Anyone who becomes blind due to a disease of the cornea of the eye has so far had to rely on a cornea transplant from a deceased human donor. But donor corneas are rare and transplantation is complicated. Researchers have now developed a possible alternative: They have developed an implant from pig skin collagen proteins that is cheap to produce and can be inserted into the eye using a minimally invasive procedure. In a pilot study, the implant restored sight to 20 people with corneal diseases.
Diseases of the cornea, the outermost layer of the eye, are among the most common causes of blindness worldwide. Around 12.7 million people are affected worldwide. So far, the only way to regain sight is through a cornea transplant from a human donor – but due to the shortage of donor corneas, only about 1 in 70 patients receive a transplant. In addition, many of those affected live in low- and middle-income countries where access to treatment is limited.
Biomaterial based on pig skin
A team led by Mehrdad Rafat from Linköping University in Sweden has set itself the goal of making corneal implants available to more people around the world. They have now successfully tested the result of their work in a pilot study: a bioengineered corneal implant that uses collagen proteins from pig skin as the starting material. In order to create a functional artificial cornea for human eyes from the pig skin, the collagen molecules it contains are purified and compressed, resulting in a robust and at the same time sufficiently flexible, transparent material.
“The safety and effectiveness of the bioengineered implants were the focus of our work,” says Rafat. “We have made significant efforts to ensure that our invention is widely available and affordable for everyone, not just the affluent. Therefore, this technology can be used in all parts of the world.” As a by-product of the food industry, pig skin is easily and inexpensively available. The corneas made from it also have the advantage that they can be stored for two years without any loss of quality. A human donor cornea, on the other hand, has to be transplanted within two weeks.
Safe, effective and widely available
“The results show that it is possible to develop a biomaterial that meets all the criteria for use as a human implant that can be mass-produced and stored for up to two years, reaching even more people with vision problems. In this way we circumvent the problem of the lack of donated corneal tissue and the difficult access to other treatment options for eye diseases,” says Rafat’s colleague Neil Lagali. So that people in countries with little developed medical care can actually benefit from the implants, the researchers also developed a new, minimally invasive method for treating a common corneal disease called keratoconus. The cornea becomes thinner and bulges, so that those affected initially only see blurred and eventually go blind.
In previous treatment, the patient’s cornea is surgically removed and replaced with a donated cornea that is attached with surgical sutures. This type of surgery is invasive and only performed in larger university hospitals. “A less invasive method could be used in more hospitals and help more people. With our method, the surgeon does not have to remove the patient’s own tissue. Instead, a small incision is made through which the implant is inserted into the existing cornea,” explains Lagali. No sutures are required and the incision can be made with either an advanced precision laser or simple surgical tools, depending on the tools available.
Implant restores sight to 20 people
After successful tests in the animal model, the researchers started a pilot study. In India and Iran, two countries where many people suffer from corneal blindness, surgeons used the new method to insert the biotechnical implant into 20 blind or visually impaired people. As the researchers report, the operations were uneventful. The tissue healed quickly and eight weeks of treatment with immunosuppressive eye drops was sufficient to prevent implant rejection. With conventional corneal transplants, the drugs have to be taken for several years. “Within two years of follow-up, we found no complications,” the authors write.
The vision of the participants in the pilot study improved as much as would be expected after a classic corneal transplant. All 20 test persons regained their sight, some of them even completely, some of them additionally supported by glasses or contact lenses. “This work demonstrates that vision restoration is possible with an approach that is potentially as effective, safer, easier and more widely available than transplanting donor corneas,” the researchers said. Before the implant can be used in healthcare, a larger clinical study with subsequent market approval by the regulatory authorities is required. The researchers also want to investigate whether the technology can be used to treat other eye diseases and whether the implant can be customized for even greater effectiveness.
Source: Mehrdad Rafat (LinkoCare Life Sciences AB and Linköping University, Sweden) et al., Nature Biotechnology, doi: 10.1038/s41587-022-01408-w