The disembodied human tear glands, grown in Petri dishes in a laboratory in the Netherlands, have the ability to cry – and the scientists who created them have already grafted them into the eyes of living mice.
The series of experiments, detailed in a new study published online March 16 in the journal Cell Stem Cell, can represent a major breakthrough in the science of treating dry eye – a condition that affects about 5% of adults worldwide and can lead to blindness in severe cases.
Petri dish body parts have become more common in laboratory experiments, but are generally much smaller and simpler than their natural counterparts. “Minibrains”, for example, are unconscious organoids the size of smooth peas that resemble only vaguely the original organs, Live Science reported. The lacrimal glands in the Petri dish, however, were very close to reality, according to Marie Bannier-Hélaouët, co-lead author of the study and a researcher at the Hubrecht Institute in Utrecht, The Netherlands.
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Human tear glands, Bannier-Hélaouët told Live Science, have two components: acinar cells and ductal cells.
“Both can cause tears, but the duct cells have an additional function: they act as a channel to bring tears to the surface of the eye. [lab-made] The organoids look like this channel, “she said.” The difference is that, as there is no eye on the plate to bring tears, the organoids look like a dead end channel. They are balloons. “
These balloons are similar in size to what you would find in a human being, growing to about a hundredth of an inch (half a millimeter) in width.
The researchers divided the study into three experiments. In the first, they developed human tear glands in petri dishes and caused them to produce tears.
Cultivating organoids was one thing, said Bannier-Hélaouët. Making them cry was another, as it involves brain chemicals called neurotransmitters.
“Preparing the perfect cocktail [of neurotransmitters] making organoids cry was the most challenging part. It took me about three or four months and about seven to 10 tests, “she said.” What is surprising is that this final cocktail contains very few ingredients. One is simply an antioxidant molecule. “
After perfecting the cocktail, the researchers observed the glands swelling with tears that had nowhere to go.
Then, they implanted some of these lab-made glands into the tear ducts of live mice. They found that implanted human cells could still produce tears, but they did not release them into the ducts as normal glands would. In the end, she said, it will be important to find out how to make the glands act normally in the live tear ducts.
“We already have ideas on how to do this,” said Bannier-Hélaouët.
In the final part of the study, the researchers focused on identifying the origin of a form of chronic dry eye known as Sjogren’s syndrome, an autoimmune disease that also causes dry mouth.
In Petri dishes, the researchers cultured the lacrimal glands of mice that were modified with gene editing technology to not express a gene known as Pax6. The researchers had previously established that people with dry eye often lack Pax6 in the eye tissue and that the gene plays an important role in the development of the eye. The experiment showed that the organoids of mice modified to not have Pax6 produced fewer tears, reinforcing the idea that the gene is linked to the medical problem.
Originally published on Live Science.