Long Lived Sperm

Understanding where sperm cells are stored in a woman’s body and how long they can live prior to fertilizing an egg is critically important, both for couples who want to conceive, as well as those who don’t. Yet little progress has been made in this field, due to the difficulty of studying the small Fallopian tube, where fertilization occurs in normal women.

However, research conducted by Joanna Ellington in WSU Spokane’s Health Research and Education Center is changing our understanding of human fertility.

Ellington describes the knowledge gap: “Throughout the past two decades, you have had medical textbooks teaching that sperm survive one to three days [in women]. There is no original source or study that provided this information —it’s just there. On the other hand, scientific journal articles were looking at real-life conception rates for people with long intervals — six days or more —between intercourse and ovulation.” She is now working with Spokane-area physicians, whom she describes as enthusiastic collaborators, to solve this contradiction.

Ellington credits her background of research in large-animal veterinary medicine for the fresh perspective she brings to questions about human fertility and reproduction. In contrast to studies of people, a great deal has been learned over the past decade about how sperm are stored in females of other species. This has been done in part by use of an in vitro coculture system Ellington developed while working on her doctorate at Cornell. This system grows cells from the Fallopian tube (oviduct) of a female animal in a petri dish. Sperm will then interact with these oviduct cells when cocultured with them, simulating what happens in the tube itself.

Comparing sperm function in this coculture system to what is seen in tubes removed surgically from animals has allowed Ellington and others in her field to map out where exactly sperm are stored in the female and how long they live for each species. Sperm survival time in domestic animals ranges from two days in cows to a week or more in horses and dogs. Such knowledge has helped optimize the production of normal offspring.

Recently, in collaboration with Ray Wright of the Department of Animal Sciences and Spokane-area physicians, Ellington has modified her coculture system to study human sperm in contact with tubal cells. Her results suggest that many of the assumed details about human reproduction are incorrect. Her research team’s record for survival of human sperm is 10 days — far longer than the one to three days your doctor will tell you about — and sperm appear to be stored directly in the Fallopian tubes, as well as in the cervix.

Ellington and co-workers have now begun studies to determine whether sperm stored in the tube for longer time periods are damaged. Some earlier research found that couples in whom the time between coitus and ovulation was extended — that is, in whom fertilization occurred from “aged” sperm in the woman’s body — had an increased incidence of children with chromosomal defects.

So far, they have found that sugars and proteins made by the tubal cells actually protect sperm from any breakdown or DNA damage during coculture. In fact, contact of sperm with the tubal cells allows sperm to live longer and maintain normal function two to three times longer than sperm in salt solutions in the laboratory.

“The Fallopian tube is not just a passive ‘pipe’ where sperm and eggs meet,” says Ellington. “Fallopian tube cells make a whole new set of products when sperm attach to them, and these products protect sperm and allow them to live at the internal body temperature of the woman, as opposed to living in the scrotum of men, while they wait for an egg to appear.”

Ellington and co-workers are currently isolating these tubal factors for use in clinically assisted reproduction techniques to improve reproductive outcomes for procedures like artificial insemination and in vitro fertilization, which currently fail more than half the time. The oviductal product they are developing yields selective attachment of sperm with better quality DNA than those normally retrieved using currently available products. Use of this product will thus improve the quality of the embryos fertilized with that sperm.

“You’re not going to stop the rapid adoption of new clinical techniques, because people want babies. So we need to improve the outcomes,” Ellington says. “There has been little FDA testing or efficacy data compiled on products currently in use—products which are often intended for scientific research, not for wholesale use in humans.”

Ellington’s previous research in collaboration with Sylvia Adams Oliver, associate director of the Health Research and Education Center, has already led to one product that has helped produce healthy babies. Quik Wash, licensed by AB Technology, is used to wash sperm prior to clinical procedures. It works twice as fast as similar products and acts to decrease the amount of free radical and chromosomal damage to sperm during handling. Other products for sperm freezing are also being tested, and several patents have been approved. Now Ellington seeks to follow up these commercial successes with further scholarly research on oviductal products and related compounds, so that the environment sperm are exposed to during in vitro procedures will seem more like “home” to them, thus improving their function.

Treating infertility is a $2 billion industry in the United States alone. Increasing positive outcomes—from fertilization to the health of the embryo—will help couples seeking to become parents. Understanding the mechanisms of reproductive physiology may also lead down the road to improved methods of contraception, helping couples who seek not to become parents.

Ellington’s research was funded by the National Institutes of Health.

Source: http://www.wsu.edu/NIS/Universe/sperm.htm

Category: Male Fertility