Chemical genetics of regeneration: Contrasting temporal effects of CoCl(2) on axolotl tail regeneration.

BACKGROUND: Histone deacetylases (HDACs) regulate transcriptional responses to injury stimuli that are critical for successful tissue regeneration. Previously we showed that HDAC inhibitor romidepsin potently inhibits axolotl tail regeneration when applied for only 1-minute postamputation (MPA). RESULTS: Here we tested CoCl(2,) a chemical that induces hypoxia and cellular stress, for potential to reverse romidepsin inhibition of tail regeneration. Partial rescue of regeneration was observed among embryos co-treated with romidepsin and CoCl(2) for 1 MPA, however, extending the CoCl(2) dosage window either inhibited regeneration (CoCl(2) :0 to 30 MPA) or was lethal (CoCl(2) :0 to 24 hours postamputation; HPA). CoCl(2) :0 to 30 MPA caused tissue damage, tissue loss, and cell death at the distal tail tip, while CoCl(2) treatment of non-amputated embryos or CoCl(2) :60 to 90 MPA treatment after re-epithelialization did not inhibit tail regeneration. CoCl(2) -romidepsin:1 MPA treatment partially restored expression of transcription factors that are typical of appendage regeneration, while CoCl(2) :0 to 30 MPA significantly increased expression of genes associated with cell stress and inflammation. Additional experiments showed that CoCl(2) :0 to 1 MPA and CoCl(2) :0 to 30 MPA significantly increased levels of glutathione and reactive oxygen species, respectively. CONCLUSION: Our study identifies a temporal window from tail amputation to re-epithelialization, within which injury activated cells are highly sensitive to CoCl(2) perturbation of redox homeostasis.