Scientists have developed mini-lung models in the lab, infected these with SARS-CoV-2, and watched the battle between the lung cells and the virus.
The novel coronavirus is known to attack primarily the lungs, but how the attack unfolds is still a subject of research.
- In both studies, scientists observed how the virus damages the alveoli in the lungs. Alveoli are balloon-like air sacs that take up the oxygen we breathe and release the carbon dioxide we exhale.
- Damage to alveoli causes pneumonia and acute respiratory distress, the leading cause of death in Covid-19.
- Both teams developed the model using “mini-lungs” or lung organoids. The organoids were grown from the stem cells that repair the deepest portions of the lungs where SARS-CoV-2 attacks. These are called AT2 cells.
- The team got a single lung cell to multiply into thousands of copies and create a structure that resembles breathing tissues of the human lung. Once infected with the virus, the model showed an inflammatory response.
- The team reprogramed the AT2 cells back to their earlier “stem cell” stage. They grew self-organising, alveolar-like 3D structures that mimic the behaviour of key lung tissue. When the 3D models were exposed to SARS-CoV-2, the virus began to replicate rapidly.
- In six hours, cells began to produce interferons, proteins that act as warning signals to neighbouring cells. After 48 hours, the cells started fighting back.
- And after 60 hours from infection, some of the alveolar cells began to disintegrate, leading to cell death and damage to the tissue.
- The team also witnessed the cytokine storm, the hyper reaction of immune molecules the lungs launch to fight the infection.