Secretion of stem cell factor by alveolar fibroblasts in interstitial lungdiseases

Sarcoidosis (SA) and diffuse interstitial fibrosis (DIF) are characterized by alveolitis, mast cell hyperplasia and increased fibroblast proliferation . Stem cell factor (SCF) stimulates proliferation of hematopoietic progenit or cells involved in mast and stromal cell interaction. We assessed the rol e of SCF secreted by alveolar fibroblasts (AFb) in the development of fibro sis of DIF and SA in six patients with SA and six patients with DIF. Bronch oalveolar lavage (BAL) was performed by conventional methods. A total of 50 0 cells were differentially counted from Giemsa-stained cytopreps. AFb and supernatants were recovered from long-term cultures of BAL cells and from 2 4 h cultures of confluent AFb. Levels of SCF were measured by ELISA. Alpha actin content of AFb was characterized by irnmunohistochemistry. The expres sion of AFb mRNA for IL1-alpha. and beta, TGF-beta, IFN-gamma, IL-2, IL-4. IL-5 and IL-6 was determined by RT-PCR. There was a lymphocytic predominanc e in the SA patients and an increase in neutrophils and eosinophils in DIF. SCF secreted by AFb from DIF was significantly higher than in SA. TNF + IL -1 significantly decreased the secretion of SCF by AFb. There was a positiv e correlation between SCF levels and the percentage eosinophils but not for metachromatic cells. alpha-Actin expression of AFb in DIF was significantl y higher than in SA. Cytokine mRNA was extracted from AFb of two SA and two DIF patients. The profile showed that only in stimulated AFb isolated from the DIF patients can IL-5 transcripts be visualized. In conclusion, AFb ca n contribute to the onset of fibrosis by secreting SCF and IL-5 which, in t urn, may recruit eosinophils. (C) 1999 Elsevier Science B.V. All rights res erved.