Gonadotropin stimulation in mice leads to ovarian accumulation of immature myeloid cells and altered expression of proangiogenic genes.

OBJECTIVE: Ovarian hyperstimulation syndrome is associated with increased angiogenesis and vascular leakage. Immature myeloid cells (IMCs) and dendritic cells have been shown to be actively involved in angiogenesis in several disease models in mice and humans. Nevertheless, little is known about the role of these cells in the ovary. As such, this study sought to determine whether alterations in these ovarian myeloid cell populations are associated with gonadotropin stimulation in a mouse model. STUDY DESIGN: Four-week-old pre-pubertal C57Bl/6 female mice were allocated into three groups: high-dose stimulation (n=4; pregnant mare serum gonadotropins (PMSG) 20U for 2 days), low-dose stimulation (n=5; PMSG 5U for 1 day) and sham-treated controls (n=4). Human chorionic gonadotropin 5U was injected on Day 3, and the mice were killed on Day 5. Ovaries were analysed by flow cytometry, confocal microscopy and quantitative polymerase chain reaction. RESULTS: Gonadotropin stimulation increased the proportion of CD11b(+)Gr1(+) IMCs among the ovarian myeloid cells: 22.6±8.1% (high dose), 7.2±1.6% (low dose) and 4.1±0.3% (control) (p=0.02). Conversely, gonadotropin stimulation decreased the proportion of ovarian CD11c(+)MHCII(+) dendritic cells: 15.1±1.9% (high dose), 20.7±4.8% (low dose) and 27.3±8.2% (control) (p=0.02). IMCs, unlike dendritic cells, were localized adjacent to PECAM1(+) endothelial cells. Finally, gonadotropin stimulation was associated with increased expression of S100A8, S100A9, Vcan and Dmbt1, and decreased expression of MMP12. CONCLUSIONS: Gonadotropin stimulation is associated with proangiogenic myeloid cell alterations, reflected by a dose-dependent increase in ovarian IMCs and a parallel decrease in dendritic cells. Recruited IMCs localize strategically at sites of angiogenesis. These changes are associated with differential expression of key proangiogenic genes.

Unique expression patterns associated with preferential recruitment of immature myeloid cells into angiogenic versus dormant tumors.

Cancer progression from microscopic dormant tumors into disseminated disease involves tumor angiogenesis, and is commonly referred to as the 'angiogenic switch'. CD11b(+)Gr1(+) immature myeloid cells (IMCs) were reported to promote angiogenesis and tumor progression. Here, we studied a model of tumor dormancy, in which Lewis Lung Carcinoma tumor cells were inoculated intra-abdominally into C57Bl/6J mice. Dormancy versus expansive growth was determined by the site of tumor implantation (lower vs upper abdomen). Global gene expression of IMCs was evaluated in different stages of recruitment, starting in the bone marrow, followed by the peripheral blood and finally in the vascular versus dormant tumors. We first demonstrated a ∼3 fold enrichment of IMCs within vascular tumors as compared with dormant tumors, correlating with tumor-infiltrating CD31(+) endothelial cells. Although their migration from the PB into dormant tumors led to differential expression of a relatively small number of genes, recruitment of IMCs into the upper tumors was associated with a profound transcriptional response. Importantly, a large set of proangiogenic genes were significantly upregulated in IMCs derived from vascular tumors compared with those derived from dormant tumors. We therefore, suggest that proangiogenic versus nonangiogenic transcriptional patterns is associated with the ability of IMCs to promote tumor angiogenesis.

TGFbeta-dependent gene expression profile during maturation of dendritic cells.

Primary immune response to pathogens involves the maturation of antigen-presenting dendritic cells (DC). Bacterial lipopolysacharride (LPS) is a potent inducer of DC maturation, whereas the transforming growth factor beta (TGFbeta) attenuates much of this process. Here, we analyzed the global gene expression pattern in LPS-treated bone marrow derived DC during inhibition of their maturation process by TGFbeta. Exposure of DC to LPS induces a pronounced cell response, manifested in altered expression of a large number of genes. Interestingly, TGFbeta did not affect most of the LPS responding genes. Nevertheless, analysis identified a subset of genes that did respond to TGFbeta, among them the two inflammatory cytokines interleukin (IL)-12 and IL-18. Expression of IL-12, the major proinflammatory cytokine secreted by mature DC, was downregulated by TGFbeta, whereas the expression level of the proinflammatory cytokine IL-18, known to potentiate the IL-12 effect, was upregulated. Expression of the peroxisome proliferator-activated receptor gamma (PPARgamma) increased in response to TGFbeta, concomitantly with reduced expression of chemokine receptor 7 (CCR7). This finding supports the possibility that TGFbeta-dependent inhibition of CCR7 expression in DC is mediated by PPARgamma.