Laminin expression patterns in human ureteral tissue.

PURPOSE

Laminins are extracellular matrix proteins that are involved in various cellular functions, including adhesion, proliferation and differentiation. In this study we examined the expression patterns of the laminin chains in human ureteral tissue in vitro and in vivo.

MATERIALS AND METHODS

We screened the expression of laminin chains at the mRNA level and determined the major laminins expressed in epithelial and stromal cells of human ureteral tissue by reverse transcriptase-polymerase chain reaction and Western blot analysis. We also examined their expression in vivo by immunofluorescence study.

RESULTS

Reverse transcriptase-polymerase chain reaction analysis revealed that urothelial cells in vitro expressed laminins alpha1, alpha3, alpha5, beta1, beta2, beta3, gamma1 and gamma2, while stromal cells expressed alpha1, alpha2, alpha4, alpha5, beta1, beta2 and gamma1. Western blot analysis under reduced conditions confirmed that urothelial cells expressed laminin alpha3 and alpha5, while stromal cells strongly expressed alpha4 and alpha2. Immunofluorescence labeling with antilaminin alpha chain antibodies in human ureteral tissues confirmed that laminin alpha2, alpha3 and alpha5 chains were strongly expressed in the basement membrane of the urothelium, while alpha4 was expressed predominantly in smooth muscle cells.

CONCLUSIONS

The most prominent laminin of urothelial cells was laminin 5 (alpha3beta3gamma2), whereas in stromal cells we noted laminins 8/9 (alpha4beta1/2gamma1). Laminin alpha5 showed the widest distribution pattern in vivo. Our data may be useful for understanding the mechanism involved not only in cell growth and differentiation, but also in cancer invasion in the urinary tract.