British researchers have been able to grow stem cells without using animal products, it has been revealed.
Embryonic stem cells have the ability to become any kind of tissue, and scientists hope they can one day be used to treat a range of diseases.
But there has been concern that the animal products used in stem cell development could contaminate them.
However, New Scientist reports scientists at the Roslin Institute successfully used human cells instead.
In the procedure currently used, embryonic stem (ES) cells are cultivated in "feeder layers" consisting of a nutrient material derived from live animal cells.
Animal derived serum has also been used.
But this means there is a theoretical risk of viruses and other harmful agents being transmitted from the animal cells to the stem cells, and thus on to patients who receive stem cell therapy.
'No direct exposure'
Dr Paul de Souza and his team at the Roslin Institute isolated stem cells from embryos created, but not needed, for IVF treatment.
They were then placed on a layer of human protein called laminin, which is the material that separates growing human cells from each other.
They then used "feeder" layers of human neonatal foreskin cells to provide the nutrients and growth factors normally supplied by mouse feeder cells.
Four new cultures of embryonic stem cells were established.
Three were then given additional growth factors and nutrients derived from cows, as is usual.
But the fourth was given a mixture composed completely of human growth factors and proteins.
Dr de Souza says this makes it the first embryonic stem cell line not directly exposed to any animal products at any stage.
However, he said the foreskin cells had been exposed to animal products during their production.
"That still means there is a possibility that unknown pathogens which could be transferred through these helper cells to the stem cells themselves."
Another team of researchers at the IVI Foundation in Valencia, Spain, have carried out similar research using placental skin-like cells instead of the foreskin cells used by the Edinburgh team.
And scientists at Advanced Cell Technology in Massachusetts, US, have produced embryonic stem cells without using any feeder cells.
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