Regulation of fibronectin expression and splicing in migrating epithelial cells: Migrating MDCK cells produce a lesser amount of, but more active, fibronectin

Previously we have demonstrated that in MDCK epithelial cells not only tran sforming growth factor-beta (TGF-beta) but also hepatocyte growth factor/sc atter factor (HGF/SF) regulates fibronectin (FN) splicing by increasing the ratio of EDA-containing FN (EDA+ FN) mRNA to EDA-minus FN (EDA- FN) mRNA ( EDA+/EDA- ratio). EDA+ FN is known to be upregulated in tissues where cells actively migrate, such as those during morphogenesis, wound healing, and t umorigenesis. However, a direct association between cell migration and FN s plicing at the EDA region has never been investigated. In this work, we hav e shown by using an in vitro wound migration assay that migrating epithelia l cells regulate FN production and splicing differently compared to nonmigr ating cells. Wounds were introduced as migration stimuli into the 10-day-ol d confluent cell sheet, where the EDA+/EDA- ratio and FN mRNA expression le vels were stable. In migrating cells at the wound edge, the FN mRNA level d ecreased by 0.73-fold and the EDA+/EDA- ratio increased by 1.32-fold when c ompared with nonmigrating cells apart from the wound edge. HGF/SF significa ntly stimulated cell migration at the wound edge and concomitantly decrease d the FN mRNA level by 0.60-fold and increased the EDA+/EDA- ratio by 1.84- fold in migrating cells. In nonmigrating cells apart from the wound edge, F N mRNA expression and splicing were not influenced by either wound stimulat ion or HGF/SF, EDA+ FN stimulates cell migration more effectively than EDA- FN and thus is considered to be a more active variant of FN. Taken togethe r, migrating MDCK cells appear to regulate FN mRNA expression and splicing to produce a lesser amount of, but more active, FN. (C) 2001 Academic Press .