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Physical human tear glands crying sound like something out of a sci-fi movie. But in the Netherlands, functional tear glands that do not cling to someone’s eyes (or emotions) play into their own real drama.
Researchers from the Hubrecht Institute and UMC Utrecht used stem cells to grow small tear glands in a petri dish that mimics the real thing. They hope that these so-called organoids can serve as models to study how the cells in human lacrimal glands produce tears. The ultimate goal: to better understand and treat conditions such as dry eye diseases or the autoimmune disorder Sjögren syndrome, as well as lacrimal gland cancer.
“Hopefully, in the future, these types of organoids can even be transplanted into patients with non-functioning tear glands,” says Marie Bannier-Hélaouët, a doctoral candidate at the Hubrecht Institute for Developmental Biology and stem cell research. She was co-author of a study published Tuesday in the journal Cell Stem Cell, outlining the project.
Organoids are built in vitro, in 3D suspension, from a small number of stem cells that eventually multiply to form something that looks like a real organ, such as a mini-brain, bladder or, in this case, the glands in the upper eyelid. .
Tears, or lacrimal glands, constantly produce fluid that wipes across the surface of the eye each time we blink and then drains into small holes in the corners of our upper and lower lids before moving through our tear ducts to the nose. In addition to emotion, the fluid is essential for the health of the eye, it lubricates the cornea and helps repel bacteria. Tear gland dysfunction can be irritating, which can cause scratching, stinging or burning sensations and sensitivity to light. But it can also be serious, which in the most severe cases can lead to abrasions or ulcers or even blindness.
Tear glands consist of different types of cells. The laboratory-grown glands from the Netherlands consist of only one species, tube, and cry in response to chemical stimuli such as noradrenaline, a neurotransmitter that sends a message from our neurons to our lacrimal 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 dish,” says Bannier-Hélaouët about the artificial glands. Bannier-Hélaouët works in the laboratory of molecular biologist Hans Clevers, which focuses on creating organoids for modeling diseases, and has snake venom glands and mice that previously recreated tear glands.
It’s not like you walk into Clevers’ lab and see large teardrop-shaped droplets floating in pots. The cells shed tears on the inside of the organoid, called the lumen. It causes the organoid to swell like a balloon, with the size indicating how much tear production and secretion is going on.
This is not the first time that scientists have created human eye components from stem cells. In 2018, a team from John Hopkins University created eyeball parts in hopes of better understanding how and why we developed ‘trichromatic vision’ – the ability to see in red, blue and green.
The Dutch researchers acknowledge the limitations on their lacrimal gland, as it consists of only one of the most important cell types found in the gland. They say they want to eventually grow a full lacrimal gland from the wider range of cells that make it up, which gives us a better understanding of how our tears form.