adult stem cells, Bioethics, cord blood, embryonic stem cells, induced Pluripotent Stem Cells, iPS, umbilical cord stem cells

>More Questions on Embryonic Stem Cells

>Lydia asked about my comments on embryonic-like cells derived from umbilical cord blood.

Umbilical cord blood itself appears to be at least multipotent. However, Texan and British researchers worked with NASA to produce “embryonic-like” stem cells by manipulating them with filters and a special centrifuge. Here’s my post from August, 2005 on those cells.

And here’s the press release from McGuckin’s university in the UK.

And here’s the abstract from the Journal, Cell Proliferation,

“Production of stem cells with embryonic characteristics from human umbilical cord blood”

C. P. McGuckin, N. Forraz, M.-O. Baradez, S. Navran, Synthecon Corporation, Houston, and J. Zhao, R. Urban, Tilton, L. Denner

When will embryonic stem cells reach the clinic? The answer is simple – not soon! To produce large quantities of homogeneous tissue for transplantation, without feeder layers, and with the appropriate recipient’s immunological phenotype, is a significant scientific hindrance, although adult stem (ADS) cells provide an alternative, more ethically acceptable, source. The annual global 100 million human birth rate proposes umbilical cord blood (UCB) as the largest untouched stem cell source, with advantages of naive immune status and relatively unshortened telomere length. Here, we report the world’s first reproducible production of cells expressing embryonic stem cell markers, – cord-blood-derived embryonic-like stem cells (CBEs). UCB, after elective birth by Caesarean section, has been separated by sequential immunomagnetic removal of nucleate granulocytes, erythrocytes and haemopoietic myeloid/lymphoid progenitors. After 7 days of high density culture in microflasks, (105 cells/ml, IMDM, FCS 10%, thrombopoietin 10 ng/ml, flt3-ligand 50 ng/ml, c-kit ligand 20 ng/ml). CBE colonies formed adherent to the substrata; these were maintained for 6 weeks, then were subcultured and continued for a minimum 13 weeks. CBEs were positive for TRA-1-60, TRA-1-81, SSEA-4, SSEA-3 and Oct-4, but not SSEA-1, indicative of restriction in the human stem cell compartment. The CBEs were also microgravity–bioreactor cultured with hepatocyte growth medium (IMDM, FCS 10%, HGF 20 ng/ml, bFGF 10 ng/ml, EGF 10 ng/ml, c-kit ligand 10 ng/ml). After 4 weeks the cells were found to express characteristic hepatic markers, cytokeratin-18, α-foetoprotein and albumin. Thus, such CBEs are a viable human alternative from embryonic stem cells for stem cell research, without ethical constraint and with potential for clinical applications.

These cells were later used to produce functional liver tissue and alveolar lung cells.

There have also been bone marrow cells that share the characteristic markers of embryonic stem cells. (Reported here.)

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6 thoughts on “>More Questions on Embryonic Stem Cells

  1. >Can you explain this sentence a little?"CBEs were positive for TRA-1-60, TRA-1-81, SSEA-4, SSEA-3 and Oct-4, but not SSEA-1, indicative of restriction in the human stem cell compartment."Were these the protein markers, and is the idea that they had several of the usual markers taken to indicate pluripotency but not one of them?I'm trying to get on the ball with this whole "protein marker" thing. For example, the article on the bone marrow ones said they have a similar structure and protein markers to embryonic stem-cells, but is that supposed to mean they are fully pluripotent, or what?

