Co-localization of matrix metalloproteinase-1 and mast cell tryptase in the human uterus.

The endometrium displays characteristic cyclical changes involving proliferation and differentiation. The differentiation that takes place requires major tissue remodelling involving the matrix metalloproteinase (MMP) family as key enzymes in this process. Mast cells, containing the tryptase and chymase enzymes that are capable of stimulating the MMP cascade, have been identified in the endometrium, but their role is still unclear. In this study, we observed that the majority of mast cells in the uterus reside in the myometrium and that they co-express mast cell tryptase and MMP-1 in the same intracellular granules. In endometrium exposed to synthetic progestogen via an intrauterine levonorgestrel system a significant increase in mast cells numbers was observed in women experiencing breakthrough bleeding compared to those in women with no reported bleeding. We conclude that mast cells contain MMP-1 and we postulate a potential role for mast cells in breakthrough bleeding.

Regulation of bcl-2 gene family members in human endometrium by antiprogestin administration in vivo.

It is likely that the changes which occur in the endometrium throughout the menstrual cycle involve apoptosis, and that expression of associated genes, such as the bcl-2 family, are regulated by sex steroids. The aim of this study was to investigate the presence of bcl-2, Bax and oestrogen receptor proteins in secretory endometrium collected from ten patients with normal ovulatory cycles 4 or 6 days after the LH surge, and on the same days in a subsequent cycle in which the formation of secretory changes was inhibited by the administration of the antiprogestin mifepristone (RU486) 2 days after the onset of the LH surge. Since some stromal cells display positive immunoreactivity, leucocyte subpopulations of macrophages (CD68-positive) and large granular lymphocytes (CD56-positive) were identified in serial sections. After administration of mifepristone on day 2 after the LH surge, a significant increase in bcl-2 immunoreactivity was observed in glandular and surface epithelium. A positive correlation (0.874) with nuclear oestrogen receptor immunoreactivity in endometrial glands was demonstrated. Subsets of stromal cells, identified as CD68-positive macrophages and CD56-positive large granular lymphocytes displayed positive immunoreactivity for the bcl-2 epitope, which was unaffected by mifepristone administration. Bax immunostaining was similar in control and antiprogestin-treated endometrium. These data indicate that antiprogestin administration inhibits progesterone downregulation of steroid receptors in endometrial glands, resulting in persistence of a proliferative endometrium and accompanying bcl-2 secretion.

Perivascular interleukin-8 messenger ribonucleic acid expression in human endometrium varies across the menstrual cycle and in early pregnancy decidua.

Human endometrium and decidua contain large numbers of different leukocyte populations, the concentration of which fluctuates during the menstrual cycle and pregnancy. There is, for example, a large influx of neutrophils into premenstrual endometrium associated with an increased expression of interleukin (IL)-8 protein, which is chemotactic for neutrophils. Our aim in this study was to localize IL-8 messenger RNA (mRNA) expression in endometrium and decidua using in situ hybridization. In situ hybridization was carried out with a 35S-uridine 5'-triphosphate-labeled riboprobe using standard procedures. Late secretory endometrial and decidual biopsies demonstrated clear perivascular localization of IL-8 mRNA, with additional expression colocalized to activated macrophages. Midluteal endometrium showed minimal IL-8 expression, whereas endometrium obtained from women administered progesterone for 4 days from (LH peak + 8 days), to simulate luteal regression, demonstrated significantly increased localization of IL-8 mRNA, 48 h after withdrawal of progesterone. In conclusion, IL-8 mRNA expression is localized to perivascular cells of late secretory endometrium and decidua.

Role of inflammatory mediators in human endometrium during progesterone withdrawal and early pregnancy.

The role of progesterone (P4) in the regulation of inflammatory mediators interleukin-8 (IL-8), monocyte chemoattractant protein-1, and cyclooxygenase-2 (COX-2) and in the recruitment of leukocyte subpopulations in the endometrium has been examined, by employing a model of P4 withdrawal and maintenance in vivo. Messenger RNA and protein expression have been investigated in endometrial biopsies: 1) during the midsecretory phase (LH+8 to 10); during the maintained luteal phase (P4 administered vaginally for 4 days from LH+8) and biopsies collected 2) 24 h and 3) 48 h post withdrawal of P4; and 4) during pseudo pregnancy (lifespan of corpus luteum extended by 7 days with CG; (decidua collected from women with 5) an ectopic gestation and 6) from women undergoing first-trimester termination of pregnancy). CD56+ large granular lymphocytes remain the major leukocyte subtype, both 24 and 48 h after P4 withdrawal, and in decidua (CG supported or ectopic). Higher numbers (P < 0.05) of macrophages (CD68+) were present in endometrium 48 h post P4 withdrawal and in pseudo pregnant endometrium, compared with normal decidua. Significantly more macrophages (P < 0.01) were present in decidua from an ectopic pregnancy. A significant elevation of IL-8 (P < 0.01) and COX-2 (P < 0.05) messenger RNA was detected 48 h post P4 withdrawal. Evidence is provided for up-regulation of IL-8 and COX-2 in response to P4 withdrawal.

