TGF-beta1 induces alveolar epithelial to mesenchymal transition in vitro

Life Sci. 2004 Nov 19;76(1):29-37. doi: 10.1016/j.lfs.2004.06.019.


The aim of this study was to investigate whether transforming growth factor-beta1 (TGF-beta1) could induce alveolar epithelial to mesenchymal transition (EMT) in vitro. Alveolar epithelial cells (AECs) from SD rats were isolated by elastase cell dispersion and IgG panning. Expression of alpha-smooth muscle actin (alpha-SMA) was assayed using Western blotting and immunostaining analysis. Morphological changes, the markers of epithelial cell (E-cadherin), and stress fiber by actin reorganization were detected by an indirect immunostaining. The contents of collagen I were determined by spectrophotometry. The levels of endogenous TGF-beta1 were measured with ELISA. Incubation of AECs with TGF-beta1 (0.1 approximately 10 ng/mL) induced abundant expression of alpha-SMA protein, and alpha-SMA expression in AECs reached a plateau when TGF-beta1 was > 3 ng/mL. Furthermore, we found that TGF-beta1 (3 ng/mL) exposure of AECs induced an authentic EMT characterized by abundant expression of alpha-smooth muscle actin, transformation of myofibroblastic morphology, increased formation of stress fiber by actin reorganization, and loss of epithelial marker E-cadherin. Meanwhile, significant increase in the levels of collagen I from 32.0 +/- 6.6 mg/g in control to 98 +/- 10.8 mg/g in TGF-beta1-treated group was found over a 72 h incubation period. Moreover, following stimulated by TGF-beta1 (3 ng/mL), a marked and time-dependent increase in endogenous TGF-beta1 released from AECs was observed. At time points 72 h, TGF-beta1 release mounted to 3451 pg/ml, which was much enough to induce EMT in vitro. These results demonstrated that AECs, under stimulation of TGF-beta1, underwent a conversion process into myofibroblasts in vitro.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Retracted Publication

MeSH terms

  • Actins / metabolism
  • Animals
  • Cadherins / metabolism
  • Cells, Cultured
  • Collagen Type I / metabolism
  • Enzyme-Linked Immunosorbent Assay
  • Epithelium / physiology
  • Immunoblotting
  • Immunohistochemistry
  • In Vitro Techniques
  • Male
  • Mesoderm / physiology
  • Muscle, Smooth / metabolism
  • Pulmonary Alveoli / physiopathology*
  • Pulmonary Fibrosis / physiopathology*
  • Rats
  • Rats, Sprague-Dawley
  • Spectrophotometry
  • Time Factors
  • Transforming Growth Factor beta / metabolism*
  • Transforming Growth Factor beta / physiology


  • Actins
  • Cadherins
  • Collagen Type I
  • Transforming Growth Factor beta