Human stem cells obtained via rabbit eggs

Researchers in China have 'reprogrammed' human cells by fusing them with rabbit eggs emptied of their own genetic material, and have also managed to isolate stem cells from the resulting embryos, reported last week's Nature. The team, based at the Shanghai Second Medical University, think that the stem cells derived in this way could provide an alternative to stem cells isolated from human embryos. Human embryo stem cells are the body's 'master cells', capable of developing into a wide range of different tissues.

Using a variation of the nuclear transfer technique used to create Dolly the   cloned sheep, the scientists fused human cells with 'empty' rabbit eggs - that is, they first removed the nucleus, which contains almost all the egg's genetic information. They then reprogrammed the resulting fused cells, so that they began to grow and divide as if they were embryos. After five to seven days the scientists retrieved stem cells from the growing embryos, although it is unclear how long the resulting cell-lines can survive. Using foreskin cells from two five-year old boys and two men, and facial cells from a 60-year old woman, the team created more than 400 fusion embryos, 100 of which survived to the blastocyst stage. The research 'is the first paper to convincingly show that you get human reprogramming' says UK biologist Robin Lovell-Badge. Details of the findings will be published online in the journal Cell Research, and will appear in print later this month.

Team leader Huizhen Sheng now plans to test the embryo stem cells generated by the reprogramming experiments, by transplanting them into an animal. 'It will be important to see whether they will be tolerated by the immune system and whether they can correct an animal model of human disease' she said. Although she has no plans to use the cells in the treatment of human disease, she points out that if it were proved safe enough 'it could provide a solution to human egg shortages for reprogramming in the future'. So-called therapeutic cloning research aims to develop new disease treatments by using stem cells isolated from cloned early embryos.