Stem cells from bone marrow may be far more versatile than scientists originally thought.

University of Florida researchers found that bone marrow stem cells can grow not only into blood cells, but also into blood vessels. The finding could mean that stem cells from the marrow could be used to grow many different types of tissue, perhaps even organs.

One of the big questions in stem cell biology is whether stem cells are plastic, or changeable. We showed for the first time that an adult stem cell from bone marrow can make more than just blood. It can make blood vessels as well.

The researchers discovered the versatility of the marrow stem cells through an experiment with mice developed to be models for retinopathy, a disorder that can be caused by diabetes and sometimes leads to blindness.

In diabetic retinopathy, high levels of sugar in the blood damage blood vessels in the eye. When the body tries to repair this damage, it creates new capillaries. But the capillaries often grow in the wrong place, worsening the condition.

To see if bone marrow stem cells had anything to do with the growth of these abnormal capillaries, researchers injected each of the mice with a single bone marrow cell from special lab mice that have a gene for phosphorescence. Every cell in the phosphorescent mice will glow green under ultraviolet light.

When they checked the retinopathic mice later, the investigators found that new capillaries had grown and that the capillaries were phosphorescent green.
Everything that glowed green in those animals, therefore, came from a single cel. That was our formal proof that it was indeed a blood stem cell that was making these blood vessels.

And it wasn't just a few animals, the researchers saw green blood vessels form in every animal we tested. This isn't something that happens a little bit of the time. It's very robust.

The research may one day help people with diabetic retinopathy. Understanding how the body goes wrong in making blood vessels in inappropriate spots may help researchers devise a way to turn off this self-destructive behavior.

The new research also may change the understanding of how the body repairs injuries.

Until 5 years ago, everyone thought that an injured blood vessel was repaired by local regeneration. Then people recently showed that there were cells circulating in the blood that might come from the bone marrow. The researchers showed that it is these cells that do the repair.

Nature Medicine June 2002;8:607-612

This pivotal discovery is one of a series of studies all pointing to the incredible promise of adult stem cell research. Unlike destructive research on embryonic stem cells, which has demonstrated no such promise, adult stem cell research holds tremendous potential to assist our patients with serious diseases.

The scientific evidence suggests that we can achieve our desire to cure diabetes, Alzheimer's and a host of other diseases by following the moral path of adult stem cell research. It is time for the NIH to direct funding to these ethical research projects rather than to those involving the destruction of human lives.

When we arrive at our destination, we will be glad to find we have not paid the price of progress with our most precious ethical principles.

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