- In a first-of-its-kind experiment, scientists grew human tear glands in the lab and tried to make them cry
- They succeeded, and said the results could help with developing treatments for tear gland disorders, such as 'dry eye'
- Going forward, they will study structures resembling tear glands in crocodiles
Crying has incredible health benefits, thanks to the release of feel-good chemicals, or endorphins, easing both our physical and emotional pain. In fact, it is “an important safety valve”, notes Harvard Health, because keeping feelings – happy or sad – inside can be bad for our health. Unfortunately, for some people, shedding emotional tears is impossible due to dry eye disorders.
However, new research, reported in Cell Stem Cell, offers a glimmer of hope for these individuals. In a first-ever study, a team of researchers grew tear glands from human stem cells in a dish and induced them to produce tears – an exceptional triumph which could be a huge step towards assisting scientists with developing treatments for people with tear-gland disorders (dry eye disease).
Tear glands, medically known as "lacrimal glands", are located above each eyeball. They are the organs responsible for keeping our eyes lubricated and protecting them against infections.
In some people, however, the tear glands don’t function properly, and can lead to their eyes feeling itchy or sore – a disease known as “dry eye”. According to the authors, dry eye occurs in at least 5% of the adult population worldwide.
Although treatments for these conditions do exist, such as eye drops, they are limited. This is largely because studies of this disease were hindered by the lack of a good human tear gland model, which they, therefore, decided to establish.
During the study, getting these tear glands to weep initially took up to a day, but with further experience and persistence, they managed to succeed in half an hour. So how did they do it?
“Most organs in the adult human body are capable of regeneration, which means they renew their cells to keep the tissue healthy and functional,” study co-authors, Marie Bannier-Hélaouët, PhD Student, Hubrecht Institute, and molecular geneticist Professor Hans Clevers, both based at Utrecht University in the Netherlands, wrote in an article for The Conversation.
This capacity of regeneration is made possible through adult stem cells, which are present in most organs. In essence, these stem cells divide in order to create new cells that replace older, damaged ones, they explained.
The team obtained tear gland samples from a hospital, and processed them into small pieces. Isolating and growing the stem cells in the lab resulted in the forming of tiny, three-dimensional (3D) replicas of the organs from which they were extracted to resemble miniature versions of organs, known as “organoids”.
Together with their colleague Yorick Post, they produced a human tear gland organoid, which they then managed to make cry organoid tears – “not by being nasty, of course”, they jested.
Instead, what they did was subject the organoid to adrenaline, the fight-or-flight hormone released in response to a stressful, exciting, or threatening situation, and when humans are subjected to pain.
Mice tear glands also involved
The team also wanted to test the possibility of using tear gland organoids for transplantation. To do this, they took some of their human lacrimal cells, and transplanted them into the lacrimal glands of four mice.
Within just two weeks, the cells were grafted and integrated into the gland, and were forming duct structures. A more noteworthy finding was that that they remained in the gland for at least two months, and some of the human cells continued to grow and divide two months later – to the point that they produced tear proteins.
The tearful cultures are described as the first tear-gland organoids in the world.
"We hope that scientists will use our model to identify new treatment options for patients with tear-gland disorders by either testing new drugs on a patient's organoids or expanding healthy cells and, one day, using them for transplantation [into human patients]," said Clevers.
According to their article, Clevers’ lab will be teaming up with Dutch naturalist and television-show host Freek Vonk to study structures resembling tear glands in crocodiles. “One other tissue we have our eye on is the tear gland of a crocodile – which is remarkably similar to human tear glands, but with some interesting differences.
"One day soon we may grow crocodile tear gland organoids in our lab, producing “crocodile tears” in the clinical environment of a Petri dish for the very first time,” they wrote.