, were examined using metabolic tests to determine glucose tolerance and insulin secretion. Pancreas histology and proteins in isolated islets were examined to determine the expression of beta cell transcription factors, proliferation and intracellular signalling. To determine the role of insulin receptor signalling in ageing c-KitβTg mice, we generated beta cell-specific inducible insulin receptor knockout in ageing c-KitβTg mice (c-KitβTg;βIRKO mice) and examined the ageing mice for glucose tolerance and islet histology.

RESULTS

Ageing c-KitβTg mice progressively developed glucose intolerance, compared with age-matched wild-type littermates, due to impaired insulin secretion. Increased beta cell mass, proliferation and nuclear forkhead box transcription factor O1 (FOXO1) expression and reduced exocytotic protein levels were detected in ageing c-KitβTg mouse islets. Protein analyses of isolated islets showed increased insulin receptor, phosphorylated IRS-1^Ser612 and cleaved poly(ADP-ribose) polymerase levels in ageing c-KitβTg mice. Ageing c-KitβTg mouse islets treated ex vivo with insulin demonstrated reduced Akt phosphorylation, indicating that prolonged c-Kit induced beta cell insulin insensitivity. Ageing c-KitβTg;βIRKO mice displayed improved glucose tolerance and beta cell function compared with ageing c-KitβTg mice.

CONCLUSIONS/INTERPRETATION

These findings indicate that long-term c-Kit overexpression in beta cells has a negative impact on insulin exocytosis and that temporally dependent regulation of c-Kit-insulin receptor signalling is important for optimal beta cell function.

KIT as a therapeutic target for non-oncological diseases

KIT is a receptor tyrosine kinase that after binding to its ligand stem cell factor activates signaling cascades linked to biological processes such as proliferation, differentiation, migration and cell survival. Based on studies performed on SCF and/or KIT mutant animals that presented anemia, sterility, and/or pigmentation disorders, KIT signaling was mainly considered to be involved in the regulation of hematopoiesis, gametogenesis, and melanogenesis. More recently, novel animal models and ameliorated cellular and molecular techniques have led to the discovery of a widen repertoire of tissue compartments and functions that are being modulated by KIT. This is the case for the lung, heart, nervous system, gastrointestinal tract, pancreas, kidney, liver, and bone. For this reason, the tyrosine kinase inhibitors that were originally developed for the treatment of hemato-oncological diseases are being currently investigated for the treatment of non-oncological disorders such as asthma, rheumatoid arthritis, and alzheimer's disease, among others. The beneficial effects of some of these tyrosine kinase inhibitors have been proven to depend on KIT inhibition. This review will focus on KIT expression and regulation in healthy and pathologic conditions other than cancer. Moreover, advances in the development of anti-KIT therapies, including tyrosine kinase inhibitors, and their application will be discussed.

Oxidative stress and NO generation in the rat pancreatitis induced by pancreatic duct ligation

The interaction between nitric oxide (NO) and superoxides is critical in the development of an acute pancreatitis. Previously, we reported that the expression of superoxides and of the NO-generating enzyme (NO synthase, NOS) was up-regulated in the human pancreatitis, especially within the exocrine compartment indicating an exceptional susceptibility of the exocrine parenchyma to oxidative stress. The aim of the present study was to compare the regulation of NO signalling pathways in the human pancreatitis and in an animal model of an acute pancreatitis induced by pancreatic duct ligation (PDL) in rats. In the PDL-induced rat pancreatitis, we revealed a similar pattern of oxidative stress and NOS up-regulation in acinar and in ductal compartments, like in the human pancreatitis. This demonstrates that the PDL-induced rat pancreatitis is a proper model for further studies of acute pancreatitis development in humans.

A survival Kit for pancreatic beta cells: stem cell factor and c-Kit receptor tyrosine kinase

The interactions between c-Kit and its ligand, stem cell factor (SCF), play an important role in haematopoiesis, pigmentation and gametogenesis. c-Kit is also found in the pancreas, and recent studies have revealed that c-Kit marks a subpopulation of highly proliferative pancreatic endocrine cells that may harbour islet precursors. c-Kit governs and maintains pancreatic endocrine cell maturation and function via multiple signalling pathways. In this review we address the importance of c-Kit signalling within the pancreas, including its profound role in islet morphogenesis, islet vascularisation, and beta cell survival and function. We also discuss the impact of c-Kit signalling in pancreatic disease and the use of c-Kit as a potential target for the development of cell-based and novel drug therapies in the treatment of diabetes.

