Cystic fibrosis: production of high levels of uromodulin-like protein by HLA-DR blood monocytes differentiating towards a fibroblastic phenotype

Abstract

We report here the spontaneous in vitro transformation of blood monocytes into fibroblasts, in a patient suffering from cystic fibrosis (CF). The blood monocytes with this capacity express HLA-DR specificity. Monocytes were identified by non-specific esterase activity and by immunofluorescence using monoclonal antibodies against monocytes/macrophages antigens. Neo-fibroblasts were identified by electron microscopy and immunofluorescence using monoclonal antibodies against a cytoplasmic enzyme specifically involved in the synthesis of collagen. The secretion of collagen was evidenced using antibodies against type I collagen. Both monocytes/macrophages and neo-fibroblasts express the monocytic and the fibroblastic markers and synthesize type I collagen. This transformation observed in vitro might mimick the process of fibrosis development which takes place in vivo, particularly in pancreatic acini, lungs and intestine of patients with CF. Interestingly, the whole process in vitro is inhibited when T lymphocytes are properly stimulated by IL2. In addition, both monocytes and neo-fibroblasts secrete high quantities of uromodulin-like glycoprotein. The significance of this finding is discussed in relation to the thick mucus secretion which characterizes the disease. In addition, from a fundamental point of view, it confirmed in a large series of patients that this observation may have significant implications, since CF mutation impairs the gene coding for cAMP-regulated Cl- channel and that it has been proposed that uromodulin might be implicated in Cl- transport. Therefore the question of the relationships between uromodulin and the cAMP-regulated Cl- channel arises.