Washington/ London:
In a long-awaited breakthrough in human cloning, scientists have successfully turned human skin cells into early-stage embryos that can be used to create specialised tissue cells for transplant operations.
The achievement, which comes 17 years after the birth of Dolly the sheep, represents a major turning point in human cloning research which could now lead to new tissue-transplant operations for a range of debilitating disorders, such as Parkinson's disease, multiple sclerosis, heart disease and spinal cord injuries.
Researchers who made the advance emphasised that the work is designed to produce replacement tissue for transplant operations from a patient's own skin cells, rather than to improve the chances of so-called "reproductive cloning".
Other scientists believe the achievement inevitably brings the prospect of cloned babies a step nearer, The Independent reported.
The technique used by the team led by Shoukhrat Mitalipov, a senior scientist at Oregon National Primate Research Center (ONPRC), is a variation of the commonly used method called somatic cell nuclear transfer, or SCNT.
It involves transplanting the nucleus of one cell, containing an individual's DNA, into an egg cell that has had its genetic material removed. The unfertilised egg cell then develops and eventually produces stem cells.
The important technical advances by the team enabled the cloned human embryos to survive to the 150-cell stage, known as a blastocyst, when embryonic stem cells can be extracted for growing in the laboratory into specialised tissue cells, such as nerve cells or cardiac muscle.
"A thorough examination of the stem cells derived through this technique demonstrated their ability to convert just like normal embryonic stem cells, into several different cell types, including nerve cells, liver cells and heart cells," Mitalipov said in a statement.
"Furthermore, because these reprogrammed cells can be generated with nuclear genetic material from a patient, there is no concern of transplant rejection," Mitalipov said.
The research was directly aimed at generating embryonic stem cells for treating serious disorders from a patient's skin cells, and not at improving the chances of producing cloned babies, Mitalipov added.
"This is not our focus, nor do we believe our findings might be used by others to advance the possibility of human reproductive cloning," he said.
The breakthrough may also raise serious ethical concerns about the creation of human embryos for medical purposes.
The study was published in the journal Cell.