Oregon scientists used human skin cells to create fertilizable eggs, a step in the quest to develop lab-grown eggs or sperm to one day help people conceive.

But the experiment resulted in abnormalities in the chromosomes, prompting the Oregon Health & Science University team to caution it could take a decade of additional research before such a technique might be ready for trials in people.

The work published Tuesday in Nature Communications may offer lessons as scientists try to learn to create eggs and sperm in a lab for the infertile or to help same-sex couples have children genetically related to both partners.

The OHSU team removed the nucleus from a human egg cell and replaced it with the nucleus from a human skin cell. But a skin cell contains two sets of chromosomes, and eggs and sperm are supposed to each contain only one set that combine during fertilization. The researchers therefore induced the egg-like cells to discard extra chromosomes, injected donated sperm and jumpstarted post-fertilization development.

About 9% lasted for six days in lab dishes, reaching the blastocyst stage of early embryo development, before the experiment was stopped.

The main problem: The chromosomes were abnormal in several ways.

“We kind of developed this new cell division that can reduce chromosome number,” said study senior author Shoukhrat Mitalipov, OHSU’s embryonic cell and gene therapy director. “It’s still not good enough to make embryos or eggs genetically normal.” He called the initial findings proof-of-concept and said his team is working on improvements.

Scientists not involved in the work had mixed reactions. Columbia University stem cell researcher Dietrich Egli was troubled by the abnormalities.

But Dr. Eve Feinberg, who agreed that the chromosome problems were critical, said it "seems like this team figured out how to reduce the number, just not well yet. But it’s an important step and very exciting.”