J. Craig Venter, the pioneer biologist and entrepreneur famous for sequencing the human genome, is partnering with biotechnology company United Therapeutics' Lung Biotechnology Inc. to develop the first humanized pig organs suitable for use in lung transplants.
Lung diseases currently kill more people worldwide than any other disease, with some 9.5 million deaths in 2008. Lower respiratory infections and chronic obstructive pulmonary disease (COPD) account for the lion’s share. But despite the mass prevalence of these diseases, the number of lung transplants that take place each year still totals in the thousands — a challenge borne out by a delicate organ that requires a near-perfect match if it’s to function properly.
The latest partnership has hopes of eliminating the need for a match. Xenotransplantation, the use of animal organs for human transplant, has failed in the past because the delivering organs don’t feature compatible genomes. It’s Venter’s task now, and that of United Therapeutics, to reorganize pig genomes in such a way that compatibility becomes irrelevant.
"We're going to start with generating a brand new super-accurate sequence of the pig genome, and then go through in detail and compare it to the human genome," Venter told Reuters. "The goal is to go in and edit, and where necessary, rewrite using our synthetic genomic tools, the pig genes that seem to be associated with immune responses.”
The partnership works by a kind of tag-team. Venter’s role will be to edit and rewrite the sequence of the pig genome, which is accomplished through one of several techniques that relies on performing microsurgery on certain genes. Once Venter and his team have changed the desired DNA sequences, they hand the cells off to United Therapeutics, which will then transplant them into pig eggs. Eventually these grow into embryos equipped with humanized lungs that can be used in transplants.
Venter says the work on his end to develop the cells will take several years alone. Transplanting the cells into the actual pig and testing them to make sure they are safe and effective is likely going to take many more. The upside to this extended timeline, he points out, is that because lungs are so delicate, testing on alternate organs, such as kidneys and hearts, won’t pose as much of a challenge in the future. The technology will already be optimized for the most fragile surgery.
"We want to get it so there is no acute or chronic rejection," he said.
Transplantation of this order is something Venter concedes would have sounded like science fiction even five years ago. But due to the leaps made in genome sequencing and preservation techniques during lung transplants, scientists and surgeons have been able to improve the procedure dramatically. In October of 2013, a team of transplant specialists in Belgium performed a record-breaking double transplant that required the lungs to sit outside the patient’s body for 11 hours, while the other organ, a liver, was transplanted first.
And last week, the National Heart, Lung, and Blood Institute reported that they grafted a genetically altered pig heart into a baboon’s abdomen. Over a year later, aided by the animal’s natural heart, the pig heart was still functioning.