Salk Institute Creates Human-Pig Hybrid Embryo


The Salk Institute has successfully implanted a human-pig hybrid into a sow and observed its successful development over the course of a month.

Infant “pluripotent” cells — that is, those that have the potential to develop into any adult cell — were placed inside pig embryos and successfully combined into an embryonic hybrid. Once that was accomplished, scientists from the Salk Institute implanted the experiment into the womb of a mature sow and observed the embryo’s maturation over the course of a month.

Lead Researcher Izpisua Belmonte wanted to “know whether human cells can contribute at all to address the ‘yes or no’ question,” regarding the potential for growing human organs from pigs. She’s concluded that the study was “long enough for us to try to understand how the human and pig cells mix together early on without raising ethical concerns about mature chimeric animals.”

Despite the success of the experiment, the resulting cells were very weak. Still, it was an “important first step” that brings Belmonte and his peers closer to the “ultimate goal” to “grow functional and transplantable tissue or organs.” And while he believes “we are still far away from that,” they do have a lead: “Now that we know the answer is yes, our next challenge is to improve efficiency and guide the human cells into forming a particular organ in pigs.”

To do so, they will need to edit the pig genome itself, to make it a better host for the development of human cellular structures. Pigs are already our best candidates for such work — their organs are extremely similar to our own. With a lack of human donors on the proverbial table, the research could provide our best hope yet for manufacturing human organs for transplant. It might be the only way to save the twenty-two people who die every day waiting for an organ transplant.

There are, of course, a multitude of ethical concerns in the creation of human-animal hybrids. The Salk Institute has been forced to rely on private donations to fund the experiment, because such experiments remain ineligible for government funding.

All told, the research has created 186 surviving chimeric embryos, each with about 1 in 100,000 human cells. The human cells also seemed to slow the overall growth rate. University of North Carolina stem cell expert Ke Cheng says that the overwhelming predominance of pig tissue would very likely cause human bodies to resist the creations in their current form. And while there are “other steps to take,” he’s called the development “very intriguing.”

This isn’t the first experiment, nor will it be the last. Recently, human glial brain cells were implanted in mice. The mice solved mazes and memory tests twice as fast as their unmodified competitors. It’s a new scientific frontier, with as many hard questions — both moral and methodological — as it has potential answers.

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