[chris (OP)]

Richard is wondering:

I read about a Chinese guy who asked for his transplanted hands t be removed since he found them so creepy.  If he had waited would they have eventually become his cells and thus his hands?
 
Love the show – listen since day zero – keeps me educated on my bus ride to work in chilly Moscow.

What does everyone think?

[chris (OP)]

Nice question; the answer is no, recipient organs are not ultimately replaced by new host cells.

The main reason a transplant often works is because the cell population from which the transplanted organ is derived does not come from the new host and hence is not affected by the same disease that necessitated the recipient having a transplant in the first place.

For instance, a person with cystic fibrosis is functionally "cured" of their chest problem by a lung transplant. This is because the donor lungs are built from a cell population - and repair themselves using a stem cell pool - that does not have the genetic problem that causes CF.

However, this is not to say that there is no host cell ingress - blood, after all, will fill the donated body part and also deliver immune cells that will migrate out into the graft.

[evan_au]

If he had waited would they have eventually become his cells and thus his hands?

During development, cells become specialized into particular tissues (eg skin cells, nerve cells, liver cells, etc), and this is configured by epigenetic markers on the DNA.
A small number of cells remain as stem cells, which are partially programmed with epigenetic markers, but are still able to divide and turn into a number of related tissues within the particular organ; it is thought that this residual population of stem cells are the source of regrowth and repair after injury.

Those animals (like salamanders) that can regenerate whole limbs after trauma seem to be able to remove the epigenetic markers and return to undifferentiated cells, which can take biochemical and electrical cues from the surrounding tissues to regrow bones, muscles, tendon and skin into a fully-functioning limb.

Once humans leave childhood, these epigenetic markers are locked-in, and regrowth opportunities seem very limited. So while children can regrow a lost fingertip, and an adult will repair a cut finger, an adult won't regrow a whole hand.

https://en.wikipedia.org/wiki/Stem_cell

[MayoFlyFarmer]

To be clear, I don't think a child would re-grow a whole hand either.

(also, after a careless incident in the kitchen last year, I can say from personal experience that adults can re-grow fingertips!)

[RD]

Richard is wondering:
I read about a Chinese guy who asked for his transplanted hands t be removed since he found them so creepy.

Are you sure it was his hands ? ...

[Chinese]Man rejects first penis transplant ...
Although the operation was a surgical success, surgeons said they had to remove the penis two weeks later. "Because of a severe psychological problem of the recipient and his wife, the transplanted penis regretfully had to be cut off," Dr Hu said. An examination of the organ showed no signs of it being rejected by the body.

https://www.theguardian.com/science/2006/sep/18/medicineandhealth.china