title: Human sperm rheotaxis: a passive physical process.
abstract: A long-standing question in natural reproduction is how mammalian sperm navigate inside female reproductive tract and finally reach the egg cell, or oocyte. Recently, fluid flow was proposed as a long-range guidance cue for sperm navigation. Coitus induces fluid flow from oviduct to uterus, and sperm align themselves against the flow direction and swim upstream, a phenomenon termed rheotaxis. Whether sperm rheotaxis is a passive process dominated by fluid mechanics, or sperm actively sense and adapt to fluid flow remains controversial. Here we report the first quantitative study of sperm flagellar motion during human sperm rheotaxis and provide direct evidence indicating that sperm rheotaxis is a passive process. Experimental results show that there is no significant difference in flagellar beating amplitude and asymmetry between rheotaxis-turning sperm and those sperm swimming freely in the absence of fluid flow. Additionally, fluorescence image tracking shows no Ca(2+) influx during sperm rheotaxis turning, further suggesting there is no active signal transduction during human sperm rheotaxis.
authors.affiliation: Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, ON, Canada.
authors.forename: Zhuoran
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, ON, Canada.
authors.forename: Jun
authors.initials: J
authors.lastname: Liu
authors.affiliation: LifeQuest Centre for Reproductive Medicine, Toronto, ON, Canada.
authors.forename: Jim
authors.initials: J
authors.lastname: Meriano
authors.affiliation: Jiangsu Provincial Key Laboratory of Advanced Robotics &Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, China.
authors.forename: Changhai
authors.initials: C
authors.lastname: Ru
authors.affiliation: Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, ON, Canada.|Department of Mechatronic Engineering, Shanghai University, China.
authors.forename: Shaorong
authors.initials: S
authors.lastname: Xie
authors.affiliation: Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, ON, Canada.|Department of Mechatronic Engineering, Shanghai University, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Luo
authors.affiliation: Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, ON, Canada.|Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, ON, Canada.|Department of Electrical and Computer Engineering, University of Toronto, Toronto, ON, Canada.
authors.forename: Yu
authors.initials: Y
authors.lastname: Sun
mesh_terms: D055592:Biophysical Phenomena; D002118:Calcium / Q000378:metabolism; D058948:Cell Tracking / Q000379:methods; D005260:Female; D006801:Humans; D057446:Hydrodynamics; D008297:Male; D008954:Models, Biological; D061848:Optical Imaging / Q000379:methods; D010063:Ovum / Q000502:physiology; D013081:Sperm Motility / Q000502:physiology*; D013094:Spermatozoa / Q000502:physiology*
chemical_list: D002118:Calcium