Molecular events involved in the morphogenesis of multicystic dysplastic kidney.

INTRODUCTION Wnt-1 is capable of inducing metanephric mesenchyme to undergo tubulogenesis. A relationship between the degree of cystogenesis and reduced E-cadherin (E-cad) expression was described. Syndecan-1 (Sdc-1) has a critical role in kidney development. MATERIALS AND METHODS Ten multicystic dysplastic kidneys (MCDKs) were stained with hematoxylin and eosin and immunohistochemistry was performed using Wnt-1, E-cad and Sdc-1 antibodies. Eight unaffected kidneys were used as controls. RESULTS Strong Wnt-1 immunostaining occurred inside cystic/tubular epithelial cells and in blastematous foci. An immunoreaction was observed in glomerular epithelial cells. In controls, just weak cytoplasmic Wnt-1 positivity was seen in tubular epithelial cells. E-cad reaction was negative in MCDKs while strong immunostaining was common in tubular cells of controls. A strong Sdc-1 immunoreaction depicted cystic, tubular and glomerular epithelial cells in MCDKs while Sdc-1 expression documented weak positivity in tubular epithelium alone. CONCLUSIONS Our data are in accordance with an involvement of Wnt-1 in normal nephrogenesis and with its role in altered epithelial differentiation of metanephric mesenchyme in MCDKs. Wnt-1 signal may function to suppress E-cad expression, a predisposing event for cystogenesis. High expression of Sdc-1 in tubular/cystic epithelial cells of MCDKs might alter the normal transition of stages of the developmental process and modify the anion charge of the glomerular barrier.