Involvement of the parasympathetic nervous system in the initiation of regeneration of pancreatic β-cells

The mechanism that initiates regeneration of pancreatic β-cells is not clear at present. The vagal nerve is implicated in the regulation of gastrointestinal functions, glucose metabolism and proliferation of pancreatic β-cells under physiological conditions. To elucidate the triggering mechanism of the regeneration of pancreatic β-cells, we examined the involvement of the vagal nerve. To this end, we employed a rat pancreatic duct ligation (DL) model, in which profound β-cell neogenesis and β-cell proliferation were observed within a week. We administered atropine to block the vagal nerve. Administration of atropine inhibited proliferation of β-cells in both islets and islet-like cell clusters (ICC), without affecting ductal cell proliferation in the ligated pancreas. The numbers of PDX-1 and MafB-positive cells in or attaching to the ducts were significantly reduced by atropine. MafB/glucagon and MafB/insulin double-positive cells were also decreased by atropine. Finally, atropine reduced the number of MafA-positive ductal cells, all of which were positive for insulin, by 50% on day 5. These results strongly suggest that the vagal nerve is involved in β-cell proliferation, induction of endocrine progenitors and neogenesis of α- and β-cells.

The impact of potential islet precursor cells on islet autotransplantation outcomes

Islet autotransplant patients represent excellent subjects to assess the posttransplant impact of islet precursors, as chronic pancreatitis (CP) causes an elevation of ductal cells, pancreatic precursors cells, and hormone-positive acinar cells. The relationship between these cell types and autograft outcomes should be more apparent than would be the case in the context of an allograft program with confounding immunological variables. To improve diabetic control following total pancreatectomy for CP, nonpurified islets were autotransplanted into the liver. Pancreas specimens were recovered from 23 patients and stained for antigens including: insulin, glucagon, cytokeratin 19, cytokeratin 7, and PDX-1. In line with previous reports, the prevalence of ductal cells, non-islet endocrine cells and non-islet PDX-1-expressing cells was significantly higher in CP glands compared with normal pancreata. When correlating follow-up data (i.e., fasting and stimulated C-peptide/glucose levels and HbA1c%) with pancreas immunoreactivity, high levels of ductal cells, non-islet PDX-1-positive cells, and non-islet glucagon-positive cells were associated with superior outcomes, detectable up to 2 years posttransplant. To conclude, the acinar parenchyma and ductal epithelium of the CP pancreas show an upregulation of both endocrine and pre-endocrine cell types, which appear to have a positive effect on islet graft outcomes in autotransplantation setting.

Critical role of c-Kit in beta cell function: increased insulin secretion and protection against diabetes in a mouse model

AIMS/HYPOTHESIS

The receptor tyrosine kinase, c-Kit, and its ligand, stem cell factor, control a variety of cellular processes, including pancreatic beta cell survival and differentiation as revealed in c-Kit ( Wv ) mice, which have a point mutation in the c-Kit allele leading to loss of kinase activity and develop diabetes. The present study further investigated the intrinsic role of c-Kit in beta cells, especially the underlying mechanisms that influence beta cell function.

METHODS

We generated a novel transgenic mouse model with c-KIT overexpression specifically in beta cells (c-KitβTg) to further examine the physiological and functional roles of c-Kit in beta cells. Isolated islets from these mice were used to investigate the underlying molecular pathway of c-Kit in beta cells. We also characterised the ability of c-Kit to protect animals from high-fat-diet-induced diabetes, as well as to rescue c-Kit ( Wv ) mice from early onset of diabetes.

RESULTS

c-KitβTg mice exhibited improved beta cell function, with significantly improved insulin secretion, and increased beta cell mass and proliferation in response to high-fat-diet-induced diabetes. c-KitβTg islets exhibited upregulation of: (1) insulin receptor and IRSs; (2) Akt and glycogen synthase kinase 3β phosphorylation; and (3) transcription factors important for islet function. c-KIT overexpression in beta cells also rescued diabetes observed in c-Kit ( Wv ) mice.

CONCLUSIONS/INTERPRETATION

These findings demonstrate that c-Kit plays a direct protective role in beta cells, by regulating glucose metabolism and beta cell function. c-Kit may therefore represent a novel target for treating diabetes.

