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Bodyless human tear glands crying sound like something out of a science fiction movie. But in the Netherlands, functional tear glands that do not attach to someone’s eyes (or emotions) play the leading role in their own real-life drama.
Researchers from the Hubrecht Institute and UMC Utrecht have used stem cells to grow tiny tear glands in a petri dish to mimic the real thing. They hope that these so-called organoids can serve as models to study how the cells in human tear glands produce tears. The ultimate goal: to better understand and treat conditions such as dry eyes or the autoimmune disease Sjogren’s syndrome and cancers of the lacrimal gland.
“Hopefully, this type of organoid can even be transplanted to patients with non-functioning lacrimal glands in the future,” said Marie Bannier-Hélaouët, a PhD student at the Hubrecht Institute for developmental biology and stem cell research. She co-authored a study published Tuesday in the journal Cell Stem Cell detailing the project.
Organoids are built in vitro, in 3D suspension, from a small number of stem cells that eventually multiply to form something that resembles a real organ, such as a mini-brain, bladder or, in this case, the glands in the upper eyelid. .
Tear or tear glands continuously supply fluid that is swept across the surface of the eye every time we blink and then drained into tiny holes in the corners of our upper and lower lids before passing through our tear ducts to the nose. In addition to showing emotion, the fluid is essential for eye health, lubricating the cornea and helping to ward off bacteria. Dysfunction of the lacrimal gland can be annoying and cause scratching, stinging or burning sensations and sensitivity to light. But it can also be serious and in the most severe cases lead to corneal abrasions or ulceration, or even blindness.
Lacrimal glands are made up of different types of cells. The lab-grown glands from the Netherlands consist of only one type, ductal, and cry in response to chemical stimuli such as norepinephrine, a neurotransmitter that sends a message from our neurons to our tear glands.
The cells shed tears on the inside of the organoid, causing it to swell.
Marie Bannier-Hélaouët / Hubrecht Institute
“Our eyes are always wet, just like the tear glands in a shell,” says Bannier-Hélaouët of the artificial glands. Bannier-Hélaouët works in molecular biologist Hans Clevers’ laboratory, which focuses on making organoids for disease modeling and has previously recreated snake venom and tear glands in mice.
It’s not like walking into Clevers’s laboratory and seeing large teardrop-shaped droplets floating in jars. The cells shed tears on the inside of the organoid called the lumen. This causes the organoid to swell like a balloon, with its size indicating how much tear production and secretion is going on.
This isn’t the first time scientists have made human eye components from stem cells. In 2018, a team at John Hopkins University created eyeball components in the hope of better understanding how and why we developed “trichromatic vision” – the ability to see in red, blue, and green.
The Dutch researchers recognize the limitations of their lacrimal gland, as it consists of only one of the main cell types found in the gland. They say they would eventually like to grow a full lacrimal gland from the wider array of cells that make up it, giving them an even better understanding of how we form tears.