title: Senescence determines the fate of activated rat pancreatic stellate cells.
abstract: In chronic pancreatitis (CP), persistent activation of pancreatic stellate cells (PSC) converts wound healing into a pathological process resulting in organ fibrosis. Here, we have analysed senescence as a novel mechanism involved in the termination of PSC activation and tissue repair. PSC senescence was first studied in vitro by establishing long-term cultures and by applying chemical triggers, using senescence-associated β-Galactosidase (SA β-Gal) as a surrogate marker. Subsequently, susceptibility of PSC to immune cell-mediated cytolysis was investigated employing cocultures. Using the model of dibutyltin dichloride-induced CP in rats, appearance of senescent cells was monitored by immunohistochemistry and immunofluorescence, and correlated with the progression of tissue damage and repair, immune cell infiltration and fibrosis. The results indicated that long-term culture and exposure of PSC to stressors (doxorubicin, H(2) O(2)  and staurosporine) induced senescence. Senescent PSC highly expressed CDKN1A/p21, mdm2 and interleukin (IL)-6, but displayed low levels of α-smooth muscle actin. Senescence increased the susceptibility of PSC to cytolysis. In CP, the number of senescent cells correlated with the severity of inflammation and the extension of fibrosis. Areas staining positive for SA β-Gal overlapped with regions of fibrosis and dense infiltrates of immune cells. Furthermore, a close physical proximity of immune cells and activated PSC was observed. We conclude that inflammation, PSC activation and cellular senescence are timely coupled processes which take place in the same microenvironment of the inflamed pancreas. Lymphocytes may play a dual-specific role in pancreatic fibrogenesis, triggering both the initiation of wound healing by activating PSC, and its completion by killing senescent stellate cells.
authors.affiliation: Department of Medicine II, Division of Gastroenterology, University of Rostock, Rostock, Germany.
authors.forename: Brit
authors.initials: B
authors.lastname: Fitzner
authors.forename: Sarah
authors.initials: S
authors.lastname: Müller
authors.forename: Michael
authors.initials: M
authors.lastname: Walther
authors.forename: Madlen
authors.initials: M
authors.lastname: Fischer
authors.forename: Robby
authors.initials: R
authors.lastname: Engelmann
authors.forename: Brigitte
authors.initials: B
authors.lastname: Müller-Hilke
authors.forename: Brigitte M
authors.initials: BM
authors.lastname: Pützer
authors.forename: Michael
authors.initials: M
authors.lastname: Kreutzer
authors.forename: Horst
authors.initials: H
authors.lastname: Nizze
authors.forename: Robert
authors.initials: R
authors.lastname: Jaster
mesh_terms: D000818:Animals; D015415:Biomarkers; D002478:Cells, Cultured; D016922:Cellular Senescence / Q000187:drug effects / Q000235:genetics; D018920:Coculture Techniques; D004317:Doxorubicin / Q000494:pharmacology; D005355:Fibrosis; D015870:Gene Expression; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007694:Killer Cells, Natural / Q000166:cytology / Q000276:immunology; D008297:Male; D009947:Organotin Compounds / Q000633:toxicity; D010179:Pancreas / Q000473:pathology; D058954:Pancreatic Stellate Cells / Q000187:drug effects / Q000473:pathology* / Q000502:physiology; D050500:Pancreatitis, Chronic / Q000139:chemically induced / Q000473:pathology*; D051381:Rats; D011917:Rats, Inbred Lew; D013154:Spleen / Q000166:cytology; D019311:Staurosporine / Q000494:pharmacology; D001616:beta-Galactosidase / Q000378:metabolism
chemical_list: D015415:Biomarkers; D009947:Organotin Compounds; D004317:Doxorubicin; D006861:Hydrogen Peroxide; D001616:beta-Galactosidase; D019311:Staurosporine; C020735:dibutyldichlorotin