Dynamic Changes in Pancreatic Endocrine Cell Abundance, Distribution, and Function in Antigen-Induced and Spontaneous Autoimmune Diabetes

Dynamic Changes in Pancreatic Endocrine Cell Abundance, Distribution, and Function in Antigen-Induced and Spontaneous Autoimmune Diabetes Klaus Pechhold 1 , Xiaolong Zhu 1 , Victor S. Harrison 1 , Janet Lee 1 , Sagarika Chakrabarty 1 , Kerstin Koczwara 1 , 2 , Oksana Gavrilova 3 and David M. Harlan 1 1 Diabetes Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland; the 2 Institute for Diabetes Research, Research Group for Diabetes at the Helmholtz Center, Munich, Germany; and the 3 Mouse Metabolism Core, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland. Corresponding author: Klaus Pechhold, klausp{at}intra.niddk.nih.gov . Abstract OBJECTIVE Insulin deficiency in type 1 diabetes and in rodent autoimmune diabetes models is caused by β-cell–specific killing by autoreactive T-cells. Less is known about β-cell numbers and phenotype remaining at diabetes onset and the fate of other pancreatic endocrine cellular constituents. RESEARCH DESIGN AND METHODS We applied multicolor flow cytometry, confocal microscopy, and immunohistochemistry, supported by quantitative RT-PCR, to simultaneously track pancreatic endocrine cell frequencies and phenotypes during a T-cell–mediated β-cell–destructive process using two independent autoimmune diabetes models, an inducible autoantigen-specific model and the spontaneously diabetic NOD mouse. RESULTS The proportion of pancreatic insulin-positive β-cells to glucagon-positive α-cells was about 4:1 in nondiabetic mice. Islets isolated from newly diabetic mice exhibited the expected severe β-cell depletion accompanied by phenotypic β-cell changes (i.e., hypertrophy and degranulation), but they also revealed a substantial loss of α-cells, which was further confirmed by quantitative immunohistochemisty. While maintaining normal randomly timed serum glucagon levels, newly diabetic mice displayed an impaired glucagon secretory response to non–insulin-induced hypoglycemia. CONCLUSIONS Systematically applying multicolor flow cytometry and immunohistochemistry to track declining β-cell numbers in recently diabetic mice revealed an altered endocrine cell composition that is consistent with a prominent and unexpected islet α-cell loss. These alterations were observed in induced and spontaneous autoimmune diabetes models, became apparent at diabetes onset, and differed markedly within islets compared with sub