The world is one step closer to a human animal hybrid, according to researchers at the Salk Institute in La, Jolla, California. Stem cell scientists created a pig embryo partially made up of human cells, successfully overcoming a major hurdle in growing human organs in animals for transplants.

“We see the human cells become the precursors of the cardiomyocytes – the heart – and also the liver, the pancreas and the gut,” Jason Wu, a scientist at the Salk Institute and the study’s lead author, told San Diego Public Radio. “So the potential is here.”

The research team, whose work was published Thursday in Cell magazine, is hoping to eventually be able to take human cells from a patient in need of a transplant then grow them in an animal embryo in order to transplant them back into the patient without being rejected.

The resulting pig embryo with human cells is known as a chimera, the name for an animal with a combination of cells from different species. However, the creation of chimeras, and research with stem cells in general, is not without issues. The topic is hotly debated and the ethics, to some, are murky. Stem cells come from a human blastula, the cluster of cells that grows from a fertilized egg. Critics of the research argue that using blastulas destroys what is technically an unborn child, while proponents say that a blastula is not yet a child.

Chimeras, on the other hand, run the risk of consciousness or having human-like features if a high enough concentration of human cells is added to the brain, according to a report published in Stem Cell Research and Therapy.

The success of the experiment bodes well for human organ transplants, complicated medical procedures that often result in the body’s rejection of the organ or death before an organ can be acquired.

“The advances here make me confident that a solution will be found and human organs will be made routinely in animals,” Scripps Research Institute stem cell scientist Jeanne Loring told San Diego Public Radio.

There are currently more than 119,000 people on the national waiting list for a transplant, according to the U.S. Department of Health and Human Services, and 22 people die every day while waiting for a transplant.

GettyImages-103686234 Stem cells are viewed on a computer screen at the University of Connecticut's Stem Cell Institute in Farmington, Connecticut, Aug. 27, 2010. Photo: Getty