Inhibition of Gsk3β activity improves β-cell function in c-KitWv/+ male mice

Previous studies have shown that the stem cell marker, c-Kit, is involved in glucose homeostasis. We recently reported that c-Kit(Wv/+) male mice displayed the onset of diabetes at 8 weeks of age; however, the mechanisms by which c-Kit regulates β-cell proliferation and function are unknown. The purpose of this study is to examine if c-Kit(Wv/+) mutation-induced β-cell dysfunction is associated with downregulation of the phospho-Akt/Gsk3β pathway in c-Kit(Wv/+) male mice. Histology and cell signaling were examined in C57BL/6J/Kit(Wv/+) (c-Kit(Wv/+)) and wild-type (c-Kit(+/+)) mice using immunofluorescence and western blotting approaches. The Gsk3β inhibitor, 1-azakenpaullone (1-AKP), was administered to c-Kit(Wv/+) and c-Kit(+/+) mice for 2 weeks, whereby alterations in glucose metabolism were examined and morphometric analyses were performed. A significant reduction in phosphorylated Akt was observed in the islets of c-Kit(Wv/+) mice (P<0.05) along with a decrease in phosphorylated Gsk3β (P<0.05), and cyclin D1 protein level (P<0.01) when compared with c-Kit(+/+) mice. However, c-Kit(Wv/+) mice that received 1-AKP treatment demonstrated normal fasting blood glucose with significantly improved glucose tolerance. 1-AKP-treated c-Kit(Wv/+) mice also showed increased β-catenin, cyclin D1 and Pdx-1 levels in islets, demonstrating that inhibition of Gsk3β activity led to increased β-cell proliferation and insulin secretion. These data suggest that c-Kit(Wv/+) male mice had alterations in the Akt/Gsk3β signaling pathway, which lead to β-cell dysfunction by decreasing Pdx-1 and cyclin D1 levels. Inhibition of Gsk3β could prevent the onset of diabetes by improving glucose tolerance and β-cell function.

Potential therapeutic effect of bone marrow-derived mesenchymal stem cells in acute pancreatitis

Acute pancreatitis is an inflammatory disease with dropsical, hemorrhagic or even necrotic conditions of the pancreas caused by several factors. It has significant morbidity and mortality, but no specific therapy is available so far. Bone marrow-derived mesenchymal stem cells (BMSCs) have multiple differentiation potential. They can not only differentiate to form endoderm and ectoblast cells, but also participate in tissue regeneration, repair and anti-inflammation. Recent studies have demonstrated that BMSCs have potential therapeutical effect in acute pancreatitis. BMSCs can migrate to injury tissue, multiply, be transformed to pancreatic stem cells and then participate in the process of regeneration. They also renovate vascular endothelium to improve blood circulation, adjust and control the cytokines to decrease inflammation, and regulate immunization. Here we review the recent advances in understanding the role of BMSCs in the treatment of acute pancreatitis.

Beta cell mass regulation in the rat pancreas through glucocorticoids and thyroid hormones

OBJECTIVES

To compare the effects of glucocorticoids and thyroid hormones on the regulation of the beta cell mass in the pancreas, the rats were treated and analyzed for cell cycle changes in islet and duct cells as a source for beta cell neogenesis.

METHODS

Different rat pancreases were morphometrically analyzed after immunohistochemical staining for markers of proliferation and apoptosis.

RESULTS

Hydrocortisone increased the beta cell mass of rat pancreases through an increase of proliferation. This effect was counteracted by an increase of apoptosis. In contrast, thyroxine decreased the beta cell mass through an increase of apoptosis. This effect was counteracted by an increased rate of proliferation. Combined treatment with both hormones nullified the antagonistic effects on proliferation, apoptosis, and beta cell mass, thereby contributing to the maintenance of a stable total beta cell volume of the pancreas.

CONCLUSIONS

Hydrocortisone and thyroxine induced analogous changes in pancreatic duct cells, which represent a crucial pool for new beta cells through neogenesis. This may explain the positive effects of glucocorticoids in the immunosuppressive therapy regimen after whole pancreas transplantation upon long-term insulin independence, which is not achievable with isolated islets because of the loss of duct cells during the islet process before transplantation.

