Research furthers fertility work
UH lab tests involving mice hold challenges for in vitro fertilization
Dr. Thomas Huang, laboratory director of the Pacific In Vitro Fertilization Institute, hopes to apply research findings by a University of Hawaii team that could improve the in vitro pregnancy rate.
The embryologist is a longtime friend and colleague of Dr. Ryuzo Yanagimachi, a professor of anatomy and reproductive biology who heads the UH Institute of Biogenesis Research.
Yanagimachi and Dr. Kazuto Morozumi, an obstetrician-gynecologist from Fukushima Medical University in Japan, discovered that an intracytoplasmic sperm injection (ICSI) might be hazardous to developing an embryo.
Experimenting with mice, they found that removing the acrosome, a caplike structure covering the sperm's head, before injection could increase the procedure's success.
Huang said he has begun collaborating with Yanagimachi's group to explore the possibility of transferring their laboratory findings to a clinical setting with humans.
Huang first worked with Yanagimachi in 1980 as a National institutes of Health postdoctoral fellow doing in vitro fertilization research with experimental animal models.
He has continued to collaborate with Yanagimachi, adapting the researcher's laboratory findings and techniques to clinical infertility treatments at the Pacific In Vitro Fertilization Institute.
He was able to apply Yanagimachi's early work on ICSI to the clinical laboratory.
As a result, he said, the Pacific In Vitro Fertilization Institute was one of the first of five in vitro fertilization clinics in the nation to achieve a successful pregnancy through the technique.
In their latest investigation, reported in the Proceedings of the National Academy of Sciences, Yanagimachi and Morozumi suggested removing the acrosome from sperm before injection to improve the technique's success.
Working with mice, they found sperm cells with intact acrosomes caused damage and sometimes death to eggs. They believe enzymes in the acrosomes caused the problems, pointing out that acrosomes do not enter the egg in the natural fertilization process.
Huang said some technical challenges must be resolved before the UH researchers' findings can be used to help women have babies.
Yanagimachi's process of removing the acrosome before egg injection improves fertilization in a rodent model system, Huang said.
"In rodents the acrosomes are rather large compared to humans, and injecting the sperm with the acrosome still intact seems to result in subsequent damage to the interior of the egg from the enzymes that are released."
However, he said, "Human sperm are different from those in rodents in that their acrosomes are considerably smaller and the amount of enzymes contained appear not to damage the egg, at least visually."
And while Yanagimachi's process of removing the acrosome before egg injection improves fertilization in rodents, Huang said, "It isn't clear yet if removing the acrosome will improve human ICSI results, but it is certainly rational to do so and should be attempted."
The reason it has not been attempted, he explained, is because the human sperm acrosome is so small it cannot be seen unless the sperm is stained in some way with agents that prevent it from being used for injection.
Also, he said the treatments used by Yanagimachi and Morozumi do not remove all of the acrosomes from all of the sperm, "so the embryologists cannot tell for sure whether the treatment has actually worked on sperm being used for injection."
Huang said he hopes the technical challenges can be overcome by his institute and Yanagimachi's group so they can begin using the technique in the clinic and evaluate "if and how it might improve the success of ICSI."