A team led by Rutledge Ellis-Behnke at the Massachusetts Institute of Technology’s Department of Brain and Cognitive Science have used self-assembling peptide nanofibre scaffolds to partially restore the sight of hamsters blinded by damage to a nerve tract in their brains’ visual systems. The findings are published in this week’s online issue of Proceedings of the National Academy of Sciences.
Peptides are fragments of proteins which occur naturally. The peptides used in these experiments are synthetic and assemble themselves into a mesh on which the damaged nerve fibres could regrow. This fabricated biological nanomaterial has been nick-named ‘molecular cement’ by the research team and is modelled on a yeast protein which also forms scaffolds.
After hamsters had the neural pathway in their visual systems severed, a clear solution containing the self-assembling nanofibres was injected into their brains up to 45 minutes later. The synthetic peptides assembled themselves into an interwoven mesh similar to the extracellular matrix which holds tissues together. The mesh proved to be permissive to the regrowth of the damaged nerve fibres, with up to 20% of the damaged cells in both young and adult hamsters regrowing. The cells also re-established connections with each other so that the hamsters’ vision was partially restored within about six weeks.
Although more animal experiments are needed, nanofibre scaffolds could eventually be used to treat other forms of brain damage, such as stroke, and spinal injuries.
The complexity of the human brain makes it extremely inaccessible. Scar tissue which forms around damaged areas of the brain makes surgery difficult. The nanofibre solution was shown to fill the gaps around the injured area, preventing the formation of scar tissue. Because the scaffold is made of natural molecules it can be broken down into amino acids and is not recognized by the immune system.
Associate Director of the department, Shuguang Zhang, discovered self-assembling peptides by accident 15 years ago and has been working on them ever since. He and Ellis-Behnke have been using the scaffolds for tissue engineering – growing lines of embyronic stem cells and letting them differentiate into a particular type of cell, which then grows to form a specific type of tissue.