Thursday, April 05, 2007

Pork Pancreas, Anyone?

So, how comfortable are you with the concept of animal tissue being transplanted into your body to replace your own failing organs? There are a lot of people on the "needing a transplant" list who really have no hope of a suitable organ becoming available. The list is too long for the number of human donors to keep up. However, according to Andy Coghlan at New Scientist, scientists right here in the U.S. are developing genetically engineered pigs to provide hearts, livers and kidneys to humans waiting for donor organs. People at the bottom of the list could find themselves with viable transplant options. They just can't be too choosy about the species of the donor!! I realize the whole pig thing makes this an out-of-the-question scenario for Muslims, but it is a decision that some of the rest of us may be called on to make at some point, as science progresses and global populations continue to live longer.

How about something a little less overwhelming than an entire organ? What if it were just a few cells to give a bit of help to a system that's falling down on the job? If you had diabetes, for example, would you let doctors implant pancreatic cells from a pig to help your insulin deficient system keep your blood glucose stable? Michael Helyer, a man from Auckland, New Zealand, was faced with that choice, and made the decision to be a guinea pig for medical science. (Sorry, the pun couldn't be avoided.) His doctors implanted the cells 10 years ago, hoping that they would produce the insulin his own pancreas was unable to supply. Their hopes did not go unanswered. The cells did not provide all the insulin that Helyer's body required, but the porcine cells did, indeed, set up their own little insulin-producing factory, helping to keep his blood sugar levels in check. Coghlan explains that the cells aren't putting out what they once did, but even now, 10 years later, at least some of Porky's cells are still bringing home the bacon, or the insulin as the case may be:

Though Helyer still has to inject himself with insulin, the amount he needed fell by up to a third in the year following the transplant. This effect then faded, but Helyer, who lives in Auckland, New Zealand, says his diabetes remains under better control - a claim supported by data showing that his blood glucose is more stable than before treatment.

The part I found most fascinating about this story is the way that the doctors kept the cells alive--and kept Helyer's body from recognizing the pig cells as foreign and moving in for the kill:

In 1996, LCT [Living Cell Technologies] injected 1.3 million capsules of alginate, a resin derived from seaweed, into Helyer's peritoneal cavity. Each capsule contained about 500 insulin-producing islet cells isolated from the pancreases of newly born piglets. "The alginate lets insulin out of the capsule and nutrients in, to keep the cells alive," explains Elliott. Importantly, it also hides the "alien" pig cells from the human immune system.
Coghlan goes on to add:

Recent samples taken from the capsules suggest that many of the cells are still alive, and a few were found to still produce insulin when exposed to glucose in the lab. Chemical analysis also showed that traces of pig insulin appeared in Helyer's blood shortly after he ate a large amount of glucose.

The fact that these cells are still kicking after all this time is giving doctors reason enough to do further trials. LCT is going to be implanting cells in 14 new people soon, and the new subjects could also receive a second dose of pig cells to see if this can counter the falling off of effectiveness experienced by Helyer.

It's pretty amazing that they found a way to hide the pig cells from Helyer's immune system. I found myself wondering whether the same technique might somehow prove useful in other transplants, even the ones where the donor is human. Naturally, it would be a lot harder to disguise a whole organ from all those pesky white blood cells. How do you take a heart, say, and convince the blood pumping through it that it really should pay no attention to the pig behind the curtain? You can't encase the innards of the heart in seaweed resin, after all.

It is encouraging, though, that they found a way to work around the whole immune system thing in this case, without turning the entire system down or off, as they currently have to do with human organ transplants. Perhaps they can learn from this technique, and come up with other solutions. The alternative is a never-ending regimen of anti-rejection medication. I have a friend waiting for a kidney right now, and she knows that when she gets it she'll be on a strict schedule of drugs to prevent her body from saying, "You don't belong here. Prepare to die." She's mentally prepped for the process though, because she gave one of her kidneys to her brother 20 years ago, and she's seen the routine first hand. One good thing about that is that, since she is a kidney donor herself, she automatically moves to the top of the recipient list as soon as she's medically cleared for transplant. So, she won't have to choose whether it's better to take a porcine kidney than wait for a human one that might never become available.

It's an interesting choice to face, don't you think? Apart from religious objections that would make accepting animal organs, or even a few cells, objectionable to some, for most of us there would probably be a certain "that's just not right" factor that would have to be reasoned through. Is it any different though, really, from human organ donation? Both are alien to you, right? So, what's the difference? I don't know, but for me, on an emotional level at least, there would be more to process if I received an animal organ, rather than a human one. I'm not saying I wouldn't take an animal organ--as my husband said when he read this, "If it work, it works." At the same time, I would be a tad more squeamish about it I suspect, however irrationally. Actually, I hope to circumvent the problem altogether, by never needing an organ transplant, but if I do, I'm hoping that science will have progressed to the point where they can simply grow me another organ in a lab, from my own stem cells, from my own bone marrow, or some such thing. I'd like to skip the whole "pig organ, or death" question. I don't really object to a few pig or cow cells in my body, but generally, I want to chew them as they go inside.

How about the rest of you? Any reaction?