Nerve stem cells live in scattered groups in various areas of the brain. They are capable of becoming several different types of cells, not all of which are nerve cells.
In the study, rodent nerve stem cells from an area of the brain called the hippocampus were cultured with Isx-9. They clustered together and developed spiky appendages called neurites, which typically happens when nerve cells are grown in culture.
Isx-9 also prevented the stem cells from developing into non-nerve cells and was more potent than other neurogenic substances in stimulating nerve-cell development. The molecule generated two to three times more nerve cells than other commonly used compounds.
Neuroscientists believed for decades that the adult mammalian brain could not grow new nerve cells. Instead, they thought, learning and memory were strictly a matter of the brain making new connections between existing cells.
It is now known, however, that the brain constantly creates new nerve cells. In the hippocampus, which is involved with learning and memory, stem cells mature into full-blown nerve cells at a rate of thousands a day, Dr. Hsieh said.
Scientists know that when a mature nerve cell sends a chemical signal called a neurotransmitter to a stem cell, the immature cell begins to mature, but they don't know what biochemical pathways or genes are involved, Dr. Hsieh said.
"The big gap in our knowledge is how to control these stem cells," she said.
Isx-9 appeared to act like a neurotransmitter-like signal on the nerve stem cells, the researchers found. By culturing the stem cells with the compound, the scientists identified a possible biochemical pathway by which stem cells begin to become nerve cells.
The researchers next plan to test Isx-9 on a large number of different combinations of RNA, the chemical cousin of DNA, to see on which genes the compound might be work
|Contact: Aline McKenzie|
UT Southwestern Medical Center