A self-described science nerd is the latest American to get an experimental pig kidney transplant, at a crucial point in the quest to use animal organs for people.

The 54-year-old New Hampshire man is easing back into work less than three months after his operation, doctors at Massachusetts General Hospital announced Monday.

"I really wanted to contribute to the science of it," said pig kidney recipient, Bill Stewart. "I've always been a little bit of a science nerd."

And an earlier pig kidney recipient has set a record – faring well for seven months and counting, as the U.S. approves pig producer eGenesis to begin a rigorous study of xenotransplantation.

Stewart's doctor said he is doing "extremely well."

Stewart's surgery comes at a point when trials are poised to begin to test animal-to-human transplants that could help ease the shortage of donated human organs.

"I think this is where xenotransplantation can really, you know, change the game for patients that are waiting for a transplant," said Dr. Leonardo Riella at Massachusetts General Hospital.

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