After having his eyesight severely impaired in one eye, a 27-year-old man from southern China has successfully regained his eyesight—following a transplantation surgery using a pig’s cornea. The surgery, while not the first, is one of the few ever carried out in the world.

The successful transplantation sheds light on the potential of xenotransplantation – the use of animal donors – as a the future of corneal transplantation. Despite the relative ease of the procedure and its high success rates, the number of procedures remains low; much in part to the lack of scientific literature and established protocols within the medical society.

Number of pig corneal transplantation remains low, despite high success rate

According to Beijing Youth Daily, the life altering surgery was carried out at a hospital linked to the Central South University in Changsha in the Hunan province. Having suffered from a condition which caused chronic inflammation in an eye leading to severely impaired eyesight, the corneal transplantation surgery was the only viable mode of restoring the young man’s vision.

Unfortunately, the number of corneal donors in China remains low. As a result, pig’s cornea was chosen as the donor of choice as it was deemed to be the next best option for transplantation. Due to the cornea contains no blood vessels, it is the perfect candidate for xenotransplantation due to the reduced chance of transplant rejection. Moreover, Dr Renhong Tang, the director of cornea transplantation at the hospital, made sure the pig’s cornea underwent prior treatment to ensure that it would better fit the man’s eye.

Following the successful surgery, the man’s corneal transplant was just one of less than ten similar procedures to have been performed in China, including hospitals in Beijing, Wuhan and Hunan provinces—despite the high success rate of over 90% so far.

“The surgery is not complicated—more or less the same as a human cornea transplant,” explained Tang. However, he cautioned, “A pig cornea is a temporary substitute, definitely not as good as a human’s.” Elaborating on the difficulty faced due to the low number of corneal donors, he said “many patients will never have a chance to get a human cornea, they can only use the alternative.”

Future outlook: Viability of pig corneas for transplantations

Since 2015, the American Society of Cataract and Refractive Surgery has recognised the potential and viability of using pig’s corneas in transplantation surgeries.

The worldwide shortage in number of corneal donors has also proven to be a severe medical problem, especially in continents such as Asia and Africa. As such, pig corneal transplantation has the potential to restore the eye sight of thousands—thus, improving both the individual and nation’s economy. Meanwhile, from an ethical standpoint, pigs represent a viable and acceptable choice because they are generally commercially available.

The cornea, the transparent outermost layer of the eye, protects the eye from infection and physical injury.
The cornea, the transparent outermost layer of the eye, protects the eye from infection and physical injury.

From a biological standpoint, a pig’s cornea is a perfect candidate for transplantation as it shares many similarities with a human’s cornea. With the use of properly treated and grafted pig’s cornea in conjunction with new immunosuppressive drugs, the transplant has the potential to prevent rejection—and even allow for long-term implementation in humans.

An expanded research by Dr Hidetaka Hara and Dr David Cooper which carried out actual transplantation studies further corroborated the society’s recommendation. Simple corneal transplantation of normal pigs already indicated good and promising results; largely in part due to the similarities of biomechanical properties between humans and pigs.

Where pig corneas are often presumed to be temporary donors due to long-term rejection—the research team believes that genetic manipulation of the donor pigs would prevent immunological rejection, and allow long-term survival of pig corneal grafts in human. While there is much optimism in this field of xenotransplantation, the biggest hurdle remains to be acquiring a viable number of genetically modified pigs for the purpose of corneal transplantation.

The cross-species transplantation may still be in its early days; nonetheless, it shows a great deal of promise especially with endorsements from ophthalmological associations and proven potential from scientific literature. With a shortage of corneal donors worldwide, pig corneal transplantation may appear to be the future of sight restoration surgery. MIMS

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