Quantitative analysis of epithelial cells in urine from men with and without urethritis: implications for studying epithelial: pathogen interactions in vivo.

Background: Epithelial cells in first catch urine (FCU) specimens from 87 men with and without urethritis were quantified. Epithelial cells were broadly categorised into transitional and squamous populations using morphological characteristics and immunostaining with anti-pan leukocyte and anti-cytokeratin monoclonal antibodies.

Findings: The majority (77/87 = 89%) of samples contained both transitional (76/87 = 87%; range 1 x 10(4) - 6 x 10(5), median 6 x 10(4)) and squamous (57/87 = 66%; range 1 x 10(4) - 8 x 10(5), median 2 x 10(4)) epithelial cells. The number of transitional cells correlated with the number of squamous cells (Spearman's rho = 0.697 p < 0.001). Squamous, but not transitional, cell numbers correlated with leukocyte numbers (Spearman's rho = 0.216 p = 0.045 and rho = 0.171 and p = 0.113, respectively). However there was no significant difference in epithelial cell numbers between men with and without urethritis. Nevertheless, some men with urethritis had relatively high numbers of transitional cells in their FCU. Transitional cells were morphologically heterogeneous and appeared to display complex cytokeratin phenotypes.

Conclusion: Further studies are required to explore the complexity of epithelial cell populations in urine. These would provide novel opportunities for studying cellular interactions of C. trachomatis in male urethral infections, about which little is currently known.