Nasal Epithelial Cells Grown in Culture Could Be Useful in CF Studies
Epithelial cells collected from the nasal passages and grown in the lab under a specialized protocol could be a useful model for studying the molecular underpinnings of cystic fibrosis (CF) and testing potential treatments, a study reported.
CF is caused by mutations in the gene CFTR, which codes for the CFTR protein. This protein normally acts like a gate on the surface of cells, controlling the movement of chloride ions (a type of salt) in and out of the cell. In CF, the CFTR protein is dysfunctional, though the extent varies depending on the specific type of CFTR mutation.
Human nasal epithelial (hNE) cells line the inside of the nasal cavity. These cells are quite similar to the cells that line the insides of the lungs, so they have been considered as a potential proxy for studying CFTR activity in the lungs, which may be useful for the development of precision therapies.
Use of nasal epithelial cells has historically been quite limited, because it is only possible to collect a small number of cells from the nose at a time, and no good techniques existed for growing these cells in lab. Recently, a method called conditional reprogramming — which involves treating the cells with a specific mixture of molecules and cell components — has made it easier to grow large numbers of these cells in a lab setting.
“Although conditionally reprogrammed hNE cells have great potential, it is unknown whether CFTR function in these hNE cells accurately reflects that of native hNE cells,” the researchers wrote.
A team led by scientists in France conducted a series of experiments on hNE cells collected from eight CF patients. Cells from five people without CF also were analyzed for comparison.
Freshly isolated cells from the two groups were compared with cells that had undergone conditional reprogramming.
Results showed that the activity and function of the CFTR protein were identical between freshly isolated hNE cells and conditionally reprogrammed hNE cells. Moreover, the flux of chloride ions did not differ between the two populations of hNE cells.
These data indicated that “conditional reprogramming culture is without effect on CFTR expression and function,” the researchers wrote.
The team then evaluated CFTR function using two methods: the sweat chloride test, a marker of CFTR dysfunction in the body that is commonly used to diagnose CF; and the nasal potential difference test, which measures the electrical potential difference, or small electrical charge, that occurs in the airway lining caused by the movement of ions through protein channels like CFTR.
In freshly isolated hNE cells, a lower CFTR function was significantly associated with higher levels of sweat chloride, while it was not significantly associated with nasal potential difference test results.
The “CFTR function measured in individual hNE cells in vitro … correlates well with that measured in primary cultures of hNE cells in vitro … but not that in the intact epithelium in vivo with the NPD assay,” the researchers wrote. (In vitro refers to tests in a lab dish or the like, while in vivo tests are those performed inside a living organism, like an animal model or a person.)
Overall, this finding “emphasizes the value of conditionally reprogrammed hNE cells in CFTR research and therapeutic testing,” the researchers concluded.