A rapid method for semi-quantitative analysis of neurite outgrowth from chick DRG explants using image analysis

Neurite outgrowth from dorsal root ganglion (DRG) explants is a method of evaluating neurotrophic activity of growth factors and neurotrophin mimetics. The drawbacks to this approach are the difficulties in quantifying the response. Neurite counts are time consuming and labour intensive, and the accuracy is often questionable due to branching and fasciculation of the neurites. We report here a method of semi-quantitative analysis of neurite outgrowth from chick DRG explants, using image analysis to quantify the area occupied by neurites emanating from the ganglion. This method is rapid, takes into account both the length and number of neurites, and is unaffected by neurite fasciculation or branching. Primary explants of chick DRGs were treated with the neurotrophins nerve growth factor (NGF) or neurotrophin-3 (NT-3) and with the compound K252a. K252b was tested for potentiation of the response to NT-3. The results show a dose dependent outgrowth of neurites from explants treated with NGF, NT-3 and K252a, and potentiation of the NT-3 response by K252b. These responses were quantified by neurite area quantification using image analysis. We conclude that neurite area measurement using image analysis provides a robust means of evaluating neurotrophic activity of growth factors and neurotrophin mimetics in vitro.