1st model of human eye tissue makes ‘tears in a dish’

London : A team of researchers from the Netherlands has developed the first organoid model of the human conjunctiva, a tissue involved in tear production.

Our eyes produce tears to protect themselves from injuries and infections. The conjunctiva, a tissue that covers the white of the eye and the inside of the eyelids, is partially responsible for the production of these tears through the release of mucus.

This mucus allows the tears to stick to the ocular surface and protects it from pathogens. In the study, published in the journal Cell Stem Cell, the team used cells from an actual human conjunctiva and grew them into 3D structures in a dish. These miniature structures are called organoids and function as real human conjunctiva.

"Once we had these functioning organoids, we wanted to know how the conjunctiva is involved in the production of tears," said lead researcher Marie Bannier-Helaouet, from the Organoid group at the Hubrecht Institute in Netherlands.

"We discovered that the conjunctiva makes antimicrobial components and therefore contributes to tear production in more ways than by simply making mucus," she added. The researchers then altered the conditions in the dish with the miniature conjunctivae to mimic allergies.

"The organoids started to produce completely different tears: There was more mucus but there were also more antimicrobial components," said Bannier-Helaouet. Under these conditions, they also found a new cell type in the organoids: Tuft cells.

"Similar cells have been discovered in other tissues, but not in the human conjunctiva." The tuft cells became more abundant under the allergy-like conditions, suggesting they play a role in the eye's reaction to allergies.

Several diseases and disorders affect the conjunctiva, such as dry eye disease, cancer, allergies and infections. In severe cases, dysfunction of this conjunctiva tissue can also lead to blindness.

The newly-developed organoid model opens the door for research into diseases affecting the conjunctiva. "We can use our model to test drugs for allergies or dry eye disease, for example," Bannier-Helaouet said.

In the long term, it may even be possible to make replacement conjunctivae for people with ocular burns, ocular cancers or maybe even genetic disorders. "We are now running preclinical studies in rabbits to assess whether this approach is feasible and helpful," Bannier-Helaouet said.