Pancreatic stellate cells – Multi-functional cells in the pancreas

There is accumulating evidence that activated pancreatic stellate cells (PSCs) play a pivotal role in pancreatic fibrosis in chronic pancreatitis and pancreatic cancer. In addition, we have seen great progress in our understanding of the cell biology of PSCs and the interactions between PSCs and other cell types in the pancreas. In response to pancreatic injury or inflammation, quiescent PSCs are activated to myofibroblast-like cells. Recent studies have shown that the activation of intracellular signaling pathways such as mitogen-activated protein kinases plays a role in the activation of PSCs. microRNAs might also play a role, because the microRNA expression profiles are dramatically altered in the process of activation. In addition to producing extracellular matrix components such as type I collagen, PSCs have a wide variety of cell functions related to local immunity, inflammation, angiogenesis, and exocrine and endocrine functions in the pancreas. From this point of view, the interactions between PSCs and other cell types such as pancreatic exocrine cells, endocrine cells, and cancer cells have attracted increasing attention of researchers. PSCs might regulate exocrine functions in the pancreas through the cholecystokinin-induced release of acetylcholine. PSCs induce apoptosis and decrease insulin expression in β-cells, suggesting a novel mechanism of diabetes in diseased pancreas. PSCs promote the progression of pancreatic cancer by multiple mechanisms. Recent studies have shown that PSCs induce epithelial–mesenchymal transition and enhance the stem-cell like features of pancreatic cancer cells. In conclusion, PSCs should now be recognized as not only profibrogenic cells but as multi-functional cells in the pancreas.     

Human pancreatic duct cells can produce tumour necrosis factor-α that damages neighbouring beta cells and activates dendritic cells

Aims/hypothesis In the human pancreas, a close topographic relationship exists between duct cells and beta cells. This explains the high proportion of duct cells in isolated human islet preparations. We investigated whether human duct cells are a source of TNF-mediated interactions with beta cells and immune cells. This cytokine has been implicated in the development of autoimmune diabetes in mice.Methods Human duct cells were isolated from donor pancreases and examined for their ability to produce TNF following a stress-signalling pathway. Duct-cell-released TNF was tested for its in vitro effects on survival of human beta cells and on activation of human dendritic cells.Results Exposure of human pancreatic duct cells to interleukin-1 (IL-1) induces TNF gene expression, synthesis of the 26,000 M_r TNF precursor and conversion to the 17,000 M_r mature form, which is rapidly released. This effect is NO-independent and involves p38 MAPK and NF-B signalling. Duct-cell-released TNF contributed to cytokine-induced apoptosis of isolated human beta cells. It also induced activation of human dendritic cells.Conclusions/interpretation Human pancreatic duct cells are a potential source of TNF that can cause apoptosis of neighbouring beta cells and initiate an immune response through activation of dendritic cells. They may thus actively participate in inflammatory and immune processes that threaten beta cells during development of diabetes or after human islet cell grafts have been implanted.Abbreviations CK-19 Cytokeratin 19 - DuC duct cell - iNOS inducible nitric oxide synthetase - JNK jun N-terminal kinase - MAPK mitogen activated protein kinase - NF-B nuclear factor kappa B - NOD mouse non-obese diabetic mouse     

Stem cells for the heart

See related article,pages 101-107.Cardiovascular disease is one of the major health con-cerns of modern societies.In the United States in the year2001 alone,an estimated 64 million people had had one ormore forms of cardiovascular disease,claiming almost onemillion lives,38.5 percent of all deaths(American HeartAssociation).     

