Finally, Cloned Human Embryonic Stem Cells
Researchers led by Shoukhrat Mitalipov at Oregon Health & Science University using somatic cell nuclear transfer have for the first time been able to produce human stem cell lines matched to the specific genetics of individuals. Such stem cells produced through therapeutic cloning could be used as perfect cell and tissue repair transplants for individual patients. The technique involves installing genes taken from the nucleus of a patient's skin cell and installing it in an enucleated human egg. The researchers have developed techniques that can reliably jump start the process of getting the egg to develop and produce cloned embryonic stem cells.
As the New York Times reports:
The researchers, at Oregon Health and Science University, took skin cells from a baby with a genetic disease and fused them with donated human eggs to create human embryos that were genetically identical to the 8-month-old. They then extracted stem cells from those embryos.
The embryo-creation technique is essentially the same as that used to create Dolly the sheep and the many cloned animals that have followed. In those cases, the embryos were implanted in the wombs of surrogate mothers.
The Oregon researchers, led by Prof. Shoukhrat Mitalipov, did not implant their human embryos and said they had no intention of doing so. They say their technique, in any case, would not lead to the birth of a viable baby. The same technique, tried in monkeys for years, never resulted in the birth of a cloned monkey, they said.
However, thanks to other breakthroughs made possible by prior research on embryonic stem cells, therapeutic cloning may have been superseded as a way to produce transplant tissues. For example, induced pluripotent stem cells (iPSC) can be produced by dosing cells taken from a patient with various factors so that they can be transformed into nearly any type of cell line or tissue.
On the other hand, this technique could be a step toward using cloned embryos as a way to address infertility for some people.
The abstract from the paper in Cell reports:
Reprogramming somatic cells into pluripotent embryonic stem cells (ESCs) by somatic cell nuclear transfer (SCNT) has been envisioned as an approach for generating patient-matched nuclear transfer (NT)-ESCs for studies of disease mechanisms and for developing specific therapies. Past attempts to produce human NT-ESCs have failed secondary to early embryonic arrest of SCNT embryos. Here, we identified premature exit from meiosis in human oocytes and suboptimal activation as key factors that are responsible for these outcomes. Optimized SCNT approaches designed to circumvent these limitations allowed derivation of human NT-ESCs. When applied to premium quality human oocytes, NT-ESC lines were derived from as few as two oocytes. NT-ESCs displayed normal diploid karyotypes and inherited their nuclear genome exclusively from parental somatic cells. Gene expression and differentiation profiles in human NT-ESCs were similar to embryo-derived ESCs, suggesting efficient reprogramming of somatic cells to a pluripotent state.
Look for this research to reignite the fight over the moral status of human embryos. Speaking of which, see my column, "Is Heaven Populated Chiefly by the Souls of Embryos?"