Proliferation of pancreatic endocrine cells using disaggregation-expansion- reaggregation technology in isolated rat islets

Donor scarcity is a major obstacle for clinical islet transplantation. Hence, the effective use of the limited number of available islets is necessary for successful islet transplantation. We have developed a new technology that could produce pseudo-islets. Morphologic and functional evaluation was performed to test the feasibility of using these cells for transplantation. A 3-step procedure known as disaggregation-expansion-reaggregation (DER) was employed for pseudo-islet preparation. Islets isolated from 200 to 250-g male Lewis rats by collagenase digestion were separated into single cells by trypsinization. These pancreatic endocrine cells (PECs) were expanded by serial passages in culture before being aggregated at a high cell-density in a suspended state. After DER, cells were morphologically analyzed over time, and gene expression evaluated by reverse transcriptase polymerase chain reaction (RT-PCR). Through expansion by passage for 2 weeks in continuous cultures, approximately 1 million PECs were recovered after aggregation. By phase-contrast microscopy, they presented with spherical shapes and similar sizes compared with naïve islets (50-800 μm). RT-PCR results indicated expression of insulin, glucagon, and pancreatic and duodenal homeobox gene 1, which were observed in primary isolated islets as well. The insulin secretion capacity of pseudo-islets was confirmed by enzyme-linked immunosorbent assay. In conclusion, PECs treated with DER showed potential to serve as a cell source for pseudo-islet generation after in vitro cellular expansion. These cells were both morphologically and genetically similar to naïve islets. Our new technique could be a potential method to overcome the scarcity of donor islets in the near future.