Dexamethasone suppresses the expansion and transdifferentiation of transplanted porcine neonatal pancreas cell clusters (NPCCs) into β-cells in normal nude mice

Objectives: This study was performed to investigate the effect of dexamethasone on the expansion and transdifferentiation of transplanted neonatal pancreas cell clusters (NPCCs) in vivo. Methods: Porcine NPCCs were generated from 1 to 3-day-old neonatal pigs. After transplantation (Tx) of 4000 islet equivalents (IEqs) of NPCCs beneath the renal subcapsular space of normoglycemic nude mice, dexamethasone (Dx, 1 mg/kg) or vehicles were injected daily. Intraperitoneal glucose tolerance testing (ip-GTT) was performed at 4 weeks (n = 4) and 10 weeks (n = 7) after Tx. After harvesting the grafts, total graft and β-cell graft mass were determined by morphometric analysis. Results: Although the mean value of AUCg was elevated in the Dx-treated group at 10 weeks after Tx, the glucose levels of all the animals by ip-GTT were within the normal range. At 10 weeks after Tx, the relative volume, absolute mass of β-cells in the graft, and total graft mass were significantly lower in the Dx-treated group (relative volume of β-cells: 22.0% versus 35.3%, P < 0.05; β-cells mass: 1.0 ± 1.2 mg versus 2.2 ± 5.6 mg, P < 0.05, total graft mass: 4.4 ± 5.4 mg versus 6.3 ± 1.3 mg, P < 0.05, Dx-treated versus control), but there was no difference at 4 weeks. Morphologically prominent cystic structures were observed in the Dx group at 10 weeks. Conclusion: Our results suggest that dexamethasone suppresses the expansion and transdifferentiation of transplanted porcine NPCCs into β-cells in normal nude mice.