[Effects of cyclic stretch on the induction of the transdifferentiation in human lung epithelial cells].

Objective: To investigate the effect of mechanical stretch induced epithelial-mesenchymal transition in human lung epithelial cells BEAS-2B in vitro.

Methods: The human lung epithelial cells BEAS-2B were subjected to cyclic stretch by the FX-5000T system at 0.33 Hz of 10% or 20% elongation for 24, 48 and 72 hours respectively. The morphologic changes were observed by microscopy. The mRNA and protein expressions of E-cadherin, Cytokeratin-8 (CK-8), α-smooth muscle actin (α-SMA) and Vimentin were evaluated by immunofluorescence before and after mechanical stretch and fluorescent quantitation reverse transcription-polymerase chain reaction (qRT-PCR).

Results: (1) When stretch by 20% elongation for 48 hours, the morphological changes in BEAS-2B cells from cobblestone-like structure to elongated shape and obviously when stretch for up to 72 hours, while 10% elongation showed no significant morphological changes comparing to control. (2) Decreasing E-cadherin and CK-8 protein expression was associated with increased immunostaining for α-SMA protein at 72 hours after 20% mechanical stretch. (3) Expression of E-cadherin mRNA was decreased to 0.388±0.056 and 0.247±0.064 after 20% mechanical stretch for 48 hours and 72 hours compared with control without stretch (set 1, both P<0.05), expression of CK-8 mRNA was decreased to 0.436±0.060 at 72 hours after 20% mechanical stretch (P<0.01), α-SMA mRNA was increased to 1.437±0.267 (48 hours) and 1.261±0.247 (72 hours) after 20% mechanical stretch (both P<0.05), and Vimentin mRNA was increased to 1.679±0.172 (48 hours) after 20% mechanical stretch (P<0.05). Expression of E-cadherin mRNA was decreased to 0.387±0.081 at 72 hours after 10% mechanical stretch (P<0.05), Vimentin mRNA was increased to 1.688±0.179 at 48 hours after 10% mechanical stretch while other markers showed no significant changes comparing with control.

Conclusions: Excessive mechanical stretch could induce epithelial-mesenchymal transition in lung epithelial cells BEAS-2B in vitro.