Huang Yuanzhen has had a pig's cornea in her right eye for five years.
She's able to joke about it now, telling this fact to people she meets to surprise them. But when she first heard that doctors wanted to implant a slice of pig eye into her body, she was frightened and disgusted.
In 2010, the then 52-year-old farmer living in Songzi township, Central China's Hubei Province, accidentally poked her right eye with a bamboo splint while working in the field. She immediately felt pain and couldn't open her eye.
When she could, finally, she could see nothing but darkness. In the next few months, she went from hospital to hospital to seek help, accompanied by her family. She was told by doctors that she had an ulcer that covered more than half of her cornea, and was diagnosed as blind in that eye.
But the turning point came soon, when her doctor at Wuhan Union Hospital, Zhang Mingchang, asked whether she'd be open to transplanting an artificial cornea into her eye. She was also told a pig cornea was the main material for this new invention.
"I felt scared about it being a pig's eye," Huang said. "But the doctor said if I choose this, the company [that developed the cornea] would pay for the surgery." Besides, she constantly fell or bumped into people with only one eye, and her right eye throbbed with pain.
She decided to accept the surgery.
Vision for a cure
About 10 years before Huang accepted her surgery, Jin Yan, a professor and researcher at The Fourth Military Medical University, received a request from Hong Kong-based company China Regenerative Medicine International (CRMI).
The company asked him if he would like to cooperate with them to develop artificial corneas.
In China, keratitis, or inflammation of the cornea, is the second biggest cause of blindness, after cataracts. According to World Health Organization data, there are more than 4 million patients with keratitis in China, and the number is increasing by 100,000 each year.
The surgical solution for the disease is a cornea transplant. But there is a large gap between the number of patients and cornea donations.
"There are about 5,000 donations every year, it covers only a very small number of patients," Jin said.
Many teams around the world have tried developing artificial corneas. But so far none succeeded beyond clinical tests.
"Doctors and researchers have long been trying to develop artificial corneas," he said. "But due to its complex structure and fragility nobody has succeeded before."
Jin had previously worked with CRMI in developing a prosthetic skin, which speeds up patients' healing process and is an effective treatment for ulcers. So when he started trying to develop artificial corneas, he thought of using collagen.
But soon his team ran into the same dilemma as international researchers. They found out that there's no way collagen can imitate the thin but complicated fiber structures in a human cornea. That's when the team turned to animals.
The animal's eye needed to be similar to a human's. The animal need to be easy to raise and keep healthy. Based on these needs, the team considered cats and goats, and finally settled on pigs.
Choosing an animal was just the first step. The more difficult part was to figure out how to counter rejection by the host body after transplantation.
The most common way is to remove donor cells and antigen molecules to diminish the host immune reaction, but it was hard to find a method that could both remove the cells and leave the pig cornea's structure intact.
Developing this procedure took a few years.
After that, Jin's team conducted thousands of animal experiments. More than 10,000 pigs were used by the research team.
The team later named the artificial cornea "Aixintong," a generic sounding name that offers no clue to the product's porcine pedigree.