Combinations of growth factors enhance the potency of islets in vitro

Proliferation and functional assessment of pseudo-islets with the use of pancreatic endocrine cells

Many obstacles beset islet transplantation, particularly insufficient tissue mass. Previously, we reported production of pseudo-islets. In addition, there have been reports in which coculture with pancreatic islet and bone marrow mesenchymal stem cells (BMSCs) demonstrated positive effects on pancreatic islet function. The purpose of this study was to perform morphologic and functional evaluations of pancreatic pseudo-islets cocultured with BMSCs. Pancreatic endocrine cells (PECs) were collected with a previously reported method; bone marrow was aspirated from the rat femur. Subsequently, PECs and BMSCs cocultured at high density on low-cell-binding culture dishes kept suspended by shaking. The functionality and characteristics of the mixed cell complexes were evaluated by glucose challenge, insulin enzyme-linked immunosorbent assay, reverse-transcription polymerase chain reaction, and immunohistochemistry. Through expansion for 2 weeks in continuous culture passages, ∼1 million PECs were recovered after aggregation. They presented spherical shapes and sizes similar to naïve islets, according to phase-contrast microscopy. The spheroid aggregates of pancreatic islet cells and BMSCs showed fortified functions and maintained viability. In conclusion, PECs served as a cell source for pseudo-islets, which were both morphologically and genetically similar to naïve islets. We also suggest a manufacturing method for mixed cellular complexes from 2 different origins that can improve secretion ability and cell differentiation.

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 microm). 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.

Immune modulation of co-transplantation mesenchymal stem cells with islet on T and dendritic cells

Allogeneic pancreatic islet transplantation theoretically represents a cure for type 1 diabetes. However, current immune suppressive therapies are often associated with undesired side effects. Given this problem, and the shortage of human islet donors, the majority of type 1 diabetes patients cannot currently be offered an islet transplant. However, it has been found that mesenchymal stem cells (MSCs) could exert unique immunosuppressive effects both in vitro and in vivo. Herein we transplanted allogeneic 200 islets alone or in combination with MSCs (3 x 10(6) cells) under the kidney capsules of diabetic C57LB/6 mouse. We found that the ratios of T helper type 1 (Th1) to Th2 and Tc1 to Tc2 were reduced, and the numbers of naive and memory T cells were down-regulated in peripheral blood after transplantation. In addition, the maturation, endocytosis and interleukin-12 secretion of dendritic cell (DCs)-derived bone marrow cells (BMCs) from receptor mice were suppressed. Rejection reaction was alleviated by MSCs which exerted suppressive effects through T lymphocyte subsets and DCs.