The good news about stem cells is that they can develop into any kind of cell or tissue. The bad news is that scientists have had trouble making them grow into the kinds of cells they want.

This ScienCentral News video reports that brain scientists have found a solution, at least when it comes to nerve cells.

Stem Cell Breakthrough

Stem cells have the capability to differentiate into any kind of cell or tissue in the body. This makes stem cell research fascinating because by studying them, we may gain information and knowledge about the complex mechanisms involved in the development of the human body.

According to the National Institutes of Health, stem cells have three general properties: they are capable of dividing and renewing themselves for long periods; they are unspecialized; and they can give rise to specialized cell types.

Stem cells directed to differentiate into specific cell types could be used as a renewable source of replacement cells and tissues to treat various diseases, including Parkinson's, Alzheimer's, amyotrophic lateral sclerosis (ALS, or Lou Gehrig’s disease), heart diseases, spinal cord injury, stroke, burns, and various other conditions. However, scientists agree that there is still much ground to cover between the promise of stem cells and the realization of these uses. The many technical hurdles will only be overcome by continued intensive stem cell research.

There are three different types of stem cells: embryonic stem cells, fetal stem cells, and adult stem cells. Fetal stem cells are malleable cells harvested from aborted fetuses. Whether they are embryonic, fetal or adult stem cells, only a few stem cells develop into neurons when placed in most areas of the brain and spinal cord. The majority of the cells either fail to develop or grow into other kinds of cells.

At the University of Texas Medical Brach at Galveston, Texas, Ping Wu, assistant professor in the department of Anatomy and Neurosciences, Richard Coggeshall, and others have successfully made a majority of human fetal stem cells develop into neurons when implanted in the brains and spinal cord of rats. Wu, the lead author of the study published in the journal Nature Neuroscience, believes this is a significant finding as they can now grow a large quantity of cells that can become neurons with the potential of replacing lost neurons due to neurodegenerative diseases.

Wu screened many proteins and chemicals that play a role in neuron development, and developed a blend of two proteins and a sugar-like molecule to make a protein cocktail. Wu and her team then treated the fetal neural stem cells in this cocktail in a culture dish for a week. They then injected those cells into the brains and spinal cords of normal rats. After a month they collected the tissue samples of the rat’s brain and spinal cord and found that the majority of the fetal stem cells had developed into a specific type of pure population neurons.

“The protein cocktail seems to direct the neural stem cells into a particular plastic stage, and when we transplant those cells into adult rat’s brain and spinal chord, they then turn into specific type of neurons, in the spinal chord, also in the cortex, medial septum and hippocampus of the brain,” says Wu. “And those areas are important for learning and memory.”

Although this is a significant breakthrough, the scientists agree that there is always the risk of implanted stem cells forming tumors.

“We have not yet waited long enough to make certain that [tumors] don’t develop,” says Coggeshall. “However since the cells placed into the nervous system are already differentiated into the young neurons, the possibility is relatively low. Nevertheless this has to be checked very carefully before any further steps are undertaken.”

The scientists still have a long way to go before they can test whether the neural stem cells will grow, survive and develop into neurons when placed into humans. Next, they are preparing to study animals that have nervous system diseases. Wu says they also want to know whether, “these human neural stem cell-derived neurons can make correct connections to their targets. For example, we want to know if human neural stem cells can become motor neurons in the damaged spinal cord, and whether those motor neurons can reach their target muscles. And then finally, we need to know whether these cells, these new motor neurons, can make those paralyzed animals walk again.”

Wu's research was supported by the John Sealy Memorial Endowment Fund, the Mission Connect of the Institute for Rehabilitation and Research Foundation, and the National Institute on Drug Abuse.