I'll give a shoutout to Slashdot for alerting me to this surprising item. Researchers at the University of Nevada at Reno have created a herd of sheep whose organs are, at a cellular level, 15% human. This article describes the research, but raises more questions than it answers. I found a more thorough article from 2003 in New Scientist.
The original goal of the UNR work was to study possible methods for in-utero correction of genetic defects. The idea is that stem cells can be taken from the developing human embryo, given some gene therapy to correct the disorder, and then transplanted back to outcompete the defective cells as the fetus matures. Naturally, such experiments cannot be done with human embryos. So the team used sheep fetuses. They injected them with human stem cells and some human growth factors. They then let the fetal sheep develop and observed what happened to the human cells. The lead researcher's paper can be found here.
The transplanted human cells could have all died off, but as the sheep fetus was pre-immune, they did not. Instead some became persistent human stem cells (as for bone marrow). Others, however, committed and became human organ cells. The human cells apparently coexist with the sheep cells in the organs. This has raised the possibility that such "humanized" sheep could be used as a source of tissue, or even whole organs, for transplant. Imagine a patient who sustains severe liver damage. Both the lack of available organs for transplant, and the difficulty of tissue rejection make for a dire prognosis. But this research offers a different approach as it suggests a method whereby the patient's own stem cells could be used to develop replacement organ tissue that would be harvested from the sheep after birth.
Getting stem cells to specialize and grow into organs in the lab isn't something we can expect in the near future. However by using the sheep fetus as a natural factory for tissue development the team has already succeeded. I'm surprised that the major US media have not jumped on this story. Both the medical promise and the ethical issues raised are big news. In the UK several groups are now wading through government bioethics panels so that they can begin similar research.
--Per
The market is Open
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Whatever it is that would have once made my internal icky/horror response go off at the thought of, you know, man/animal hybrids has apparently died, because I'm no longer at all creeped out by things like this.
I can just imagine the animal-related product slogans of the future: "Sheep! Now 30% Human! And the other 70% is...well, anyway, it's not human."
"Well, I'm raising five transgenics in case of accident or disease. Let's see, that's Kidney, and over there is Liver and Lung. Brain and Artery are grazing out back."
"Did you say Brain?"
"Them sheeps what we rustled taste funny. More like pig than sheep."
Spokespeople for Pet Select admitted that they use harvested or obsoleted transgenic sheep for their Lamb Special Cuts dog food. They claim that the meat content of the food is less than 10% human tissue. In times past some human cultures used to prepare and eat dogs. Now, it seems, the canines get to eat us.
MRI studies of Tufty revealed that the sheep's cerebrum has a neocortex as developed as a human's. Originally intended to serve as a source of astroglial cells for an Alzheimer's patient, Tufty appears to have developed a brain that is 90% human. While this explains the animal's ability to understand speech and it's attempts to communicate, it also takes the bioethics debate to a new level. Should Tufty be sacrificed for the (unnamed) patient, or does the animal have a human right to live?
Six of the handlers at New Hope Transgenic Farms have already died, and three more barely cling to life. The new disease appears to be a mutated sheep virus. It jumped species while incubating in transgenic tissue. While the original virus only causes flu-like symptoms in sheep, the mutated form is exceptionally deadly to humans since we have no defenses for this new pathogen.
Feelings of icky-ness... returning?
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