I have been reading about the human liver and zebra fish heart muscle having the ability to regenerate. It seems to me that these organs have very little chance to become damaged or worn out. At the very least their chances of being damaged are comparable to other internal organs. So why those particular organs have the regenerative capability?
It is not really essential that all vital organs should have regenerative potential (for example brain).
The cellular composition of a tissue is a big factor in deciding if the organ/tissue will regenerate or not. Some cells divide while others do not; highly specialized and polarized cells like neurons do not divide perhaps because the act of division itself will compromise their function. That doesn't mean these tissues cannot regenerate; they would need stem cells that can differentiate into the type of cells that died.
So regeneration can happen via:
- Division of the tissue cells (skin healing, liver regeneration)
- Differentiation of stem cells (erythropoesis, muscle regeneration)
Organs that do not have non-dividing cells can regenerate by simply proliferating whereas others would need to maintain a stem cell niche- which is not possible in all tissues. Maintenance of stem cells also adds up to the cost of metabolism; so there is some tradeoff.