CHIMERA AXOLOTL HOW TO

The cells that make up the blastema are thought to be bone, cartilage, muscle, or other cells that de-differentiate (lose their identity) to become similar to stem cells, which are cells that can become one of many different kinds of cells. Shortly thereafter, the cells underneath the epidermis also begin to rapidly divide, forming a cone-shaped structure known as a blastema ( D). During the next few days, the cells of the wound epidermis grow and divide rapidly. After this, a layer of cells works to quickly cover the plane of amputation, forming a structure called a wound epidermis ( C). Following limb loss ( B), a clot of blood cells rapidly stops bleeding at the cut site. In axolotls, the process that results in regeneration of an entire limb ( Figure 2) involves a complex orchestration of the limb’s surviving cells. While this ability has undoubtedly helped some people in the event a traumatic injury, it is a far cry from the axolotl’s ability to regenerate a fully-formed limb with all of its normal muscles, cartilage, and other tissues. Unfortunately, this response gets weaker as the site of loss occurs closer to the palm. Multiple clinical reports in the past decades have documented such instances following traumatic injury. Humans have also been known to regenerate the tips of the fingers, including the bone and skin. It has been observed that mice can regenerate the tips of their toes, though loss further up the foot results in the same scarring that humans see after amputation. While there are no known mammals that can fully regenerate missing appendages, many harbor hints of regenerative potential-humans included. Figure 1: Many animals undergo regeneration (at least to some degree). While the axolotl is not the sole master of regeneration in the animal kingdom, it is the only vertebrate that can regenerate many body parts throughout its entire life. On the other hand, the axolotl retains it throughout its entire life, making it unique among vertebrates and a great model to study in regeneration research. Young frogs are known to regrow limbs, though they lose this ability when they change from tadpoles to adult frogs. Even among vertebrates (animals that do have spines), the axolotl isn’t the only animal capable of regeneration. Flatworms and hydra, for instance, can regrow their entire bodies from only a tiny piece of their original selves. But the axolotl is not the only member of the animal kingdom that can do this ( Figure 1), as many invertebrates (animals without a spine) are masters of regeneration. Unlike humans, it has the “superpower” of regenerating its limbs, spinal cord, heart, and other organs.

A prime example is the axolotl ( Ambystoma mexicanum), a species of aquatic salamander.

CHIMERA AXOLOTL HOW TO

To begin thinking about how to accomplish human limb regeneration, scientists have taken note of animals that already show this ability.

So what if instead of relying upon a wooden or metallic impostor, we might one day just regrow a lost limb? Many animals have the power of regeneration But while replacement artificial limbs have been able to replace the form of the lost limb, their function remains severely lacking, especially when the lost appendage is an entire arm or leg. Unfortunately, the current therapeutic options following amputation are not much changed from centuries ago, with prosthetic limbs remaining the only option for replacement. If the incidence of diabetes continues to rise, there will likely be a corresponding increase in the number of people who must confront limb amputation. One such disease is diabetes, in which gradual declines in blood flow to a patient’s lower extremities can eventually lead to loss of the entire limb. While many instances are related to traumatic events like car accidents, the majority of limb loss cases are caused by diseases that affect the body’s blood vessels. Limb loss affects nearly 2 million people in the United States alone.

Chimera axolotl