A bomb with a delayed-action fuse was set in Montreal on Oct.13. At a meeting of the American Fertility Society (AFS),reproductive biologist Jerry Hall of George WashingtonUniversity Medical Center reported that he and his team hadsplit early human clusters of fertilized eggs into separate, still-totipotent embryos.His presentation, "Experimental Cloning of Human PolyploidEmbryos Using an Artificial Zona Pellucida," won the society'saward for "General Program Prize Paper."
Bioscience journalist Rebecca Kolberg, a Medical News Networkstaffer who covered the session, put out the story to thenetwork's clients PP publications serving physicians and health-care providers.Ten days later, Hall and the director of the in vitro fertilizationclinic, Robert Stillman, found themselves on national televisiontalk shows explaining what their experiment could and couldn'tdo PP as well as should and should not do.
Meanwhile, Science commissioned Kolberg to write a researchnews editorial, which she subtitled, "Cloned human embryoshave potential applications in in vitro fertilization, but beforethat can happen, some serious ethical issues will have to beaddressed."
As Hall and Stillman described in their paper, they obtainedfrom in vitro fertilization clinic patients 17 intact embryos PPeight two-cell, two three-cell, five four-cell and two eight-cell,for a total of 48 blastomeres. These had been discarded fortechnical reasons but were still capable of cleavage. Theycoated each blastomere in these clusters with an artificial zonapellucida protective sheath consisting of sodium alginate.
In culture, blastomeres from four-cell embryos developed onlyto the 16-cell state; none from eight-cell stage went beyondeight cells. But two-cell blastomeres divided repeatedly up tothe morula, or next embryonic development stage. All theembryos were discarded six days after fertilization.
"This initial study confirms that experimental cloning ortwinning of human embryos is feasible," Hall told his AFSaudience. He added the caveat that "extending these studieswould require obtaining permission to clone and cryopreserveblastomeres from supernumerary diploid embryos remainingafter a transfer of fresh embryos."
Hall's team obtained clearance for the preliminary study fromthe university's institutional review board. It did not seekgovernment authorization, as no federal funding was involvedin the project.
Fertility clinician Joe Massey, co-director of ReproductiveBiology Associates in Atlanta, has studied twinning in abnormalhuman embryos with an extra set of chromosomes. When heasked the AFS's ethics committee last winter to advise him onpotential clinical applications, he was referred to thegovernment-supported National Advisory Board on Ethics inReproduction, which declined to help because his work is notfederally funded.
Massey said that the C-word, "cloning," is not only an ethicallyincendiary phrase but scientifically inappropriate.
"Cloning will never be done in humans," he told BioWorld,because there's no compelling medical reason to do it." Theword cloning, he said, means making multiple copies, which isdone in cattle. What Hall and his team achieved, Masseypointed out, was to split a two-cell embryo in half, not mincelarge clusters into eight or 16 embryos, as is done for cows bynuclear transfer. This two-way splitting is best described inhumans as twinning, he stated, for the purpose of enhancingthe chance of a pregnancy resulting from in vitro fertilization.
"I think twinning would be socially acceptable for infertilitypatients who need to have more embryos than they have whenthey go through in vitro fertilization," Massey said. "Then youdon't have to worry about all this crazy speculation over usingembryos for spare parts. That will not be relevant because theinfertility parents would be putting these split embryos back totry to have one child.
"The side effect would be an occasional set of identical twins,which I think society would accept. We're trying to help peopleget pregnant," he said.
Hall's main achievement, Massey emphasized, was to show thatalginate works as an artificial zona pellucida to shield fertilizedhuman eggs, at least at the early stage, "so twinning nowbecomes technically feasible.".Since "Baby Louise" Brown became the first infant born by invitro fertilization 16 years ago in Britain, some 200 infertilityclinics have sprung up in the U.S. alone, with 23,000 live birthsto their credit.
Reacting to the Hall experiment, the American Fertility Societyissued a press statement that observed: "At some point in thefuture the technique could benefit infertile couples. However,this experiment also raises ethical questions that must beaddressed. ... Relevant guidelines should be established at thenational level."
While welcoming "open discussion on the possible limitations"of human embryo twinning, Massey declared, "I hate for apossible good technique like this to get lost in the furor ofpeople's imaginations running wild over cloning, which will notbe done in humans, in my opinion."
-- David N. Leff Science Editor
(c) 1997 American Health Consultants. All rights reserved.