Re: What are the chemical signals used to transform stem cells?

Wow, great question . . . and one scientists have been trying to answer for the past 10 years. I mean, if we find the answer to that question, we’ve found the Holy Grail, right? What makes embryonic stem cells (ESCs) so unique is that they are pluripotent; that is, they are precursor cells whose fate is not yet determined. They have the potential to develop into any cell type (skin, muscle, gut, brain, nerve) if they receive the proper signal. In theory, if we could identify all of the signals that direct undifferentiated (pluripotent) stem cells to begin transforming into heart cells or endothelial (skin) cells or nerve cells or brain cells, then all we would need to do would be to add that protein to the cell culture medium and the stem cells would begin to grow into any tissue type we need. That’s in theory. But, like all of cell biology, it’s actually much more complicated than that and so I will try to keep my explanation short and to the point.

Researchers have actually identified numerous biochemical signals, both internal and external, that seem to play a role in controlling stem cell differentiation. The internal signals are controlled by the cell’s genes. It is believed that, at certain stages of embryonic development, a gene or a group of genes within each cell is “switched on.” The protein products of these genes are the signals that determine the fate of that cell. But what tells the cell to “switch on” those genes? The external signals.

External signals can be biomolecules or chemicals in the extracellular matrix (outside the cell membrane) or even physical contact with other cells via cell surface receptors. One important group of proteins that act as external cell signals is known as the growth factor. Specifically, the superfamily known as transforming growth factors (TGFs) seems to be of particular interest. Researchers frequently add TGF-beta (along with many other factors and nutritional components) to the culture medium of stem cells to trigger differentiation. Keep in mind, however, that, while this factor does play an important role in vitro (in a test tube), it is likely TGFs in combination with other signals that cause stem cell differentiation in vivo (in a living organism).

For more information on stem cells, visit this website: Incell. They have great information in everyday language with a lot of helpful analogies to help you understand the concepts.

Thanks for your question.
Sue Baker, Dept. of Biological Sciences, Lehigh University