The tiny white speck darts about the laboratory dish like a crazed firefly. A tiny cylinder maneuvers in hot pursuit.
“He’s haulin’,” muttered Dr. David Battaglia. “He doesn’t know where he’s going.” More specks appear and disappear. The cylinder, a hair-thin laboratory pipette, keeps chasing. Finally, “a clean pickup,” Battaglia said triumphantly.
Battaglia smiled in the small, cluttered side room of the University of Washington Medical Center’s Women’s Care Center in Seattle. He had just shown-on a microscope videotape-how he corralled and injected a human sperm into an egg in a lab dish.
This high-tech conception is the key portion of a new procedure to help infertile couples have children.
The technique-called ICSI for intracytoplasmic sperm injection-is designed for male infertility: Sperm is directly injected into a waiting egg, then is transferred to the uterus.
“It’s providing new hope to people who had no alternative other than donor sperm,” said Battaglia, lab director for the UW’s Fertility and Endocrine Center.
The first couple to achieve pregnancy through the technique at the UW center expect to deliver twins in December. A dozen other attempts have been made at the UW center.
Perfected at the Center for Reproductive Medicine in Brussels, the microinjection procedure builds on technology developed through in vitro fertilization-introducing sperm and egg in a laboratory dish.
It takes another biological shortcut to help the sperm reach its target.
Experts estimate about two million men in the U.S. are incapable of fathering children naturally. This “male-factor infertility” may result from one or several causes:
– Low sperm count-fewer than about 20 million sperm per milliliter of semen.
– Poor motility-sperm may be malformed and unable to swim or inexplicably don’t swim forward.
– Biochemical dysfunction-cap of the sperm doesn’t come off as it normally does in preparation for fertilization. Or the sperm doesn’t bind to the egg’s surface to begin penetration.
– Antibody reaction-the man forms antibodies to his sperm, causing them to clump.
In many cases, physicians can’t figure out why the sperm don’t function properly.
“Knowledge of sperm function is relatively primitive,” said Dr. Nancy Klein, medical director of the UW fertility center.
The new ICSI procedure begins as in vitro fertilization. At the appropriate time of the month, a woman is given hormonal fertility drugs to stimulate development of more than one egg in the ovaries. Physicians carefully monitor the ovaries with ultrasound-sound-produced images-to see when the egg-containing follicles begin to bud out on the surface of the ovaries.
With precise timing, the doctor removes the available eggs, an average of nine, with an ultrasound-guided probe threaded through the vagina to the ovaries. The eggs are placed in a laboratory dish to await fertilization, secure in a saline solution similar to that of the oviducts, which the egg travels to reach the uterus.
Male semen, meanwhile, is spun around in a machine, causing the sperm to move to the bottom of the test tube. They are removed, washed and placed in a viscous solution on one side of the same laboratory dish that contains the eggs. The dish rests on a microscope platform kept precisely at human body temperature.
The end of a pipette, a thin glass cylinder, is heated and stretched until it becomes thinner than a human hair. Then its tip is beveled to produce an even sharper point so it can puncture the egg easily. The tiny diameter allows the sperm to enter and escape, but limits the amount of fluid entering the egg when it is expelled from the pipette.
After about two days, when the resulting embryo develops to four cells, it is transferred to the woman’s uterus with any others that are available from microinjections during that cycle. At four cells, it is nearly ready to attach to the uterine wall.
More than one embryo is always transferred, so there is about a 30 percent chance of a multiple pregnancy.
“I am the Egg Man,” Battaglia, a cell biologist, said with a chuckle as he watched the videotape and explained the delicate procedure.
It has a 20 to 30 percent chance of achieving a pregnancy, about the same as through sexual intercourse, Klein and Battaglia said. In several hundred births resulting from the procedure in the Brussels clinic, there is no higher incidence of birth defects than in the general population, they said.
