Human skin is quite good at repairing itself. A cut on the hand will quickly heal on its own. An interesting question to consider is how organs like the heart, liver or kidneys work to heal themselves when they get injured. Normally, when tissue gets injured, cells start replicating and make new tissue. Does this also occur in the heart? All those specialized cells can't exactly take time off to replicate like mad: they need to keep doing their regular jobs, like pumping blood, to keep the already struggling organ from totally failing.
As it turns out, two different processes kick in when an organ starts failing. One of them is the replication just mentioned, but with a twist: the cells replicate the DNA inside of them, but don't take the last step of actually dividing into two. That way, the cell can keep functioning because it isn't too busy dividing, plus it increases the work it can do, so it can take up the slack of the dead cells.
Scientists found that organs also have small amounts of stem-like cells that can divide really quickly to replace the lost tissue.
There's a tradeoff, however. Having a lot of stem-like cells that can divide quickly increases the risk of cancer in the organ. Meanwhile, having too many giant cells with double the DNA can lead to chronic organ dysfunction in the long term. That's why organs use both processes.
Sources and Further Reading
- People can survive organ failure, a review explores how. Science Daily, March 29, 2019.
- Lazzeri, E. Surviviing Acute Organ Failure: Cell Polyploidization and Progenitor Proliferation. Trends in Molecular Medicine. 25 (5), 366-381.