Sheep-human hybrid : Birth of a new chimera organism.

Researchers from University of California have been successful in producing  a chimera organism from DNA of sheep and human.The main purpose of this experiment was xenogenic generation of new organs. It is meant to change the future of organ donation- body parts synthesized from genetically modified sheep to save millions of lives waiting for organ donation.

The process used here is by the infusion of  human DNA in host (here sheep) embryo.It is based on the interspecies blastocyst complementation. The chimera DNA molecule is prepared using the CRISPR- Cas9 mediated genome editing of the zygote to disable the genes that are responsible for the production of the particular organ and then infusing with the complementary genes(from human pluripotent stem cells(hPSCs)) responsible for formation of the organs in humans.It results in a hybrid creature that's more than 99 percent sheep – but also a tiny, little bit like you and me. The human portion of the embryos created in the experiment – before they were destroyed after 28 days – is exceedingly small, but the fact it exists at all is what generates considerable controversy in this field of research.

"The contribution of human cells so far is very small. It's nothing like a pig with a human face or human brain," stem cell biologist Hiro Nakauchi from Stanford University told media at a presentation of the research this week in Austin, Texas, explaining that, by cell count, only about one in 10,000 cells (or less) in the sheep embryos are human.

The research builds on previous experiments by some of the same team that saw scientists successfully grow human cells inside early-stage pig embryos in the lab, creating pig-human hybrids that the researchers described as interspecies chimeras.
 
"Even today the best matched organs, except if they come from identical twins, don't last very long because with time the immune system continuously is attacking them," says one of the team, reproductive biologist Pablo Ross from the University of California, Davis.

The research is still in its infant stage. we shouldn't expect hybrid organs readily available anytime soon. for this to happen the percent of human DNA should be at least more than 1 percent. But it also raises ethical questions on whether should we raise organisms only for the sake of harvesting its organs.
"I have the same concerns," Ross explains.
"Let's say that if our results indicate that the human cells all go to the brain of the animal, then we may never carry this forward."

There are no easy answers to the kinds of ethical questions this sort of research raises, but with someone being added to a US transplant waiting list every 10 minutes, the researchers say we shouldn't discount the possibilities of what chimeras could one day do for us.

"All of these approaches are controversial, and none of them are perfect, but they offer hope to people who are dying on a daily basis," Ross says.
"We need to explore all possible alternatives to provide organs to ailing people."

The findings were presented over the weekend at the annual meeting of the American Association for the Advancement of Science in Austin, Texas.