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Osteopontin gene expression and immunolocalization in the rabbit urinary tract
H A Arafat1, A J Wein, S Chacko
1Division of Urology and Department of Pathobiology, University of Pennsylvania, Philadelphia 19104, USA.
The Journal of Urology
|January 17, 2002
Summary
Osteopontin is expressed in the rabbit lower urinary tract, including the bladder epithelium and smooth muscle cells. This finding suggests osteopontin
Area of Science:
- Urology
- Cell Biology
- Biochemistry
Background:
- Osteopontin is a phosphorylated sialoprotein with known receptors (vitronectin receptor/alphavbeta3 integrin and hyaluronan receptor/CD44) expressed in the bladder.
- Osteopontin protein is detectable in urine, suggesting its production within the urinary tract.
Purpose of the Study:
- To investigate the expression of osteopontin and its receptors in the lower urinary tract.
- To determine if osteopontin is produced by bladder tissues.
Main Methods:
- Analysis of osteopontin messenger RNA (mRNA) and protein in adult and neonatal rabbit urinary tracts using RT-PCR and immunohistochemistry.
- Localization of osteopontin receptors (alphavbeta3 integrin and CD44) in adult bladders and cultured detrusor myocytes.
Main Results:
- Significant osteopontin mRNA levels were found in the adult renal pelvis, ureter, bladder, urethra, and neonatal bladders.
- Immunohistochemistry confirmed osteopontin expression in all bladder epithelial layers, co-localizing with alphavbeta3 integrin and CD44.
- Osteopontin was detected in detrusor smooth muscle cells, and its mRNA expression was stable in cultured myocytes, modulated by growth factors.
Conclusions:
- Adult and neonatal rabbit detrusors are significant sources of osteopontin, both in vivo and in vitro.
- Epithelial osteopontin may contribute to urinary osteopontin levels.
- Osteopontin's co-localization with its receptors in the bladder epithelium suggests a role in maintaining bladder integrity and impermeability.