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14th August 2022

Bioengineered cornea restores vision

A bioengineered cornea made from pig's skin is shown to restore vision to blind people. It can be mass produced and stored for up to two years, unlike donated human corneas that are scarce and must be used within two weeks.

 

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Credit: Thor Balkhed

 

Scientists have developed a new implant made of collagen protein from pig's skin, which resembles the human cornea. In a pilot study, the implant restored vision to 20 people with diseased corneas, most of whom were blind prior to receiving the implant.

A study on the breakthrough – jointly led by researchers at Linköping University (LiU) and LinkoCare Life Sciences AB – is published this week in the journal Nature Biotechnology. The promising results bring hope to those suffering from corneal blindness and low vision by providing an alternative to the transplantation of donated human corneas, which are scarce in countries where the need for them is greatest.

"These results show that it is possible to develop a biomaterial that meets all the criteria for being used as human implants, which can be mass-produced and stored up to two years and thereby reach even more people with vision problems," explained Neil Lagali, Professor of Experimental Ophthalmology at LiU in southern Sweden. "This gets us around the problem of shortage of donated corneal tissue and access to other treatments for eye diseases."

 

cornea donation future timeline
Credit: Thor Balkhed

 

An estimated 12.7 million people around the world are blind due to damaged or destroyed corneas – the outermost, transparent layer of the eye. Their only way of regaining vision is to receive a transplanted cornea from a human donor. However, just one in 70 patients will receive a cornea transplant. Most of those who need treatment live in low and middle-income countries, in which access to healthcare is often very limited.

"Safety and effectiveness of the bioengineered implants have been the core of our work," said Mehrdad Rafat, Associate Professor of Tissue Engineering at LiU's Department of Biomedical Engineering who is also founder and CEO of LinkoCare Life Sciences AB, which manufactures the corneas used in this study.

"We've made significant efforts to ensure that our invention will be widely available and affordable by all and not just by the wealthy. That's why this technology can be used in all parts of the world."

A cornea consists mainly of the protein collagen. To create an alternative to human corneas, the researchers used collagen molecules derived from pig skin that were highly purified and produced under strict conditions for human use. The pig skin used is a byproduct of the food industry, making it easy to access and economically advantageous. In the process of constructing the implant, the researchers stabilised the loose collagen molecules, forming a robust and transparent material able to withstand handling and implantation in the eye. While donated corneas must be used within two weeks, the bioengineered corneas can be stored for up to two years before use.

 

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Credit: Blausen Medical (CC BY 3.0)

 

In addition, the researchers have developed a new, minimally invasive method for treating the disease keratoconus, in which the cornea becomes so thin that it can lead to blindness. Today, a keratoconus patient's cornea at advanced stage is surgically removed and replaced by a donated cornea, which is sewn into place using surgical sutures. This kind of surgery is invasive and only done at larger university hospitals.

"A less invasive method could be used in more hospitals, thereby helping more people," explained Professor Lagali. "With our method, the surgeon doesn't need to remove the patient's own tissue. Instead, a small incision is made, through which the implant is inserted into the existing cornea."

No stitches are needed following this new surgical method. An incision can be made with very high precision thanks to an advanced laser, but also, when needed, by hand with simple surgical instruments. First tested on pigs, it turned out to be simpler and safer than a conventional cornea transplant.

 

cornea donation future timeline
Femtosecond laser interface used for cutting the cornea. Credit: Thor Balkhed

 

Surgeons trialled the new method and implants on 20 patients in India and Iran – two countries where many people suffer from corneal blindness and low vision, but where donated corneas and treatment options are limited. Each patient, either blind or on the verge of losing sight due to advanced keratoconus, achieved a result free from complications; the tissue healed fast; and an eight-week treatment with immunosuppressive eye drops prevented rejection of the implant. Conventional cornea transplants require medicine to be taken for several years. After two years, none of the patients experienced any problems.

This pilot study had a main purpose of assessing safety. The implant not only met the required standards but actually surpassed expectations. All the participants' sight improved as much as it would have with tissue from human donors, while three of the 14 who had been blind prior to the study had perfect (20/20) vision after the operation. The research team observed both corneal thickness and curvature restored to normal.

A larger clinical study followed by market approval by regulatory authorities is needed before the implant can be used in healthcare. The researchers also want to verify if their technology can be used to treat other eye diseases, and whether it can be adapted to the individual for even greater efficacy.

 

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