how come we can’t scaffold animal hearts and use them for organ transplants?


is there just something fundamentally different about animal hearts?

In: Biology

I mean we use pig valves in some valve replacement procedures, but the reason why whole heart transplants don’t happen from animals is because your body rejects the transplant. There is a LOT of research being done right now to try and make pig hearts viable for human transplantation

Yes they are incompatible with our blood type and are treated as foreign objects by the body and will get rejected.

There are various widely fundamental differences between hearts of different animals. Firstly there is an immune system in place here looking for foreign cells trying to destroy them. We are often able to trick it to accept another human heart but even that requires a great deal of effort. Getting it to accept an animal heart would be extremely hard. For one the animals have different blood antigens, not just A, B and rhesus D. So you are dealing with a whole new set of blood type compatability problem. In addition the animal hearts are all specialized for different heart rates, different blood pressures, different blood flow, they interact with the neurons and hormones differently, etc.

But even through all of these problems we are actually working on this. Out of all the animals it happens that the one closest to humans physiological is the common farm pig. Turns out that a diet of trash food, low activity levels and high cholesterol does make us pigs. Joking aside we are able to do some transplants from pigs into humans but it requires quite a bit of work and we basically have to flush out all the pig cells first. You could not do that to the entire heart, at least not yet but we are working towards it.

Now, I’m not entirely sure but I think the main reason is that organs we typically do that with (like a heart valve or a trachea) are usually rich in connective tissue and have a dense collagen structure. When you acellularize these organs there will be a good mesh left made up of organic material which is similar between individuals and, unlike cellular tissue, does not display molecules like the MHC which trigger an immune response in graft recipients. The myocardium, i.e. the bulk of the heart, is mostly made up of muscle cells and specialized muscle cells and I doubt you could acellularize the heart while maintaining its structure to a satisfactory degree. At least I think that describes some of the major obstacles which may make a project like that less probable to succeed than some other similar grafts.