Two new studies led by scientists in the UK found enough similarities between some types of cells in mouse embryos and human embryonic stem cells that it may be possible to use them for research into human diseases. This could, for instance, make it easier to mass produce tissue for research purposes, and perhaps one day replace that damaged by diseases like Parkinson's, Alzheimer's and diabetes.

The articles are published in the early online edition of the journal Nature.

Previous studies suggested that only cells taken from mouse embryos before being implanted in the uterus would yield useful embryonic stem cells with the potential to develop into almost any cell.

However, one study led by Richard Gardner of Oxford University in the UK showed that cells from the epiblast, a tissue that develops once the embryo is in the uterus, have properties that are just as powerful as pre-implantation embryonic stem cells, and not only this, but these properties are more similar to human embryonic stem cells than the pre-implantation embryonic mouse stem cells.

More specifically, the post-implantation epiblast derived stem cells (EpiSCs) were able to express transcription factors that regulate pluripotency, they kept their genomic integrity, and were able to create all the major cell types needed by the body (including cells that behave like stem cells).

In other words EpiSCs are just as robust at being "master cells" as the pre-implantation embryonic stem (ES) cells. The main difference seems to lie in how they go about it, for instance the signals that control their differentiation are different. However, mouse EpiSCs and human embryonic stem (ES) cells have the same patterns of gene expression and signalling.

The researchers said their results showed that epiblast cells can be used as stable cell lines and "interrogated" to find out how "pluripotent cells" control cell differentiation during early development.

At the same time, another team of scientists at Cambridge University in the UK led by Roger Pedersen came independently to the same conclusions, something which both teams welcomed, as this adds weight to their findings.

In the Cambridge study scientists also explained that mouse ES cells use a different signaling system to human ES cells. The mouse ES cells depend on leukaemia inhibitory factor and bone morphogenetic protein while the human ones rely on activin (INHBA)/nodal (NODAL) and fibroblast growth factor (FGF).

And they were able to show that the late epibalst layer of post-implantation mouse and rat embryos yielded pluripotent stem cells that creates a medium that is good enough for long term maintenance of human ES cells. They concluded that:

"Epiblast stem cells provide a valuable experimental system for determining whether distinctions between mouse and human embryonic stem cells reflect species differences or diverse temporal origins."

Embryonic stem cells are cells that can renew themselves indefinitely and can differentiate into any cell of the body, that is why they are considered by many scientists to be "superior" to other stem cells such as adult stem cells. They have the potential to replace damaged tissue but their therapeutic use is controversial because they involve the destruction of embryos and the possibility of human cloning.

As well as presenting scientists with ethical difficulties, harvesting cells from embryos for treating disease would be expensive and technically very difficult. The genetic material from unfertilized human eggs has to be replaced with that of the patient, and then several stages of division have to take place before the stem cells are ready to be harvested.

It is possible that many will see these new discoveries as opening a mouse model alternative to human embryonic stem cell research because of lower costs and fewer (and presumably less controversial) ethical problems.

"New cell lines from mouse epiblast share defining features with human embryonic stem cells."
Paul J. Tesar, Josh G. Chenoweth, Frances A. Brook, Timothy J. Davies, Edward P. Evans, David L. Mack, Richard L. Gardner and Ronald D. G. McKay.
Nature advance online publication 27 June 2007.

Click here for Abstract.

"Derivation of pluripotent epiblast stem cells from mammalian embryos."
I. Gabrielle M. Brons, Lucy E. Smithers, Matthew W. B. Trotter, Peter Rugg-Gunn, Bowen Sun, Susana M. Chuva de Sousa Lopes, Sarah K. Howlett, Amanda Clarkson, Lars Ahrlund-Richter, Roger A. Pedersen and Ludovic Vallier.
Nature advance online publication 27 June 2007.

Click here for Abstract.

Click to read about Scientists Make Stem Cells From Skin Of Mice Instead Of Embryos.

: Catharine Paddock
Writer: blog

Tag Cloud