Isolation of amniotic stem cell lines with potential for therapy
Submitted by Ganesh Nagaraj
Isolation of amniotic stem cell lines with potential for therapy
Paolo De Coppi, Georg Bartsch, Jr, M Minhaj Siddiqui, Tao Xu, Cesar C Santos, Laura Perin, Gustavo Mostoslavsky, Angeline C Serre, Evan Y Snyder, James J Yoo, Mark E Furth, Shay Soker & Anthony Atala
Nature Biotechnology: Volume 25, Number 1: January 2007
Summary
Stem cells, or cells which have the possibility to both renew themselves and differentiate into one of multiple types of cell, are promising for potential therapeutic medical applications. In the present paper, Coppi et al. attempt to demonstrate the usefulness of amniotic stem cells for therapy. In particular, three goals were emphasized: determining whether cells from amniotic fluid can express embryonic and stem cell markers; evaluating the potential for therapeutic use of amniotic fluid-derived stem (AFS) cells; and developing an alternative source of stem cells that is ethically acceptable.
The authors isolated magnetic beads for immunoselection to isolate cells from human fetal fluid which expressed the stem cell factor receptor c-Kit. These cells (amniotic fluid-derived stem, or AFS, cells) were shown to exhibit some embryonic and adult stem cell markers via flow cytometry. The AFS cells were shown to retain long telomeres and a normal karyotype over many population doublings using a Telomere Length Assay kit (Figure 1). Moreover, the ability of the cells to differentiate into various lineages, including adipogenic, osteogenic, myogenic, endothelial, neurogenic and hepatic, was supported using limiting dilution and retroviral marking.
The particular methodology used to support the functionality of the AFS cells and their promise in future therapy had some issues. For example, using particular features of a cell line to support the claim that it has differentiated into a particular cell type, such as urea secretion to support a claim of hepatogenic in-vitro differentiation (Figure 5), does not support the cell line's ability to function in-vivo. In addition, the image of growth of tissue engineered bone provided in Figure 6 shows an outgrowth of bone which not only appears abnormal, but would likely not be able to provide structural support in the mouse it was transplanted into, due to the nearly random growth of bone in the area transplanted with stem cells.
Significance
The significance of the area of amniotic fluid-derived stem cells is largely in the fact that they can provide an alternative source of stem cells that is ethically sound to more people. Coppi et al. demonstrate that AFS cells are promising for therapy, but their work also reveals that many issues need to be addressed before AFS cells can actually be used in practice. The techniques used in the paper relate to Bioengineering 115 because of methods used to assess gene expression, such as RT-PCR (reverse transcriptase PCR) and Southern blot analysis (Figure 2).
8 comments:
A few questions:
1. What exactly is this "magnetic bead" technique to isolate the AFS?
2. How do AFS compare to regular embryonic and stem cells in terms of size and/or degree of differentiation?
Isn't urea naturally excreted as a metabolic byproduct of proteins? Perhaps they noticed high levels of urea excretion...
Your post refers to some figures, it maybe be useful for you to post these figures on the blog.
Besides being more ethically acceptable, are there any other advantages of AFS cells compared to stem cells? What procedures did the researchers use to allow for AFS cell differentiation? And what is the rate of AFS cell growth and differentiation?
Thank you for posting this paper. I'm in BE 113, the stem cell class right now. So this is interesting to know.
And I also have some question regarding if the authors did mention about the purpose why they chose AFS rather than other types or other locations of stem cells? As for some other research that I've read, there is also a very promising source of mesenchymal stem cells from Wharton's Jelly of human umbilical cord. In this paper, I dont really see clearly why AFS makes its priority in stem cell research and how, in molecular level, it differentiate into desired cells.
Kiran,
1. Magnetic beads coated with antibodies can be used to separate cells by applying a magnetic field to separate cells which interact with the antibodies and those which do not. To get a better idea of what I mean, visit http://www.bdbiosciences.com/features/products/display_product.php?keyID=32.
2. AFS cells are not capable of differentiating into every cell type, and thus are not totipotent, and I believe they can differentiate into fewer cell types than embryonic stem cells (i.e., are less pluripotent). At the same time, AFS cells can differentiate into more cell types than adult stem cells, as is supported by the paper.
As far as the difference in size between AFS cells and embryonic stem cells or adult (germline) stem cells, I am not sure what the general range of observed sizes are. This would be an interesting property to characterize, though.
Yifei,
From my brief reading of Wikipedia regarding urea production in the human body, it does seem that it is a natural byproduct of metabolism in other parts of the body than the liver. However, I think that the urea levels demonstrated by the cells (see Fig 5) were much higher than what we would see as a normal metabolic product (i.e., in non-hepatic cells).
Was there any lineages these cell lines could not differentiate into?
Also, what are the markers for embryo and stem cells?
Hi Ganesh, I have several questions for you:
(1) Do you know how AFS cells are collected? (How soon after birth must they be harvested? Do they have to rip open the placenta?)
(2) Are these AFS cells the same as or similar to the umbilical cord stem cells that I keep hearing about?
(3) Do these AFS cells have the same degree of multipotency as umbilical cord stem cells?
Post a Comment