New fertility probes help researchers identify viable eggs

Researchers have developed two tiny probes that may be a first step in finding and treating egg abnormalities in infertile women. Testing with the probes could allow the women to use their own eggs successfully to bear children.

PROVIDENCE, R.I. -- A research team has developed two tiny sensor-tipped probes that may help determine a woman's fertility by gauging the viability of her eggs.

The probes may become a first step in finding and treating egg abnormalities in infertile women to allow them to use their own eggs to bear children. More than 2.5 million U.S. women suffer from infertility. As more women have delayed child-bearing, age-related impairment of eggs has reached epidemic levels.

The scientists are from Brown University, Women & Infants Hospital of Rhode Island and the Woods Hole Marine Biological Laboratory. Their experiments with animals indicate the probes can be used to examine eggs removed from the ovary during in-vitro fertilization treatments.

Each probe involves an electrode with a 1-micron vibrating tip that oscillates at the edge of an egg or embryo. Information gathered by the electrode is analyzed by computer. One probe assesses an egg's calcium flow while the other appraises oxygen uptake. Calcium discharge and oxygen consumption are critical physiologic functions in eggs and developing embryos.

Embryos found viable could be transferred to the patient.

"Because they provide non-invasive measure of a cell's health, the probes work like electrocardiograms for an individual cell," said David L. Keefe, M.D., associate professor of obstetrics and gynecology in the Brown University School of Medicine. Keefe, who is based at Women & Infants Hospital of Rhode Island, and Peter Smith, of Woods Hole Marine Biological Laboratory, developed this application for the probe technology.

Currently, older infertile women who want children must pursue costly tests and often undergo expensive, largely ineffective reproductive technologies that depend upon their own eggs. Some older women receive eggs donated by a younger woman; others choose to adopt.

"By measuring calcium exchange and oxygen uptake at the edge of the cell membrane, the probes allow us to separate normal from abnormal eggs," Keefe said. Other research techniques can perform the same task, but rely on tests that destroy the eggs. They are not clinically useful.

Donation of eggs from younger to older women nullifies the effects of age on fertility and confers a 10-fold increase in fertility rate compared to conventional treatments, Keefe said. Other treatments, such as transfer of multiple fertilized eggs back into a woman, may lead to triplet pregnancies, carrying high economic costs and long-term health risks.

Today, 85 percent of U.S. triplets arise from infertility treatments. Virtually all triplet births are premature. On average, a triplet spends 60 days in the hospital immediately after birth. The hospital care for a newborn triplet averages about $100,000.

"The probe may allow us to determine up front which embryos have developmental problems," Keefe said. "By identifying the healthy embryos, we could limit use of reproductive technologies that produce several newborns at once."

Keefe and his Woods Hole colleagues have filed patent applications for the probes. The researchers will exhibit and discuss their research Feb. 27-28, 1998, at a bioengineering symposium at the National Institutes of Health in Bethesda, Md. The public meeting will highlight 50 recent biomedical findings with significant health-care applications.

In experiments, the calcium electrode differentiated between viable and non-viable frozen and thawed rodent embryos indistinguishable by microscope. Experiments with the oxygen probe showed it detected oxygen uptake associated with embryo development.

"Our hope is to develop treatments to conserve nuclear genome in a recipient's eggs," he said. "Hopefully our research will help avoid widespread use of costly and possibly ineffective cytoplasmic manipulation treatments in women with unexplained infertility."