    Posted by Lydia McGrew | November 23, 2007, 1:29 am
  2. >You ask tough questions – I had to study up! I think I got it right, but this is the sort of thing that getting the wrong word can make the whole paragraph untrue. Think of it as very simplistic.(or it may be too much information – you may just want the first and last two paragraphs)All of these proteins or "antigens" are called "markers" because they can be tested for by adding special antibodies to the petri dish. The antibodies can be bought from commercial sources and are manufactured so they will fluoresce or turn colors only when they bind or match themselves to their opposites, the antigens or marker proteins. Think of it like putting a key in a lock and the two light up, but they only light up when they match. This way, researchers can get pictures to follow whether the markers are there, a fair idea of how much is there, and prove to other people what they did.Evidently, there's very complicated coordination or regulation to make the cell produce an appropriate amount of Oct3/4 and some of the other proteins that make the cell keep on keepin' on.Oct4 or Oct3/4 (I haven't figured out why some people call it one and some people call it the other – could Oct4 just be an abbreviation for Oct3/4?) is the gene for the transcription factor (the protein called by the same name) that is only present when the cell is pluripotent – able to make all or most of the cells except the trophoblast, the part that becomes the placenta. If Oct3/4 is made too much or too early, in the embryo, those cells won't make trophoblast cells, and the placenta won't form. If there's not enough of it made by a given cell, that cell begins to differentiate.The protein Oct3/4 works with other genes and proteins to make a cell copy itself instead of differentiating to a more specialized cell, that can't make as many kinds of different cells. Transcription factors are proteins that turn genes on and off by attaching to a certain area of a section of DNA, blocking it or making it readable by the RNA. To make a protein, the RNA comes into the nucleus and makes a copy of the gene, then it goes out of the nucleus and into the cell to take the blueprint to the protein factories, the ribosomes, where the protein is made that the gene codes for.If I understand this article, (Tumor Rejection Antigen) TRA-1-60, TRA-1-81, (stage-specific embryonic antigens) SSEA-4, SSEA-3 are proteins that are present in Embryonic stem cells but decrease as the cells differentiate. SSEA-1 is not found on the surface of the embryonic stem cells, but increases as the cells differentiate. So the combination reported in the article on cord blood means that the cells have the same phenotype – they function and look the same way by our tests – that embryonic stem cells do.

    Posted by | November 23, 2007, 5:00 am
  3. >Thanks very much. That's what I was wondering: The absence of SSEA-1 is actually another indicator of "embryonic cell-like" status, rather than a difference between these cells and embryonic stem cells.Well. This is making me rethink some of my ideas. I had previously thought that human pluripotent stem cells were found "in nature" only as the inner cell mass of the blastocyst. That is, I had thought that you had to do some elaborate reprograming (as in the most recent research) or cloning-like technique (as in Hurlbut's altered nuclear transfer idea) in order to get them in any way other than through embryo-destroying research. But it now appears that at least these "very small" ones are floating about in our bodies all the time.I'm guessing that the reason that this was not hailed as a solution all by itself to the whole ES cell issue and that the recent reprograming news _has_ been so hailed is sheerly a matter of quantity: The naturally-occuring probably-pluripotent cells (from bone marrow and cord blood) are too rare and few to be very useful for research. Does that sound right?That is ethically interesting, too. I had argued in a blog post that Hurlbut's ANT program would be making something analogous to the "dead body" of an embryo (by making cells like those of the ICM) even if it never made a live embryo. My argument was that this was macabre and ethically questionable–like making a headless body in the lab–even if it avoided live embryo destruction. But if cells of this sort occur naturally in the body, then that ethical analogy is called into question and I will have to rethink.

    Posted by Lydia McGrew | November 23, 2007, 3:05 pm
  4. >My first reaction to the idea of altered nuclear transplant was that the process would produce a purposefully abnormal or impaired embryo. He proposed altering only the Oct4 gene, so I worried that we'd end up with a mass of cells that for all practical purposes are similar to the ICM, but which couldn't form a trophoblast. However, Dr. Hurlbut convinced me that the technique would be proved in animals first. and that he believed that the process would create a teratoma-like structure that would yield embryonic stem cells. He was/is certain that there would never be any self-directed organization that appeared to be a stunted or impaired embryonic organism.In a way, the reprogramming process skipped straight to the products of the ANT structure. When they are grown to form embryoid bodies or teratomas, we see the culture/structure that Dr. Hurlbut predicted. Unfortunately, Thomson decided to do the basic research with embryonic stem cells and fetal cell cultures, in contrast to Yamanaka's team, who did the ethically correct research in mice, first. The big advantage is that no oocytes are needed.

    Posted by | November 23, 2007, 4:52 pm

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