The newest paper from Lanza’s group at Advanced Cell Technology appears at first glance to be a real breakthrough, and perhaps it is in some ways. The paper claims that a human embryonic stem cell line can be made from a single blastomere biopsied from an 8-10 cell human embryo (similar to what is done in preimplantation genetic diagnosis or PGD). This claim appears to be MOSTLY true in my reading of the paper. However, my reading also tells me that the way that the work was actually done did not spare the remaining embryo. In fact, it looks like the ENTIRE embryo was broken up, all of the individual blastomeres plated into tissue culture dishes, where a few grew into cell lines (2 of 35 blastomeres taken from 6 embryos). So, can single blastomeres form a human ES cell line? Yes. That’s cool. Were there any residual, spared embryos left over corresponding to those from which those two cell lines came? No. I don’t think so.
Problem is, Lanza’s group cannot know in advance which blastomere in the embryo is capable of making a cell line. In fact, their data suggests that maybe only ONE of them can, and with a low sucess rate at that. How can we know in advance which one that is? Maybe someday we will. That day is not today. Maybe each blastomere has a low probability of being able to make an ES cell line. If that’s the case, the technique also has a long way to go in order to prove itself as it is most likely that any given blastomere will NOT be able to make a cell line. Here, the embryo is exposed to the risk of damage during the biopsy with only a very low probability for a successful ES cell derivation (in this paper, 2/35 or less than 6%). Thus, while this paper is certainly interesting, it does not appear to be all that it is touted to be. Far from it in fact. It appears to be a valid statement based on the data that single human blastomeres can be used to create embryonic stem cell lines. However, did they publish the experiment that the press is widely reporting, the experiment where ONE AND ONLY ONE blastomere was removed, a cell line made, and a residual embryo left for possible implantation? No. Not in my reading of the paper.
Even if Lanza and his team did demonstrate that they are able to consistently remove cells from embryos without destroying them, it still may not be enough to placate the critics concerned about the loss of embryos. I heard an interview on NPR this morning with Kathy Hudson, director of the Genetics and Public Policy Center at Johns Hopkins University (http://www.npr.org/templates/story/story.php?storyId=5701628).
She said the one way to do this is to show that the children/adults resulting from embryos from which a cell was removed (for preimplantation genetic diagnosis or for stem cell derivation) grow up normal and healthy. That is, critics will want to see that taking a cell from the embryo doesn’t put it at any additional risk. Since this technology is still quite new, it’s too early to tell what kind of risk is involved, if any. So despite Lanza’s and other scientists’ efforts to find an ethical solution, the debate isn’t going away anytime soon.
I think that the bar for Lanza’s technique is even higher than that. When such a biopsy is done for a genetic test, all one needs is DNA from the cells you remove. Thus, there is a greater certainty that the biopsy will lead to the results one wants (to know if a disease-causing mutation is present before the embryo is implanted). There is data to show that PGD embryos lead to healthy children, though certainly none of it is long term (the first “test tube baby” was only born in the late 1970’s).
However, Lanza’s work seeks to do more than a DNA test. They need the cell that is removed to grow, and grow, and grow. Though this is but the first experiment (of many more to come in order to improve the technique) the chance that this growth will happen from a single cell is very low (either 2 in 35 or 2 in 91 if you count all the cells they used) and in my mind, too low to justify putting the embryo at risk. Of course, if you believe that the preimplantation embryo is not a person and may be used in research to begin with, then the risk does not matter (and Lanza’s technique simply makes the process overly cumbersome compared to derivation by plating whole embryos or immunosurgery).
The REAL experiment would have been to remove single cells from many 8-celled embryos (leaving the remaining 7 cells intact as an embryo) and then to see how many of them led to ES cell lines. My guess is that it would be even fewer than 2 in 35 (as not all blastomeres may have the same developmental potential and one has only blind chance in choosing which one to remove from the embryo). What if the experiment I suggest made ES lines only 1 in 100 times or 1 in 500 times? Would the chances for such a low probability of success sway anyone to give it a try with an otherwise healthy embryo that they want to use in family planning? I don’t think so.
My bottom line: if Lanza’s group can show that they can actually make an ES cell line by doing what the press is reporting (remove one and ONLY one blastomere from the embryo) and we know how often that works, then we can have the conversation about whether or not it represents an “alternative”. Such a day is likely in the distant future. My worry is that techniques that are seen to be “alternatives” yet are far from proven (as this is in my mind) will impair our ability to conduct research that does work. Lanza’s paper is fascinating and significant in my mind (as a person studying human ES cells and early development not to mention my background in medical genetics) but it does not appear to be what many in the press are reporting.