Reporting their work today (April 19) in the journal Human Gene Therapy, the scientists directed certain types of neural stem cells to secrete a neuron-protecting protein before injecting them into the rat spinal cord where motor neurons reside. Motor neurons dictate muscle movement by relaying messages from the spinal cord and brain to the rest of the body. ALS causes the neurons to progressively decay and die.
Notably, the UW-Madison stem cell researchers did not work with human embryonic stem cells, blank-slate cells that arise during the earliest stages of development and can develop into any of the 220 tissue and cell types in humans. Scientists have long regarded these cells as a crucial ingredient in the quest to cure spinal injuries and neurodegenerative disease.
Rather, the scientists worked with more specialized neural stem cells -- known as neural progenitor cells -- that arise from primitive stem cells during the first few weeks of human brain development. Unlike embryonic stem cells, they can only develop into neural tissue and they are incapable of living forever, as embryonic stem cells can. But the neural progenitor cells are much more appropriate for clinical use because, unlike embryonic stem cells, they can grow in the absence of animal derivatives that are considered a potential source of contamination, says co-author Clive Svendsen, a professor of anatomy based at the university's Waisman Center, and a leading authority on neural progenitor cells.
"This is the first study that shows that certain types of stem cells can survive and release powerful protective proteins in the spinal cord of rats with a genetic form of ALS," says Svendsen.