Substrate Modulation of Morphology, Growth, and Tear Protein Production by Cultured Human Lacrimal Gland Epithelial Cells

Abstract

Human lacrimal gland biopsies were serially incubated in chelating and enzymatic solutions. Viable single cells were evaluated for outgrowth in growth factor enriched medium using the following culture substrates: Matrigel, Type I collagen gel with or without fibroblasts, and plastic. Each epithelial outgrowth was characterized morphologically and immunohistochemically, and their growth and viability were examined by BrdU labeling and a quantitative cell viability assay. Synthesized proteins were evaluated by ELISA, SDS-PAGE, and 14C-labeled amino acid incorporation. Lacrimal gland epithelial cells plated on Matrigel formed clusters with central cavities that contained lactoferrin, mimicking acinar complexes in vivo. Cells plated on collagen gel or collagen gel containing fibroblasts formed islands or a monolayer, and lactoferrin was detected in incomplete cavities of epithelia on the latter substrate. Epithelial cells plated on plastic formed a monolayer and cellular expression of lactoferrin was weak and sporadic. Cellular release of lactoferrin measured by ELISA supported the results of immunohistochemistry. Cells grown on plastic had the highest proliferative rate, whereas those grown on Matrigel showed the lowest proliferative rate. These results indicate that different substrates modulate lacrimal gland epithelial cell morphology, proliferative rate, and production of the tear protein lactoferrin. Matrigel promotes acinar differentiation to a greater extent than collagen gel and plastic. Incorporation of fibroblasts in collagen gel substrate promotes significant effects on growth and differentiation.