Molecular aspects of mast-cell-mediated mitogenesis in fibroblasts and mesothelial cells in situ.

Mast-cell-mediated mitogenesis in intact tissues is a paracrine reaction the molecular mechanisms of which still have to be elucidated. One strategy worth exploring is to study the mitogenic reaction under as defined conditions as possible. The present study demonstrates that in the virtually avascular rat mesentery, organ-cultured in a biochemically-defined medium, activation of mast cells induced a mitogenic reaction in fibroblasts and mesothelial cells, the two predominant, morphologically distinct neighboring cell types. Thus the system provides a means of studying the influence of defined molecules in the growth medium on the outcome of a mitogenic response in these two cell types in situ. It was further observed that exogenous platelet-derived growth factor (PDGF) was not essential for this mast-cell-mediated mitogenic reaction to occur in the tissue-bound fibroblasts and mesothelial cells.