Objective: To study mucus secretion and aquaporin-5 (AQP5) expression of bronchial epithelium cultured at the air-liquid interface of hypotonic medium, and to elucidate the role of AQP5 and osmotic pressure in airway mucus hypersecretion process.
Methods: With the air-liquid interface culture model, rabbit tracheal epithelium was cultured at the air-liquid interface. One week after culture, media of 235, 255 and 270 mmol/L were used for experimental groups, and that of 282 mmol/L for culture in control group. Twelve hours after the culture, reverse transcriptase polymerase chain reaction (RT-PCR) was used to detect AQP5 mRNA in each experimental group, and Western blotting to determine mucin5AC (MUC5AC) in the supernatant. The same procedures were done in control group.
Results: Multilayers of cultured cells were observed with inverted microscope in each group. MUC5AC expressions in experimental groups were significantly higher, whereas AQP5 mRNA levels were obviously lower compared with those in control group (all P<0.001), the changes in 235 mmol/L group were most obvious. Moreover, AQP5 mRNA and MUC5AC in experimental groups were notably negatively correlated (r=-0.77, P<0.001).
Conclusion: The model of air-liquid interface culture could increase MUC5AC expression, which provides an environment closely resembles that in the body is an ideal framework for the research of mucus hypersecretion of chronic obstructive pulmonary disease (COPD). Expressions of AQP5 mRNA and MUC5AC are negatively correlated. Hypotonicity and reduction of AQP5 mRNA may play critical roles in airway mucus secretion process in COPD.