Scientists Say Sperm Crawl and Collide Their Way to Egg
Posted on May 9, 2012
Sperm have been described as swimming their way to fertilize the egg, but scientists say the a human sperm cell's journey to the egg is far less glamorous and involves a lot of crawling and collisions. Sperms cells were injected into hair-thin microchannels for the study. Research results published in the Proceedings of the National Academy of Sciences (PNAS) provide fresh insight into how sperm find their way to the egg.
Scientists led by Dr Petr Denissenko, of the School of Engineering at the University of Warwick, and Dr Jackson Kirkman-Brown, lead in reproductive biology at the University of Birmingham, explored what properties distinguish the tens of cells which make it to the egg from the millions of sperm cells ejaculated. Contrary to popular belief, the authors report, sperm rarely swim in the central part of the three-dimensional female tract. Instead they travel along the walls, as they meander through complex and convoluted channels filled with viscous fluids.
The authors say in their report, "When the channel turns sharply, cells leave the corner, continuing ahead until hitting the opposite wall of the channel. As a consequence of swimming along the corners, the domain occupied by cells becomes essentially one-dimensional. This leads to frequent collisions and needs to be accounted for when modelling the behaviour of populations of migratory cells."
Dr Kirkman-Brown, who is also Science Lead for the Birmingham Women's Fertility Centre, said, "In basic terms - how do we find the 'Usain Bolt' among the millions of sperm in an ejaculate. Through research like this we are learning how the good sperm navigate by sending them through mini-mazes."
Dr Denissenko of the University of Warwick, added, "Sperm cell following walls is one of those cases when a complicated physiological system obeys very simple mechanical rules. I study fluids in a variety of environments, but moving to work with live human sperm was quite a change. I couldn't resist a laugh the first time I saw sperm cells persistently swerving on tight turns and crashing head-on into the opposite wall of a micro-channel. More seriously, it's great being part of an internationally leading team based out of the Midlands addressing a key problem."