Scientists have used a cloning technique to create embryonic stem cells to grow on a human cell for the first time.
The test, reported in the journal Nature, is a significant development in the controversial research, say researchers from the New York Stem Cell Foundation.
A new study has found that fertility treatment can lead to major birth defects.
The results could have a huge impact on the study and treatment of diseases such as Alzheimer's, diabetes and Parkinson's.
Genetic material was taken from an adult egg and transferred into a human egg, which was grown to produce an early embryo.
Stem cells have huge potential in the medicine world as they can transform into any other cell type in the body.
The technique that was used to create the embryo, somatic cell nuclear transfer (SCNT), first shot to fame when Dolly the sheep - the first mammal to be cloned - was unveiled to the world.
The standard cloning technique involves removing the nucleus from an egg. The core is then replaced with the nucleus of a cell from the donor and nurtured in laboratories.
This technique involved leaving the egg's DNA intact and added DNA from an adult donor cell. But the cells that resulted had an abnormal number of chromosomes so they are not yet ready for therapeutic use, the researchers added.
"This paper will be seen as significant both by those who are trying to use SCNT to produce human patient-specific embryonic stem cell lines and by those who oppose human 'cloning' experiments," said Professor Robin Lovell-Badge, a division head at Britain's National Institute for Medical Research.
"The ultimate goal of this study is to save and enhance lives by finding better treatments and eventually cures for diabetes, Alzheimer's, Parkinson's and other debilitating diseases and injuries affecting millions of people across the U.S. and the globe," said Susan Solomon, chief executive officer of the Stem Cell Foundation.
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