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A solid scaffold made of self-assembling nanofibers can selectively direct differentiation of neural progenitor cells, according to a new report [Science, published Jan. 22, http://www.sciencemag.org/cgi/content/abstract/1093783v1]. Samuel I. Stupp, professor of materials science, chemistry, and medicine at Northwestern University, and his colleagues direct the differentiation of neural progenitor cells using peptide amphiphiles that self-assemble into nanofibers in the presence of cells or tissue. The nanofibers have peptide sequences (epitopes) on their surface that are known to promote and direct the growth of dendrites and axons. Neural progenitor cells that are encapsulated in the gel-like matrix formed by the aggregation of these fibers rapidly differentiate into neurons, with about 35% testing positive for a neuron marker protein after only one day. In contrast, the researchers observe little formation of astrocytes, another type of neural cell, after seven days. By mixing nanofibers containing the active epitopes with others that don't, Stupp and his colleagues find that the epitope density plays a major role in the observed differentiation.
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