Chlamydia muridarum induction of glandular duct dilation in mice

Although Chlamydia-induced hydrosalpinx in women and mice has been used as a surrogate marker for tubal infertility, the medical relevance of nontubal pathologies, such as uterine horn dilation, developed in mice following chlamydial infection remains unclear. We now report that the uterine horn dilation correlates with glandular duct dilation detected microscopically following Chlamydia muridarum infection. The dilated glandular ducts pushed the uterine horn lumen to closure or dilation and even broke through the myometrium to develop extrusion outside the uterine horn. The severity scores of uterine horn dilation observed macroscopically correlated well with the number of cross sections of the dilated glandular ducts counted under microscopy. Chlamydial infection was detected in the glandular epithelial cells, potentially leading to inflammation and dilation of the glandular ducts. Direct delivery of C. muridarum into the mouse uterus increased both uterine horn/glandular duct dilation and hydrosalpinx. However, the chlamydial plasmid, which is essential for the induction of hydrosalpinx, was not required for the induction of uterine horn/glandular duct dilation. Screening 12 strains of mice for uterine horn dilation following C. muridarum infection revealed that B10.D2, C57BL/10J, and C57BL/6J mice were most susceptible, followed by BALB/cJ and A/J mice. Deficiency in host genes involved in immune responses failed to significantly alter the C. muridarum induction of uterine horn dilation. Nevertheless, the chlamydial induction of uterine horn/glandular duct dilation may be used to evaluate plasmid-independent pathogenicity of Chlamydia in susceptible mice.