engleski

Characteristics of human podocytes in developing, healthy postnatal and nephrotic kidneys

Introduction. Morphological and immunohistochemical characteristics of human podocytes were analyzed during normal kidney development, and during postnatal period in healthy and nephrotic kidneys. Materials and methods. Tissue pieces were dissected from embryos and fetuses (8th to 22nd postovulatory weeks), and from postnatal healthy and nephrotic kidneys, including nephrotic syndrome of the Finnish type (CNF) and focal segmental glomerulosclerosis (FSGS). Glomerules were analyzed by immunohistochemical and double immunofluorescent techniques, applying proliferation marker Ki-67, differentiation marker Oct-4 and α-tubulin marker for detection of primary cilia. Ultrastructural characteristics of podocytes were analyzed by transmission electron microscopy. Results. Between the 8th and 22nd developmental week, S- forms of immature nephrons were characterized by presence of the short primary cilia at the luminal surfaces of differentiating glomerules and strong Oct-4 expression. During further progression of development, in glomerules of fetal kidneys and in healthy postnatal kidneys, the primary cilia gradually disappeared from the surfaces of the podocytes, while they retained on the parietal layer of Bowman's capsule. Oct-4 expression gradually decreased during development as well. Ultrastructurally, healthy postnatal podocytes had characteristic foot processes, forming part of the glomerular filtration barier (GFB). In contrast, podocytes of postnatal nephrotic kidneys displayed numerous cilia on their surfaces, while their Oct-4 expression remained strong. At places, increased proliferation characterized parietal cells of Bowman's membrane. Ultrastructurally, podocytes of nephrotic kidneys showed absence of foot processes, but had numerous microvili on their surfaces. Conclusions. Differentiation of healthy human podocytes during development and postnatal life is characterized by disappearance of primary cilia from their surfaces, decrease of Oct-4 expression and appearance of podocyte foot processes. In nephrotic kidneys, podocytes are not completely differentiated as some of them retain primary cilia on their surfaces, showing also increased Oct-4 expression and depletion of foot processes.

human podocytes; embryo; kidneys

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