Acceleration of functional maturation and differentiation of neonatal porcine islet cell monolayers shortly in vitro cocultured with microencapsulated sertoli cells

The limited availability of cadaveric human donor pancreata as well as the incomplete success of the Edmonton protocol for human islet allografts fasten search for new sources of insulin the producing cells for substitution cell therapy of insulin-dependent diabetes mellitus (T1DM). Starting from isolated neonatal porcine pancreatic islets (NPIs), we have obtained cell monolayers that were exposed to microencapsulated monolayered Sertoli cells (ESCs) for different time periods (7, 14, 21 days). To assess the development of the cocultured cell monolayers, we have studied either endocrine cell phenotype differentiation markers or c-kit, a hematopoietic stem cell marker, has recently been involved with growth and differentiation of β-cell subpopulations in human as well as rodent animal models. ESC which were found to either accelerate maturation and differentiation of the NPIs β-cell phenotype or identify an islet cell subpopulation that was marked positively for c-kit. The insulin/c-kit positive cells might represent a new, still unknown functionally immature β-cell like element in the porcine pancreas. Acceleration of maturation and differentiation of our NPI cell monolayers might generate a potential new opportunity to develop insulin-producing cells that may suite experimental trials for cell therapy of T1DM.

MIN6 is not a pure beta cell line but a mixed cell line with other pancreatic endocrine hormones

MIN6 cells retains glucose-stimulated insulin secretion (GSIS) as isolated islets. We comprehensively evaluated the gene expression and production of other islet hormones in MIN6 cells. Islet hormones were demonstrated by immunohistochemical staining and measured by ELISA. The gene expression profiles of MIN6 cells were compared with those in the mouse islets obtained by the laser capture micro-dissection (LCM). MIN6 cells excreted insulin, glucagon, somatostatin and ghrelin. They expressed mRNAs of insulin I and II, proglucagon, somatostatin, pancreatic polypeptide (PP) and ghrelin which were shown in the mouse pancreatic islet core and periphery obtained by LCM. A variety of genes closely related to the islet hormone producing cells were expressed in MIN6. Confocal laser scanning microscopy revealed that MIN6 cells included not only insulin positive cells but also insulin and glucagon or somatostin double positive cells. Glucagon, somatostatin and ghrelin were detectable in the culture medium. The present study clearly demonstrated that MIN6 produce pancreatic endocrine cells. It would be possible to use this cell line as a model to research the development, cell differentiation and function of pancreatic islets.

Regenerative biology: a historical perspective and modern applications

Chronic diseases are both common and deadly. Due to the limitations of conventional therapies for chronic diseases such as advanced heart failure and diabetes mellitus, recent interest has been directed towards regenerative medicine. In this review, we examine the history of regenerative biology and emphasize the dynamic and multidisciplinary growth of this field. We highlight the spectrum of adult tissues that have a remarkable regenerative capacity (i.e., skeletal muscle) versus those that have a more limited regenerative capacity (i.e., heart). We further emphasize the use of relevant contemporary models for the study of regenerative biology (i.e., pancreatic regeneration), which highlight both the challenges for this field of study and the potential for regenerative medicine, including the use of cell-based strategies, to revolutionize medical therapies for chronic diseases.

c-Kit in early onset of diabetes: a morphological and functional analysis of pancreatic beta-cells in c-KitW-v mutant mice

c-Kit tyrosine receptor kinase, a well-established stem cell marker, is expressed in a variety of tissues including the pancreas. The involvement of c-Kit in fetal rat and human endocrine pancreatic development, survival, and function has been well characterized but primarily using in vitro experimental approaches. Therefore, the aim of the current study was to examine whether deficiency of a functional c-Kit receptor would have physiological and functional implications in vivo. We characterized the c-Kit mutant mouse, c-Kit(W-v/+), to evaluate the in vivo role of c-Kit in beta-cell growth and function. Here we report that male c-Kit(W-v/+) mice, at 8 wk of age, showed high fasting blood glucose levels and impaired glucose tolerance, which was associated with low levels of insulin secretion after glucose stimulation in vivo and in isolated islets. Morphometric analysis revealed that beta-cell mass was significantly reduced (50%) in male c-Kit(W-v/+) mice when compared with controls (c-Kit(+/+)) (P < 0.05). In parallel, a reduction in pancreatic duodenal homeobox-1 and insulin gene expression in whole pancreas as well as isolated islets of c-Kit(W-v/+) male mice was noted along with a decrease in pancreatic insulin content. Furthermore, the reduction in beta-cell mass in male c-Kit(W-v/+) mice was associated with a decrease in beta-cell proliferation. Interestingly, these changes were not observed in female c-Kit(W-v/+) mice until 40 wk of age. Our results clearly demonstrate that the c-Kit receptor is involved in the regulation of glucose metabolism, likely through an important role in beta-cell development and function.

