A novel role for SALL4 during scar-free wound healing in axolotl

Salamanders, such as the Mexican axolotl, are some of the few vertebrates fortunate in their ability to regenerate diverse structures after injury. Unlike mammals they are able to regenerate a fully functional spinal cord after injury. Throughout human life, many cells and certain tissues, such as hair follicle stem cells and liver, can be continuously replaced to maintain functional integrity in response to normal daily wear and tear. However, the human response to more serious tissue damage is limited to relatively primitive wound healing, whereby collagenous scar tissue fills the injury site, assuring the tissue’s structural integrity but often resulting in a debilitating loss of functionality. In contrast many vertebrates, including axolotls, have remarkable regenerative capacity including the functional regeneration of full thickness wounds. Here, we have identified a novel role for SALL4 in regulating collagen transcriptional after injury that is essential to ensure perfect skin regeneration in axolotl. All axolotls used in these experiments were bred in the axolotl facility at the University of Minnesota under the IACUC protocol1411-32049A. Adult axolotls and larval axolotls of 2–3 cm were used for all in vivo experiments, and animals were kept in separate containers and fed daily with artemia; water was changed daily. Animals were anesthetized in 0.01% p-amino benzocaine (Sigma) before microinjection was performed. Experimental Design: Ivermectin injection Ivermectin or vehicle only (water) was pressure injected into the central canal of the spinal cord, and this was visualized by the addition of Fast Green into the solution. Directly after injection, a portion of the spinal cord was surgically removed and the animals were placed back into water in individual containers. One day post injury (1dpi) animals were anesthetized again and the area of the injury was removed. Tissue from 10 animals were pooled for each microarray replicate.