In 2013, Mitalipov’s group published an impressive study (Cell 153; 1228-1238, 2013) in which they reported the production of human blastocysts, and how embryonic human cell lines could be derived from them, and from these, cells of various tissues.

Regardless of the ethical difficulties of these experiments, since obtaining cell lines inevitably entails the destruction of the human blastocysts obtained, it has also been revealed that Mitalipov’s study apparently contained some errors. Thus reports an anonymous author on PubPeer, an online site in which readers can leave comments on published scientific papers (Cyranoski D and Hayden EC Nature/News 23-05-2013). In this case, the writer highlighted the existence of four errors in the Oregon authors’ study. In defence, Mitalipov stated, in the same Nature article, that it was true, but that three of the four errors were “innocent mistakes” that occurred on putting the paper together and that the fourth was not an objective problem, adding that he did not consider it to be fully substantiated.

However, apart from these errors, the study by Mitalipov et al. can be considered as the first in which a human blastocyst was cloned, and from which human embryonic cell lines could be derived.

To obtain these blastocysts, human oocytes, apparently from young women, and somatic cell donor nuclei, obtained from foetuses and infants, were used.

That same year (2014) another article was published by Egli’s group (Nature, doi: 10.1038/ natureA3287) in which skin cells from a newborn and a woman with type 1 diabetes were used to produce the cloned human embryo. Four embryonic stem cell lines were obtained from the embryo produced, which were then able to be derived into different cell types, among them pancreatic beta cells. These are insulin-producing cells, which could certainly be an important step in the treatment of patients with type 1 diabetes in the more or less near future.

However it has even gone one step further towards the production of human embryos, and specifically blastocysts, from which human embryonic stem cells can be derived. For this they used skin cells from two adult males (a 35-year-old and a 75-year-old) as nucleus donor cells (Cell Stem Cell 14; 1-4, 2014). The authors remarked that their study showed, for the first time, the possibility of using adult human cells as nucleus donors for transfer into the enucleated oocyte, for somatic cell nuclear transfer. However, also in the aforementioned paper by Egli’s group, somatic cells from a woman with type 1 diabetes were used, i.e. somatic cells from an adult.

Nevertheless, be it one way or another, it should not be forgotten that to date, only human blastocysts have been produced. It remains unknown whether or not these will be viable, so it seems rather audacious to state that human cloning has been achieved. Certainly human blastocysts have been produced, but there is a long way from that to the production of living human beings, and right now, we do not know if this distance can be overcome.

One final consideration is that, regardless of the technical importance that these advances may have in relation to regenerative and reparatory medicine, they have an insurmountable ethical difficulty, which is that all the experiments require the production of human blastocysts that must be destroyed after being produced, something that ethically seems difficult to justify. Would it not be better therefore, to direct research efforts towards the use of adult stem cells, iPS cells (Cell 126; 663-676, 2006) or STAP cells (Nature 505, 641-647, 2014.)?



Justo Aznar



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