Immunohistochemical analysis of nestin and c-kit and their significance in pancreatic tumors

The purpose of the present study was to clarify the difference of expression of two stem cell markers, nestin and c-kit, among various pancreatic epithelial tumors and evaluate their utility. Immunohistochemistry was done for 99 surgically resected pancreatic tumor specimens, including 20 ductal adenocarcinoma (DAC), two undifferentiated carcinomas (UC), 31 intraductal papillary-mucinous neoplasms (IPMN), six mucinous cystic neoplasms (MCN), five serous cystadenomas (SCA), six acinar cell carcinomas, two pancreatoblastoma (PB), eight solid-pseudopapillary neoplasms (SPN), and 19 endocrine neoplasms (EN). Nestin was widely expressed in four SPN, one PB, one SCA, sarcoma areas in two UC, one MCN, and one DAC, and an area of oncocytic component in one IPMN. Some of these SPN, SCA and sarcomatous or oncocytic components in which nestin was expressed, also coexpressed c-kit. Additionally, partial (scattered) expression of c-kit was observed in ductal elements of 16 DAC, eight IPMN, five MCN, and one UC, one SCA, and three EN. The eight c-kit-positive IPMN included four of 23 adenoma-to-border lesions and four of eight non-invasive-to-invasive carcinomas. The three EN were all carcinomas. These indicate that expression of two stem cell markers is different by tumor type, but the utility of judging direction or degree of differentiation and malignant grade on the basis of their expression status is suggested.

Expression of transcription factors and precursor cell markers during regeneration of beta cells in pancreata of rats treated with streptozotocin

An understanding of beta cell regeneration is needed if we are to develop new treatment modalities in diabetes mellitus. Lineage tracing studies have shown that all pancreatic cell types, including beta cells, arise from PDX-1-expressing precursor cells. We studied beta cell regeneration by analyzing the immunocytochemical expression of the transcription factors, PDX-1, PBX-1, and MEIS2, and that of the potential precursor cell markers, c-Kit and nestin, using the model of streptozotocin (STZ)-induced diabetes in rats. The pancreata were examined 3, 7, and 14 days after STZ administration. PDX-1 expression, but not that of MEIS2 and PBX-1, transiently increased on day 7. c-Kit expression was found to be upregulated in islet cells at all points in time, while nestin expression was lacking. Ki-67 labeling was increased in islets on days 3 and 7. These results suggest that temporary upregulation of PDX-1 and prolonged overexpression of c-Kit may play a role during beta cell regeneration.

Apoptosis, proliferation and differentiation patterns are influenced by Zebularine and SAHA in pancreatic cancer models

OBJECTIVE

Pancreatic cancer continues to be an urgent clinical problem. We used the novel DNA methyltransferase inhibitor Zebularine and the histone deacetylase inhibitor SAHA to investigate the epigenetic influence on viability and differentiation of the pancreatic cancer cell lines YAP C, DAN G and Panc-89 in vitro and in vivo.

MATERIAL AND METHODS

Cell vitality, proliferation and expression of PDX-1, cytokeratin 7 and 20, chromogranin A, vimentin, bax and bcl-2 were determined on the protein and mRNA level in vitro and in a subcutaneous xenograft model.

RESULTS

A time- and dose-dependent increase of apoptosis, paralleled by decreased proliferation, was observed after incubation with single agents or a combination therapy with lower concentrations. This was associated with up-regulation of pro-apoptotic bax and a phenotypic stabilization by the enhanced expression of cytokeratin 7. In vivo, growth of xenografts was delayed with the most pronounced effect in Panc-89 after 1 week of daily intraperitoneal injections of Zebularine paralleled with CK7 up-regulation and down-regulation of dedifferentiation markers.

CONCLUSIONS

Epigenetic modulation via inhibition of DNA methyltransferase and histone deacetylase induces apoptosis in human pancreatic cancer cells in vitro and delays xenograft growth in vivo, which is associated with a morphological/molecular phenotypic stabilization. These compounds may therefore be suitable as adjunctive therapeutic agents in the treatment of pancreatic cancer.

Marked stem cell factor expression in the airways of lung transplant recipients

BACKGROUND

Airways repair is critical to lung function following transplantation. We hypothesised that the stem cell factor (SCF) could play a role in this setting.

