Salamanders are unique among animals in their ability to regenerate lost or damaged parts. Adult salamanders can regrow heart, brain, muscles and even whole limbs. Researchers have discovered a certain type of immune cell is responsible for this fascinating ability.
Normally immune cells called macrophages migrate from the bloodstream to the site of injury in all animals from salamanders to human. In humans they are responsible or ingesting and thereby removing debris. When humans are injured the result is usually fibrotic scar tissue, limbs and most organs cannot regenerate. The researchers hoped to dissect the regeneration response in salamanders and use the learnings to apply to human regenerative medicine.In the experiment, salamanders were treated to remove their macrophages, and then underwent amputation. Without macrophages the animals could not longer regenerate tissue, proving these cells were responsible for the effect.
The authors reasoned the macrophages must release specialized chemical signals that allow regeneration. It is likely that the early arrival of macrophages into the regenerating axolotl blastema by 24 h after amputation, along with simultaneous induction of inflammatory and anti-inflammatory cytokines, is part of a distinct regenerative program.
Understanding the early regulation of expression patterns and timing of various extracellular matrix components by macrophage signaling is critical in identifying pathways permissive for appendage regeneration. Their early engagement in the secretion of anti-inflammatory cytokines and other factors promoting the efficient regeneration of axolotl limbs point to potential therapeutic strategies for preventing fibrotic scarring and promoting tissue regeneration in mammals following tissue injury.