The influence of conditioned medium from mouse intestinal epithelial cells on the proliferative activity of crypt cells: role of granulocyte-macrophage colony-stimulating factor

Background:

The aim of this work was to study the influence of soluble factors produced by native mouse intestinal epithelial cells (IECs) on the proliferative activity of freshly isolated intestinal crypt cells. Methods: The crypt cells were cultured with either conditioned medium and its ultrafiltrates or recombinant mouse granulocyte-macrophage colony-stimulating factor (GM-CSF) in the presence or absence of neutralizing anti-GM-CSF antibodies. GM-CSF in culture medium was identified by the electrochemiluminescence method. Results: It was demonstrated that the IEC conditioned medium contained GM-CSF. This cytokine led to both the upregulation and downregulation of crypt cell proliferative activity, depending on its concentration in the culture medium. The effect of native GM-CSF was reproduced with recombinant mouse GM-CSF: 25 and 5 ng/ml inhibited the proliferative activity, whereas 1 ng/ml led to its significant stimulation. Conclusions: Freshly isolated murine IECs produce GM-CSF, which plays a critical role in crypt cell proliferative activity in vitro. These results suggest the involvement of this factor in the regulation of the crypt proliferative zone, in an autocrine and/or paracrine manner.