A new system to evaluate the influence of immunosuppressive drugs on pancreatic islets using epigenetic analysis in a 3-dimensional culture.

OBJECTIVE:The present study aimed to establish a new method to evaluate the influence of immunosuppressive drugs on pancreatic islets in short-term in vitro cultures using epigenetic analysis in a 3-dimensional culture. METHODS:For this purpose, we selected (a) a 3-dimensional culture system utilizing thermoreversible gelation polymer, (b) pancreatic duodenal homeobox-1 (pdx-1)-Venus transgenic pigs expressing the green fluorescent protein, (c) FK506 as an immunosuppressive drug of the evaluation, and (d) the bisulfite sequencing technique to evaluate the methylation levels of pdx-1 and insulin genes. Each isolated pancreatic islet was cultured with several doses of FK506. The viability of the each islet was evaluated by analyzing the emission of Venus in real time and by propidium iodide staining. Epigenetic analysis was performed at several time points. RESULTS:Each single pancreatic islet was stably cultured for 30 days in this system. At day 30 in culture, we observed that insulin DNA methylation levels in the group that received a high dose of FK506 dramatically increased, although there was no change in pdx-1 DNA methylation level and configuration of the islets. CONCLUSIONS:Our system may be useful to determine immunosuppressive drugs that are specifically suitable for islet transplantation.