Researchers announced a scientific advance on Thursday that could have major benefits for those in need of organ transplants.

Through their private company called eGenesis, Harvard researchers, together with Chinese and Danish collaborators, have created genetically engineered piglets that are free of viruses that might harm humans.

According to the journal Science, the eGenesis team, led by geneticists George Church and Luhan Yang, used the controversial CRISPR gene-editing technology in order to achieve the breakthrough.

Put simply, CRISPR is a DNA sequence that can detect and destroy attacks from certain viruses. Used for the purposes of genetic editing, it can effectively act as a pair of scissors to cut out undesired parts of a genome and replace it with new strands of DNA. The process has come up against numerous detractors, wary of the path it could pave to "genetic upgrades" in humans.

While scientists had long hoped to be able to transplant animal organs to humans in need, they had always run up against the problem of so-called PERV cells. PERV cells are, according to Science, "remnants of ancient viral infections" from the animals that could harm humans.

eGenesis said it has been able to create "dozens of apparently healthy pigs with no trace of PERV genes," by using the CRISPR technique.

However, one step must still be overcome before pig-to-human transplants are viable. Researchers now face the task of removing the genetic material in pigs that may "provoke the human immune system" or create "toxic interactions with human blood."

Yang admitted that these next steps will be "probably more challenging" than those her team has already accomplished.