title: Apoptosis and beta-cell destruction in pancreatic islets of NOD mice with spontaneous and cyclophosphamide-accelerated diabetes.
abstract: Autoimmune-mediated destruction of pancreatic islet beta cells leads to insulin-dependent diabetes in non-obese diabetic (NOD) mice. Although both direct cytotoxic T cell- and indirect cytokine-, nitric oxide- or free radical-mediated mechanisms induce beta-cell apoptosis in vitro, beta-cell death in vivo in spontaneous autoimmune diabetes is not well-characterized. Furthermore, whether beta cells die gradually, or rapidly in the late pre-clinical stage, is a question of current interest. To investigate beta-cell death in vivo, we measured the frequency and intra-islet localisation of apoptosis, defined as DNA strand breaks by the terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling (TUNEL) technique, during spontaneous and cyclophosphamide-accelerated diabetes in NOD mice. In spontaneous diabetes, the frequency of apoptosis in islets correlated with the progression of beta-cell destruction with age. Although apoptosis was detected at low frequency within the reduced insulin-positive islet area of pre-diabetic mice at 90 days of age, it was rarely co-localised to beta cells. After acceleration of beta-cell destruction with cyclophosphamide, the frequency of apoptosis reached maximum at 12 days, at which time 3.2 % of apoptotic cells were beta cells. Apoptosis was most frequent in the insulin-negative islet area comprised of mononuclear cell infiltrate and was localized to CD8+ T cells. The rarity of detectable apoptotic beta cells in spontaneous pre-diabetic mice with pronounced insulitis and reduced insulin-positive islet areas most likely reflects the rapid clearance of apoptotic beta cells. Our findings are more consistent with gradual destruction of non-renewable beta-cells in spontaneous diabetes, than with their rapid, accelerated destruction (as after cyclophosphamide) in the late pre-clinical stage.
authors.affiliation: The Walter and Eliza Hall Institute of Medical Research, Parkville, Australia.
authors.forename: P
authors.initials: P
authors.lastname: Augstein
authors.forename: A G
authors.initials: AG
authors.lastname: Elefanty
authors.forename: J
authors.initials: J
authors.lastname: Allison
authors.forename: L C
authors.initials: LC
authors.lastname: Harrison
mesh_terms: D000375:Aging; D000818:Animals; D017209:Apoptosis; D003520:Cyclophosphamide / Q000494:pharmacology*; D003922:Diabetes Mellitus, Type 1 / Q000276:immunology / Q000473:pathology* / Q000503:physiopathology*; D018450:Disease Progression; D005260:Female; D020287:In Situ Nick-End Labeling; D007328:Insulin / Q000032:analysis*; D007515:Islets of Langerhans / Q000187:drug effects / Q000254:growth & development / Q000473:pathology*; D051379:Mice; D016688:Mice, Inbred NOD; D013997:Time Factors
chemical_list: D007328:Insulin; D003520:Cyclophosphamide