One of the co-authors of the controversial stem cell thesis published in Science magazine earlier this year says he is certain of the existence of the stem cells cited in the paper.

Head of Seoul-based Hanna Women’s Clinic Jang Sang-sik said in an interview Tuesday that he had granted eggs for research purposes to Hwang’s team in January and February 2005 after Hwang’s labs were polluted by fungus blown from a nearby dog farm.

Jang said he took the eggs from around 12 women who had been introduced purely for research purposes and verified by the Institutional Review Board of Hanyang University.

He stressed that no such illicit activities such as sales of human ova had been involved in the process.

The co-author also said he firmly believed in the cells’ existence, after witnessing the transfer of egg nuclei and seeing cloned embryos reach the blastocyst stage, which occurs just before the extracting of stem cells.