"I think we are just at the beginning of learning the potential of these cells, and they may be many more things than we realized," said Helen Blau, a stem cell biologist at Stanford University.

Following are some research avenues contemplated by California scientists:

Heart disease

Juan Carlos Belmonte at the Salk Institute studies how salamanders regenerate limbs as a model for studying how embryonic stem cells develop the heart's unique shape and function.

"Two major problems are how to differentiate (stem cells) into a tissue, and two, how to give cells a form, a conformation. It's not just about grafting a few cells and see what happens," Belmonte said.

Lou Gehrig's disease

Formally known as amyotrophic lateral sclerosis (ALS), Lou Gehrig's is characterized by the death of motor neurons. Without these vital nerve cells, the brain loses control of the body, leading to paralysis and death.

Using stem cells to replace dying and dead motor neurons would be a colossal task, and scientists see that approach as largely impractical. The key reason is that the long, wirelike motor neurons that extend from the spinal cord through the limbs take more than a year to grow. By then, many ALS patients are dead or very close to it.

But work by the researchers at UCSD and others has shown that improving the health of cells near motor neurons – in the neighborhood, so to speak – can extend the life of motor neurons. Scientists are studying various ways to buttress neighboring cells, and stem cells might offer one way.

Snyder said that stem cells would be useful because of their apparent innate ability to "rescue" cells by reducing inflammation, preventing scarring and releasing growth factors that nourish nearby cells.

Parkinson's disease

Characterized by trembling, stiffness and slowness of motor movements and impaired balance and coordination, Parkinson's leads to paralysis and death.

Scientists hope to study the pathology of Parkinson's disease in stem cells coaxed into developing into neurons that fail to produce dopamine.

Another approach would be to develop stem cells into healthy dopamine-producing neurons and transplant them into the brains of Parkinson's patients. Scientists would need to figure out how those neurons connect to other brain cells and how they are distributed in the normal brain.

Among California researchers working in this area are Stuart Lipton and Evan Snyder at Burnham, Fred Gage at Salk, Krys Bankiewicz at UCSF, Helen Blau at Stanford University and J. William Langston at The Parkinson's Institute in Sunnyvale.

Alzheimer's disease

Despite the connection people have drawn between Alzheimer's and the potential of stem cells, particularly after former President Reagan died last summer, it is not clear how stem cells might be used to treat this memory-robbing disease.

The primary reason is that little is known about what causes Alzheimer's, scientists say.

One approach is finding a way to activate adult stem cells in the brain that are near areas of damage. If those stem cells could be called into action, scientists hypothesize they might help repair damaged areas.

Spinal cord injury

Researchers are looking at how stem cells might be used to repopulate areas of the spinal cord where dead nerve cells have cut off connections from the spine to the rest of the body.

Biologists are looking specifically at how to replace oligodendrocytes, cells that wrap themselves around nerve cells and protect them – thereby promoting the transmission of electrical signals that enable movement.

Hans Keirstead, of UC Irvine's Reeve-Irvine Research Center, recently published a study in collaboration with the Northern California biotech company Geron Corp., describing how he coaxed human embryonic stem cells into oligodendrocytes. He then injected the cells into rodents with damaged spinal cords. The injected cells migrated to the right place in the spinal cord and wrapped around exposed nerve cells.

Mark Tuszynski at UCSD is looking at how chemicals produced by stem cells might foster nerve cell repair, as well as scaffolding technologies.

Other experts in this area include Aileen Anderson and Oswald Steward, also at the Reeve-Irvine Research Center.

Cancer and brain tumors

Stem cells do much more than merely replace diseased and damaged cells, scientists say. They also appear to home in on cancer tumors. This makes them attractive vehicles for carrying drugs, tumor-killing genes or other treatments to tumor sites.

This is "low-hanging fruit," according to Burnham's Snyder – an approach that might achieve results sooner rather than later.

Diabetes

Finding new ways to treat diabetes could dramatically change life for the estimated 18 million Americans with diabetes.

Figuring out how stem cells develop into pancreatic beta cells, growing them in the lab and transplanting them into patients is a huge challenge.

Ongoing clinical trials have focused on injecting patients with chemicals called growth factors, to induce stem cells already in the endocrine system to produce beta cells.

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