I recently complained on Facebook about a federal court ruling which outlawed public funding of embryonic stem (ES) cell research. Most comments were sympathetic, but many of my friends wanted to know why ES cells were important. What can ES cells do that adult stem cells can't?
There's only one time in our lives when we have the capacity to grow an entire heart or kidney or pancreas, and that's when we are embryos in our mother's womb. And there's only one type of cell in all of human development that can give rise to an entire heart or kidney or pancreas - and that's the embryonic stem cell. No adult stem cell in the world is likely to give rise to an entire internal organ, or an eye. If you want to grow something complex, you need to start with an embryonic stem cell, which can give rise to every organ in the body, in fact they do it every day.
Here's the answer in a nutshell. Adult stem cells are already working in your body every single day. When the body is injured, these cells divide and differentiate to replace the damaged tissue. They can do anything a healthy person can already do, like regrow a fingernail, skin, or even hair. In medicine, they are good for making grafts and even for bone marrow transplants. But what they can't do is make an entire organ, at least not a complex, vital organ like a kidney or heart. This is why heart attacks are serious business - you only get one heart.
|Complex tissues grown from human ES cells|
This becomes an important consideration when you realize that many people out there will die simply because their hearts will wear out after 80 or 90 years; many are born with serious birth defects; and many will suffer cancer, or environmental damage, to a vital organ at some stage in their lives. The reason ES cells are important is that someday, we may be able to grow an entire replacement organ from that embryonic cell. We already have ways of taking adult cells and reprogramming them into ES cells, which is an important first step. But to get ES cells to grow organs in the lab, instead of in a growing embryo, will require funding and time - perhaps 20 years. The payoff, however, would be 30, 40, or maybe even 100 years of extended human lifespan.
And that's why embryonic stem cells are important.