Nephrology Dialysis Transplantation, Vol 13, Issue 2 269-276, Copyright © 1998 by Oxford University Press
B Oertli, X Fan and R Wuthrich
Background. CD44 is the main receptor for the
extracellular polysaccharide hyaluronan (HA). We have recently shown that
CD44 is strongly induced on renal tubular epithelial cells (TEC) in
autoimmune renal injury and that HA accumulates in the renal interstitium
(Kidney Int 1996; 50: 156-163 and Nephrol
Dial Transplant 1997; 12: 1344-1353). The functional
significance of enhanced tubular CD44 expression and its interaction with
HA are not known. The purpose of the present study was to characterize
renal tubular CD44 expression and CD44-mediated HA binding in
vitro and to investigate the growth modulating effects in
response to HA binding by TEC. Methods. RT-PCR
analysis, flow cytometry, confocal microscopy and Western blotting were
used to examine cell surface and soluble CD44 expression by cultured TEC,
using SV40-transformed mouse cortical tubular (MCT) cells. HA binding
characteristics were examined by flow cytometry and effects of HA on TEC
cell growth by [3H]thymidine incorporation.
Results. By RT-PCR analysis MCT cells expressed
predominantly the standard form of CD44 mRNA, whereas the expression of
variant forms was very weak. Confocal microscopy showed that CD44 was
expressed basolaterally and apically on MCT cells with strong staining on
microvilli. Shedding of CD44 from MCT cells could be induced with
crosslinking of anti-CD44 mAbs or with PMA stimulation. MCT cells
constitutively bound HA and this binding could be modulated with anti-CD44
mAbs. Soluble and plate-bound HA markedly inhibited MCT cell growth.
Conclusions. CD44 is a regulated HA receptor on MCT
cells which can be shed into the cellular environment. Upon binding of HA,
CD44 functions as a growth inhibitory cell surface protein in MCT cells. We
speculate that the interaction of CD44 with HA may have important
regulatory effects on cell proliferation in tubulointerstitial renal
diseases. Keywords: CD44; cell growth; hyaluronan;
tubular epithelial cells
ORIGINAL ARTICLES
Characterization of CD44-mediated hyaluronan binding by renal tubular epithelial cells
Physiological Institute, University of Zurich-Irchel, Zurich, Switzerland; Division of Nephrology, University Hospital, Ramistrasse 100, CH-8091 Zurich, Switzerland; Corresponding author address
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