1. Department of Perinatal and Women’s Medicine, Tokyo Medical and Dental University, Tokyo 113-8510, Japan
2. Center for Experimental Animals, Tokyo Medical and Dental University, Tokyo 113-8510, Japan
3. Department of Microscopic Anatomy, Kyorin University School of Medicine, Tokyo 181-8611, Japan
4. Cell Biology Center, Tokyo Institute of Technology, Kanagawa 226-8503, Japan
5. Department of Veterinary Anatomy, University of Tokyo, Tokyo 113-8657, Japan