Involvement of heparin-binding EGF-like growth factor and its processing by metalloproteinases in early epithelial morphogenesis of the submandibulargland

In the present study, the role of a member of the epidermal growth factor ( EGF) family, heparin-binding EGF-like growth factor (HB-EGF), in organ deve lopment was investigated by using developing mouse submandibular gland (SMG ), in which the EGF receptor signaling and heparan sulfate chains have been implicated. HB-EGF mRNA was detected in developing SMG by RT-PCR analysis and was expressed mainly in epithelium and weakly in mesenchyme of the embr yonic SMG. Epithelial morphogenesis was inhibited by a synthetic peptide co rresponding to the heparin-binding domain of HB-EGF and by anti-HB-EGF neut ralizing antibody. An in vitro assay using an EGF receptor ligand-dependent cell line, EP170.7 cells, allowed us to detect the growth factor activity in SMG-conditioned media, which was significantly reduced by anti-HB-EGF an tibody. Furthermore, treatment of SMG rudiments with the hydroxamate-based metalloproteinase inhibitor OSU8-1, which inhibits processing of EGFR ligan ds including HB-EGF, markedly diminished the growth factor activity in cond itioned media and resulted in almost complete inhibition of SMG morphogenes is. The inhibitory effects on morphogenesis were reversed, though partially , by adding the soluble form of HB-EGF. Our results provide the first evide nce that HB-EGF is a crucial regulator of epithelial morphogenesis during o rgan development, highlighting the importance of its processing by metallop roteinases. (C) 2001 Academic Press.