1. Laboratory of Veterinary Surgery, Graduate School of Agricultural and Life Sciences, the University of Tokyo, 1–1–1 Yayoi, Bunkyo-ku, Tokyo 113–8657, Japan
2. Division of Tissue Engineering, University of Tokyo Hospital, 7–3–1 Hongo, Bunkyo-ku, Tokyo 113–0033, Japan
3. NEXT 21 K.K., 3–38–1 Hongo, Bunkyo-ku, Tokyo 113–0033, Japan