Effect of extracts of trichosanthes root tubers on HepA-H cells and HeLa cells

AIM:To investigate the cytotoxic activity of extracts oftrichosanthes root tubers (EOT) on HepA-H cells and HeLacells compared with trichosanthin (TCS),and to explorethe possible mechanism of growth inhibitory effect of EO-ron HeLa cells.METHODS:Tumor cells were cultured in vitro,and thenmicroculture tetrzoalium assay (MTT) was used toinvestigate drugs' cytotoxic activity.Scanning electronmicroscopy (SEM) and transmission electron microscopy(TEM) were used to observe ultrastructural changes ofcells,and electrophoresis was performed to detect changesof biochemical characteristics of intercellular DNA.RESULTS:TCS and EOT had no obvious effects on HepA-H cells (P>0.05),but had remarkable effects on HeLa cellsin a time and dose dependent manner (r>0.864,P<0.05or P<0.01).The inhibitory rate of EOT was much higherthan that of TCS (P<0.01).Median inhibitory rates (IC50)of TCS and EOT on HeLa cells were 610.9 mg/L and115.6 mg/L for 36 h,and 130.7 mg/L and 33.4 mg/L for 48 hrespectively.Marked morphologic changes were observedincluding microvillus disappearance or reduction,cellmembrane bledding,cell shrinkage,condensation ofchromosomes and apoptotic bodies with completemembranes.Meanwhile,apoptosis of HeLa cells wasconfirmed by DNA ladder formation on gel electrophoresis.CONCLUSION:TCS and EOT have no obvious effects onHepA-H cells,but have significant inhibitory effects on HeLacells,indicating that EOT is superior to TCS in anti-tumoractivity.     

Effects of lipopolysaccharides stimulated Kupffer cells on activation of rat hepatic stellate cells

AIM:To study the effects of Kupffer cell-conditioned medium(KCCN)derived from lipopolysaccharide(LPS)treatment onproliferation of rat hepatic stellate cells(HSC).METHODS:HSC and Kupffer cells were isolated from theliver of Wistar rats by in situ perfusion with pronase andcollagenase and density gradient centrifugation with Nycodenzand cultured.KCCM was prepared and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide(MTT)colorimetricassay was used to detect HSC proliferation.The content oftype Ⅳ collagen and laminin secreted by HSC in the HSC-conditioned medium was determined by radioimmunoassay.TGF-β_1 production in the KCCM was detected by enzyme-linked immunosorbent assay(ELISA).RESULTS:HSC and Kupffer cells isolated had high purity.One microgram per mililiter LPS-activated KCCM andunstimulated KCCM could significantly promote HSCproliferation[0.132±0.005 and 0.123±0.008 vscontrol group(0.100±0.003),P<0.01],and there was a difference betweenthem(P<0.05).Ten microgram per mililiter LPS-activatedKCCM(0.106±0.010)was unable to promote HSC proliferation(P>0.05).Adding anti-TGF-β_1 antibodies could suppress theproliferation promoted by unstimulated KCCM and LPS(1μg/ml)-activated KCCM(0.109±0.009 vs 0.123±0.008,0.115±0.008 vs 0.132±0.005,P<0.01).LPS(1μg/ml or 10μg/ml)could not promote HSC proliferation immediately(0.096±0.003 and 0.101±0.004 vs 0.100±0.003,P>0.05).Therewas a parallel behavior between HSC proliferation and increasedECM level.One microgram per mililiter LPS-activated KCCNcontained a larger amount of TGF-β_1 than unstimulated KCCM.CONCLUSION:The technique for isolation of HSC andKupffer cells described here is simple and reliable.KCCMstimulated by LPS may promote HSC proliferation and collagenaccumulation,which are associated with hepatic fibrogenesis.     

Adult stem cells and cancer stem cells: tie in or tear apart?

Stem cell research is one of the new frontiers of medical science. Because of the unique self-renewable ability and powerful potential to differentiate, stem cells can be viewed as the mother of all cells in the body and have been investigated as a possible tool for reversing the degeneration and damage on organs. Recently, successful isolating cancerous stem cells from leukemia, breast and brain cancers provide a new target for eliminate cancer; however, it hints an increasing caution in using adult stem cells for organ repair. Cancerous stem cells share the same properties of self-renewal and differentiation with normal stem cells, with the addition of similar phenotype of adult stem cells isolated from the same tissue. Some believe that cancerous stem cells are derived from mutation of the normal stem cells, whereas others suspect it to be from different origins. Further investigation of the intrinsic factor underlying the behavior of adult stem cells and cancerous stem cells will shed light on both the fields of tissue engineering and cancer therapy. In this review, recent progresses in the studies of adult stem cells and cancerous stem cells are summarized to facilitate a better understanding and elicit much attention in this field.     

