Transferrin as a fetal growth factor: acquisition of responsiveness related to embryonic induction.

Abstract

Differentiation of the metanephric mesenchyme, which is triggered by an inductive tissue interaction, proceeds in a chemically defined medium containing transferrin. Here, it is reported that neither transferrin-depleted serum nor a chemically defined medium devoid of transferrin promote differentiation and that activity can be restored by the addition of transferrin. Apparently, the serum factor required for kidney differentiation has been identified. Transferrin seems to affect differentiation by stimulating cell proliferation. A [mouse] organ-culture model system was used to show that only mesenchymes induces to differentiate by the 24-h tissue interaction respond to transferrin by proliferation and differentiation; uninduced mesenchymes remain unresponsive. The inductor tissue used is not responsive to transferrin. Short-range cell-mediated tissue interaction acts by making the nephrogenic mesenchyme responsive to the long-range mediator, which is transferrin. Transferrin may be an important circulating growth factor required for proliferation during embryogenesis.