One problem with human-animal tissue contact is the enhanced opportunity for zoonosis (cross-species diseases).
In the early 1990's there was a proposal to enclose pig Islets of Langerhans (insulin and glucagon producing) tissue in capsules with sub-cellular pores and implant them in diabetics. The idea was that rejection was less likely without direct cellular contact and the diabetics would gain something resembling natural blood-sugar regulation.
There were two problems that persist over the three decades of subsequent research: 1. rejection does still prove to be a problem, and 2. the problem was that pig viruses emitted by the transplanted capsules might eventually find an "error" that would infect the human host resulting in a brand new zoonosis shared by pigs and humans. The FDA refused trials as a result (see the last paragraph of this section in wikipedia: https://en.wikipedia.org/wiki/Pancreatic_islets#Transplantat... - that article leaves out is the distinct possibility of other porcine viruses that might cross-species given the persistent opportunity this therapy might provide).
If one is being conservative - always a good idea when the prospect of new diseases are in the offing - the process of putting human tissues in pigs and then back in humans is at least as risky as merely putting live pig tissue directly into humans.
thanks for posting this. i wrote a paper on porcine endogenous retro-viruses and their effects back in the late 90s for a basic biology class. these methods, and accompanying concerns, have been around for a while.
That might be addressed by modifying the animal to produce the dsired organ at the correct size, scrubbing out all livestock cells with strong detergents, then seeding the organ extracellular matrix with progenitor cells from the intended recipient.
There would be no livestock cells left, so no worry about zoonotic pathogens.
The only known mammalian prion is PrP, which noticeably affects animal behavior, and is detectable by testing lymph. If the animal has prion-related encephalopathy, you burn it.
Viruses cannot reproduce without living cells. Viruses that employ lipid capsids would likely be removed by the detergent along with the cells. Some viruses do embed in a type of extracellular matrix (HTLV-1). As far as I am aware, no research has been done on the transmissibility of viruses in decellularized animal organs from donor to recipient.
I presume that those facing imminent organ failure would rather catch a cold from a pig and recover in quarantine observation than die while waiting for such research to conclude.
Personally, I think people should have a choice. But I'm guessing we'll see both: Some will rethink their dogma, and others will put their money where their mouth is.
Retroviruses were the major showstopper, now they can identify them and remove them from the genome. Maybe they run into another roadblock, but... Maybe it works this time.
In the early 1990's there was a proposal to enclose pig Islets of Langerhans (insulin and glucagon producing) tissue in capsules with sub-cellular pores and implant them in diabetics. The idea was that rejection was less likely without direct cellular contact and the diabetics would gain something resembling natural blood-sugar regulation.
There were two problems that persist over the three decades of subsequent research: 1. rejection does still prove to be a problem, and 2. the problem was that pig viruses emitted by the transplanted capsules might eventually find an "error" that would infect the human host resulting in a brand new zoonosis shared by pigs and humans. The FDA refused trials as a result (see the last paragraph of this section in wikipedia: https://en.wikipedia.org/wiki/Pancreatic_islets#Transplantat... - that article leaves out is the distinct possibility of other porcine viruses that might cross-species given the persistent opportunity this therapy might provide).
If one is being conservative - always a good idea when the prospect of new diseases are in the offing - the process of putting human tissues in pigs and then back in humans is at least as risky as merely putting live pig tissue directly into humans.