Striated microfilament bundles (SMF) in the glomerular cells of human kidneys

Rhizoplast or striated rootlet is a rarely described cytoplasmic organelle in non-ciliated mammalian cells. We observed the centrosome related rhizoplast like structures relatively often in the human renal glomerular cells. Of 226 kidney biopsies striated microfilament bundles (SMF) have been found in 41 cases in a total of 64 cells. More than half of these organelles were found in podocytes, about a quarter in endothelial cells, fewer in mesangial cells and they rarely occurred in the parietal epithelium. The majority of SMF are connected with the centrosome, but not in direct connection with the centriole. The longer bundles have often been located near the Golgi complex. The thickness of the SMF varies, their cross striation has a periodicity of 88 +/- 13.4 nm. The occurrence of SMF does not show any connection with the age of the patients, the type of disease, the morphological changes or therapy. It is difficult to say whether they are normal or pathological organelles. Their presence can be regarded as a metaplastic process in functionally overloaded cells.