Stem cells derived by somatic cell nuclear transfer (SCNT) have the potential to transform into any cell type, such as bone or brain tissue cells. They can be used to treat and help understand a wide range of conditions and health problems.
Stem cells come from two main sources:
- Embryos formed during the blastocyst phase of embryological development (embryonic stem cells)
- Adult tissue, i.e. adult stem cells.
Experts are describing this latest achievement as one of the biggest breakthroughs in stem cell research since last year when Isreali scientistssuccessfully created the first human embryonic stem cell (hESC) lines that are free of animal contamination and whose production complies with Good Manufacturing Practices (GMP).
Lead author, Shoukhrat Mitalipov, PhD, of Oregon Health & Science University in Portland, Ore., said:
"Our finding offers new ways of generating stem cells for patients with dysfunctional or damaged tissues and organs. Such stem cells can regenerate and replace those damaged cells and tissues and alleviate diseases that affect millions of people."
SCNT involves removing the nucleus of a donor cell and transferring it to an egg cell that has had its nucleus removed. SCNT creates embryos which are nearly identical to those of the donor.
In the past, creating identical cells in this manner has been a major challenge. Normally a female germ cell begins to divide when it has about 150 cells - at this point stem cells can be harvested. However, scientists were not able to get to this stage before. In fact, many experts were starting to wonder whether it might be impossible.
The scientific team from Oregon Health & Science University managed to create identical cells "with stunning efficiency".
"It was thought that, to make human SCNT work, many thousands of human eggs would be needed. We were able to produce one ESC line using just two human eggs, which would make this approach practical for widespread therapeutic"
This is the first time that scientists have been able to use SCNT to create human embryonic stem cells (hESCs).
There are other ways of producing patient-specific stem cells, such as induced pluripotent stem cells (iPS). However, because iPS can sometimes cause unexpected mutations in the cells, researchers have been seeking alternative methods.
According to Chris Mason, a professor of regenerative medicine at University College London:
"They've done the same as the Wright brothers really. They've looked around at where are all the best bits of how to do this from different groups all over the place and basically amalgamated it.
The Wright brothers took off and this has actually managed to make embryonic stem cells."
Is human cloning ethical?Many people wonder whether it is right for scientists to be conducting experiments on human embryos which could eventually grow up to become fully formed human beings.
Dr David King, from the campaign group Human Genetics Alert, said:
"Scientists have finally delivered the baby that would-be human cloners have been waiting for: a method for reliably creating cloned human embryos.
This makes it imperative that we create an international legal ban on human cloning before any more research like this takes place. It is irresponsible in the extreme to have published this research."