For more than 30 years, stem cells have been the great hope of medical science. Given their remarkable ability to turn into any type of cell in the body, researchers have theorized that they could be used to treat and perhaps even cure all sorts of diseases and conditions from spinal cord injury to baldness.

Progress has been painfully slow for most areas of research but this week researchers in Sweden are reporting a major advancein a possible stem cell treatment for Parkinson's. While the treatment has only been tried in rats, the scientists -- led byMalin Parmar, an associate professor of regenerative neurobiology at the Lund University -- said they believe the results are promising enoughto move to clinical trials in humans within a few years.

A degenerative condition of the central nervous system, Parkinson's affects an estimated 7 to 10 million people worldwide. Actor Michael J. Fox has Parkinson's and Google co-founder Sergey Brin has a gene that makes him susceptible to the disease. Both have not only raised awareness of the disease through their celebrity but have contributed millions of dollars to advance research.

Parkinson's is caused by the loss of dopamine-producing cells in the brain that help regulate things like movement and emotions. The scientistsat the Lund University found that when they turned human embryonic stem cells into neurons that produce dopamine and injected them into the brains of rats, something remarkable happened. The damage from the disease seemed to reverse.

The scientists wrote that while they believe their research was "rigorous," they pointed out that "a number of crucial issues" still need to be addressed before the treatment can be tested in humans. For instance, they need to make sure the cells continue to work the way they are supposed to over longer time periods.

Read more:

Parkinsons disease and depression often go hand in hand

Stem cell study shows promising results for severe stroke patients

Growing stem cells using cloning techniques reopens ethics debate

Dance for Parkinson's: movement as medicine

Read more here:
New hope for Parkinsons patients in stem cell treatment