Laminin expression by human periodontal ligament fibroblasts

Our previous study demonstrated that a laminin-like molecule produced by periodontal ligament fibroblasts (PLFs) induces gingival epithelial cell chemotaxis. The aim of this study was to identify the laminin isoforms that are expressed by PLFs. Proteins in PLF-conditioned medium from serum-free cultures were separated by gel filtration followed by gelatin-affinity chromatography to remove fibronectin. Protein expression of laminin isoforms was determined using Western blotting, and mRNA expression was examined by RT-PCR. Partially purified laminin evoked gingival epithelial cell chemotaxis, and this activity was blocked by anti-integrin α3, α6, and β1 antibodies. Although RT-PCR analysis showed PLFs expressed laminin α1 to α5, β1 to β3, γ1, and γ2 chain mRNAs, the predominant laminin chains detected by Western blotting were α4, α2, β1, β2, and γ1. These results suggest that PLFs secrete mainly laminin-8/9 (α4β1γ1/ α4β2γ1) and laminin-2/4 (α2β1γ1/ α2β2γ1). PLF-derived laminins may be involved in the pathogenesis and progression of periodontitis by inducing apical migration of epithelial cells in certain circumstances.