Significant role of laminin‐1 in branching morphogenesis of mouse salivary epithelium cultured in basement membrane matrix

Abstract

Mouse submandibular epithelium shows branching morphogenesis in mesenchyme-free conditions when covered with a basement membrane matrix (Matrigel) in medium supplemented with epidermal growth factor. In the present study, the role of laminin-1 (LN1), a major glycoprotein of Matrigel, in this culture system was defined. When the epithelium was cultured in a LN1-nidogen gel, the epithelium showed much branching, comparable to that observed with Matrigel. By electron microscopy, only a felt-like matrix was formed on the epithelial surface in the LN1-nidogen gel cultures, while an organized basal lamina structure was formed on the epithelial surface in direct or transfilter recombination cultures with mesenchyme. Next, the epithelium covered with Matrigel was cultured in medium containing either biologically active peptides from LN1, IKVAV-including peptide (2097-2108), AG10 (2183-2194), AG32 (2370-2381) or AG73 (2719-2730) from the alpha1 chain, or YIGSR-including peptide (926-933) from the beta1 chain. Only AG73 (RKRLQVQLSIRT from the alpha1 chain carboxyl-terminal globular domain) inhibited the epithelial branching in Matrigel. These results suggest that LN1-nidogen can support the branching morphogenesis of submandibular epithelium even if LN1-nidogen is not assembled into an intact basal lamina, and that the AG73 sequence is an important site on LN1, which interacts with submandibular epithelial cells.

Semaphorin signaling facilitates cleft formation in the developing salivary gland

“…We isolated the epithelial rudiments free from mesenchyme and cultured them in Matrigel with reduced growth factor. Under this culture condition, the epithelial rudiments were unable to grow and form branches (Hosokawa et al, 1999). Interestingly, addition of Sema3A into this culture did not stimulate branching of the SMG epithelia (Fig.…”

Gene expression profiles of mouse submandibular gland development: FGFR1 regulates branching morphogenesis in vitro through BMP- and FGF-dependent mechanisms

“…Branching morphogenesis of SMGs in vitro involves EGF signaling (Kashimata and Gresik, 1997;Kashimata et al, 2000;Morita and Nogawa, 1999), integrin α6, laminin-1 (Hosokawa et al, 1999;Kadoya et al, 1995), the TNF/TNFR1/IL6 pathways (Melnick et al, 2001b;Melnick et al, 2001c), and FGF7 (Morita and Nogawa, 1999). Fibroblast growth factors (FGFs) and their receptors (FGFRs) are important in many developmental events, including branching morphogenesis in other organs (Martin, 1998;Metzger and Krasnow, 1999;Ornitz, 2000;Spencer-Dene et al, 2001).…”

Lysophosphatidic acid cooperates with EGF in inducing branching morphogenesis of embryonic mouse salivary epithelium

“…The salivary epithelium thereby was proved to perform branching morphogenesis when embedded in a laminin-rich basementmembrane-like matrix and stimulated by epidermal growth factor (EGF; Nogawa and Takahashi, 1991). Since then, many studies have reported the involvement of EGF family ligands (transforming growth factor ␣, heparin-binding EGF, and neuregulin) and laminins in the branching morphogenesis of the salivary gland (Kadoya et al, 1995;Kashimata and Gresik, 1997;Hosokawa et al, 1999;Kashimata et al, 2000;Umeda et al, 2001;Koyama et al, 2003;Miyazaki et al, 2004;Kadoya and Yamashina, 2005). During the development of the mesenchyme-free culture of salivary epithelium, we introduced a serum-supplemented medium but paid little attention to the serum, because we had typically added serum as a source of nutrients for in vitro organ cultures.…”