Morphological and functional features of endometrial decidualization following long-term intrauterine levonorgestrel delivery.

Irregular bleeding remains a common reason for the discontinuation of progestin-only contraception. The levonorgestrel releasing intrauterine system (LNG-IUS) has profound morphological effects upon the endometrium. Specific features are gland atrophy and extensive decidual transformation of the stroma. Morphological changes in the endometrium may be associated with perturbation of mechanisms regulating normal endometrial function. This study describes endometrial stromal and glandular features prior to and up to 12 months following insertion of the LNG-IUS. Comparison is made with first trimester decidua. In order to elucidate further mechanisms governing endometrial function with local intrauterine delivery of LNG, we here report histological features consistent with decidualization; a significant increase in granulocyte-macrophage colony stimulating factor (GM-CSF) immunoreactivity in decidualized stromal cells; glandular and stromal prolactin receptor expression and an infiltrate of CD56 + large granular lymphocytes and CD68 + macrophages. We are unaware of previous reports which have documented longitudinally both morphological and functional observations in endometrium exposed to local intrauterine levonorgestrel delivery. These studies demonstrate that long-term administration of intrauterine levonorgestrel results in features of altered morphology and function. No correlation was apparent between the end points in the study and the bleeding patterns described by the subjects. Further evaluation of these features in the context of menstrual bleeding experience may contribute to a better understanding of this troublesome side-effect which often leads to dissatisfaction and discontinuation of the intrauterine system.

PIP: The levonorgestrel-releasing intrauterine system (LNG-IUS) has profound morphologic effects on the endometrium, including gland atrophy and extensive decidual transformation of the stroma. The present study investigated these morphologic changes in tissue samples collected from 14 UK women up to 12 months after insertion of the LNG-IUS. Observed histologic features consistent with decidualization included a significant increase in granulocyte-macrophage colony stimulating factor immunoreactivity in decidualized stromal cells, glandular and stromal prolactin receptor expression, and an infiltrate of CD56+ large granular lymphocytes and CD68+ macrophages. The features of pseudo-decidualization closely resembled the morphology of early pregnancy decidua. These findings confirm that the stromal compartment of the endometrium undergoes changes consistent with decidualization for at least up to 12 months after insertion of an LNG-IUS. There was no correlation between the study endpoints and the menstrual patterns reported by study subjects. Further study of the decidualized nature of the stromal cells in the LNG-exposed endometrium should enhance understanding of the mechanisms responsible for breakthrough bleeding in users of progestogen-only contraceptives.

Sex steroid regulation of leukocyte traffic in human decidua.

Endometrial leukocyte subpopulations vary over the reproductive cycle, but no data exist on the mechanism regulating their recruitment into uterine tissue. This study has evaluated the role of progesterone in the recruitment of selected leukocyte populations in early pregnancy decidua. Decidua was collected from women in early pregnancy at the time of vacuum aspiration of the uterus 6, 12, 24 and 36 h after taking 200 mg mifepristone (RU486). Standard immunohistochemical techniques were employed to demonstrate the selected leukocyte populations in decidual tissue and these were analysed using imaged analysis. Fresh decidua was incubated in medium for 24 h and supernatants assayed for interleukin (IL-8) (neutrophil chemotactic factor) and MCP-1 (monocyte chemoattractant protein-1) content. Analysis of variance demonstrated a significant increase in tissue monocyte number in decidua 12-36 h after mifepristone administration. No significant changes in other leukocyte subpopulations were observed. Decidua IL-8 concentrations were significantly increased (P = 0.019) 6 h after mifepristone and decidual MCP-1 concentration rose (non-significant) and fell significantly (P = 0.029) between 6 and 12 h after mifepristone. Progesterone withdrawal may initiate a local cascade of events involving inflammatory mediators which in turn are responsible for the influx of monocytes. This influx may be essential in the process of shedding of endometrium or decidua since monocytes and neutrophils are important sources of proteases and collagenases. Furthermore, these cells are potential local sources of immunomodulatory cytokines.