The answer to regenerative medicine's most compelling question -- why some organisms can regenerate major body parts such as hearts and limbs while others, such as humans, cannot -- may lie with the body's innate immune system, according to a new study of heart regeneration in the axolotl, or Mexican salamander, an organism that takes the prize as nature's champion of regeneration.
The study, which was conducted by James Godwin, Ph.D., of the MDI Biological Laboratory in Bar Harbor, Maine, found that the formation of new heart muscle tissue in the adult axolotl after an artificially induced heart attack is dependent on the presence of macrophages, a type of white blood cell. When macrophages were depleted, the salamanders formed permanent scar tissue that blocked regeneration.
The study has significant implications for human health. Since salamanders and humans have evolved from a common ancestor, it's possible that the ability to regenerate is also built into our genetic code.
Godwin's research demonstrates that scar formation plays a critical role in blocking the program for regeneration. "The scar shoots down the program for regeneration," he said. "No macrophages means no cardiac regeneration."
Godwin's goal is to activate regeneration in humans through the use of drug therapies derived from macrophages that would promote scar-free healing directly, or those that would trigger the genetic programs controlling the formation of macrophages, which in turn could promote scar-free healing. His team is already looking at molecular targets for drug therapies to influence these genetic programs.