"We have created new materials that because of their chemical structure interact with cells of the central nervous system in ways that may help prevent the formation of the scar that is often linked to paralysis after spinal cord injury," said Samuel I. Stupp, Board of Trustees Professor of Materials Science and Engineering, Chemistry and Medicine.
Similar to earlier experiments that promoted bone growth, the scientists now have successfully grown nerve cells using an artificial three-dimensional network of nanofibers, an important technique in regenerative medicine. The results will be published online Jan. 22 by the journal Science.
"We have shown that our scaffold selectively and rapidly directs cell differentiation, driving neural progenitor cells to become neurons and not astrocytes," said Stupp, who led the research team in Evanston. "Astrocytes are a major problem in spinal cord injury because they lead to scarring and act as a barrier to neuron repair."
The innovative scaffold is made up of nanofibers formed by peptide amphiphile molecules. The scientists' key breakthrough was designing the peptide amphiphiles so that when they self-assembled into the scaffold a specific sequence of five amino acids known to promote neuron growth were presented in enormous density on the outer surfaces.
"This was all done by design," said Stupp, who is also director of the University's Institute for Bioengineering and Nanoscience in Advanced Medicine. "By including a specific biological signal on the nanostructure we were able to customize the new materials for neurons."
In collaboration with the lab of John A. Kessler, Benjamin and Virginia T. Boshes Professor of Neurology at the Feinberg School of Medicine, Stupp and his team observed that when the peptide amphiphiles were placed in solution and combined with neural progenitor cells (which are present in the central nervous system and able to differentiate into different types of cells) the nanofiber scaffolds formed and led quickly to the selective differentiation of the cells into neurons.
In subsequent experiments, the researchers successfully delivered the peptide amphiphile solution, using a simple injection, to the site of a spinal cord injury in a laboratory rat. Upon contact with the tissue, the solution was transformed into a solid scaffold.
In addition to Stupp and Kessler, other authors on the Science paper are Gabriel A. Silva and Catherine Czeisler (lead authors), Krista L. Niece, Elia Beniash and Daniel Harrington, all from Northwestern University. The research was supported by the National Science Foundation, the National Institutes of Health and the U.S. Department of Energy.