Spinal cord regeneration in Xenopus tadpoles proceeds through activation of Sox2-positive cells

Background: In contrast to mammals, amphibians, such as adult urodeles (for example, newts) and anuran larvae (for example, Xenopus) can regenerate their spinal cord after injury. However, the cellular and molecular mechanisms involved in this process are still poorly understood.Results: Here, we report that tail amputation results in a global increase of Sox2 levels and proliferation of Sox2 ⁺ cells. Overexpression of a dominant negative form of Sox2 diminished proliferation of spinal cord resident cells affecting tail regeneration after amputation, suggesting that spinal cord regeneration is crucial for the whole process. After spinal cord transection, Sox2 ⁺ cells are found in the ablation gap forming aggregates. Furthermore, Sox2 levels correlated with regenerative capabilities during metamorphosis, observing a decrease in Sox2 levels at non-regenerative stages.Conclusions: Sox2 ⁺ cells contribute to the regeneration of spinal cord after tail amputation and transection. Sox2 levels decreases during metamorphosis concomitantly with the lost of regenerative capabilities. Our results lead to a working hypothesis in which spinal cord damage activates proliferation and/or migration of Sox2 ⁺ cells, thus allowing regeneration of the spinal cord after tail amputation or reconstitution of the ependymal epithelium after spinal cord transection.