ROLE OF LAMININ-1 AND TGF-BETA-3 IN ACINAR DIFFERENTIATION OF A HUMANSUBMANDIBULAR-GLAND CELL-LINE (HSG)

Previous studies show that culturing an immortalized human submandibul ar gland cell line (HSG) on Matrigel, a basement membrane extract, ind uces cytodifferentiation. We have further defined this model system an d identified factors involved in HSG cell acinar development and cytod ifferentiation. Acinar development is marked by cell migration into mu lti-cellular spherical structures, cell proliferation and apoptosis of the centrally localized cells, In addition, functional differentiatio n was determined by indirect immunofluorescence and immunoblot analysi s for cystatin, a salivary gland acinar cell-specific protein found to be produced by differentiated HSG cells. Matrigel contains multiple e xtracellular matrix proteins, however, laminin-1 was identified as the major matrix component that induced HSG cell acinar development and c ytodifferentiation, Antibodies against specific components of Matrigel and against cell surface adhesion molecules were added to cells in cu lture to identify components important for HSG cell acinar differentia tion. Immunostaining of HSG cell acini identified TGF-beta 2 and beta 3 as the predominant isoforms within the cells, Neutralizing antibodie s directed against TGF-beta 3 significantly decreased (P less than or equal to 0.0002) the size of acini formed, These results indicate that multiple components, including laminin-1 and TGF-beta 3, contribute t o HSG cell acinar development, This model system will be useful to stu dy acinar differentiation and salivary gland-specific protein expressi on in vitro.