In order for fertilization to happen, the sperm has to complete a gargantuan swim that, if completed, is a miracle in itself. The route is so cumbersome that, of the 200-600 MILLION sperm released in a typical male ejaculate, only a select few will ever reach the waiting egg. Of those few, only one will enter the egg to go create an embryo.
Researchers at the University of Washington are studying how male sperm make this overwhelming feat possible in an effort to help other men with low sperm mobility achieve pregnancy with their partners in the future.
Clearly, the sperm is evolutionarily designed to improve the odds of reaching the egg. The long tail and streamlined body of each sperm serves one purpose: to swim quickly. The head of the sperm is filled with mitochondrial DNA in order to give it enough energy to transverse the female reproductive system. But what else can be done to get more sperm to the egg, in hopes of having the best genetics possible on hand to create the embryo?
Researchers think that the female reproductive system may actually play a role in this process. Basic reasoning helps us deduce that it is beneficial to provide the sperm with ideal “swimming” conditions in order to help more sperm make it to the egg, usually in the woman’s fallopian tubes. The natural moisture barrier surrounding the sperm tends to be a thick, mucous texture. What researchers are learning, however, is that this thicker moisture will liquefy when it comes into contact with the fluids inside of the female’s vagina.
Researchers found that, in mice, the female reproductive system contained enzymes that break down thicker moisture types found both in the vagina and around the sperm. When this happens, the liquefied state of the sperm makes it more capable of finishing the long swim through the female’s reproductive system. No sperm was found to reach the eggs of the female mice that lacked the presence of these enzymes in their reproductive tracks.
“This information will advance research on semen liquefaction in the female reproductive tract, an area that has never been explored, and could lead to the development of diagnostic tools for unexplained infertility cases and non-invasive contraception technologies,” researchers concluded.