Embryonic stem cells hold a great deal of promise in treating or even curing a range of devastating diseases. But potential isn’t reality, and, even with all their promise, embryonic stem cells can’t do some things — at least, we don’t think they can.
Unfortunately, these nuances are often missed or blurred when a promising idea or test captures headlines. So here’s a summary of what we really know about embryonic cells: what they can do, what they can’t do, and what we think they may be able to do — not today, but in the relatively near future.
To figure out how cells develop normally and what goes wrong when they don’t, you need a lot of cells to observe and test. Perhaps the most useful property of embryonic stem cells, at least for today’s researchers is that when you grow them properly, you can make lots and lots and lots of embryonic stem cells.
And you can, in turn, use those embryonic stem cells to make lots of specific types of cells. If you want to figure out why pancreatic beta cells misbehave in some types of diabetes, for example, and then find ways to repair or replace them, you need a lot of pancreatic beta cells.
Several research groups have already started testing drugs using cells derived from embryonic stem cells, and a number of researchers are well on their way to transplanting such derivative cells into animals to test the cells’ capacity to change a disease — reduce symptoms or reverse damage. (Scientists need to do these types of tests on animals, and the results have to meet certain benchmarks before they can conduct similar tests on humans.)
Embryonic stem cells seem to be able to make all types of cells in the adult body, which makes them particularly useful in investigating the causes of and possible treatments for a wide range of diseases, from central nervous system disorders like ALS to chronic conditions like diabetes and heart disease.
What embryonic stem cells can’t do?
Even with all their wondrous abilities, embryonic stem cells have their limitations.
For example, they can’t make a baby. That’s because embryonic stem cells are derived from the inner cell mass of a blastocyst. Those inner cells can’t make the placenta that provides nourishment for a developing baby, or the umbilical cord that delivers nutrients to the fetus. Embryonic stem cells can’t be used to clone an adult (at least, as far as we know today).
And they can’t cure disease in and of themselves. You can’t just inject a syringe-full of embryonic stem cells into a mouse or a human and expect them to identify and correct a problem. You have to know what kind of cells to make from embryonic stem cells, how to purify them, and where to put them in the body.
Plus, in order to make testing any potential treatments safe (and to give those potential treatments a strong likelihood of being effective), you need a lot of reliable information about both the cells and the potential
treatment.
Perhaps most important, embryonic stem cells can’t solve all our medical problems and issues overnight. Even with all the exciting things we can do with them now, it’s going to take time — quite a lot of it — to fulfill many of the promises these fascinating cells seem to hold.
What embryonic stem cells may be able to do?
With good ideas and rigorous research, scientists see virtually no limit to what we may be able to do with embryonic stem cells a generation or two from now. The ideas are the key: Creative ideas lead to realities that nobody ever imagined. (After all, do you think the guys who invented the first computer foresaw the Internet?)
Some of the things scientists are daring to imagine now:
✓ Creating cells and tissues that can be transplanted into humans
✓ Developing drugs that are cheaper to make and more effective in treating disease
✓ Testing toxins and environmental factors to see how they affect human development and health
✓ Growing “replacement parts” — new limbs, organs, and tissues that the body accepts as its own, without suppressing the immune system or running the risk of infection
We’re years away from realizing many of these dreams, of course. Human embryonic stem cell research is only about 10 years old; work with adult stem cells, on the other hand, is more than 40 years old, which is why we know so much about some kinds of adult stem cells and have been able to develop some practical applications for them.
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