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, w e 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 immunofluo rescent methods. Biochemical measurements were done by dry chemistry. Contr action was performed by a gel contraction assay. Afb alpha -SM actin measur ed by ELISA was higher in IPF than in SA (p = 0.042). Vimentin, desmin, myo sin, and fibroblast markers were expressed equally. Only in IPF did the Afb reveal the myofibroblast phenotype showing a-SM actin immunofluorescence l abeling 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 ad dition of ET-1 increased contraction in all groups. Dry chemistry analysis showed higher levels (p = 0.0065) of creatine phosphokinase (CPK), lower le vels of glucose (p = 0.0082), and similar levels of Ca2+ and lactate in the IPF and SA Afb. Dinitrofluorobenzene (DNFB), a potent inhibitor of CPK, co mpletely abolished spontaneous cell contraction. Afb differentiates into my ofibroblasts with different biochemical and energetic properties in IPF. Mo reover, Afb from IPF patients showed increased contractile properties. This may explain the difference in the behavior patterns and outcomes of the tw o diseases.