Researchers from the Hubrecht Institute and UMC Utrecht recently used stem cells to grow tiny disembodied tear glands in a petri dish. As detailed in a study published in the journal Cell Stem Cell, the researchers are able to make the so-called organoids cry on command.
They hope that by better understanding the way cells in human tear glands produce tears, they might be able to treat eye conditions including dry eye disease, as well as cancers of the tear gland.
"Hopefully in the future, this type of organoid may even be transplantable to patients with nonfunctioning tear glands," Marie Bannier-Hélaouët, a doctoral candidate at the Hubrecht Institute for developmental biology and stem cell research, explained in a press release.
The organoids are built in vitro, in 3D suspension, from stem cells that multiply to form tear glands, which are located inside the upper eyelid. These glands don't only supply fluid when we cry — a continuous supply of liquid is crucial to our eye health, as it lubricates the cornea and wards off bacteria. In the most serious of cases, tear duct dysfunction can lead to blindness.
Studying the intricacies of the eye
The lab-grown tear glands developed in the Netherlands are made of one type of human tear gland cell, called ductal. It allows the gland to cry in response to chemical stimuli such as noradrenaline, a neurotransmitter that sends a message from our neurons to our tear glands.
"Our eyes are always wet, as are the tear glands in a dish," Bannier-Hélaouët says. The cells shed tears on the inside of the organoid, called the lumen. This causes it to swell up like a balloon. The researchers use the size of the gland as an indicator for tear production.
As CNET points out, this isn't the first time scientist have created human eye parts using stem cells — a 2018 John Hopkins University team created eyeball parts to study how we developed "trichromatic vision" — the ability to see in red, blue, and green.
The Dutch researchers say they would like to eventually grow tear glands out of a wider array of cells. By doing so, they would gain a deeper understanding of what it is that makes us cry, and how it's integral to our eye health.