Tissue Healing Question?!


Question: Tissue Healing Question?
This question is about exactly how the body heals. I know the basics behind how cells divide and heal injuries, my question is this. How exactly does the body know how to heal? Why doesn't someone say, suffer a large cut and end up growing another arm. I'm curious as to exactly what manages the way tissue heals. I'm thinking it's likely DNA, if it is, does modern science know specifically what part?

Answers:

It's very complicated and in fact, research into why some animals have the ability to regrow limbs is a hot subject in science at the moment. Simplistically-speaking, it's to do with stem cells.

A stem cell is a cell which has not yet lost the potential to develop into more than one kind of cell. There are various levels of stem cell (defined by how specialised they have become e.g. a less pluripotent stem cell might be able to develop into two different types of nerve cell whilst a more pluripotent cell might be able to develop into any kind of nerve cell as well as a type of skin cell). This is called 'differentiation'. The way that stem cells develop is partially influenced by what parts of their DNA is currently 'turned on' but also by their immediate environment (e.g. other cells and chemicals that can interact with them).

Adult humans do not naturally have stem cells capable of developing into all of the components of a full limb. A wound heals by neighbouring cells migrating into it and replicating and laying down an acellular matrix, all of which forms a scar which is somewhat different from the original tissue. In animals that are able to regenerate limbs, they may possess reserves of stem cells that are capable of transforming into the various different types of cell needed to make that limb or perhaps have cells that are stimulated to 'dedifferentiate' i.e. become less specialised so that they become pluripotent again. How this process is some exactingly and intricate controlled to form a fully-functioning limb is extremely complicated and definitely not fully understood but must be triggered initially by the injury itself.

Understanding how this happens, particularly how these pluripotent cells don't divide out of control and become cancerous, is something that is being studied very intensively at the moment with the view to artificially creating new organs for transplant from the recipient's own cells.

Undergraduate degree in medical science, clinical medical student.




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