Immunocytochemical localization of cleaved caspase-3 in pancreatic islets from type 1 diabetic subjects

AIMS/ HYPOTHESIS: Caspase-3 is a main effector caspase of the apoptotic cascade. Involvement of caspase-3 has been implicated in a β cell cloned cell line from type 1 diabetic subjects and in isolated islets from type 2 diabetic subjects.

The control islets revealed cleaved caspase-3 positive cells in about 4.7 % in the total islet cells with large and small islets positive at 4.1 % and 6.8%, respectively. The islets from type 1 diabetic patients showed higher immunopositive cells at 16 % in the total islets with large and small islets positive at 14% and 17%, respectively, 3.4, 3.6 and 2.4 times that of the corresponding control values.

Using commercially available rabbit anti-cleaved caspase-3 antibody, immunocytochemical staining was performed on 8 cases of pancreatic tissues from type 1 diabetic subjects and age-matched controls obtained at autopsy. Islets were divided into large islets containing more than 34 islet cells and small islets containing less than 34 islet cells. Cleaved caspase-3 immunostained islet cells were calculated for large and small islets, respectively, with total number of islet cells and total percentage of cleaved caspase-3 positive cells.

The islets from type 1 diabetics were a mixture of major small-sized islets consisting of insulin-poor and glucagon-rich cells with more caspase-3 positive cells, and occasional large islets, consisting of non-insulin-cells (> 1%) but glucagon- , somatostatin- and PP-rich cells with normal caspase-3 positive cells. The more positive staining for caspase-3 in islets from type 1 diabetics may correspond to accelerated apoptosis cascade in the islets before processing to eventual cell death.