Growth related secretion and production of GM-CSF by epithelial cell line

Granulocyte-macrophage colony stimulating factor (GM-CSF) is a growth factor that supports the clonal development of normal granulocyte-macrophage progenitors. Especially in the skin, GM-CSF from keratinocytes may be a critical factor in the melanogenesis of the skin. In addition, GM-CSF is thought to play an important role in impaired wound healing. However, little is known regarding the synthesis and secretion of GM-CSF by keratinocytes of the skin. This investigation evaluated the effects of cell density on the production of GM-CSF by keratinocytes and the changes in the cell cycle. Interestingly, GM-CSF protein secretions and mRNA expressions were highly elevated in sub-confluent HaCat cells, and decreased in confluent state. In particular, GM-CSF production decreased in a density-dependent manner. We also found that the percentage of cells in the S phase of the cell cycle decreased markedly from 50 to 10% when HaCat cells reached a confluent state. These results showed that GM-CSF synthesis and secretion by HaCat cells increases when cells are rapidly proliferating such as in the wound healing process. Thus, it might be said that GM-CSF produced by proliferating keratinocytes possibly contributes to wound healing and melanogenesis at the site of injury.