METHODS

We studied 9 lung transplant recipients (LTx recipients) during their first year postgraft, and evaluated SCF mRNA expression in bronchial biopsy specimens using on-line fluorescent PCR and SCF protein levels in bronchoalveolar lavage (BAL) and serum using ELISA. The expression of SCF receptor Kit was assessed using immunostaining of paraffin-embedded bronchial sections.

RESULTS

SCF mRNA was highly expressed during the early postgraft period [Month (M)1-M3] (300% increase vs controls: 356 vs 1.2 pg SCF/microg GAPDH cDNA, p < 0.001) and decreased thereafter (M4-M12: 187 pg/microg), although remaining at all times 10-100 times higher than in controls. While SCF protein levels in BAL were similar in LTx recipients and in controls, the SCF serum levels were at all times higher in LTx recipients than in controls (p < 0.05), with no relationship between these levels and the acute complications of the graft. Finally, Kit was strongly expressed by the mast cells as well as by the bronchial epithelium of LTx recipients.

CONCLUSION

SCF and Kit are expressed in bronchial biopsies from lung transplant recipients irrespective of the clinical status of the graft. A role for these factors in tissue repair following lung transplantation is hypothesised.

How can we get more beta cells?

The need for a reliable source of functional beta cells has led to many new investigations in an effort to drive the differentiation of embryonic stem cells, of putative stem cells, or of pancreatic progenitor cells to form new beta cells. There appears to be a plasticity of pancreatic cells in vitro that may be exploited to generate the necessary beta cells. Major questions still remain: whether there are true pancreatic stem cells, what are the pancreatic progenitor cells after birth, and whether expanded beta cells themselves could serve as the source.

Lymphatic spread of ductal pancreatic adenocarcinoma is independent of lymphangiogenesis

Early lymph node metastasis is common in pancreatic ductal adenocarcinoma (PDAC). The present study has examined the relationship of lymphatic spread to lymph vessel development and the expression of lymphangiogenic cytokines in a series of well-characterized PDACs. The hot spot method revealed the intratumoural and peritumoural lymphatic vessel density (LVD) to be slightly higher in PDACs than in the normal pancreas. The average intratumoural LVD, however, was strikingly decreased. There was no overexpression of vascular endothelial growth factor (VEGF)-C and VEGF-D in PDACs compared with the normal pancreas. LVD and expression of lymphangiogenic cytokines were not related to any of the biological tumour features or to patient survival. Three orthotopic nude mouse PDAC models did not reveal any increase in tumour-associated LVD, despite a high rate of lymph node metastasis. Lymph vessel proliferation was comparable in PDAC and chronic pancreatitis, in both humans and mice. In conclusion, increased lymphangiogenic activity is not required for and does not significantly affect the lymphatic spread of PDAC. The reduced number of human and murine intratumoural lymph vessels indicates that lymphatic metastasis takes place predominantly via peritumoural lymphatic vessels. The weak expression of lymphangiogenic cytokines in neoplastic cells and lymphatic vessel proliferation in peritumoural regions and chronic pancreatitis indicate that inflammation may be the reason for the low rate of lymphangiogenesis.

Historical, current and future perspectives on gastrointestinal and pancreatic endocrine tumors

Gastrointestinal and pancreatic endocrine tumors are neoplasms of which the pathogenesis is not completely understood and of which the clinical behavior is difficult to predict. Originally, Masson suggested that the cell of origin was an endocrine cell derived from the gastrointestinal epithelium. However, Pearse showed that the endocrine cells throughout the body shared various features, among others the amine precursor uptake and decarboxylation (APUD) capacity, and postulated the neural crest as the common origin for all APUD cells, a hypothesis that received support from the scientific community for many years. Now, biologists start to elucidate the various transcription factors that drive gastrointestinal development, and it has become evident that Masson was presumably right. Transcription factors relevant for development may also operate during tumorigenesis, and their expression may determine tumor biology. With other genetic factors, they may play a role in the pathogenesis of gastrointestinal and pancreatic endocrine tumors, and perhaps, their expression will turn out to be of prognostic or therapeutic value. In this review, current knowledge on the development of endocrine cells, hypotheses on the origin of endocrine tumors, genetic alterations, and prognostic factors are discussed. It is suggested that the increasing understanding of the normal development of gastrointestinal and pancreatic endocrine cells, the accumulating data on genetic alterations in endocrine tumors and the reappraisal of the hypotheses on their pathogenesis formulated in the past may help in elucidating their pathogenesis and in more accurately predicting prognosis.

