The elimination of this risk allows scientists to produce enough long-term, self-renewing, primitive neural precursor cells to use in clinical trials and treatments in the field of regenerative medicine.

UCSD Ophthalmology and Human Genetics Professor Kang Zhang and Gladstone Institute Chemistry Professor Sheng Ding produced the neural stem cells by adding inhibitors to the embryonic cells, or hESCs, so they can become primitive neural precursor cells. The inhibitors also prevent cells from continuing to differentiate — which can eventually lead to tumors — so that the researchers can differentiate the stem cells into mature neurons without the risk of forming tumors.

“It’s a big step forward,” Zhang said in an April 25 statement. “It means we can generate stable, renewable neural stem cells or downstream products quickly, in great quantities and in clinical grade — millions in less than a week — that can be used for clinical trials and eventually for clinical treatments. Until now, that has not been possible.”

Researchers found that no tumors formed when these cells were introduced into laboratory mice.

Although past research showed that hESCs can act as regenerative medicine because of their ability to become any kind of cell needed to repair and restore damaged tissues, the risk that some of these cells might form tumors during the process of growing them in usable quantities has hindered the development of hESC-based treatments.

Zhang also explained the other advantages of the research. “Because it doesn’t use any gene transfer technologies or exogenous cell products, there’s minimal risk of introducing mutations or outside contamination,” Zhang said.

The development of this technology will lead to further research in potential clinical applications for neurodegenerative diseases. “[For example], you can generate neurons for specific conditions like amyotrophic lateral sclerosis (ALS or Lou Gehrig’s disease), Parkinson’s disease or, in the case of my particular research area, eye-specific neurons that are lost in macular degeneration, retinitis pigmentosa or glaucoma,” Zhang said.

This method can also be applied to induce pluripotent stem cells, or stem cells artificially derived from adult cells, to become neural stem cells, which may lead to the creation of other types of stem cells capable of becoming heart, pancreas or muscle cells.

According to Zhang, more research will be done to explore the use of these stem cells to treat different types of neurodegenerative diseases, such as degeneration in the macula (the area of the retina responsible for detailed vision) or glaucoma in animal models.