what happens with a donor organ’s DNA after a successful transplant?


My assumption is that over time the organ regenerates new cells with the host’s DNA. Or do the two stay distinct for life, or do they merge into a mix of the two? If they stay separate, is there a definite boundary, and does the host’s future offspring bear the DNA of three bloodlines instead of two?

In: Biology

The host cells keep the host’s DNA and the implanted organ’s cells keep the donor’s DNA, and certainly possible future offspring will have the host’s DNA only. They do not mix, the host cannot regenerate cells he does not have anymore only the organ itself can regenerate those cells (if it can regenerate), the host actually has immunosuppressants for the rest of his life so his immune system does not destroy the implanted organ.

They stay distinct. Transplant recipients will take immunosupressants for the rest of their life (or more likely to come first; the duration of the graft’s survival) so the recipient’s body doesn’t reject the graft.

If you’re interested in learning a bit more, “when death becomes life” is an interesting, and easy to read, book by a transplant surgeon.

An organ will regenerate by splitting some of its existing cells into two “new” cells in a process called mitosis. When a cell is preparing for mitosis, it first creates a second replicate copy of its DNA. Its more complex than this but as mitosis progresses, the two replicate copies of DNA get moved to opposite ends of the cell. The cell divides in the middle and now you have two cells, each with its own copy of DNA.

So to answer your question, since the cells of the donor organ will under go mitosis and split, the donor’s DNA will always persist in the organs cells and remain separate to that of the recipient.

I’m not sure what you mean by boundary, but donor DNA would only be found in cells that originated from the donor organ. The recipients offspring would only get DNA from the recipient, as sperm/egg DNA is not derived from the organ donors dna

It is possible that there will be some mixing of cells, given the possibility of cells to enter the cell flow and exit in a different district (fibroblasts, macrophages), but they will generally stay separated. There is also the possibility that DNA or RNA shed from the host or donor cells are uptaken by the other type of cells, but I don’t know if this phenomenon has been studied.

>My assumption is that over time the organ regenerates new cells with the host’s DNA

This is incorrect. The reason we need organ transplants in the first place is that we few exceptions, we can’t regenerate organs. The donor organ remains the donor organ. That’s why organ recipients have to take immunosupressant drugs for life so they don’t reject the donor organ. The “definite boundary” is the organ itself. I think you’re overthinking it. If I donate a kidney to you, the kidney has my DNA, and the rest of your body still has your DNA. Offspring do not get any. DNA from transplanted organs. Transplanted organs have nothing to do with the creation of sperm cells, and in women, all of their egg cells already exist at birth.

How about new cells in the donor’s organ? What DNA do they have when new cells grow?

I have very very minimal knowledge of this, but my mom had a double lung transplant in 2017 and I think the reason that rejection can occur at literally any time is because the DNA is different. Which is also why my mom can’t take any sort of immune system boosting meds like emergen-C because it would encourage her body to fight off the foreign cells/dna.
Just my thoughts though, I never talked to the doctor about that specifically.

To add to the existing replies:

*does the host’s future offspring bear the DNA of three bloodlines instead of two?* If you got a gonads transplant, your offspring will bear the DNA of the donor. If you are male and only transplant one of your goands, I’m not sure what happens.

Others have already answered the question (the donor organ keeps its own DNA), but I wanted to add a little something:

There’s a condition known as genetic chimerism, it occurs when a mother has twins in the womb but, early in development, the cells of one twin engulf the other.

This leads to a single child with genetic information from two people.

In some cases this leads to random sections and splotches of your twins DNA around your body, other times it can lead to specific organs belonging to your twin.

There was a case a while back of a woman who failed a maternity test for her own children because the DNA of most of her body and the DNA of her ovaries differed; in essense, her twin had acted as an ovum donor.

More commonly, you’ll see people with patches of different coloured hair or things like Heterochromia, where each eye is a different color.

I was told I was a chimera earlier in my life, while most of my hair is dark brown, about a third is fire-engine red, I have Darwin’s Tubercle on one side and not the other, I had a bunch of complications at birth due to a hernia resulting from the two sets of skin not correctly fusing and a DNA scrape of the inside of my mouth doesn’t match the DNA of a blood test.

I’d also be interested in an ELI5 on transplant patients that do not need to take immunosuppressants [like Demi-Lee Brennan](https://www.google.com/amp/s/amp.smh.com.au/national/transplant-girls-blood-change-a-miracle-20080125-gdry7w.html)