An article at News at Nature today describes an advance in making human embryonic stem cells through nuclear transfer, or therapeutic cloning. Also, this month, a separate article describes making human embryonic stem cells by taking cells from embryos without destroying them.
The cloning group at California company Stemagen credits their success not with the technique reported for the successful derivation of cloned monkey stem cells but with a supply of oocytes freshly collected from women donors.
The group did not make a cell line but rather generated the early stage “hollow ball” embryos from which stem cell lines are normally produced. The group said they did not try to make a cell line because they didn’t have as many blastocysts as are normally needed to successfully make a cell line. Instead, they sent the blastocysts off for analysis to show that the cloning process worked. Robert Lanza, an unaffiliated researcher at Advanced Cell Technology (ACT) says that the blastocysts didn’t look very healthy.
The Stemagen accopmplishment is similar to what has been done before with two improvements: first that the cloned blastocysts were made using cells derived from adult cells. An earlier group had also gotten cloned human embryos to this stage, but without using adult cells. Another group at ACT that cloned human embryos could not make them grow past the six-cell stage.
Earlier this month, researchers at Advanced Cell Technology published results they had made several stem cell lines from embryos without destroying them. ( This follows on an announcement that Nature Reports first reported in June. ) The peer-reviewed article in Cell Stem Cell describes the production of five lines from individual cells taken from very early embryos without destroying them.
Conventional techniques pulls cells from the inside of the “hollow ball” stage of the embryo and destroy it in the process. This plucks one cell from the earlier “solid ball” stage when the embryo has around eight cells. The process is similar to that used in preimplantation genetic diagnosis. The team used frozen one-cell embryos that they cultured to the 8-cell stage. After the biopsy, the cells remaining in the embryo were allowed to continue growing.
In one set of experiments, one of the 26 embryos yielded a cell line, and 22 of 26 biopsied embryos continued development. A second set of experiments yielded a much higher efficiency, but a similar number of embryos that made it to the blastocyst stage after biopsy. A third set tweaks culture conditions and shows that biopsy-desrived embryonic stem cells don’t need to be cocultured with human embryonic stem cells. I saw no mention of how many frozen embryos would be expected to make it to the blastocyst stage without biopsy.