As the protective, outermost layer of the human eye, the cornea has an important role in focusing vision.

It is responsible for the transmission and refraction of incident light beams that are in turn focused onto the retina by the lens.

Yet there is a significant shortage of corneas available to transplant.

The World Health Organisation estimates that 10 million people worldwide require surgery to prevent corneal blindness as a result of trachoma, with a further 4.9 million suffering from total blindness due to corneal scarring.

The unmet clinical need for cornea donors has led to increasing effort in the development of artificial corneal substitutes, which must meet specific criteria if they are to functionally mimic the native cornea.

Newcastle University’s Professor Che Connon and colleagues examined the feasibility of generating artificial, biological corneas using pneumatic 3D extrusion bioprinting.

By creating a ‘bio-ink’ using human corneal stromal cells mixed together with alginate and collagen, the researchers were able to print the corneas using a simple low-cost 3D bioprinter.

The bio-ink was successfully extruded in concentric circles to form the shape of a human cornea. It took less than 10 min to print. The stromal cells were then shown to culture — or grow.

“Many teams across the world have been chasing the ideal bio-ink to make this process feasible,” Professor Connon said.

“Our unique gel keeps the stem cells alive whilst producing a material which is stiff enough to hold its shape but soft enough to be squeezed out the nozzle of a 3D printer.”

“This builds upon our previous work in which we kept cells alive for weeks at room temperature within a similar hydrogel.”

“Now we have a ready to use bio-ink containing stem cells allowing users to start printing tissues without having to worry about growing the cells separately.”

The scientists also demonstrated that they could build a cornea to match a patient’s unique specifications.

The dimensions of the printed tissue were originally taken from an actual cornea. By scanning a patient’s eye, the researchers could use the data to rapidly print a cornea which matched the size and shape.

“Our 3D printed corneas will now have to undergo further testing and it will be several years before we could be in the position where we are using them for transplants,” Professor Connon said.

“However, what we have shown is that it is feasible to print corneas using coordinates taken from a patient eye and that this approach has potential to combat the world-wide shortage.”

“We are delighted at the success of researchers at Newcastle University in developing 3D printing of corneas using human tissue,” said Dr. Neil Ebenezer, director of research, policy and innovation at Fight for Sight.

“This research highlights the significant progress that has been made in this area and this study is important in bringing us one step closer to reducing the need for donor corneas, which would positively impact some patients living with sight loss.”

A paper reporting this work will be published in the August 2018 issue of the journal Experimental Eye Research.

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Abigail Isaacson et al. 2018. 3D bioprinting of a corneal stroma equivalent. Experimental Eye Research 173: 188-193; doi: 10.1016/j.exer.2018.05.010

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