Role of laminin-1 and TGF-β3 in acinar differentiation of a human submandibular gland cell line (HSG)

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Abstract
Previous studies show that culturing an immortalized human submandibular gland cell line (HSG) on Matrigel, a basement membrane extract, induces cytodifferentiation. We have further defined this model system and identified factors involved in HSG cell acinar development and cytodifferentiation. Acinar development is marked by cell migration into multi-cellular spherical structures, cell proliferation and apoptosis of the centrally localized cells. In addition, functional differentiation was determined by indirect immunofluorescence and immunoblot analysis for cystatin, a salivary gland acinar cell-specific protein found to be produced by differentiated HSG cells. Matrigel contains multiple extracellular matrix proteins, however, laminin-1 was identified as the major matrix component that induced HSG cell acinar development and cytodifferentiation. Antibodies against specific components of Matrigel and against cell surface adhesion molecules were added to cells in culture to identify components important for HSG cell acinar differentiation. Immunostaining of HSG cell acini identified TGF-β2 and β3 as the predominant isoforms within the cells. Neutralizing antibodies directed against TGF-β3 significantly decreased (P≤0.0002) the size of acini formed. These results indicate that multiple components, including laminin-1 and TGF-β3, contribute to HSG cell acinar development. This model system will be useful to study acinar differentiation and salivary glandspecific protein expression in vitro.