Fig. 3.

H-wounds inflicted on dormant tails induce regeneration in an ERK-dependent manner. a Distinct cellular responses occur in planarians undergoing wound healing (after H-wounds) or regeneration (after R-wounds). b “Dormant” tails that were re-amputated, whether immediately or 5 days after drug removal, fully regenerated. c Tail fragments did not regenerate after a 5-day PD treatment and recovery period unless re-injured; as in the case of re-amputations, incisions that cut through the animal along the DV axis but do not involve tissue loss led to the formation of the anterior regeneration pole (marked by notum; sample numbers indicated in each image) and full regeneration of heads and medial structures (see Supplementary Fig. 6 for representative images of immediate wounds). During the recovery period (blue in scheme), animals were kept in DMSO-containing water. d Induction of regeneration through re-injury was inhibited by PD treatment. e Animals that had formed blastemas were considered to be “regenerating” if they later also regenerated eyes. f–g Corresponding proliferative responses at 4 d.p.a. (f) and functional recovery (g) were observed. Bars in graphs represent mean ± s.d.; two-sided t test (compared with uninjured PD-removed animals (first bar, dark gray), unless indicated otherwise), *p < 0.05, **p < 0.01, ***p < 0.001, NS, not significant. h Increased pERK levels were observed at 3 h post-wounding in conditions that induced regeneration. d.p.w. days post-wounding, scale bars: 200 μm