Direct Conversion of Adult Human Fibroblasts into Induced Neural Precursor Cells by Non-Viral Transfection.

Direct reprogramming offers a unique approach by which to generate mature neural lineages for the study and treatment of neurological diseases and neurodevelopmental disorders. However, few studies have directly generated neural stem/precursor cells (iNPs) from adult human fibroblasts that are capable of producing a wide range of mature neuronal phenotypes. Further, current reprogramming protocols require the use of viral-mediated gene delivery to induce the generation of iNPs from human fibroblasts. Here we describe a robust and efficient protocol to directly reprogram adult human fibroblasts to expandable iNPs using transient non-viral gene delivery in a feeder-free cell culture system. The two transfection factors required for direct conversion to iNP cells, SOX2 and PAX6, do not generate a pluripotent cell state, reducing the potential risk of tumor formation following transplantation. By following the current protocol, iNPs are observed 6-9 weeks after transfection. Upon differentiation, iNPs generate both astrocytes and a range of phenotype-specific neurons.