The occurrence of uterine stromal and intraepithelial monocytes and heterophils during normal late pregnancy in the rat

Modeling Trophoblast Cell-Guided Uterine Spiral Artery Transformation in the Rat

The rat possesses hemochorial placentation with deep intrauterine trophoblast cell invasion and trophoblast-guided uterine spiral artery remodeling, which resembles human placentation. Uterine spiral arteries are extensively remodeled to deliver sufficient supply of maternal blood and nutrients to the developing fetus. Inadequacies in these key processes negatively impact fetal growth and development. Recent innovations in genome editing combined with effective phenotyping strategies have provided new insights into placental development. Application of these research approaches has highlighted both conserved and species-specific features of hemochorial placentation. The review provides foundational information on rat hemochorial placental development and function during physiological and pathological states, especially as related to the invasive trophoblast cell-guided transformation of uterine spiral arteries. Our goal is to showcase the utility of the rat as a model for in vivo mechanistic investigations targeting regulatory events within the uterine-placental interface.

Mifepristone acts as progesterone antagonist of non-genomic responses but inhibits phytohemagglutinin-induced proliferation in human T cells

BACKGROUND

Progesterone is an endogenous immunomodulator that suppresses T cell activation during pregnancy. The stimulation of membrane progesterone receptors (mPRs) would seem to be the cause of rapid non-genomic responses in human peripheral T cells, such as an elevation of intracellular calcium ([Ca(2+)](i)) and decreased intracellular pH (pH(i)). Mifepristone (RU486) produces mixed agonist/antagonist effects on immune cells compared with progesterone. We explored whether RU486 is an antagonist to mPRs and can block rapid non-genomic responses and the induction by phytohemagglutinin (PHA) of cell proliferation.

METHODS

Human male peripheral T cell responses in terms of pH(i) and [Ca(2+)](i) changes were measured using the fluorescent dyes, 2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein (BCECF) and fura-2, respectively. Expression of mPR mRNA was determined by RT-PCR analysis. Cell proliferation and cell toxicity were determined by [(3)H]-thymidine incorporation and MTT assay, respectively.

RESULTS

The mRNAs of mPRalpha, mPRbeta and mPRgamma were expressed in T cells. RU486 blocked progesterone-mediated rapid responses including, the [Ca(2+)](i) increase and pH(i) decrease, in a dose related manner. RU486 did not block, but enhanced, the inhibitory effect of progesterone on PHA induced cell proliferation. RU486 alone inhibited proliferation induced by PHA and at >25 microM seems to be cytotoxic against resting T cells (P < 0.01).

CONCLUSIONS

RU486 is antagonistic to the rapid mPR-mediated non-genomic responses, but is synergistic with progesterone with respect to the inhibition of PHA-induced cell proliferation. Our findings shine new light on RU486's clinical application and how this relates to the non-genomic rapid physiological responses caused by progesterone.

Intrauterine fate of invasive trophoblast cells

Invasion of trophoblast cells into the uterine spiral arteries and the uterine wall is characteristic of hemochorial placentation. In the rat, trophoblast cells penetrate through the uterine decidua and well into the metrial gland. In this report, we examined the fate of these invasive trophoblast cells following parturition. Invasive trophoblast endocrine cells were retained in the postpartum mesometrial uterus in the rat. The demise of invasive trophoblast cells was followed by the appearance of differentiated smooth muscle cells surrounding blood vessels previously lined by invasive trophoblast cells and an infiltration of macrophages. Regulation of intrauterine trophoblast cell fate was investigated following premature removal of the fetus or removal of the fetus and chorioallantoic placenta. The presence of the fetus affected the distribution of invasive trophoblast cells within the uterus but did not negatively impact their survival. Premature removal of all chorioallantoic placentas and associated fetuses from a uterus resulted in extensive removal of intrauterine trophoblast cells. In summary, the postpartum demise of intrauterine invasive trophoblast cells is a dynamic developmental event regulated in part by the removal of trophic signals emanating from the chorioallantoic placenta.

The non-genomic effects on Na+/H+-exchange 1 by progesterone and 20α-hydroxyprogesterone in human T cells

Progesterone is an endogenous immunomodulator and can suppress T-cell activation during pregnancy. We have previously shown that the non-genomic effects of progesterone, especially acidification, are exerted via plasma membrane sites and suppress cellular genomic responses to mitogens. This study aimed to show that acidification is due to a non-genomic inhibition of Na(+)/H(+)-exchange 1 (NHE1) by progesterone and correlate this with immunosuppressive phytohemagglutinin (PHA)-induced T-cell proliferation. The presence of amiloride-sensitive NHE 1 was identified in T cells. The activity of NHE1 was inhibited by progesterone but not by 20alpha-hydroxyprogesterone (20alpha-OHP). Furthermore, 20alpha-OHP was able to compete with progesterone and release the inhibitory effect on the NHE1. The inhibition of NHE1 activity by progesterone-BSA demonstrated non-genomic action via plasma membrane sites. Finally, co-stimulation with PHA and progesterone or amiloride, (5-(N, N-dimethyl)-amiloride, DMA), inhibited PHA-induced T-cell proliferation, but this inhibition did not occur with 20alpha-OHP and PHA co-stimulation. However, when DMA was applied 72 h after PHA stimulation, it was able to suppress PHA-induced T-cell proliferation. This is the first study to show that progesterone causes a rapid non-genomic inhibition of plasma membrane NHE1 activity in T cells within minutes which is released by 20alpha-OHP. The inhibition of NHE1 leads to immunosuppressive T-cell proliferation and suggests that progesterone might exert a major rapid non-genomic suppressive effect on NHE1 activity at the maternal-fetal interface in vivo and that 20alpha-OHP may possibly be able to quickly release the suppression when T cells circulated away from the interface.

