Growth factors and medium hyperglycemia induce Sox9+ ductal cell differentiation into β cells in mice with reversal of diabetes.

We previously reported that long-term administration of a low dose of gastrin and epidermal growth factor (GE) augments β-cell neogenesis in late-stage diabetic autoimmune mice after eliminating insulitis by induction of mixed chimerism. However, the source of β-cell neogenesis is still unknown. SRY (sex-determining region Y)-box 9(+) (Sox9(+)) ductal cells in the adult pancreas are clonogenic and can give rise to insulin-producing β cells in an in vitro culture. Whether Sox9(+) ductal cells in the adult pancreas can give rise to β cells in vivo remains controversial. Here, using lineage-tracing with genetic labeling of Insulin- or Sox9-expressing cells, we show that hyperglycemia (>300 mg/dL) is required for inducing Sox9(+) ductal cell differentiation into insulin-producing β cells, and medium hyperglycemia (300-450 mg/dL) in combination with long-term administration of low-dose GE synergistically augments differentiation and is associated with normalization of blood glucose in nonautoimmune diabetic C57BL/6 mice. Short-term administration of high-dose GE cannot augment differentiation, although it can augment preexisting β-cell replication. These results indicate that medium hyperglycemia combined with long-term administration of low-dose GE represents one way to induce Sox9(+) ductal cell differentiation into β cells in adult mice.