Characterization and Isolation of Promoter-Defined Nestin-Positive Cells from the Human Fetal Pancreas

Studies using adult human islets and mouse embryonic stem cells have suggested that the neurepithelial precursor cell marker nestin also identifies and can be used to purify β-cell precursors. To determine whether nestin can be used to identify β-cell progenitors in the developing human pancreas, we characterized nestin expression from 12 to 24 gestational weeks, purified nestin + cells using an enhancer/promoter-driven selection plasmid, and determined whether nestin + cells can differentiate into β-cells. Nestin was visualized in the platelet endothelial cell adhesion molecule and α smooth muscle actin–positive blood vessels and colocalized with vimentin in the interstitium. Nestin was not observed in pan cytokeratin (pCK)-positive ductal epithelium or insulin cells. Purified nestin + cells also coexpressed vimentin and lacked pCK immunoreactivity. Purified adult and fetal pancreatic fibroblasts also expressed nestin. The nestin enhancer/promoter used in the selection plasmid was sufficient to drive reporter gene expression, green fluorescent protein, in human fetal pancreatic tissue. Exposure of selected nestin + cells to nicotinamide, hepatocyte growth factor/scatter factor, betacellulin, activin A, or exendin-4 failed to induce pancreatic and duodenal homeobox gene-1 or insulin message as determined by RT-PCR. Transplantation of nestin + cells and fetal pancreatic fibroblasts into athymic mice also failed to result in the development of β-cells, whereas nestin − fetal pancreatic epithelial cells gave rise to functional insulin-secreting β-cells. We conclude that nestin is not a specific marker of β-cell precursors in the developing human pancreas.