Label-retaining cells in the rat pancreas: location and differentiation potential in vitro.

Islets of Langerhans are micro-organs scattered throughout the pancreas that contain insulin-producing cells, called beta-cells. Although new light has been recently shed on beta-cell development, information on the phenotype and location of beta-stem cells remains scarce. Here, we provide evidence that beta-stem cells are slow-cycling cells located within and around the islets of Langerhans. First, using a bromodeoxyuridine (BrdU) pulse/chase approach, we detected BrdU-retaining cells in vivo in the islet area of rat pancreata. These cells were negative for endocrine markers but expressed Pdx1, a marker for pancreatic stem cells. Next, using an in vitro model that mimicked endocrine cell development, we found that BrdU-retaining cells were capable of differentiating into beta-cells. Taken together, these observations demonstrate that BrdU retention is a property of beta-stem cells.