A role for CXC chemokine receptor-2 in the pathogenesis of urogenital Chlamydia muridarum infection in mice.

We tested the hypothesis that a specific chemokine receptor, CXC chemokine receptor-2 (CXCR2), mediates acute inflammatory damage during chlamydial urogenital infection, which ultimately leads to the chronic sequelae of hydrosalpinx - a surrogate marker of infertility. Homozygous CXCR2 genetic knockouts (CXCR2-/-), heterozygous littermates (CXCR2+/-) or homozygous wild-type (wt) controls (CXCR2+/+) were infected intravaginally with Chlamydia muridarum. Although no change was observed in the infection in the lower genital tract based on CXCR zygosity, a delay in the ascension of infection into the upper genital tract was seen in CXCR2-/- mice. Significantly elevated peripheral blood neutrophil counts were observed in CXCR2-/- mice when compared with controls. Reduced rates of acute inflammatory indices were observed in the affected tissue, indicating reduced neutrophil extravasation capacity in the absence of CXCR2. Of note was a reduction in the postinfection development of hydrosalpinx that correlated with CXCR2 zygosity, with both CXCR2-/- (13%) and their CXCR2+/- (35%) littermates displaying significantly lower rates of hydrosalpinx formation than the wt CXCR2-sufficient mice (93%). We conclude that CXCR2 ligands are a major chemotactic signal that induces damaging acute inflammation and the resulting chronic pathology during the repair phase of the host response, but are dispensable for the resolution of infection.

A link between neutrophils and chronic disease manifestations of Chlamydia muridarum urogenital infection of mice.

Vigorous acute inflammatory responses accompany Chlamydia muridarum infections in mice and are positively correlated with adverse urogenital and respiratory tract infection outcomes in the mouse model. Thus, we tested the hypothesis that neutrophils induce an acute inflammatory insult that, in the repair phase, leads to the chronic sequelae of hydrosalpinx - a surrogate marker of infertility in the mouse model. To this end, we induced neutropenia in mice using a neutrophil-depleting monoclonal antibody during acute phases of C. muridarum urogenital infection only (days 2-21 postinfection). To prove induced neutropenia, peripheral blood was monitored for neutrophils during the treatment regimen. Neutropenic mice had a similar infection course as control mice, but had significantly reduced levels of certain histopathological parameters, reduced production of matrix metalloproteinase-9 (MMP-9) and reduced rates of hydrosalpinx following resolution of the infection. We conclude that neutrophils are a major source of MMP-9, a previously proved pathological factor in this model. Further, we conclude that acute inflammation in the form of neutrophils and neutrophil activation products are at least partially responsible for inducing the histological changes that ultimately result in fibrosis and infertility in the mouse model of chlamydial upper genital tract disease.

Melanotic neuroectodermal tumor of infancy presenting in the subcutaneous soft tissue of the thigh.

Melanotic neuroectodermal tumor of infancy (MNTI) is a rare and diagnostically challenging neoplasm typically presenting in the bones of the maxilla, skull, or mandible. Only 6 of approximately 357 reported cases have involved the subcutis. We describe a case of MNTI presenting as a palpable, subcutaneous, thigh mass in a 5-month-old girl. By ultrasound, the mass was round with well-defined borders, minimal vascularity, and heterogeneous echogenicity. Microscopically, the tumor consisted of nested foci of primitive-appearing small round blue cells with an increased nuclear to cytoplasmic ratio, stippled chromatin, and occasional mitotic figures. A larger and more epithelioid second cell population exhibited eosinophilic cytoplasm and sparse pigmented granules. The background stroma was fibrous and densely sclerotic. The differential diagnosis of soft tissue MNTI can include melanoma, neuroblastoma, rhabdomyosarcoma, desmoplastic small round cell tumor, and other pediatric "small round cell" neoplasms. The tumor had the characteristic immunophenotype of MNTI: cytokeratin+, HMB-45+, neuron-specific enolase+, and synaptophysin+. MNTI should be considered in the differential diagnosis of pigmented soft tissue lesions in children. Our patient remains disease-free 40 months after excision, although these tumors can locally recur (10%-20%) and rarely metastasize.

A role for matrix metalloproteinase-9 in pathogenesis of urogenital Chlamydia muridarum infection in mice.

Matrix metalloproteinases (MMPs) are a family of host-derived enzymes involved in the turnover of extracellular matrix (ECM) molecules and the processing of cytokines, chemokines and growth factors. We have previously reported that global inhibition of MMP in Chlamydia muridarum urogenital tract infection of susceptible strains of female mice impeded ascension of C. muridarum into the upper genital tract, blunted acute inflammatory responses and reduced the rate of formation of chronic disease. Because we have also observed that MMP-9 (also known as gelatinase B) is expressed in relatively large quantities in susceptible strains of mice in response to infection during acute phases of infection, we explored this further in a more selected fashion. We infected MMP-9 gene knockout mice and wild type controls intravaginally with C. muridarum. Both groups of mice had similar isolation rates from the lower urogenital tract but the absence of MMP-9 resulted in a slightly lower isolation rate in the upper genital tract, blunted acute inflammatory indices in the affected tissues and a reduced rate of formation of hydrosalpinx-a surrogate marker of infertility. These results imply that MMP-9 is involved in pathogenesis of chlamydial infection in this model possibly by amplifying inflammatory responses.