Glial fibrillary acidic protein-positive cells of the kidney are capable of raising a protective biochemical barrier similar to astrocytes: expression of metallothionein in podocytes.
Blood-tissue exchange and homeostasis within the organs depend on various interactions between endothelial and perivascular cells (Buniatian, 2001). Podocytes possess anatomical and cellular features intermediate between those of astrocytes and hepatic stellate cells (HSCs). Podocytes, like HSCs, are associated with fenestrated capillaries and, similar to astrocytes, interact with the capillaries via the basement membrane and participate in permeability-limiting ultrafiltration. The fact that podocytes come in direct contact with xenobiotics prompted us to investigate whether they express metallothionein (MT), an anticytotoxic system characteristic of astrocytes. In comparative studies, cryosections of 1- and 3-month-old rat kidney and adult rat brain, as well as podocytes and astrocytes from early and prolonged primary cultures of glomerular explants and newborn rat brain, respectively, were investigated. The cells were double-labeled with antiserum against glial fibrillary acidic protein (GFAP) and monoclonal antibody (MAb) against the lysine-containing epitope of Cd/Zn-MT-I (MAb MT) or MAb against alpha-actin. In kidney sections, MT immunoreactivity was detected in GFAP-positive glomerular cells and in interstitial fibroblasts. The pattern of staining for MT and GFAP in glomerular cells was similar to that of astrocytes in vivo. In glomerular cell cultures, MT was expressed in cobblestone-like podocytes which contained Wilms' tumor protein and lacked desmin. MT was upregulated at later culture periods, during which podocytes acquired features typical of undifferentiated astrocytes. This study hints at the existence of common regulatory mechanisms of blood-tissue interactions by neural and non-neural perivascular cells. These mechanisms appear to be used in an organ-specific manner.
Physiologisch-Chemisches Institut der Universität, Hoppe-Seyler-Strasse 4, D-72076 Tübingen, Germany. buniatan@web.de
Gayane Hrachia
GH
Buniatian
Hans-Jürgen
HJ
Hartmann
Peter
P
Traub
Heinrich
H
Wiesinger
Margitta
M
Albinus
Wolfgang
W
Nagel
Robert
R
Shoeman
Dieter
D
Mecke
Ulrich
U
Weser
D000199:Actins / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D000911:Antibodies, Monoclonal; D001253:Astrocytes / Q000166:cytology / Q000378:metabolism*; D002199:Capillary Permeability / Q000502:physiology*; D002478:Cells, Cultured; D019084:Fluorescent Antibody Technique, Indirect; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism*; D007150:Immunohistochemistry; D007678:Kidney Glomerulus / Q000098:blood supply / Q000166:cytology* / Q000378:metabolism*; D008668:Metallothionein / Q000096:biosynthesis*; D051381:Rats; D017207:Rats, Sprague-Dawley
D000199:Actins; D000911:Antibodies, Monoclonal; D005904:Glial Fibrillary Acidic Protein; D008668:Metallothionein