Human embryonic stem cells are a revolutionary and easily accessible tool for the treatment of many diseases which remain difficult to cure. We hear such statements quite often. But new international research involving the team of Petr Dvořák of the Department of Biology of Masaryk University's Faculty of Medicine now says that researchers have not yet reached a full understanding of the genetic diversity of embryonic stem cells. Information about this diversity is necessary for the wide application of stem cell-based therapies.
The research shows that the knowledge we have about population diversity in existing human stem-cell lines allows the providing of future stem cell therapy or disease modelling using stem cells preferably to Europeans and people of Middle Eastern origin. It does not cover people from Africa, Asia or the native people of America.
“A very important prerequisite for every embryonic stem cell-based therapy or efficient disease modelling is the genetic similarity of graft cells and the host, meaning the patient we want to cure,” says Dvořák. The establishment of large international cell bank, in which lines of embryonic human stem cells are deposited, should help. If scientists find in banks cell line that is at various parameters genetically close to the patient, this cell line can be taken from the bank and therapy can start.
Up till now scientists have presumed that genetic banks having human embryonic stem cells are extensive enough in terms of genetic diversity to provide cell therapy or disease modelling theoretically to the majority of the human population. But the research, whose results were published in the prestigious science magazine New England Journal of Medicine, shows that this assumption is flawed. “We presume that several hundreds of lines we have at our disposal corresponds to the same number of different human genotypes, thus that it is basically enough and we can stop further derivations. It should eliminate the ethical problem surrounding the acquiring of more embryonic stem cell lines,” says Dvořák, adding that a brand new ethical problem has appeared.
Banks actually contain cell lines whose genetic origins are mostly in Europe. The reason is simple: embryos for isolation of stem cells come from clinics of assisted reproduction. “It is understandable that native Americans in North America and black people in Africa – in comparison with Europeans – are not in need of assisted reproduction. It has been ascertained that American stem-cell lines are, in terms of their origin, also European,” explains Dvořák.
Profit from stem cell research just for some regions
Scientists point out that this is a dangerous tendency which could finally lead to treatment by stem cell-based therapies being dedicated to people from certain geographic regions only.
“From the very beginning it has been intensively proclaimed that this therapy will be accessible to all. This fact is now contested. At the same time it is a big challenge for those who try to create banks for so-called induced pluripotent stem cells,” explains Dvořák. These recently discovered and revolutionary stem cell type can be obtained by genetic manipulation from practically every somatic cell and with no relation to embryos. But the problem is that the creating of these banks could turn into the same process of selection as the one mentioned above. “Lines are created only in certain highly-developed countries, probably in correspondence with corresponding genetic diversity,” warns Dvořák.