Mitogenic effects of EGF/TGF\alpha and immunolocalization of cognate receptors in human fetal kidneys

Article type: Research Article

Authors: Chailler, Pierre | Brière, Normand^;

Affiliations: Département d’Anatomie et de Biologie Cellulaire, Faculté de Médecine, Université de Sherbrooke, Sherbrooke, Québec, Canada J1H 5N4

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Abstract: The involvement of epidermal growth factor (EGF) and homologous transforming growth factor (TGF) in human kidney development was studied by analyzing their effects on the regulation of DNA synthesis in organ culture and by localizing their cognate receptors. Both peptides significantly increased ^{3}H‐thymidine incorporation when added at 10–100 ng/ml, but not at 1–5 ng/ml. Furthermore, addition of an anti‐EGF receptor antibody not only reduced the effect of exogenous EGF (100 ng/ml) on DNA synthesis but decreased basal ^{3}H‐thymidine incorporation. These results indicate that EGF/TGF\alpha are both mitogenic in vitro and further suggest that human fetal kidneys release an endogenous EGF‐related substance masking the effects of low amounts of growth factors added to culture medium. Radioautographic analyses show that EGF (100 ng/ml) increased DNA synthesis in poorly‐differentiated cells of the nephrogenic zone, particularly in subcapsular mesenchyme and peritubular cells; although less responsive, epithelial cells in early nephric tubules represented another target of EGF action. The pattern of EGF/TGF\alpha receptor expression was revealed immunohistochemically at different gestational ages and was shown to be related to the proliferation status. It was maximal in condensing nephrogenic cells, relatively high in newly‐induced epithelium and cortical branches of ureteric epithelium, low in differentiating nephronic cells and nearly absent from renal stroma and medullary collecting ducts. Together, our results indicate that the EGF/TGF\alpha system is directly involved in the regulation of nephrogenic cell proliferation during human metanephrogenesis and it is progressively down‐regulated after conversion of mesenchyme into epithelium.

Keywords: Epidermal growth factor, transforming growth factor‐[TeX:] \alpha , epidermal growth factor receptor, fetal kidney, metanephrogenesis

Journal: Biofactors, vol. 7, no. 4, pp. 323-335, 1998