Organ regeneration/regrowth

 

Living things are magical when it comes to the ability to repair and regrow. We need this ability to maintain the healthy functioning of our bodies so as to increase the chance of survival. Some animals have better regeneration ability than human, here is a video to show how salamander regenerates its limb:


The salamander is known for its regeneration capacity. They can regrow the limb, heart, tail, brain, eye tissues, kidney and spinal cord. To understand how they do it, let's look at what stem cells are.

Stem cells

Our body is made up of different types of cell. Most cells have a specific function, such as red blood cells, nerve cells, and heart cells. Stem cells provide new cells for the body and replace lost or damaged cells. They can divide into new stem cells or specialised cells that made up other body parts.
Image credit: Genome Research Limited


There are 3 types of stem cell: embryonic, adult, and induced pluripotent stem cells. Embryonic stem cells make new cells for an embryo to develop into a baby. They are pluripotent, meaning they can develop into all kinds of cells in the body. Adult stem cells provide new cells for an organism as it grows or injured. These stem cells are multipotent, meaning that they can only develop into certain cell type in the body. For example, adult blood stem cells in bone marrow can only replace old blood cells but not the skin. Induced pluripotent stem cells are reprogrammed stem cells made by scientists in a laboratory. 


Stem cell research is important because it helps scientists to understand how our bodies grow and develop, test new medication on living cells before testing on the human body, and most importantly it may be a cure to patients with damaged or lost cells/tissues/organs. Recently, scientists have successfully cultivated small-scale human organs in laboratories. In 2014, a study successfully transplant lab-grown vaginas in four girls between age 13 and 18 with underdeveloped or missing vagina and uterus. These young girls were examined annually for eight years and the transplanted organs functioned normally.

Organ regrow in human

In salamanders, skin cells close the wound after cutting the limb off. Matured cells (which had stopped dividing after the animal reached a mature stage) move into the wound and de-differentiate, meaning they reverse cell life stages and become unspecialised stem cells. These cells start dividing again like at the embryonic stage to replace the lost tissue A new limb can grow in as short as 90 days. We still do not fully understand how the reversion is triggered under the wound and how do these regenerating cells know where and what they should be. 


In the human body, the liver is one of the few organs that have the ability to regrow. In a study of 27 living liver donors, it took only a month after donation for their liver to function normally and less than a year to regrow back to its normal mass. However, it is not recommended to donate your liver more than once because it regrows but not regenerate. Instead of dedifferentiation like the case of salamanders, what mostly happens is a variety of mature liver cells just multiply to make up for the loss. The regrown tissue has some structure and functions like a new one, but it does not have the exact layout of a fresh liver, from cell organisation to the arrangement of blood vessels. This makes it harder for doctors to cut off part of the liver of a repeat donor as well as to connect that to the transplant patient.


My skin also heals!

Skin cells are replaced every couple of weeks. Nevertheless, healing is different from tissue regrow. After a cut, your skin will bleed and form a blood clot to stop bleeding. Then, immune cells flood the area to clear bacteria and prevent infection. Next, the wound is filled with collagen and other proteins that provide the tissue with structure. Collagen is the material that keeps your skin firm, smooth, and stretchy. However, this process results in scars because the new tissue has a different arrangement of collagen fibres than normal skin tissue, making the scar tissue more stiff and weak. That's because evolution has selected speed over perfection, to protect us from infection and prolonged bleeding. 


All in all, the human body is very complicated and if we find the key to programme stem cells, it would be a big step forward to treat diseases that have no treatment for now and save lives.

References

Youtube channel: SciShow




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