The aim of our research is to analyze DNA and mRNA of human islet, mainly pancreatic β cells. Additionally, we are researching the clinical application and the establishment of generating insulin^–producing cells (IPC) from mesenchymal stem cells (adipose^–derived stem cells) with 3D culture methods using regenerative medicine technology. This generated IPCs might be a surrogate model of human β cells which are considered as being difficult to be cultured, thus it might be directly linked to drug development. Moreover, we have focused on pancreatic islet transplantation as a radical therapy for type 1 diabetes mellitus, especially are researching genetic analysis and immune-monitoring of Foxp3 regulatory T cells, the induction of donor-specific immunological tolerance.