A clinical trial restored sight to 20 people with corneas made from an unlikely source

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Pigskin implants have restored sight to 20 people with diseased corneas, in an exciting pilot clinical trial. Many of the patients were blind before being helped by this bioengineered tissue.

Incredibly, after two years, all 14 blind people had their vision back and three of them, and three of them now have perfect 20/20 vision.

“This brings us around the problem of [a] shortage of donated corneal tissue and access to other treatments for eye diseases,” says Neil Lagali, ophthalmology researcher at Linköping University.

While around 12.7 million people suffer from vision loss due to problems with their corneas, only 1 in 70 manage to receive a cornea transplant, the only way to restore their vision.

Because the means to provide these transplants are expensive and donated corneas are in short supply, most people in the world do not have access to effective treatment.

“We have made significant efforts to ensure that our invention is widely available and affordable for everyone and not just the rich. That is why this technology can be used in all parts of the world,” says the biomedical engineer from Linköping University. Mehrdad Rafat.

To accomplish this, Rafat and his colleagues developed a new technique that does not require stitches so that doctors can perform the implant procedure with less specialized conditions and equipment.

“A less invasive method could be used in more hospitals, thus helping more people. With our method, the surgeon does not need to remove the patient’s own tissue. Instead, a small incision is made through which the implant into the existing cornea,” explains Lagali.

Furthermore, the material used to create the implant is a by-product of the food industry, and thanks to specially developed packaging and sterilization processes, the final product can be stored for up to two years. In contrast, donated human corneas must be used within two weeks.

Our cornea, the transparent screen over the front of our eye that protects the iris and pupil, is mainly made up of different types of collagen. This structure can gradually thin over time, causing it to bulge out and distort our vision in a condition called keratoconus.

While the exact cause of this thinning is not known, genetics, vigorous eye rubbing, and conditions such as hay fever, asthma, Down syndrome, and Ehlers-Danlos syndrome can increase your chances of developing keratoconus .

The researchers then purified collagen from pig skin to create a new layer of cornea. They used chemical and photochemical methods to strengthen this usually soft material, making it more stable, resulting in a hydrogel they called bioengineered porcine construct, double cross-linked (BPCDX).

Changes in the thickness of the cornea with arrows indicating the contour of the implant after the operation (bottom). (Rafat et al., Nature Biotechnology2022)

Refining their techniques in animal models, the researchers developed a simple method to insert BPCDX into the recipient’s cornea, eliminating the need to remove existing tissue.

Here, the implant flattens the warped cornea and provides lost thickness, repairing the eye’s ability to focus.

Minimally invasive surgery leaves the corneal nerves and cell layers intact, allowing the wound to heal quickly.

After implantation through a 2-millimeter incision, the BPCDX was successfully kept transparent. There was no scar formation or adverse reactions, and no further intensive therapy or surgery was required; just an eight-week course of immunosuppressive eye drops and a bandage.

The bioengineered cornea checked all the safety boxes.

After two years, the participants from Iran and India experienced an average increase of more than 200 micrometers in the thickness of their cornea and a decrease in its curvature, improving their vision at least to the extent of traditional cornea transplants.

Biomaterial implants previously tried in the eye ended up thinning out, but the fortified pig cell collagen remained strong and kept the implant stable, even after eight years, the team reported based on their previous studies and unpublished data. .

“To our knowledge, no previous study has achieved complete corneal transparency in vivo with sufficient corneal thickening and flattening, or with significant visual acuity gains as reported here,” the researchers wrote in their paper.

A larger clinical trial is now being planned, but if the pilot is any indication, the researchers are hopeful of additional promising results that will help the new procedure meet regulatory approvals.

“The results show that it is possible to develop a biomaterial that meets all the criteria to be used as human implants, that can be mass-produced and stored for up to two years and thus reach more people with vision problems,” concludes Lagali.

This research was published in Nature Biotechnology.

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