Morphological and biochemical properties of alveolar fibroblasts in interstitial lung diseases

The phenotype of alveolar-associated fibroblasts (Afb) in sarcoidosis (SA) and idiopathic pulmonary fibrosis (IPF) is unclear. In the present study, we characterized the cytoskeletal proteins and the contraction properties in alveolar-associated fibroblasts recovered by bronchoalveolar lavage (BAL) in the two diseases. Afb were studied from BAL cells in eight IPF and seven SA patients. Cytoskeletal proteins were identified by ELISA and immunofluorescent methods. Biochemical measurements were done by dry chemistry. Contraction was performed by a gel contraction assay. Afb alpha-SM actin measured by ELISA was higher in IPF than in SA (p = 0.042). Vimentin, desmin, myosin, and fibroblast markers were expressed equally. Only in IPF did the Afb reveal the myofibroblast phenotype showing alpha-SM actin immunofluorescence labeling and, by electron microscopy, filaments with associated dense bodies with rough endoplasmic reticulum. Gel contraction showed that cells in IPF contracted significantly more than in SA (p = 0.046 IPF versus SA). The addition of ET-1 increased contraction in all groups. Dry chemistry analysis showed higher levels (p = 0.0065) of creatine phosphokinase (CPK), lower levels of glucose (p = 0.0082), and similar levels of Ca(2+) and lactate in the IPF and SA Afb. Dinitrofluorobenzene (DNFB), a potent inhibitor of CPK, completely abolished spontaneous cell contraction. Afb differentiates into myofibroblasts with different biochemical and energetic properties in IPF. Moreover, Afb from IPF patients showed increased contractile properties. This may explain the difference in the behavior patterns and outcomes of the two diseases.