Way back in 2017, I wrote a post about how scientists might one day use pigs to grow human organs. These “human-pig chimeras” could provide replacement organs to people with diseases like diabetes.
I recently learned that researchers are also trying to make pig organs suitable for transplant into humans. Their work doesn’t rely on putting human cells in pigs; they don’t need to make chimeras. Instead, these researchers use genetic engineering techniques to make pig organs more acceptable to the human body. Their modifications prevent the immune system from attacking and rejecting the pig organs. Thus, they hope to make pigs the future heroes of organ transplantation.
This research holds a lot of promise for patients in need of organs. Yet, it’s reasonable to worry that we devalue pigs by using them to produce human organs. My take is, if we accept pigs are sources of food, we should accept them as sources of organs. Nonetheless, I believe that we should develop transplant and food systems that don’t rely on living animals. Learning how to grow organs in pigs may help us move in this direction. Hopefully, we’ll eventually know enough about organ development to simply grow organs (and meat for consumption) in the lab.
One day we may be able to transplant pig pancreases (pigcreases?) like this to patients in need.
“Receptor.” It’s yet another bit of biological jargon. It sounds like receptors should be small spacecraft launched to defend an alien mothership. Or maybe receptors are courtly underlings who receive guests before their presentation to the queen? In truth, receptors are cool and important biological structures that reside on cell surfaces.
As you might remember from my post on cell membranes, the layers of fat that surround cells are quite complex. They are studded with proteins that perform many functions. Some of these proteins are receptors.
Receptors all detect stimuli and cause cells to respond in some way. Often, receptors grab onto specific molecules floating nearby. Then they signal to the cell that they’ve done so.
The exact cellular response to a receptor signal depends on the receptor and on the stimulus detected. Some signals cause cells to grow. Others cause cells to move. Still others coordinate behaviors among many cells. Receptors are critical for many of life’s complicated processes.
Unfortunately, receptors have a darker side too. Many viruses use receptors as handles. With a good hold a on receptor, a virus can barge into a cell. Thus viruses hijack receptors to infect cells and cause disease.
A virus grabbing onto a receptor to infect a cell.
Using receptor biology to prevent viral infection
Interestingly, scientists are using receptors to fight viral infections. They reason that, if they get rid of receptors used by viruses, the viruses will have no way of infecting cells. Many receptors are only important under specific circumstances. Thus, getting rid of them will have some small negative consequences, but the benefits of resisting viral infection are worth it.
Indeed, a scientist in China recently claimed to have modified babies to make them resistant to HIV (these are the so-called “CRISPR babies”). This scientist used a genetic technique to delete one of the receptors hijacked by HIV. The researcher performed this technique in embryos. Thus all the modified babies’ should be able to pass their modifications to their offspring.
What this scientist did was foolish for many reasons. Some of them include:
It is unclear if the technique was safe.
It is unclear if the technique accomplished its goal.
There are effective ways to prevent HIV transmission that don’t require this technique.
Some types of HIV use other receptors. Thus, the children won’t be protected from all types of HIV.
On top of all this, the scientist’s use of this technique raises many ethical questions. Most of these stem from the fact that the babies can pass on their human-designed modifications to their offspring. Should we modify the human gene pool in this way? Do we know enough about the potential consequences? Can we use similar techniques to do more than treat disease? Society at large must face all of these questions before we decide to use any similar techniques again.
This unfortunate work aside, other techniques modify receptors on adult cells. Future generations can’t inherit the modifications. Thus we can use these techniques following standard regulatory rules. Indeed, clinical trials using modified adult cells to treat HIV have had very promising results! Scientists can also give immune cells receptors that make them better at fighting cancer (see my previous discussion of CAR-T cells in this post). Receptors play a role in so many biological processes that we’ll likely see many more cool uses of them soon!
The next time you see a picture of smooth, round cell, remember that it’s studded with receptors and they do a lot!
