Dec. 31, 2009
Two recent papers--one published online by the New England Journal of Medicine and one just published in Nature Methods--analyzed the genetic ethnic diversity of some of the existing human embryonic stem cell (hESC) lines. One group examined 47 hESC lines, while another checked 42 hESC lines; there were 9 lines that both groups checked, for a total of 80 different lines investigated, including some of the most-used hESC lines and some of the few newly-approved hESC lines.
Not surprisingly, they found that most of the hESC lines represent a limited genetic ethnic diversity, primarily from European and Middle Eastern, as well as some East Asian, descent. The University of Michigan group seems to think this is surprising, but in truth it is not surprising and has been noted for years.
Why is this lack of genetic diversity not surprising? Thus far, the embryos destroyed for hESC lines are all taken from in vitro fertilization (IVF) clinics. As many have pointed out for years regarding the hESC lines, the IVF technique is expensive, so the sample is self-selected for those who can afford the IVF practice. The sample is further restricted to those parents who are willing to sacrifice their so-called "leftover" embryos to science. They also found that more than one cell line came from the same embryo donors; again, common sense would have indicated that given the selection, this would be the case.
Perhaps the Michigan group was simply naive regarding their expectations of wider genetic ethnic diversity in the hESC lines. The source of the embryos is sometimes actually given in the published hESC papers, e.g., Thomson's original 1998 paper noted "IVF clinics at the University of Wisconsin School of Medicine and at the Rambam Medical Center"; and four of the five original lines did indeed come from Israeli embryos.
A 2003 publication discussing a potential American embryonic stem cell bank noted that
"The existing human embryonic stem cell lines will not be sufficient to allow for equitable biological access"
"Unless the problem of biological access is carefully addressed, an American stem cell bank may benefit white Americans to the relative exclusion of the rest of the population."
Of course, their proposed solution at that time was to use SCNT cloning, or to recruit gamete donors so that embryos could be manufactured specifically for use in hESC harvesting.
Another group in 2005 noted the same problems:
"However, because of their rarity, the chance of researchers fortuitously obtaining the relevant homozygous hES-cell lines needed for such a bank from in vitro fertilisation clinics is very low"
and suggested the same solutions--cloning embryos or soliciting gamete donors for specific creation of embryos to derive the desired hESC lines.
And another group in 2006 stated that for good matching in a U.S. embryonic stem cell bank
"many thousands of hESC lines would need to be available"
"the current hESC lines were obtained from only a few localities and thus are unlikely to reflect the ethnic diversity of the U.S. population pool."
Of course, it's also not a surprise that the embryonic stem cell researchers want more embryos, especially minority embryos, from whom to wring their embryonic stem cells. It's never enough with some of these people. Supposedly having at their disposal several hundred new hESC lines was satisfactory, plus the open-ended promise from President Obama of as many fertility-clinic embryos as they would like. But Michigan's Sean Morrison
"will also make it a priority to derive new embryonic stem cell lines from underrepresented groups, including African-Americans."
So, apparently Prof. Morrison is going to be stalking minority couples at IVF clinics, targeting their embryos for his lab. Or soliciting egg and sperm donors to create custom-made embryos specifically for the experiments. Or trying to make cloning work. All of this is legal in the U.S. But not all of this can garner federal taxpayer dollars. The next step, already propounded in a Detroit Free Press editorial (complete with the usual hype about "potential" embryonic stem cell medicine), is to do away with any federal limits on the use of taxpayer funds for human embryo research.
There are easier, better, and already-fundable routes, of course. One is creation of new iPS cell (induced pluripotent stem cell) lines, which can be created directly from virtually any tissue of any person. Morrison mentions this in passing in his paper, but Laurent et al. actually analyze several human iPS cell lines, and point out:
"In fact, given that hiPSCs can be generated from hematopoietic stem cells (HSCs) isolated from human cord blood, existing cord blood banks could become a valuable source of ethnically diverse cells for reprogramming into hiPSCs."
But a real way to address social justice in the stem cell realm would be to focus on making more adult stem cell treatments available to patients. Such as treatments for sickle cell anemia, including for adult sickle-cell patients, and treatments for multiple sclerosis, and spinal cord injury. Focus on the patients first.