Fig. 4

AxonTracer identifies injury induced CST sprouting above level of injury. Membrane-targeted tdTomato-AAV8 was injected into the motor cortex of adult rats. Transverse spinal cord sections at cervical level 2 (C2) were fluorescently labeled for the cortical spinal tract (CST) and the neuronal cell body marker (NeuN) to indicate the spinal cord grey matter. b, d, f, h Rats received a cervical (C4) dorsal column lesion 5 days post injection. a, c, e, g Rats in uninjured group did not receive a lesion. a, b Unprocessed raw images are used for analysis by AxonTracer (Input). c–i Shows output data automatically created by AxonTracer. c, d Input images with ROI (white outline) defined by spinal cord grey matter (NeuN). e, f Axon channel in greyscale cropped to ROI showing CST axons in white. g, h Automated CST axon tracing superimposed (yellow lines) on greyscale images. i Quantification of length of collateral CST axons in grey matter shows increased sprouting in response to injury. Mean ± SEM. p^* < 0.05, t test