1 Center for Regenerative Medicine, National Center for Child Health and Development, Tokyo, Japan; Department of Gastroenterological Surgery, Hirosaki University Graduate School of Medicine, Hirosaki, Japan.
2 Center for Regenerative Medicine, National Center for Child Health and Development, Tokyo, Japan.
3 Department of Nutritional Science and Food Safety, Faculty of Applied Bioscience, Tokyo University of Agriculture, Tokyo, Japan.
4 Electron Microscope Laboratory, Keio University School of Medicine, Tokyo, Japan; Division of Microscopic Anatomy, Graduate School of Medical and Dental Sciences, Niigata University, Niigata, Japan.
5 Electron Microscope Laboratory, Keio University School of Medicine, Tokyo, Japan.
6 Department of Maternal-Fetal Biology, National Research Institute for Child Health and Development, Tokyo, Japan.
7 Department of Gastroenterological Surgery, Hirosaki University Graduate School of Medicine, Hirosaki, Japan.