Mimicking the environment experienced by cells in the windpipe is enough to transform stem cells into a range of different lung cells. Such 鈥減hysical鈥� techniques could be used to create specialised tissues when growth factors alone aren鈥檛 enough.
of the Free University of Brussels (VUB) in Belgium and colleagues spread human embryonic stem cells onto a porous membrane. The cells were fed from beneath by nutrients and from above by a fluid that encouraged them to multiply. Removing two chemicals from the growth fluid kickstarted differentiation.
Four days later, the team removed the fluid covering the cells, leaving them open to the air while still being sustained and supported from below, as they would be in the trachea. After 24 days the cells had developed surface proteins that identified them as specific types of lung cell, including alveolar cells, which allow the exchange of gases, and cilia, which expel bacteria and dirt.
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Physical influence
鈥淥ur study proves differentiation into lung cells is influenced by physical forces,鈥� says Van Haute. Previously, stem cells have been made to differentiate into lung cells using a cocktail of different growth factors, but Haute says using physical forces might be simpler.
鈥淧hysical forces are certainly a factor in getting the lung lining to be fully functional,鈥� says at Imperial College London, who has made alveolar cells from mouse stem cells using growth factors alone. 鈥淏ut I find it difficult to believe that raw stem cells would differentiate through to these uncommon types of cells solely in response to physical forces.鈥�
Haute鈥檚 team plans to use the cells they created to study lung diseases, such as cystic fibrosis. Such cells might one day be used to treat people with damaged lung tissue, but only if the cells can be made from a person鈥檚 own tissue. This could be done by converting the cells first into induced pluripotent stem cells.
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