Funding for this research was provided by:
Japan Society for the Promotion of Science (19591726)
Received: 7 March 2019
Accepted: 9 September 2019
First Online: 11 October 2019
Ethics approval and consent to participate
: This study was approved by institutional review board of Sapporo medical university. All specimens were obtained from the body donation program run by the Sapporo Medical University (Shiragiku-kai). This program donates their bodies for medical education and research after death. The donation was agreed to by the members while they are alive.
: Not applicable.
: The authors declare no competing interests associated with this manuscript.