In search of the best candidate for regeneration of ischemic tissues: are embryonic/fetal stem cells more advantageous than adult counterparts?

Human stem cells and progenitor cells from the bone marrow have been proposed for the regeneration of ischemic cardiac tissues. Early clinical trials indicate that infusion of autologous bone-marrow cells into the infarcted heart enhances ventricular function, albeit the long-term benefit remains to be ascertained. Alternatively, angiogenic growth factors could be used to stimulate the recruitment of vascular progenitor cells into tissues in need of regeneration. Unfortunately, in atherosclerotic patients, the curative potential of autologous stem cells might be impoverished by underlying disease and associated risk factors. Thus, research is focusing on the use of embryonic stem cells which are capable of unlimited self-renewal and have the potential to give rise to all tissue types in the body. Ethical problems and technical hurdles may limit the immediate application of embryonic stem cells. In the meanwhile, fetal hematopoietic stem cells,which have been routinely used to reconstitute the hematopoietic system in man, could represent an alternative, owing to their juvenile phenotype and ability to differentiate into vascular endothelial, muscular, and neuronal cell lineages. With progresses in stem cell expansion, the blood of a single cord could be sufficient to transplant an adult. These observations raise the exciting possibility of using fetal cells as a new way to speed up the healing of damaged tissues.

Stem cell factor/c-Kit interactions regulate human islet-epithelial cluster proliferation and differentiation

Stem cell factor (SCF), a progenitor cell growth factor, binds to and activates the c-Kit receptor tyrosine kinase, which is critical for early stem cell differentiation in haematopoiesis and gametogenesis. Nothing is known regarding these interactions during islet development in the human fetal pancreas. The present study was to investigate whether an increase in c-Kit receptor activity in isolated human fetal islet-epithelial clusters, by giving exogenous SCF, would promote beta-cell development. In the intact fetal pancreas, SCF and c-Kit were observed co-localizing with cytokeratin 19 in both ductal and newly forming islet cells. Islet cells isolated from 14 to 16 weeks fetal pancreata were cultured with SCF (50 ng/ml) or vehicle for 48 h. We observed an increase in the number of c-Kit-, pancreatic and duodenal homeobox gene 1- (PDX-1-), insulin- and glucagon-expressing cells in the SCF-treated group (PDX-1 and insulin, p < 0.05). PDX-1 and c-Kit mRNA levels were also up-regulated in the SCF group (PDX-1, p < 0.05), with no change in preproinsulin or proglucagon gene expression. Co-localization of insulin with PDX-1 or c-Kit was observed frequently in SCF-treated cultures. A significantly (p < 0.05) greater proliferative capacity of islet-epithelial clusters was found in the SCF group in parallel with increased (p < 0.02) phosphorylation of Akt in a phosphatidylinositol-3 kinase (PI3K)-dependent manner. Our results demonstrate that SCF/c-Kit interactions are likely to be involved in mediating islet cell differentiation and proliferation during human fetal pancreatic development, and that phosphorylated Akt may have a role downstream of SCF/c-Kit signaling.

Endocrine pancreatic tissue plasticity in obese humans is associated with cytoplasmic expression of PBX-1 in pancreatic ductal cells

In vivo lineage tracing experiments in mice have recently cast doubt on the potential islet neogenesis from ductal precursors in adult mammals. We examined, in human obesity, a model for pancreatic endocrine tissue plasticity, the gene and protein expression of PBX-1-a transcription factor expressed in regenerating rat ductules and potentially implicated in the pancreatic development, alone or in association with PDX-1. When comparing gene expression, by quantitative real-time RT-PCR, in pancreatic exocrine tissue from obese non-diabetic subjects with increased islet mass, we found that Pbx-1 and Pdx-1 were up-regulated (5.9+/-1.2 and 2.4+/-0.6 versus non-obese). Immunohistochemistry confirmed PBX-1 over-expression and its cytoplasmic sequestration in ductal cells of obese subjects, associated with pronounced islet neogenesis (cytokeratin 19/chromogranin A double labeling). cDNA microarray analysis also showed up-regulation of other genes implicated in islet regeneration, including betacellulin, laminin, TGFa, NeuroD1, Pax6, substantiating the role of the islet neogenesis pathway in human obesity.