BBC Science Focus
Off with my head!
The ‘organoids’ teared up as part of a study looking to stop dry eye diseases
Sea slugs lose their heads… but live on to grow new bodies
Researchers in the Netherlands have grown tear glands in a lab – and then made them cry. Don’t worry, this isn’t the result of evil scientists with too much time on their hands; the cluster of cells was created to help the researchers understand eye diseases.
Using stem cells and a cocktail of growth factors, experts at University Medical Centre Utrecht were able to build tear ‘organoids’ – a three-dimensional collection of cells designed to resemble miniature tear glands (also known as lacrimal glands). In order to mimic the wetness of the human eye, these organoids were suspended in liquid.
In humans, tear production is controlled by nerves which release neurotransmitters that trigger the secretion of tears. The scientists soon discovered that the glands reacted to the same neurotransmitters, but as the organoids lacked ducts to secrete the tears, they swelled up like balloons and some ruptured. Once transplanted into mice, however, the organoids eventually developed duct-like structures.
“Further experiments revealed that different cells in the tear gland make different components of tears. And these cells respond differently to tear-inducing stimuli,” said Dr Yorick Post, who took part in the project.
Tear glands aren’t only useful to convey emotions in humans, but they also lubricate the eye, providing a protective layer of liquid over the cornea. Unhealthy glands can therefore lead to serious medical problems.
“Dysfunction of the tear gland, for example in Sjögren’s syndrome, can have serious consequences, including dryness of the eye or even ulceration of the cornea. This can, in severe cases, lead to blindness,” said Dr Rachel Kalmann, ophthalmologist and researcher on the project.
It’s hoped the development of the tear organoids can help when it comes to testing new drugs and will enable scientists to understand how cancers in the gland form.
“Hopefully in the future, this type of organoid may even be transplantable to patients with non-functioning tear glands,” added PhD student Marie Bannier-Hélaouët, who worked on the project.
This isn’t the first time that sections of the eye have been sculpted using stem cells. In 2018, a team from Johns Hopkins University in the US grew human retinas to investigate how colour vision in humans developed.
“Hopefully in the future, this type of organoid may even be transplantable”