Previously we wrote about an advance on generating embryonic stem (ES) cell-like cells from men
by isolating spermatagonial stem cells from testes. These cells were powerful, and appeared to do most of what ES cells would do, at least in mice. Now bona fide ES cells can be derived using oocytes
to create parthenogenic
embryonic stem cells (or pES cells). Here's the abstract from the Science article:
Genetically matched pluripotent embryonic stem cells generated via nuclear transfer (ntES cells) or parthenogenesis (pES cells) are a potential source of histocompatible cells and tissues for transplantation. Following parthenogenetic activation of murine oocytes and interruption of meiosis I or II, we have isolated and genotyped pES cells and characterized those that carry the full complement of major histocompatibility complex (MHC) antigens of the oocyte donor. Differentiated tissues from these pES cells engraft in immunocompetent MHC-matched mouse recipients, demonstrating that selected pES cells can serve as a source of histocompatible tissues for transplantation.
So, basically what the researchers did is freeze the cells destined to become mature oocytes (or eggs) in meiosis
, which is the division of a diploid (in humans it's 2 x 23 chromosomes) cell that ultimately results in halving of the genetic material to create a haploid cell (once copy of each of the 23 chromosomes). The problem is that it's more complicated because of exchange of genetic material between chromatids could generate homozygosities where heterozygosities existed before, but the researchers accounted for this by subsequently screening the cell lines they generated for the correct Major Histocompatibility Complex (MHC) genotype. Apparently natural killer cells can also detect the absence
of a MHC complex in what is known as "hybrid resistance" so a homozygosity generated in this process could potentially be detrimental for the recipient.
I realize that's complicated, but here I'll state it more simply. The researchers have figured out a way to make embryonic stem cells that are immunologically compatible to the woman who donates the oocyte, and additionally are nearly genetically identical. Because of recombination in meiosis, a heterozygous locus may become homozygous, but at least no new
genes will be introduced that the body would then attack as foreign.
This is cool for many reasons. If this can be generalized to humans, which is likely, this means that women can have embryonic stem cells made that are highly-genetically matched to them, and immunologically compatible for the generation of replacement tissues. Initially I think treatments for diabetes - pancreatic islet cells - will follow, as well as hematopoietic stem cells for bone marrow transplant, and possibly liver and other tissues. Also, many lines can be generated and banked based on MHC profile.
The second reason it's cool is because it bypasses the idiotic religious belief some people have that life begins
by some sperm-magic at conception. Not only does life not begin
since it is continuous, but the whole sperm-magic thing is so tiresome. If they object to this procedure it can't be because a conception has been terminated, they'll have to come up with a new dogma to attack this.
Sadly, women won't be able to use this to bypass men altogether and just reproduce themselves (although I think they could if they figured out how to fuse two eggs and induce them to enter embryogenesis), since it would be the ultimate form of inbreeding. Pretty much any dangerous recessive gene you have would have the potential for becoming homozygous, and generating genetic disorders in the offspring. But for tissue generation? This is really cool.
Labels: embryonic stem cells, science