By Garry Kranz
Small Times Correspondent
Aug. 21, 2001 – About 210 tots owe their existence and even their genders to small tech.
Since 1995, a U.S. fertility clinic has been using a machine that sorts sperm into separate boys’ and girls’ schools — mostly for parents who pine for daughters. The
 |
| At top is MicroSort’s XSort procedure, which tries to screen out the boys. Pink identifies female sperm and blue is for male. After a YSort procedure, at bottom, male sperm contain a green spot and females are red. Photo courtesy of MicroSort |
Researchers at the Fairfax, Va.-based Genetics and IVF Institute (GIVF) say the sex-sorting technique increases the percentage of female embryos produced through in vitro fertilization to about 90 percent, up from an average of about 50 percent. The clinic is thought to be the first to develop sex-sorting procedures for use in humans.
The process, which the clinic calls MicroSort, has resulted in more than 300 pregnancies and about 210 live births of healthy children. Scientists at the institute claim the technique could make it possible for parents to dictate the gender of their children prior to conception. By dramatically boosting the odds, researchers claim, parents can achieve a well-balanced family — the ability to add daughters to a household of boys, for instance.
Moreover, the sex-sorting procedure may help parents with known genetic disorders avoid passing the afflictions on to their offspring, scientists say. This is especially important since a number of inherited disorders, including hemophilia and muscular dystrophy, are about twice as likely to be passed on to male children by parents who have the diseases.
The MicroSort technique uses a fluorescent dye that latches on to individual spermatozoa and identifies its gender as male or female, based on the fact that X chromosome sperm cells contain 2.8 percent more DNA than spermatozoa with a Y chromosome. A sorting device using flow cytometry then is used to segregate sperm cells that carry the Y chromosome, which produces males, from sperm cells that carry the female-producing X chromosome.
Flow cytometry measures properties of cells as they flow in liquid. It’s a piece of an overall microfluidic system, an emerging type of microsystem that is being used to automate genomic and pharmaceutical experiments for discovering new drugs and in the creation of implantable drug-delivery devices.
In the MicroSort system, sorting the sperm produces enriched samples in which about 90 percent of the cells have a female-bearing X chromosome, MicroSort researchers have reported. Parents wishing to spawn boys, however, do not immediately gain the same odds. When Y-bearing sperm were targeted for sorting, 73 percent of the sorted spermatozoa were found to contain a Y chromosome.
Once the sperm have been distinguished and sorted, doctors are able to perform artificial insemination.
The Fairfax clinic did not respond to repeated requests by Small Times for information about its research. But in a 1998 paper on its technology published in the journal, “Human Reproduction,” the Institute summed up a major reason behind the development of the MicroSort procedure. Using language that echoes the U.S. Constitution, the scientists proclaimed “fundamental principles of liberty affirm that couples should be free to choose their own reproductive options.” The MicroSort procedure does not guarantee a pregnancy 90 percent of the time. Sorted and stained sperm that are artificially inseminated in a woman’s womb have resulted in pregnancy about 17 percent of the time since clinical trials began several years ago, according to figures on MicroSort’s Web site. In 2001, the figure rose to 21.5 percent.
In other words, out of 100 couples undergoing the procedure, only about 21 couples are likely to achieve a successful pregnancy. Of those 21 couples, about 90 percent will spawn a child of the desired gender. “So 79 couples will be disappointed because they don’t get pregnant, while at least one or two couples could be outraged” by giving birth to a child whose gender is opposite of what they originally desired, said Dr. Thomas Schulte, a Redmond, Wash.-based expert in flow cytometry.
Still, MicroSort’s reported success rate of conception resulting in live births is impressive, Schulte said. “When you think about how often natural sexual intercourse leads to pregnancy, usually the odds are not that great – about 10 percent to 30 percent would be a believable number. So I think the 17 percent figure the Institute is claiming sounds about right.”
The fact these pregnancies are occurring using sperm that have been stained with a dye is even more stunning, Schulte said. Voluminous published medical research had suggested such an approach could cause mutations that lead to birth defects, but the MicroSort procedure has been tested using scientifically accepted methods and the company’s published journal research indicates no problems have been encountered, Schulte said.
“If somebody had told me they were going to stain DNA with this dye, sort it and then use it to try and conceive a child, I would have called them crazy. My knee-jerk reaction when I first read about this was that it seemed unbelievably reckless. But these researchers have followed the right path and haven’t seen a difficulty,” Schulte said.
“I think they’re getting to the point where (federal) regulators are going to get comfortable with the procedure and the results,” Schulte added.
Other medical experts are curious but wary. They cite concerns about flow cytometry, which uses a high-energy laser beam that creates ionizing radiation. That radiation, along with the fluorescent dye that is attached to DNA, raises fears that the procedure could cause genetic damage.
The concept as devised by the GIVF involves allowing individually stained sperm to be subject to a high-powered microscopic laser, said Dr. E. Scott Sills, a reproductive physician familiar with the MicroSort technology.
“The laser is targeted to each individual sperm as it passes through a gated channel. These microscopic droplets are gated such that there’s only one sperm cell per droplet. It’s precisely regulated so one droplet is emitted per interval of time,” said Sills, associate medical director with Georgia Reproductive Specialists,
Sills said the laser emits a wavelength of 351 nanometers to 364 nanometers, which creates enough ionizing radiation to potentially damage DNA.
“These two aspects – the dye and subjecting sperm cell to laser energy – are problematic. Any cell-sorting technique using that method should be carefully studied to make sure there are no deleterious effects.”
Sills said his Atlanta-based practice fields calls from parents inquiring about the MicroSort technology at least once a month.
“To me the MicroSort procedure is something that may have clinical applicability in highly selected cases, but our practice has developed a philosophy not to offer elective sex selection at the embryo level or the sperm level,” Sills said. “We don’t think being a boy or being a girl is a medical handicap; therefore, we don’t feel we should be screening for those kinds of things.”
Biotechnology investors also question how viable the MicroSort technology will be, despite the feverish research and development springing from the Human Genome Project. Sloan Ventures of Birmingham, Mich., funds several portfolio companies that are developing technologies that could lead to advances in personalized medicine. But Richard Sloan, the venture capital firm’s managing director, said it’s too early to gauge public sentiment for manipulating human DNA.
“To write a market plan, for example, on what the market size is for this service would be fallacious. First of all, there’s no way to know what will be legal or what’s going to be accepted by society,” Sloan said. “This is a much more risky issue than personalized medicine or genetically engineered crops.”