Stem cells and cancer： Evidence for bone marrow stem cells in epithelial cancers

Cancer commonly arises at the sites of chronic inflam-mation and infection.Although this association has longbeen recognized,the reason has remained unclear.With-in the gastrointestinal tract,there are many examplesof inflammatory conditions associated with cancer,andthese include reflux disease and Barrett's adenocarcino-ma of the esophagus,Helicobacter infection and gastriccancer,inflammatory bowel disease and colorectal cancerand viral hepatitis leading to hepatocellular carcinoma.There are several mechanisms by which chronic inflam-mation has been postulated to lead to cancer whichincludes enhanced proliferation in an endless attempt toheal damage,the presence of a persistent inflammatoryenvironment creating a pro-carcinogenic environmentand more recently a role for engraftment of circulatingmarrow-derived stem cells which may contribute to thestromal components of the tumor as well as the tumormass itself.Here we review the recent advances in ourunderstanding of the contributions of circulating bonemarrow-derived stem cells to the formation of tumors inanimal models as well as in human beings.     

Autophagy deficiency in β cells blunts incretin-induced suppression of glucagon release from α cells

Incretin-based therapy such as GLP-1 receptor agonists and DPP-4 inhibitors for type 2 diabetes mellitus is characterized by glucose-dependent insulin secretion and glucose-inhibited glucagon secretion. Recently, autophagy deficiency in islet β cells has been shown to contribute to the pathogenesis of type 2 diabetes mellitus however, with the role of incretin has not been established. To evaluate the role of autophagy in incretin effects, 8-week-old male β cell-specific Atg7 knockout (Atg7^{Δβ cell}) mice and wild-type mice were administered vildagliptin for 12 weeks. Vildagliptin treatment improved glucose intolerance and hypoinsulinemia; however, it failed to suppress serum glucagon levels after glucose loading in the Atg7^{Δβ cell} mice. Ex vivo glucose-induced glucagon suppression was also blunted in the islets from vildagliptin-treated Atg7^{Δβ cell} mice. The α cell mass was not affected by β cell autophagy deficiency or vildagliptin. However, glucagon mRNA expression was significantly increased by vildagliptin in the autophagy-deficient islets, and was significantly reduced by vildagliptin in wild-type islets. Pancreatic glucagon contents were not in agreement with the changes in mRNA expression, suggesting a dysregulation in glucagon translation and secretion. In vitro studies revealed that glucose-stimulated cAMP production was impaired in the autophagy-deficient islets exposed to exendin-4. Taken together, the results suggest that the constitutive autophagy in β cells could regulate incretin-induced glucagon expression and release in α cells, and that cAMP may play a role in this process.     

Hepatic differentiation capability of rat bone marrow-derived mesenchymal stem cells and hematopoietic stem cells

AIM:To investigate the different effects of mesenchymalstem cells(MSCs)and hematopoietic stem cells(HSCs)onhepatic differentiation.METHODS:MSCs from rat bone marrow were isolated andcultured by standard methods.HSCs from rat bone marrowwere isolated and purified by magnetic activated cell sorting.Both cell subsets were induced.Morphology,RT-PCR andimmunocytochemistry were used to identify the hepaticdifferentiation grade.RESULTS:MSCs exhibited round in shape after differentiation,instead of fibroblast-like morphology before differentiation.Albumin mRNA and protein were expressed positively in MSCs,without detection of alpha-fetoprotein(AFP).HSCs werepolygonal in shape after differentiation.The expression ofalbumin signal decreased and AFP signal increased.Theexpression of CK18 was continuous in MSCs and HSCs bothbefore and after induction.CONCLUSION:Both MSCs and HSCs have hepatic differentiationcapabilities.However,their capabilities are not the same.MSCs can differentiate into mature hepatocyte-like cells,never expressing early hepatic specific genes,while Thy-1.1~ cells are inclined to differentiate into hepatic stem cell-likecells,with an increasing AFP expression and a decreasingalbumin signal.CK18 mRNA is positive in Thy-1.1~ cellsand MSCs,negative in Thy-1.1 cells.It seems that CK18has some relationship with Thy-1.1 antigen,and CK18 maybe a predictive marker of hepatic differentiation capability.