Nanofibers with the right epitope support neurons (green) but not astrocytes (red).

Stupp

Tiny fibers designed by Gabriel Silva, Catherine Czeisler, John Kessler, Samuel Stupp, and colleagues (Northwestern University, Chicago, IL) provide stem cells the environment they need to make clinically desired cells. Although the researchers produced neurons, the design is amenable to many cell types.

The group has created a peptide nanofiber solution that assembles into three-dimensional networks when it contacts biological fluids. On the face of the resulting scaffold sits a laminin-derived epitope that directs neurite growth. In vitro, neural progenitors cells (NPCs) encapsulated by the scaffold differentiated into neurons. On laminin, in contrast, fewer and smaller neurons formed, and some NPCs formed astrocytes.

Astrocytes are thought to be a major obstacle in recovery from paralysis after spinal cord injury, so the nanofibers may speed healing in ways our own physiology cannot. “The [epitope] density [in the scaffold] is a thousand times higher than you would have if you packed [laminin] into a crystal and the epitopes were exposed on the surface,” says Stupp. “Somehow, this abiotic presentation causes cell differentiation to change.”

The fibers also assemble when injected in vivo. Although the experiments are still in progress, rats with spinal cord injuries seem to heal faster when treated with the nanofiber solution. With the right epitope, the nanofibers can be modified to support growth of bone, blood vessels, islet cells for diabetic patients, and other cells. ▪

Reference:

Silva, G.A., et al. 2004. Science. 10.1126/science.1093783.