TY - JOUR
T1 - Heterogeneity of osteopontin expression among nephrons in mouse kidneys and enhanced expression in sclerotic glomeruli
AU - Lopez, C. A.
AU - Hoyer, J. R.
AU - Wilson, P. D.
AU - Waterhouse, P.
AU - Denhardt, D. T.
PY - 1993
Y1 - 1993
N2 - BACKGROUND: Osteopontin (OPN) is a secreted Ca2+-binding phosphoprotein able to mediate cell attachment to bone via an RGD sequence and the α(v)β3 integrin. OPN mRNA is found at high levels in the kidney, and the protein is found in the urine. Because published reports of where the protein is produced conflict, we undertook a comprehensive study to localize OPN expression. EXPERIMENTAL DESIGN: In situ hybridization with a mouse cDNA probe and immunohistochemical staining with three different antisera to mouse OPN were used to identify those cells that contained significant levels of mRNA and protein, respectively. RESULTS: Both methods of analysis revealed that OPN expression in the normal mouse kidney was primarily restricted to the thick ascending limbs of the loop of Henle and to the distal convoluted tubules. Protein was detected predominantly at the apical surface of cells lining the lumen of a subset of tubules. The α(v)β3 integrin, which is a receptor for vitronectin and osteopontin, was uniformly localized by immunostaining not on the apical surface but rather to the baso-lateral surface of cells in the distal part of the tubule. OPN expression was not detected in healthy glomeruli, proximal tubules, thin limbs of the loop of Henle, collecting ducts, or interstitial fibroblasts. In contrast to the localization of Tamm-Horsfall protein expression, in all distal nephrons, expression of OPN was detected by both methods of analysis in only some nephrons. OPN expression (relative to male mice) was somewhat increased in female, pregnant and lactating mice and markedly increased in the parietal epithelium of glomeruli undergoing sclerosis in aging mice. OPN was also detected in the macula densa. CONCLUSIONS: OPN is synthesized and secreted into the tubule fluid by the luminal epithelia of the distal portions of a subset of kidney nephrons. As animals age expression is found in more proximal portions of the tubule. OPN may contribute to, or be a consequence of, glomerular sclerosis, and may be an indicator of subclinical injury or infection.
AB - BACKGROUND: Osteopontin (OPN) is a secreted Ca2+-binding phosphoprotein able to mediate cell attachment to bone via an RGD sequence and the α(v)β3 integrin. OPN mRNA is found at high levels in the kidney, and the protein is found in the urine. Because published reports of where the protein is produced conflict, we undertook a comprehensive study to localize OPN expression. EXPERIMENTAL DESIGN: In situ hybridization with a mouse cDNA probe and immunohistochemical staining with three different antisera to mouse OPN were used to identify those cells that contained significant levels of mRNA and protein, respectively. RESULTS: Both methods of analysis revealed that OPN expression in the normal mouse kidney was primarily restricted to the thick ascending limbs of the loop of Henle and to the distal convoluted tubules. Protein was detected predominantly at the apical surface of cells lining the lumen of a subset of tubules. The α(v)β3 integrin, which is a receptor for vitronectin and osteopontin, was uniformly localized by immunostaining not on the apical surface but rather to the baso-lateral surface of cells in the distal part of the tubule. OPN expression was not detected in healthy glomeruli, proximal tubules, thin limbs of the loop of Henle, collecting ducts, or interstitial fibroblasts. In contrast to the localization of Tamm-Horsfall protein expression, in all distal nephrons, expression of OPN was detected by both methods of analysis in only some nephrons. OPN expression (relative to male mice) was somewhat increased in female, pregnant and lactating mice and markedly increased in the parietal epithelium of glomeruli undergoing sclerosis in aging mice. OPN was also detected in the macula densa. CONCLUSIONS: OPN is synthesized and secreted into the tubule fluid by the luminal epithelia of the distal portions of a subset of kidney nephrons. As animals age expression is found in more proximal portions of the tubule. OPN may contribute to, or be a consequence of, glomerular sclerosis, and may be an indicator of subclinical injury or infection.
KW - Aging
KW - Focal gene expression
KW - Immunohistochemistry
KW - In situ hybridization
KW - Integrins
UR - http://www.scopus.com/inward/record.url?scp=0027431167&partnerID=8YFLogxK
M3 - Article
C2 - 8377476
AN - SCOPUS:0027431167
SN - 0023-6837
VL - 69
SP - 355
EP - 363
JO - Laboratory Investigation
JF - Laboratory Investigation
IS - 3
ER -