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Artificial cornea made of porcine collagen restores perfect vision to the blind

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More than 12 million people suffer from corneal blindness, making it one of the leading causes of blindness worldwide. Although this pathology can be treated with transplantation, the acute shortage of donor corneas makes it a burden, especially in low- and middle-income countries in Asia, Africa and the Middle East. Recently, Swedish researchers have developed an artificial cornea using collagen from pigskin. The implant represents a simpler and safer method than human cornea transplant while offering equivalent results. He has restored sight to several people, including three who now have 20/20 visual acuity after being virtually blind.

Keratoconus is a deformity of the cornea – the transparent covering of the iris and pupil of the eye – that gradually becomes thinner, loses its normal spherical shape and takes on an irregular cone shape. This deformity, often occurring towards the end of adolescence, causes vision problems—blurred and distorted vision and poor distance vision—that require special lenses to be worn. Keratoconus usually affects both eyes, but not with the same severity.

It is an idiopathic disease, that is, without a currently known cause. The main hypothesis is based on the possibility of excessive and abnormal degradation of collagen. The number of new cases diagnosed per year is equivalent to about 1/2000 inhabitants, making corneal loss one of the leading causes of blindness in the world.

Also, while corneal blindness can be treated with a transplant, approximately 12.7 million people worldwide are waiting for a corneal transplant, while there is only one cornea for every 70 people. In France, 5,436 corneal transplants were performed in 2019, according to the Biomedical Agency. However, most of those who need corneal transplants live in low- and middle-income countries where access to treatment is very limited. Keratoconus is a truly global burden.

Recently, Merdad Rafat of Linköping University in Sweden and colleagues developed an implant based on collagen proteins from pig skin. In a pilot study, the implant restored vision in 20 people with damaged corneas, most of whom were considered blind before the implant was placed. The results of their work are published in the journal Nature Biotechnology.

Profitable and recycled bio-implant

You should know that the cornea is mainly made up of collagen, a type of protein. Specifically, to create an alternative to the human cornea, the researchers used collagen molecules derived from highly purified porcine skin and produced under strict conditions for human use.

For a plentiful yet sustainable and profitable supply of collagen, pigskin is used, which is a by-product of the food industry. During the manufacturing process of the implant, the researchers stabilized the collagen molecules to form a transparent and durable implantable hydrogel that could withstand manipulation and implantation into the eye. While donor corneas must be used within two weeks, bioengineered corneas can be stored for up to two years before use.

Mehrdad Rafat, Senior Lecturer in LiU’s Biomedical Engineering Department and founder of LinkoCare Life Sciences AB, which manufactures the corneas used in the study, said in a statement: “We have made every effort to make our invention widely available and affordable. everyone, not just the rich. Therefore, this technology can be used in all regions of the world.”

New accessible surgical method

The second barrier to keratoconus treatment in low-income countries is the ability to access the care and supplies needed for transplantation. This is because the cornea of ​​a patient with advanced keratoconus is surgically removed and replaced with a donor cornea that is secured with surgical sutures. This type of surgery is invasive and is only performed in large teaching hospitals. In 2021, an artificial cornea has already been developed, but it still needs to be cut and sutured.

That’s why researchers have also developed a new technique for minimally invasive surgery. A small incision is made through which the implant is inserted into the existing cornea. The incision can be made with a high-precision laser and, if necessary, manually using simple surgical instruments. This new surgical method does not require sutures.

(a) Slit lamp photographs before surgery (left) and one day after surgery (right), with arrows indicating an immediate change in thickness and curvature in the central part of the cornea. (b) OCT scans showing persistent thickening and regularization of corneal curvature after implantation. © M. Rafat et al., 2022

This method was first tested in pigs and found to be simpler and potentially safer than a conventional corneal transplant. The researchers then tested it in Iran and India on 20 people who were blind or on the verge of losing their sight due to progressive keratoconus. The operations were simple, the tissues healed quickly. Eight weeks of treatment with immunosuppressive eye drops was enough to prevent implant rejection, while conventional corneal transplants have to take medication for several years. Patients were followed up for two years, no complications were noted during this period.

Hope for Perfect Vision Available to All

In the end, the researchers were surprised by their implant and its evolution. Surprisingly, the thickness and curvature of the cornea recovered to normal. Before surgery, 14 out of 20 participants became blind, the implant improved their vision to the extent that it would have been after a human cornea transplant, and restored contact lens tolerance. In addition, three of the participants who were blind prior to the study regained perfect vision (20/20) after surgery.

Before an implant can be used in healthcare, a larger clinical trial is required, followed by regulatory approval. The researchers also want to explore whether the technology can be used to treat other eye conditions. Indeed, despite the fact that the bioimplant is produced in only two thicknesses for experimental studies, the bioimplant can be adapted for individual treatment, including with uneven or tapered thickness.

Neil Lagali, professor in the Department of Biomedical and Clinical Sciences at Linköping University, one of the authors of the study, concludes: “The results show that it is possible to develop a biomaterial that meets all the criteria for use as a human implant. , which can be mass-produced and stored for up to two years and thus reach even more people with visual impairments. This allows us to bypass the problem of lack of corneal tissue for transplantation and access to other treatments for eye diseases.”

The Nature of Biotechnology

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