1. Division of Otolaryngology, Tohoku Medical and Pharmaceutical University, Sendai 981-0905, Japan
2. Division of Pathology, Tohoku Medical and Pharmaceutical University, Sendai 981-0905, Japan
3. Division of Molecular Pathology, Department of Pathology, Tottori University Faculty of Medicine, Yonago 683-8503, Japan
4. Laboratory of Gastrointestinal Regenerative Medicine, Okayama University of Science, Okayama 700-0005, Japan