Researchers at the Francis Crick Institute and AlveoliX have developed the first human 'lung-on-chip' model using stem cells taken from only one person.
These chips simulate breathing motions and lung disease in an individual, holding promise for testing treatments for infections like tuberculosis (TB) and delivering personalised medicine.
Air sacs in the lungs called alveoli are the essential site of gas exchange and also an important barrier against inhaled viruses and bacteria that cause respiratory diseases like flu or TB.
Researchers have been working to recreate the battle between human cells and bacteria in the lab by building a 'lung-on-a-chip': small units of human lung on a plastic chip containing tiny channels and compartments. In this case, they aimed to recreate air sacs to understand how they respond to infection.
Until now, these 'lung-on-chip' devices have been made of a mixture of patient-derived and commercially available cells, meaning they can't fully replicate the lung function or disease progression of a single individual.
In a study published today in Science Advances, the team at the Crick developed a new lung-on-chip model that contains only genetically identical cells derived from stem cells from a single donor.
Based on a protocol developed previously by the lab, the team produced type I and II alveolar epithelial cells and vascular endothelial cells from human-induced pluripotent stem cells, cells that can virtually become any cell in the body. These epithelial and endothelial cells are separately grown on the top and bottom of a very thin membrane in a device manufactured by biotechnology company AlveoliX to recreate an air sac barrier.
To further simulate the human lung, AlveoliX has designed specialised machines to impose rhythmic three-dimensional stretching forces on the recreated air sac barrier, mimicking the motion of breathing. This stimulates the formation of microvilli, a key feature of alveolar epithelial cells to increase surface area for lung functions (image).
Next, the scientists added immune cells called macrophages into the chip, again produced from the stem cells of the same donor, before adding TB bacteria to simulate the early stages of the disease.
In the chips infected with TB, the team reported large macrophage clusters containing 'necrotic cores', a group of dead macrophages in the centre, surrounded by live macrophages. Eventually, five days after infection, the endothelial and epithelial cell barriers collapsed, showing that the air sac function had broken down.
Max Gutierrez, Principal Group Leader of the Host-Pathogen Interactions in Tuberculosis Laboratory at the Crick and senior author, said: "Given the increasing need for non-animal technologies, organ-on-chip approaches are becoming ever more important to recreate human systems, avoiding differences in lung anatomy, makeup of immune cells and disease development between animals and humans.
"Composed of entirely genetically identical cells, the chips could be built from stem cells from people with particular genetic mutations. This would allow us to understand how infections like TB will impact an individual and test the effectiveness of treatments like antibiotics."
Jakson Luk, Postdoctoral Fellow in the Host-Pathogen Interactions in Tuberculosis Laboratory and first author, said: "TB is a slow-moving disease, with months between infection and the development of symptoms, so there's an increasing need to understand what's happening in the unseen early stages.
"We were successfully able to mimic these initial events in TB progression, giving a holistic picture of how different lung cells respond to infections. We're excited that the new model could be applied to a huge range of research, such as other respiratory infections or lung cancer, and we're now looking at refining the chip by incorporating other important cell types."
