Kamal Ghorui
For every 70 people losing sight to corneal blindness, only one donor tissue is available worldwide. And in India, where around 1 lakh new corneal transplants are needed annually, only 30,000 can be provided. Currently, corneal transplants rely entirely on donated corneas from cadavers, but demand far outstrips supply. Researchers hope to bridge that gap with a bioengineered cornea that a team from Postgraduate Institute of Medical Education and Research (PGIMER), Chandigarh has designed. These scientists have used the corneoscleral rim, a ring-shaped piece of tissue left behind after surgeons remove the diseased cornea from a patient’s eye during keratoplasty (corneal transplant). Usually discarded, this rim contains stem cells and other corneal cells that make it a powerful biological template. “People worldwide are trying to make artificial corneas, but our novelty lies in the fact that we’ve used something that surgeons reject as waste,” says Manni Luthra-Guptasarma, principal investigator and professor at PGIMER’s immunopathology department. Scientists placed the discarded corneoscleral rim in a dish to be used as a ‘mould’ into which they poured collagen, a natural protein found abundantly in the eye. The collagen, guided by the rim, formed a gel-like structure within the area that would normally be the transparent cornea, while the rest of the collagen remained more fluid. “It happened by serendipity. We put the collagen to tease cells out of the rim. My student, researcher Maryada Sharma, lifted it the next day and saw the rim had actually hosted, and possibly nucleated, the polymerisation of a cornea-like object itself,” adds Luthra-Guptasarma. This transparent structure resembled a native cornea, complete with its natural curvature and thickness. The bioengineered cornea, initially termed “cornea-like material”, underwent rigorous tests to confirm viability. It allowed light to pass through it just as it would through a human cornea. Its thickness matched that of a native cornea, and it transmitted light across the UV-visible spectrum in a manner similar to a natural cornea. Scanning electron microscopy (imaging technique that scans sample surfaces with a focused electron beam) revealed that the collagen network within the artificial cornea mirrored the intricate structure of a natural cornea, and it integrated well with the surrounding rim, essential for nutrient supply. However, they needed to improve its tensile strength (ability to withstand pulling forces) for surgical handling. So, the team introduced riboflavin (vitamin B2) and exposed the collagen to UV-A light which helps create stronger bonds within the collagen network. To make it more like natural tissue, living corneal cells were added to the developing cornea’s surface, promoting a more complex, multi-layered structure. Called “cornea-like tissue” or CLT, this version was more rigid, and easier to handle. A natural cornea is about 96-97% water, even though it’s primarily made of collagen. The bioengineered CLT astonishingly achieved the same high water content, despite being made with a much lower collagen concentration. So, the discarded rim plays a crucial role in directing the collagen’s natural remodelling. The study has been published in Molecular Biology Reports, and the scientists have been granted an Indian patent. The Indian Council of Medical Research (ICMR) has also sanctioned a three-year grant for animal trials. Dr Virender Sangwan, ophthalmologist and former director at the LV Prasad Eye Institute, Hyderabad who has been involved in bioengineered cornea research since 2011, points out that this technology is most cost-effective and doesn’t even need animal trials. “In a standard corneal transplant, surgeons use a central disc of tissue (typically 7.5 mm to 8.5 mm in diameter) from a donor cornea that measures roughly 12 mm in total. The rim is left over. This technology uses that rim as a natural mould to make corneas, guided by nature’s own creation,” he says, adding that a single donor rim can potentially serve as a scaffold multiple times, supplementing the existing eye bank system rather than trying to replace it.
