| Abstract | Cultured human islets can be dedifferentiated to duct-like structures composed mainly of cytokeratin⁺ and nestin⁺ cells. Given that these structures possess the potential to redifferentiate into islet-like structures, we sought to elucidate their specific cellular origins. Adenoviral vectors were engineered for β-, α-, δ- or PP-cell-specific GFP expression. A doublestranded system was designed whereby cultures were infected with two vectors: one expressed GFP behind the cumateinducible promoter sequence, and the other expressed the requisite transactivator behind the human insulin, glucagon, somatostatin or pancreatic polypeptide promoter. This system labels hormone⁺ cells in the islet in a cell-specific manner, allowing these cells to be tracked during the course of transformation from islet to duct-like structure. Post-infection, islets were cultured to induce dedifferentiation. Fluorescence microscopy demonstrated that α-, δ- and PP-cells contributed equally to the cytokeratin⁺ population, with minimal b-cell contribution, whereas the converse was true for nestin⁺ cells. Complementary targeted cell ablation studies, using streptozotocin or similar adenoviral expression of the Bax (Bcl2-associated X protein) toxigene, validated these findings and suggested a redundancy between α-, δ- and PP-cells with respect to cytokeratin⁺ cell derivation. These results call into question the traditional understanding of islet cells as being terminally differentiated and provide support for the concept of adult islet morphogenetic plasticity. |
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