The researchers found thatmicrofluidics – an emerging area of physics and biotechnology thatdeals with the microscopic flow of fluids – can be used successfullyfor IVF in mice. They also found that lower total numbers andconcentrations of sperm were required when using microfluidic channelsinstead of culture dishes.
"This is an extension of the workwe've done in recent years to use microfluidics to separate viablesperm from dead and immature sperm in order to maximize the potentialchances of fertilizing an egg," says Gary D. Smith, Ph.D., associateprofessor of obstetrics and gynecology, urology, and physiology at theU-M Medical School.
"Now that we are using microfluidics forfertilization, what you are starting to see is the whole IVF processhappening on a chip," says Smith, senior author of a study in HumanReproduction and director of the Assisted Reproductive TechnologiesLaboratory and of the Gamete Cryopreservation Laboratory at theComprehensive Cancer Center.
IVF is a process in which eggs areremoved from a woman's body and fertilized with sperm outside the body.Fertilized eggs are then placed in the woman's uterus, where they candevelop as in a normal pregnancy.
The study, published online inthe journal Human Reproduction, suggests that among other uses,microfluidic channels could be used in some – but not all – instanceswhen a common form of insemination, known as ICSI, otherwise would beemployed. ICSI, which stands for intracytoplasmic sperm injection,involves a single sperm being injected directly into an egg, or oocyte.
Smithsays ICSI still will be used in many situations, particularly whenother types of fertilization have failed in the past, or when the manhas an extremely low sperm count or motility. Smith does not think theuse of microfluidics will replace ICSI, but he says it could offeranother option to many couples whose situations do not require ICSI, aprocess that can cost an extra $1,500 to $2,500 in addition to standardIVF costs.
"While ICSI bypasses all natural selection, the use ofmicrofluidic channels more closely resembles in vivo insemination. Themicrofluidic environment also may possess conditions more suitable forefficient sperm-oocyte interaction than the culture dish," he says.
Duringthe early stages of the study, researchers found that, contrary totheir initial hypothesis, a much lower fertilization rate was achievedwith the microfluidic device (12 percent) than in culture dishes (43percent). They then hypothesized that as sperm concentration isdecreased, fertilization rates would improve in microchannels. At theselower concentrations, the combined fertilization rate was significantlyhigher in microchannels (27 percent) than in culture dishes (10percent).
The authors note that the research has only beenconducted on mice, and that more testing and possibly the developmentof auxiliary technology will be needed before IVF by microfluidics is aviable option for humans.
Still, the research is very promising,says lead author Ronald S. Suh, M.D., now with Urology of Indiana LLCin Indianapolis who was a resident in the U-M Department of Urologywhen he wrote the paper.
"There has been a large amount ofresearch on almost every aspect of IVF. The exciting thing we're seeinghere is going the potential of integration of all of these things. Inthe future, you will be able to take patients with low sperm counts,use microfluidics to select the best sperm, and achieve fertilizationin one step," he says. "That integration is really what is going tomake microfluidics change IVF."
In addition to Smith and Suh,other authors of the paper are Dana A. Ohl, M.D., professor of urologyat the U-M Medical School; Shuichi Takayama, Ph.D., assistant professorof biomedical engineering and of macromolecular science and engineeringat the U-M College of Engineering; Xiaoyue Zhu, research fellow inbiomedical engineering; and Nandita Phadke, research assistant inbiomedical engineering.
Portions of the research were supportedby grants from the National Institutes of Health and the College ofEngineering Technology Development Fund.
U-M has applied forpatents on the microfluidic technology involved in this study. Smithand Takayama have formed a company called Incept BioSystems and standto profit from commercialization of the products.
Citation: Human Reproduction, published online, humrep.oxfordjournals.org/, DOI: 10.1093/humrep/dei323.
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