Robust tissue repair after spinal cord transection and re-transection.

(A-D) Bright field images showing a fixed, unstained control lamprey spinal cord (A) and transected spinal cords (B-D) at the indicated time points. Axons and motor neurons (MNs) are clearly visible within the control spinal cord. At 1 wpi the proximal and distal stumps are still separated by a sizeable gap. But by 3–11 wpi, the spinal cord stumps are rejoined by extensive tissue repair. (E-H) Images showing the typical time course of lesion repair within re-transected spinal cords. Asterisks indicate the lesion center. Red arrows indicate the swollen central canal. R = rostral; C = caudal. Rostral is to the left in all images. Scale bar in A applies to B-H. (I) At 1 wpi, re-transected spinal cords exhibit a smaller gap between the proximal and distal stumps. Bars represent mean ± SD for n = 3–5 spinal cords. * indicates p(J) At 3 and 11 wpi, the lesion-to-end ratios are smaller in re-transected spinal cords. Bars represent mean ± SD for n = 3–6 spinal cords. ** indicates pn.s. = not significant by ANOVA.