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Osteopontin synthesis and localization along the human nephron
Anja Verhulst1, Veerle P Persy1, An R Van Rompay1
1Department of Nephrology-Hypertension, University of Antwerp, Belgium.
Journal of the American Society of Nephrology : JASN
|April 19, 2002
Summary
Human kidney cells (proximal tubular cells and distal tubular cells) produce and secrete osteopontin (OPN) similarly, with distinct intracellular localization patterns. This finding aids understanding of renal OPN in kidney disease.
Area of Science:
- Nephrology
- Molecular Biology
- Cell Biology
Background:
- Osteopontin (OPN) is normally found on the apical surface of distal nephron cells in human and rat kidneys.
- Renal damage, such as ischemia or toxicity, causes OPN upregulation in distal tubular cells (DTC) and de novo expression in proximal tubular cells (PTC).
Purpose of the Study:
- To compare OPN localization in human kidney biopsies with ischemic rat kidneys.
- To investigate human renal OPN synthesis, secretion, and localization using proximal tubular cell (PTC) and distal tubular cell (DTC) cultures.
Main Methods:
- Comparative analysis of OPN localization in human biopsies and rat kidneys post-ischemia.
- Immunofluorescent staining, microscopy, flow cytometry, Northern blotting, RT-PCR, Western blotting, ELISA, and confocal microscopy on cultured PTC and DTC.
Main Results:
- OPN localization in human ischemic biopsies mirrored that in rat kidneys.
- DTC showed strong plasma membrane OPN localization, while PTC exhibited perinuclear intracellular expression.
- Both cell types produced a single OPN mRNA and secreted three OPN forms of comparable amounts, with intracellular OPN localizing to the Golgi apparatus.
Conclusions:
- Human renal OPN localization in PTC and DTC cell cultures reflects in vivo patterns observed after ischemia.
- These cell cultures serve as a valuable model for studying human OPN dynamics in PTC versus DTC.
- Intracellular OPN is localized in the Golgi apparatus in both PTC and DTC, which produce and secrete similar OPN isoforms.