TOP UNANSWERED QUESTIONS TO EXPLORE ABOUT STEM CELLS

Scientists have been studying adult stem cells for more than 40 years and embryonic stem cells for more than 20 years. They’ve uncovered a lot about both kinds of stem cells, but there’s a lot they still don’t know.


Questions researchers are still seeking answers to include the following:

✓ How many kinds of adult stem cells are there?

✓ Where do adult stem cells live in specific tissues?

✓ What control mechanisms do stem cells use to maintain their selfrenewal capabilities?

✓ What genetic mechanisms control stem cells’ ability to make one or more kinds of differentiated cells?

✓ Why don’t adult stem cells differentiate automatically when they’re surrounded by differentiated cells?

✓ Why can embryonic stem cells grow and make more of themselves in the lab for a year or more, while most adult stem cells have far more limited self-renewing capabilities in a Petri dish?

✓ How do stem cells know when to make more of themselves and when to make cells for specific tissues?

✓ Why don’t all stem cells “home in” to their proper location the way blood-forming stem cells do when they’re transplanted into a living body

✓ If you introduce stem cells into specific tissues in a living body, do they stay where you put them, or do they wander aimlessly around the body’s tissues?

✓ How long do transplanted stem cells stay in the body?

✓ If you reprogram adult cells to behave like embryonic stem cells, are the reprogrammed cells completely normal, or does the reprogramming process mess with the genetic instructions?

✓ In their normal environments (known as niches), can adult stem cells really make differentiated cells for tissues other than their tissue of origin?

✓ Is there a master adult stem cell — one that, like embryonic stem cells, can make any type of cell in the body?

Modern stem cell science is pretty young, so it’s not surprising that researchers still don’t know the answers to some relatively basic questions. As Lao Tzu, the father of Taoism, is credited with saying, “The wise man knows he doesn’t know.”