Salamanders can regenerate their limbs. Instead of scar tissue, the cut is transformed into a wound epidermis, activating chemicals that cause the nerves underneath where the limb was taken away to grow again. Muscle and tissue cells regress back into unspecialized cells. Cells begin their development unspecialized. They don’t know which type of cell they will be (skin cell, lung cell, liver cell, etc.) until a gene is activated. These regressed, unspecialized cells stream toward the area that has received the massive cut. This is called a blastema. The cells here are stem cells.
These cells have a good memory about what their original function was, so they will then become muscle or cartilage or whatever type of cell they had been after they flow to the area where the cut had taken place. Once all of the cells return to their original type, the salamander has officially regenerated its limb.
To determine the number of cells needed to regenerate something, the presence of fibroblasts (connective tissue cells), levels of retinoic acid (something that mediates the function of Vitamin A), and Vitamin A (supports skin) are taken into account.
Regeneration is a very cool characteristic that if instilled in humans, could help advance medicine further. As of right now, this kind of thing can’t really be done because scientists themselves don’t really understand why this regeneration happens.
A type of cell that could help with the regeneration of salamanders is called macrophage. It was found that when salamanders’ supply of macrophages decreased, the amount of time it took to regrow something increased. And, if the salamanders didn’t have any macrophages, they wouldn’t be able to regenerate at all.
There are two main theories as to why we might not be able to regenerate. The first theory is that scar tissue is faster and able to securely seal a wound. The second theory is that regeneration looks way too similar to cancer, since both processes involve the frequent growth of cells. Not being able to regenerate a limb is favorable when compared to having cancer.
Embryos can regenerate limbs without developing any scar tissues but for adults or teenagers, regeneration is something that can’t really be induced right now.
Vaageesha Das is a junior at Morgantown High School.
Information comes from:
- SciShow. (2014, June 19). How Do Animals Re-Grow Limbs (And Why Can’t We?) [Video]. YouTube. https://www.youtube.com/watch?v=QFa6jP6WgzM;
- Westreich, S. (2020, July 22). Why Can’t We Regrow Limbs? – Sharing Science. Medium. https://medium.com/a-microbiome-scientist-at-large/why-cant-we-regrow-limbs-32ba3c42e245#:%7E:text=Humans%20can%20do%20some%20regeneration,happens%20before%20we’re%20born.&text=In%20humans%2C%20an%20embryo%20fewer,encourage%20more%20regeneration%20in%20humans.
