Abstract

BACKGROUND
A major obstacle of islet transplantation is an inadequate supply of insulin-producing tissue. Ad-PDX-1/VP16 overexpression and Exendin-4 treatment have been proved the effects on differentiation and proliferation of pancreatic stem cells. But, the study is insufficient using adult animal pancreatic stem cells. METHODS: Pancreatic cells were prepared from the non-endocrine fraction of canine pancreases. This cells were cultivated free floating state and monolayer culture after dispersion. The floating pancreatic cells were transplanted under the kidney capsule of normoglycaemic nude mice. The dispersed pancreatic cells were infected with Ad-PDX-1/VP16 or Ad-GFP. After infection, those cells were transplanted of nude mice. After transplantation, mice were treated with either 1 nmol/kg exendin-4 or saline solution by intraperitoneal injection for 10 days. RESULTS: The relative volume of the beta-cells in the grafts of the free floating cultured pancreatic cells were 23.4 +/- 13.1% at two weeks and 5.2 +/- 2.0% at eight weeks. At two weeks after transplantation, the relative volume of insulin-positive cells in the grafts of dispersed pancreatic cells were 28 +/- 5.7%, 20.5 +/- 0.7% and 31 +/- 1.4% in control, GFP and PDX-1/VP16 treated groups respectively. At eight weeks after transplantation, the relative volume of insulin-positive cells in the grafts were 11.8 +/- 5.9%, 8 +/- 7.3% and 16.6 +/- 7.4% in control, GFP and PDX-1/VP16 treated groups respectively. Exendin-4 treatment didn't show any additive effects on transdifferentiation of pancreas stem cell into beta-cells. CONCLUSION: The expansion and transdifferentiation were not observed after the transplantation of the free floating cultured pancreatic cells. PDX-1/VP16 overexpression induces the transdifferentiation of adult pancreatic cells into beta-cells. However Exendin-4 treatment hasn't any effects on the expansion and transdifferentiation of the cells in the grafts.

• Keywords: Ad-PDX-1/VP16;Beta-cell;Exendin-4;Pancreatic exocrine cell;Transdifferentiation;Transplantation;