The Stem Cell

by Christopher Scott

While mulling over today’s post, I went to this UK stem cell company’s website. ReNeuron develops stem cell therapies for stroke, Parkinson disease, Type 1 diabetes and diseases of the retina. They focus on adult stem cells for brain disease and diabetes. They isolate the cells from aborted human fetal tissue.

ReNeuron does a pretty good job of describing “the ideal characteristics of a stem cell line,” qualities important before taking their products forward into clinical tests in humans.

Here they are, plus two extra to make the magical number 11:
(explanations below each are mine)

1. Multipotent somatic cells that can develop into specific tissues
(Stem cells that make different tissues, but also the tissue required, like brain or blood or bone)

2. Cells that are derived from a single founder cell (clonal cells)
(Cells in a cloned line are homogeneous and better understood by scientists)

3. Genetically stable cells with normal chromosomes
(Culturing cells can cause chromosomes to shuffle, changing the sequence of the DNA. However, it’s conceivable that some genetic changes might make the cells better suited for some therapies)

4. Cells that have the ability to differentiate into appropriate cell types
(Similar to #1, but especially important for clinical uses. A stem cell used as a therapy will be no use—or even harmful—if it changes into the wrong type of cell or tissue)

5. Cells that can be grown in large numbers and stored
(A technical hurdle: making millions or billions of identical cells that can be frozen, shipped and stored)

6. Cells that are safe
(Similar to #1 and #5. See posts about the stem cell niche: will stem cells outside their normal environs behave normally? Also see #8)

7. Cells whose migration, once implanted, is limited to areas of tissue damage
(A property of stem cells is their ability to “home” or target the specific site of disease or injury)

8. Cells that are efficacious in recognised animal models
(Using animals such as mice and rats will test whether the cells can repair or renew, and not cause toxic or harmful effects. Even then, the animals don’t always predict what will happen in humans)

9. Cells whose provenance is fully documented
(Ah, good. A nod to ethics. Not only should the cells be ethically obtained, but also ethically delivered. But safety is only one part of this equation. Other things to consider: deciding which patients will enroll in the first trials and making sure they fully understand the risks and benefits and know where the cells come from)

I’ll add two more:

10. Cells that work
(Millions of manufactured stem cells might travel to the right place, change into the exactly the right kind of cell, and then just sit there on their cytoplasms. Stem cells and their offspring must function properly in order to produce a therapeutic effect)

11. Cells that last
(Cells can do everything above, but then die too soon. In the body, stem cells are long lived. Will engineered stem cells live as long? One way around this is to use stem cells to make the cell of choice in the laboratory, and then transplant that cell type multiple times. More differentiated cells—see 10 October’s Way Small Gonads post—don’t last as long)

(errata: comment below rightly points out that stem cells can “contribute” to repair without actually engrafting. If the problem isn’t dependent on a long-lived cell, then all the cell needs to do is last long enough to do the job.)

:: :: :: :: :: :: :: :: :: ::