The human body is teeming with regeneration. Skin cells are scratched, scraped and torn from the body, but new ones quickly take their place. Hair grows, falls out and springs up in other places. Even broken bones mend with some medical assistance.

The body heals itself from these minor injuries of everyday life.

But what happens when the body is unable to heal itself? Paralysis, Parkinson's disease, a stroke, Alzheimer's disease, a hole in your spinal cord, cancer -- these afflictions and ailments are permanent.

Cleveland scientists and doctors are researching to discover exactly why skin cells and other body parts heal and replenish themselves while others remain in their injured states. Why can't every part of the body grow back like the thousands of skin cells a human replenishes each day?

Some believe the answers lie in stem cells, the cells in the body that divide to become all other parts of the body: bone, blood, organs and nerves.

Dr. Stan Gerson, chief hematologist at University Hospitals, has treated about 2,000 patients with stem cell injections to fight leukemia and lymphoma.  

While not providing a cure, the patients are significantly better, leading researchers to believe stem cell research can result in advancements beyond stunting cancer growth.

Meanwhile, neuroscientists in Cleveland are getting closer to honing the abilities of stem cells. Although no clinical tests are even close for humans, they have proven that stem cells do indeed enhance spinal cord repair, meaning cures for neurological disorders like Alzheimer's could be discovered. With nearly $500,000 in National Institutes of Health grant money contributing to these scientists' research, experts agree an answer may be gleaned from these mysterious cells.

Scientific puzzle
Robert Miller, neuroscientist at Case Western Reserve University, has devoted the last two decades of his life to studying these cells.   He is investigating whether adult stem cells in the nervous system could be used to cure diseases such as Alzheimer's and Parkinson's, both of which destroy nerve cells.

"If skin cuts, it heals. If your nervous system gets cut, it will have a scar, but it doesn't heal," Miller says.

Why exactly nerves refuse to heal remains a scientific puzzle, but Miller says he believes they can be jump-started and forced to repair through stem cells, specifically adult stem cells from the nervous system.

In an embryo, the stem cells that exist are omnipotent, Miller says. They can and will divide until they have created every working part of the human body. These initial stem cells are embryonic. Further down the cell division line, adult stem cells will be created. These cells all have specific body systems and roles -- in Miller's research, his stem cells become nerves, brain tissue and the spinal cord.

Embryonic stem cells come from fetuses. Research of these cells is limited in the United States to embryos left over from infertility treatments. All other uses of embryonic stem cells are banned by legislation. Miller and the other researchers in Cleveland choose to look for advances in the less controversial adult stem cells.

Miller says what make these "wicked cool" stem cells appealing to researchers is their non-aging characteristics.. As cells divide and specialize, a stem cell will remain intact and unchanged -- but, in the case of the nervous system, also untapped for further use. They rest in the body, living as long as the body itself. For comparison, red blood cells have a lifespan of one month before they are replaced.

"Presumably, stem cells give a continuous source for repair," Miller says.

Five years ago it was proven that adult stem cells in a rat could divide and specialize. Prior to this, it was theorized that stem cells in the brain only could repair during the embryonic phase when brain proliferation explodes, he says.

So, stem cells are able to work, but they divide willy-nilly into whatever specialized cell they choose -- Miller's big predicament.

"We don't know how to turn stem cells into motor cells," he says. "We also have to get stem cells to migrate and repopulate where the damage is."

"How do you make cells become what you want them to become?" Miller asks.

He might as well be asking the stem cells themselves because they are the only ones holding the key.

Even so, Miller maintains his research with rats is showing improvements. For the past two years, rats in his lab have been given spinal cord injuries and then treated with a growth factor to stimulate stem cells. Miller says the rats show visible signs of improvement from this jolt to the stem cells, but it is unclear whether the cells are specializing properly. Only time will tell.

It doesn't help matters that Miller would have to target a specific cell to see if progress is occurring.

"It isn't simple," he says.