CELL-SUBSTRATE AND CELL-CELL INTERACTIONS DIFFERENTLY REGULATE CYTOSKELETAL AND EXTRACELLULAR-MATRIX PROTEIN GENE-EXPRESSION

In this study, cellular events during tissue formation were investigat ed at the mRNA level using the Northern blot technique. The levels of expression of mRNAs encoding specific proteins (beta-actin, fibronecti n, and laminin) during tissue formation on tissue culture dishes were quantitatively assessed using a Northern blot technique with autoradio graphy. The level of beta-actin mRNA increased with incubation time an d reached a maximal level near the confluent state, followed by reduce d beta-actin mRNA expression at a later stage of tissue formation. The time course of beta-actin mRNA expression corresponded well to the ti me course of morphologic changes and cytoskeletal organization in adhe rent cells. Expression of the mRNAs encoding the extracellular matrix proteins fibronectin and laminin was initiated at the proliferation st age. After maximum expression levels of these two mRNAs were reached a t the confluent stage, a gradual decrease in their expression levels w as seen during long-term culture. Expression patterns of mRNAs encodin g cytoskeletal and extracellular matrix proteins strongly depended on the type of artificial substrates used; a mRNA expression pattern simi lar to that observed during tissue formation on tissue culture dishes was observed on a cell-adhesive substrate during tissue formation, whe reas reduced expression was seen during tissue formation on a less adh esive substrate. Thus, the dynamic changes occurring during tissue for mation were quantified to investigate the roles of artificial substrat es in tissue formation at the mRNA level. (C) 1996 John Wiley & Sons, Inc.