Last week, researchers announced that they’d implanted the heart of a transgenic pig into a baboon, and kept it alive for a year. Here’s why you should care:
One day, a few decades from now, you are going to need a new organ. Maybe a heart, maybe new lungs, maybe a new kidney — they all eventually wear out. Heart disease is the leading cause of death worldwide.
The median age of a heart attack victim is only 50 years old. You can subtract your age from that number to see how long you have left for medical science to figure out a way to make new organs — because the supply from organ donation is not keeping up with demand.
Experiments like the heart study may provide a way to solve the problem. The plan is to eventually create pigs engineered to produce organs for transplantation into humans, a process called xenografting.
NIH researchers at the National Heart, Lung and Blood Institute were able to modify pigs not to express a series of marker proteins that trigger a response from primate immune systems. Those responses would normally cause rapid and severe rejection in humans and baboon transplant recipients. Additionally, some of the pigs were genetically engineered to produce specific proteins intended to reduce blood clotting, another common cause of transplant failure (a syndrome known as “acute vascular rejection”).
This represents a major step forward in the ability for scientists to genetically engineer the immune system of animals. If perfected, this might allow doctors to produce organs tailored to the immune systems of individual people, so that the recipient body treats the new organ as native tissue.
This is important because, even in the case of human-human transplants, there are plenty of rejection problems. Even for those who do get a donor organ in time, the immune suppression drugs that patients have to take to avoid their immune system killing the organ are nightmarish, and don’t even completely work. Donor kidneys only survive for a decade or two.
What doctors really want is the ability to make completely new organs from the patient’s own tissue. If doctors had a limitless supply of transgenic pig organs, they could pre-emptively replace organ systems before they fail, and treat cancer by simply removing and replacing every piece of tissue that might be affected.
One approach to making new organs is 3D printing a collagen scaffold, and then growing stem cells into it. We’ve covered the technology before (and you can watch a TED talk about the process below).
3D printing has a lot of issues. The resolution is pretty limited right now, making it difficult to build the fine structure of organs like lungs. On top of that, many organs are composed of a lot of different kinds of interwoven tissue, and it’s difficult to get stem cells to grow properly in the correct shapes. It’ll be a while before scientists can make everything through 3D printing.
The organ study shows a way around a lot of these problems. Doctors could simply grow pigs with the genes of their patients to maturity, kill the pig, vitrify the organs, and have them ready when they’re needed. Any organ (or even potentially some bones) would be available on demand as needed.
The baboon study was a promising first step, although significant challenges remain.
For starters, the hearts were not serving as functioning organs for the baboons — they were simply implanted into the body cavity to see if they’d survive. Testing their cardiac function will follow in future experiments to see if the organs are viable. However, initial results are promising: of the organs with all the modifications, the median survival rate was 200 days, and three of the five organs were still alive at time of publication.
If researchers can prove that the organs are viable organ replacements in baboons, the road ahead is clear for clinical trials in human subjects. If all goes well, in ten or twenty years, the technology might be ready to make donor-specific organs for anyone and everyone. One of the researchers responsible for the breakthrough, Dr. Mohiuddin, was optimistic:
Xenotransplantation could help to compensate for the shortage of human organs available for transplant. Our study has demonstrated that by using hearts from genetically engineered pigs in combination with target-specific immunosuppression of recipient baboons, organ survival can be significantly prolonged. Based on the data from long-term surviving grafts, we are hopeful that we will be able to repeat our results in the life-supporting model. This has potential for paving the way for the use of animal organs for transplantation into humans.
Is it possible that some day the genetic engineering or 3D printing of new organs will become the norm, while organ transplants will become an archaic relic of medical history? Will most of us have genetically engineered replacement organs in our retirement years? Share your own thoughts on this breakthrough science in the comments section below.