Funding for this research was provided by:
National Natural Science Youth Foundation of China (81500837)
Received: 19 March 2019
Accepted: 7 May 2019
First Online: 17 May 2019
Ethics approval and consent to participate
: This study was performed under an ethics protocol previously approved by Ethics Committee of the Peking University Health Science Center (Approval No: LA2018231).
: Not applicable.
: The authors declare that they have no competing interests.