Computational neuroscienceAngleJ: A new tool for the automated measurement of neurite growth orientation in tissue sections

- A plugin called AngleJ for the open source software ImageJ was developed.
- AngleJ automatically determines axonal orientation in labeled sections.
- AngleJ was validated by comparison of manual and automatic measurements.
- Automatically measured angles strongly correlate with manual measurements.
- AngleJ is freely available to the community.

BackgroundRegeneration of axons is one means to restore function after central nervous system and peripheral nervous system injury. Besides increasing the number of regenerating axons, guidance of axons over long distances into and across a lesion site are important determinants for efficient functional restoration. Quantification of axon growth directions is therefore an important measure for the efficacy of neuroregenerative approaches. While several methods exist to manually or automatically trace neurites in images of neuronal cultures to determine their length, tools to automatically measure the effect of neurite guidance in tissue sections do not exist.New methodBecause manual measurements of the orientation of regenerating axons are labor-intensive, time-consuming and unreliable, a plugin called AngleJ for the open source software ImageJ was developed that automatically determines axonal orientation in images of immunohistochemically labeled sections of the spinal cord.ResultsGiven user-defined filters and thresholds, the plugin accurately detects neurites in sections of the intact spinal cord white matter and a spinal cord hemisection lesion model and measures the distribution pattern of axonal angles.Comparison with existing methodsValues of automatically measured angles strongly correlate with angles obtained by manual measurements in ImageJ (Pearson correlation 0.88-0.97 for white matter and 0.76-0.94 for axons sprouting into a lesion site).ConclusionsAngleJ can be used as a fast alternative to manual angle measurement in conjunction with ImageJ and its source code is freely available to the community.

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