Scientists attached a temporary pig’s kidney and observed it start to function. This was a small step in the long-running quest to use animal organs to save lives.

The most recent focus for organ shortage research has been on pigs. However, there are some hurdles. One of the obstacles is that a sugar found in pig cells can cause organ rejection. This experiment used a kidney from an animal that was genetically modified to remove the sugar and prevent an immune system attack.

Two days after the death of the recipient, surgeons attached the kidney of the pig to two large blood vessels. The kidney performed its job — produced urine and filter waste — without triggering rejection.

“It had absolutely regular function,” Dr. Robert Montgomery, who was the surgeon in charge of the NYU Langone Health surgical team last month, said. “It didn’t have the immediate rejection we were concerned about.”

This research is “a significant milestone,” Dr. Andrew Adams of University of Minnesota Medical School said. He was not involved in the work. It will be reassuring to patients, regulators and researchers that we are moving in the right direction.

The idea of animal-to human transplants, or xenotransplantation, dates back to the 17th Century when there were stumbling attempts at using animal blood for transfusions. Surgeons began to transplant organs from baboons into human beings in the 20th century. This included Baby Fae, an infant who died 21 days after receiving a baboon heart.

Scientists tried to make the species gap bridge between primates and pigs but to no avail. There was much public outcry.

Pigs are more intelligent than monkeys and other apes. Pigs are bred for food so there are fewer ethical issues. Pigs are known for having large litters and short gestation times. They also have organs that are comparable to human beings.

Humans have used pig heart valves for many decades. Heparin, a blood thinner made from pig intestines, is also derived from them. Pig skin grafts can be used to treat burns. Chinese surgeons also use pig corneas for sight restoration.

After her family consented to the experiment, NYU researchers kept the body of a woman who had died on a ventilator. Although the woman wanted to donate her organs for traditional donation, they were not suitable.

Montgomery stated that Montgomery’s family believed there was a chance of some good from the gift.

Montgomery received a transplant three-years ago. It was a human heart from an organ donor who had hepatitis C. Montgomery was open to any organ. He said, “I was one those people who was waiting in an ICU and not knowing if an organ would come in time.”

Many biotech companies are working to create transplantable pig organs to ease the human organ shortage. A total of 90,000 Americans are waiting for a kidney transplant. Every day, 12 die while waiting.

Revivicor, which is a subsidiary United Therapeutics’, has won the advance. The company engineered the pigs and their cousins in a herd that was 100 animals raised in Iowa in controlled conditions.

Pigs do not have a gene for alpha-gal. This sugar triggers an immediate immune response from the human body.

The Food and Drug Administration approved gene alteration in Revivicor pigs in December as safe for human food and medicine.

However, the FDA stated that developers would have to submit additional paperwork before organs from pigs can be transplanted into human beings.

Martine Rothblatt, CEO of United Therapeutics, stated that this is a significant step towards realizing the promise xenotransplantation. This will save thousands of lives every year in the not too distant future.

Experts believe that the tests on nonhuman primates, and the experiment last month with a human body, pave the way to the first experimental pig heart or kidney transplants in living persons in the coming years.

Some people feel that raising pigs for organ donation is wrong. However, Karen Maschke, a researcher at the Hastings Center, will help to develop ethics and policy recommendations to support the first clinical trials funded by the National Institutes of Health.

Maschke stated, “The other issue will be: Should this be done just because we are able?”