Fibronectin expression increases during in vitro cellular senescence: correlation with increased cell area.

Several changes in the functional characteristics of fibronectin have been noted as cells become senescent in culture. In this report we show that steady state levels of both fibronectin mRNA and protein increase significantly during the process of cellular aging. The greatest change in the proportion of cells expressing high levels of fibronectin occurs near the end of a culture's proliferative potential. The proportion of cells unable to synthesize DNA has previously been shown to follow a similar pattern. We also found that increasing cell size correlates closely with higher levels of fibronectin expression. Thus, there is a clear correlation between increased fibronectin mRNA content and in vitro cellular senescence. It remains to be determined whether the change in fibronectin production is a contributing cause or a result of in vitro cellular senescence.