Progressive amyloid formation in human islets during culture is associated with reduced β-cell phospho-PKB levels and proliferation rate.
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(A) Paraffin-embedded sections from pre-culture and 7-day cultured human islets with or without amyloid binding dye Congo red (CR; 25 μmol/L) were immunolabelled for insulin, phospho-PKB (p-PKB), and thioflavin S (Thio S). The squares (dashed white lines) correspond to enlarged areas in each image (original magnification: X400; insert: X1000). (B) Immunolabelling for insulin or glucagon and phospho-PKB in amyloid-positive and negative human islets. The percentage of (C) thioflavin S (amyloid)-positive islets and (D) islet amyloid area. (E) Islet phospho-PKB immunofluorescence intensity (IF). The proportion of (F) PCNA-positive (proliferative) β-cells and (G) TUNEL-positive (apoptotic) β-cells in each condition. Results are expressed as mean +/- SEM of five independent studies (25–30 islets per condition in each study). For β-cell phospho-PKB IF intensity, quantifications were performed on a total of 18 amyloid (thio S)-positive 7-day cultured human islets or equal number of CR-treated islets (no or very little amyloid formation). *vs Day 0; #vs corresponding untreated group (P<0.05; one-way ANOVA).