6th ESACP Congress, Heidelberg, April 7-11, 1999

A061
DISTRIBUTION AND CHANGES OF CYTOSKELETON DURING DIFFERENTATION OF GLOMERULAR CELLS OF THE DEVELOPING HUMAN KIDNEY
Groma V

Medical Academy of Latvia, Riga, Latvia

Cytoskeleton is an essential network of filamentous proteins that contributes to practically all cellular functions, cell-surface events, interactions with extracellular matrices, and other processes undergoing during glomerulogenesis. Complex ultrastructural and immunohistochemical investigation of dynamic changes of the cytoskeleton along conversion of undifferentiated mesenchymal cellular aggregates to an epithelial phenotype and further proceeding through the well-known stages of the human kidney development is under the scope of this study. Actin appears to be the most abundant element of the cytoskeleton in the glomerular mesangial cells. A gradual decrease of cytoplasmic actins along with an increase of muscle-specific actin, in fact, alpha-smooth muscle actin, is going on during maturation of this glomerular cell that assumed to be a pericyte for invading blood vessels lined by endothelium. These phenotypic changes of the actin cytoskeleton in the mesangial cells are transient, and disappear when the differentiation of glomerulus is complete in the adult human kidney. In the podocyte the cytoskeleton is presented by microfilaments and intermediate filaments as well as microtubules. Fused foot processes reveal an abundant actin network interspersed with local densities that disappear along the differentiation. The actin cytoskeleton and proteins associated with it appear to be essential in maturation of the podocyte foot processes. In conclusion, the peculiarities of the cytoskeleton dynamics appear to be significant in cells' differentiation and cellular events occurring during the kidney development.