"All research up until now has been conducted in strict observance of the government-set guidelines," Hwang said, according to South Korea's Yonhap news agency. He didn't elaborate, saying he would "divulge everything" at an appropriate time.
Nonetheless, Schatten's accusation has cast a dark cloud over Hwang's work and is raising anew one of the thorniest ethical dilemmas cloning researchers face in collecting eggs for their work.
There are no known human cloning project ongoing in the United States, though Harvard University researchers have asked school officials for permission and the $3 billion California Institute for Regenerative Medicine said it would fund such work.
Stem cell scientists hope to clone embryos to extract stem cells in order to watch how diseases develop and create new drugs.
The basic idea of cloning is to take a patient's genetic material and plop it into an unfertilized human egg. The implanted DNA then drives the egg to develop into an embryo.
The problem is how to obtain the eggs, especially considering how inefficient cloning technology is. South Korean researchers in 2004 used 242 eggs from 16 donors to yield just one cloned human embryo, which was destroyed after 14 days.
About 100,000 American women are injected annually with hormones to stimulate their ovaries to "superovulate" each year at fertility clinics in attempts to conceive babies. The process is arduous, and there's a 1-in-50 chance a patient will over-respond to the hormones, causing complications
Critics of collecting eggs for research contend that there may be long-term health consequences of fertility drugs and that a small percentage of women who go through the process may suffer adverse effects.
The Bedford Stem Cell Research Foundation in Somerville, Mass. is the only known facility to have collected eggs purely for research. It has paid about 20 women about $4,000 each plus expenses to take fertility hormones but hasn't been active since the first of the year as it struggles financially and is reworking its own ethical guidelines.
"It all comes down to informed consent," said foundation director Ann Kiessling, who said she declined an invitation to work with the South Korea-led stem cell hub.
Two leading stem cell teams at Stanford University and the University of California, San Francisco as well the $3 billion California Institute of Regenerative Medicine also declined similar invitations to work with the stem cell hub.
