posted on 08/12/2022 06:00
(credit: Thor Balkhed/LinkÃ¶ping University)
Worldwide, an estimated 12.7 million people are on the waiting list for a corneal transplant, the outermost transparent layer of the eye. Demand, however, is high in several parts of the globe, with 70 patients for each donor. In the search for an alternative, researchers at the University of Linköping, Sweden, developed a biomaterial made from collagen from pig skin. In a pilot study published yesterday in the journal Nature Biotechnology, scientists reported that the implant is safe and has successfully restored the sight of 20 volunteers, most of whom could no longer see.
According to the researchers, despite the efforts of science in the area of tissue bioengineering for corneal transplantation, to date there have been no significant advances. At the same time, demand continues to grow, with more than 1 million more cases per year of blindness caused by illness or injury to this part of the body.
One of the main indications for transplantation is keratoconus, a progressive disease whose causes are still not well understood. In these cases, thinning and curvature of the cornea occurs, which, if treated early, can prevent blindness. However, therapies are not always able to make the disease stabilize and, in these cases, the patient can become blind.
In Linköping’s study, the scientists used the main material of the cornea: collagen. However, in this case, they invested in protein molecules derived from the epidermis of pigs, which underwent a purification process for use in humans. The researchers note that swine skin is a by-product of the food industry, which makes it an economically viable and easily accessible input.
The loose collagen molecules were stabilized and aggregated into a clear, firm material resistant to manipulation and implantation in the eye. In addition to transplantation, the researchers used the material to treat, in a minimally invasive way, non-blind patients with advanced keratoconus.
The technology, according to them, does not require the use of stitches and can be performed with simple surgical instruments. “A less invasive method could be used in more hospitals, thus helping more people,” noted, in a note, the leader of the group of scientists, Neil Lagali. “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 is inserted into the existing cornea,” he says.
The surgical method and implants were tested by surgeons in Iran and India, two countries where many people suffer from corneal blindness and low vision, and where there is also a huge shortage of donated corneas and treatment options. Twenty people who were blind or about to lose their sight due to advanced keratoconus participated in the clinical study and received the implantation of the biomaterial.
The operations did not result in complications; the tissue healed quickly; and an eight-week course of immunosuppressive eye drops was sufficient to prevent implant rejection, the researchers said. Patients were followed for two years and no complications were observed during this period. But, in addition to safety, the scientists said they were surprised by the effectiveness of the surgery.
Corneal thickness and curvature were restored to normal and participants’ vision improved as much as after a corneal transplant with donated tissue. Before the operation, 14 of the 20 volunteers were blind. After two years, everyone could see, and three of them had perfect vision, confirmed by exams. “The results show that it is possible to develop a biomaterial that meets all the criteria to be used as a human implant, which can be mass produced and stored for up to two years and thus reach even more people with vision problems. helps to overcome the problem of scarcity of donated corneal tissue and access to other treatments for eye diseases”, says Lagali.
“The main objective of any keratoconus treatment is to try to stabilize the patient’s cornea and make it have an improvement in symmetry”, says the ophthalmologist at Visão Hospital de Olhos Gustavo Serra, a specialist in corneal diseases. According to him, it is possible to treat patients in several ways, starting with the use of glasses and lenses and going through other processes, such as the implantation of a ring-shaped device to improve the asymmetry of the cornea. “Unfortunately, in some cases, the disease continues to evolve,” he says.
For Serra, the Linköping University experiment can benefit patients who need the transplant, but cannot get a donation. The specialist, however, points out that the study was small and with a limited number of patients. “Furthermore, two years of follow-up is not enough”, he says. According to the authors of the research, a more comprehensive analysis is needed before the biomaterial is available on a large scale.
three questions for
Maria Regina Chalita, associate professor at the Faculty of Medicine of the University of Brasília (UnB) and ophthalmologist at the CBV-Hospital de Olhos
credit: personal archive
Today, how is keratoconus treated?
Keratoconus is a disease where the cornea begins to thin and bulge, causing low vision and irregular astigmatism. The main treatments are conservative. We start with glasses. When the patient can no longer wear the glasses, we move on to the contact lens. When vision does not improve with the lens, we can try intracorneal rings, which are implants made inside the cornea to reduce the curvature of the keratoconus, and, only really in very advanced cases, will we recommend corneal transplantation. There is another treatment for progressing keratoconus, when the disease is advancing, which is corneal crosslinking, where we use vitamin B2 or riboflavin in the form of eye drops, along with an ultraviolet light, to strengthen the cornea, slowing or stopping the progression. of keratoconus.
What are the main limitations of the treatments available?
Considering corneal transplantation, the main limiting factor is the difficulty of obtaining corneal tissue in several countries. There are places like the United States, Europe, where we have practically no queue for corneal transplants, there is a greater supply than demand. However, we have other places, like Africa, Asia and the Middle East, where there is a very big need, and patients take years to get a donation. Here in Brazil, this varies a little between different regions. In the Federal District, the average wait is around six to eight months. But there are some states where there is practically no queue.
Does the scientists’ approach look promising?
It looks very promising. This study shows another model of what we call the artificial cornea. In fact, it is a material derived from pigs, where collagen is taken from the dermis of these animals and transformed into a biomaterial compatible with the human cornea. As we know that in keratoconus the cornea is thinner, a graft of this biomaterial is placed to try to increase the thickness of the cornea and decrease its curvature. With this, it is expected to improve the visual acuity of the patient. In the study, researchers evaluated 20 eyes and had promising results in these cases.