Michito Murayama, Takahito Iwai, Satomi Omotehara, Yusuke Kudo, Yuya Hanada, Zen-ichi Tanei, and Mutsumi Nishida declare that they have no conflicts of interest.

All procedures were in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and the Declaration of Helsinki of 1964 and later versions.