A human neuron injury model for molecular studies of axonal regeneration

The enhancement of regeneration of damaged axons in both the peripheral and central nervous systems is a widely pursued goal in clinical medicine. Although some of the molecular mechanisms involved in the intrinsic neurite regeneration program have been elucidated, much additional study is required for development of new therapeutics. The majority of studies in the field of axonal regeneration have utilized animal models due to obvious limitations of the accessibility of human neural tissues. Here we describe the use of human embryonic stem cell (hESC)-derived neurons as a novel model for studying neuronal responses to axonal injury. Neurons were generated using PA6 induction and neurites injured in vitro using trituration or laser microdissection. Lesioned neurons re-extended neurites with distinct growth cones. Expression of proteins associated with regeneration were observed in this human in vitro system, including appearance of importin beta1 in processes after neuritomy. Laser-transected hESC-derived neuronal cultures were analyzed for their transcriptional response to injury using Affymetrix expression microarrays. Profound changes in gene expression were observed over a time course of 2 to 24 hours after lesion. The expression of several genes reported to be involved in axonal injury responses in animal models changed following injury of hESC-derived neurons. Thus, hESC-derived neurons may be a useful in vitro model system for mechanistic studies on human axonal injury and regeneration.