In vitro not risky, study finds
A Hawaii researcher's work shows that tools for fertilization do not increase genetic disorders
Couples using in-vitro fertilization or other assistive techniques to have children need not fear increased genetic risks from mutations, Hawaii and Texas researchers reported today.
Results of a study examining reproductive technologies and mutations in mice "should reassure couples that these techniques do not lead to any increased risk of genetic abnormalities," said Dr. Ryuzo Yanagimachi, University of Hawaii professor emeritus.
"We expected the mutation rate to be higher because of stress (when embryos were transferred to mothers)," he said in an interview. "We didn't find it. That is good news."
Yanagimachi, a pioneering researcher on in-vitro fertilization who achieved worldwide fame in 1998 with cloning of mice, retired in December 2005 as professor of anatomy and reproductive biology.
However, he has continued to work in his laboratory at the Institute for Biogenesis Research in the John A. Burns School of Medicine on the Manoa campus. His partner in the new study, Dr. Yukiko Yamazaki, did part of the work at the new medical school in Kakaako.
They conducted the research over the past five years with a team led by John McCarrey, University of Texas-San Antonio biology professor. McCarrey's group included his graduate student Patricia Murphey and Lee Caperton, Alex McMahan and Christi Walter of the University of Texas Health Science Center in San Antonio.
The researchers compared mice produced using natural reproduction to those produced through in-vitro fertilization, embryo transfer, pre-implantation culture, intracytoplasmic sperm injection and spermatid (a round sperm with no tail) injection.
They used the latest techniques and "special" mice that were genetically manipulated to examine the DNA of each group, Yanagimachi said. They looked for "point mutations" or changes in the DNA level associated with genetic diseases in humans.
They concluded that "these methods of in-vitro conception through assisted reproductive technologies are not disrupting naturally occurring processes that are required to direct proper embryonic and fetal development."
The results were reported in this week's Proceedings of the National Academy of Sciences.
AssistIve reproductive technologies account for more than 1 percent of births in the United States and most Western countries, the researchers said. Six percent or more births are achieved through artificial reproduction methods in some countries, such as Denmark, they said.
More than 3 million people have been conceived by in-vitro fertilization and other artificial methods, Yanagimachi said.
Artificial reproductive technologies, used mostly by patients ages 35 to 40, have been controversial because of increased multiple births and congenital malformation, he said.
One problem was that doctors were transferring "too many eggs" into the womb, and there was not enough nutrition for them, he said. The trend now is to transfer no more than two embryos, he said.
Yanagimachi emphasized that "birth defects (congenital malformation at birth) and mutation are not synonymous. There are many factors contributing to the birth defects."
"Point mutations" or "genetic errors" studied by the Hawaii-Texas scientists are just one of the many factors "but very important," he said. "As far as mutations, there was no change.
"Medical researchers are trying to make assisted reproductive technologies as safe or even safer than natural conception," which is not risk-free, he added. "We can't make it zero but we can reduce it."
McCarrey was at UH for some of the work and will return to finish some studies, Yanagimachi said. Their next challenge is "to see if cloning increases mutations," he said.