Macrophage density in the pregnant rat uterine cervix is modulated by mast cell degranulation

The uterine cervix at term undergoes histomorphological changes that resemble an inflammatory process. The aim of this study was to better characterize these changes, describing the temporal and spatial pattern of macrophages and mast cells (MC) distribution in the uterine cervix and assessing whether both cells exert a coordinated action on angiogenesis. Macrophages and MC were identified by immunohistochemistry in cervical tissue from cycling, pregnant and postpartum rats. In order to inhibit MC degranulation, pregnant rats were injected with disodium cromoglycate. The expression of vascular endothelial growth factor (VEGF) by macrophages was also evaluated. Results showed that macrophage density increased towards parturition and declined at postpartum, whereas MC density showed an inverse pattern. Interestingly, disodium cromoglycate-treated rats showed an increased number of macrophages. VEGF expression in macrophages was detected neither in control nor in treated animals; however, a coordinated action between MC and macrophages on angiogenesis could not be excluded. The present study provides a detailed mapping of macrophage and MC densities and distribution in the rat uterine cervix. Moreover, an association between macrophages and MC along pregnancy is shown, and evidence that macrophage density in the rat cervix is modulated by MC degranulation is presented.

Regulation of Numbers of Macrophages in the Endometrium of the Sheep by Systemic Effects of Pregnancy, Local Presence of the Conceptus, and Progesterone

Many species exhibiting hemochorial placentation experience an accumulation of macrophages in the endometrium during pregnancy. For the present study, it was tested whether macrophages also accumulate in the endometrium of the sheep, which is a species undergoing an epitheliochorial placentation. An additional objective was to determine whether regulation of endometrial macrophage number occurs via systemic or local signals and whether progesterone is one of these signals. The approach was to evaluate presence of macrophages immunohistochemically using antibodies to CD68 and CD14. Tissues examined were from cyclic ewes in the luteal phase of the estrous cycle, unilaterally-pregnant ewes at day 140 of pregnancy in which pregnancy was surgically confined to one uterine horn, ovariectomized ewes, and ovariectomized ewes treated with progesterone for 44 days. Macrophages were localized predominately to the stromal compartment of the stratum compactum region of the endometrium. In non-pregnant ewes, macrophages were not abundant regardless of physiological status. Increased numbers of endometrial macrophages were seen for both the pregnant and non-pregnant uterine horns of unilaterally pregnant ewes. Numbers of macrophages were higher in the endometrium from the pregnant uterine horn than from endometrium from the non-pregnant uterine horn. Results indicate that macrophages accumulate in the endometrium by day 140 of pregnancy in the sheep and that this induction is because of both systemic and local signals. Progesterone appears not to be an important regulator of numbers of endometrial macrophages.

Distribution and activation of uterine mononuclear phagocytes in peripartum endometrium and myometrium of the mouse

The present study tested the hypothesis that macrophage distribution and activation are enhanced in the uterus before term. Mid-uterine horn tissue strips from mice on Days 15 and 18 of pregnancy, the day of birth (= Day 19), and one day postpartum were paraffin-embedded and then sectioned, stained with a monoclonal pan-macrophage marker (BM8), and processed for visualization and quantification of resident macrophages per nuclear area. Macrophages were dispersed throughout the endometrium and subluminal epithelium; cell numbers declined on the day before term, then increased postpartum. Within myometrium, macrophages congregated in stroma surrounding muscle bundles, and staining was enhanced near term. Macrophage numbers were similar in pregnant and postpartum uteri, enhanced more than 2-fold over those in nonpregnant controls. Uterine sections were also analyzed by laser-scanning cytometry to enumerate activated macrophages (i.e., those that express the intercellular adhesion molecule marker CD54+) and to determine cell cycle (propidium iodide fluorescence). Activated macrophages were directly proportional to cell numbers and, by cell cycle analysis, were not terminally differentiated. Highest cell numbers occurred on Day 15: 4-fold greater than those in nonpregnant controls and 2-fold higher than those at Day 18 or in postpartum groups. These findings indicate a decline in endometrial macrophage numbers at least one day before the onset of parturition and raise the possibility that trafficking of this immune cell may contribute to onset of labor.

Effect of estrophilic platinum complex on the mouse uterus

Resistance of hormone-dependent mammary carcinoma to cisplatin as a potent antitumor agent led to the synthesis of other estrophilic platinum complexes. In this investigation, the effects of a newly synthesized estrogen-receptor affine platinum complex on the mouse uterus were studied using light and electron-microscopy. The results have been compared with Tamoxifen, cisplatin and the estrophilic ligand. Both estrophilic ligand and estrophilic platinum complex produced strong estrogenic effects as well as features characteristic of the uterine epithelial cell in the luteal phase of the cycle, corresponding to a massive stimulation of the surface and glandular epithelial cells. The uteri showed large glandular lumina. An increase in the number of multivesicular and residual bodies, accompanied by a proliferation of eosinophilic granulocytes, was also seen. The appearance of inter- and intracellular lumina and the activation of smooth muscle cells represent further characteristic effects of the estrophilic ligand and estrophilic platinum complex. Anticipated increases in the incidence of cell death and/or deviant cyto-nuclear architecture in the uteri treated with cisplatin or platinum complex, were not observed.

Ia antigen expression in the rat uterus

Using indirect immunofluorescence and monoclonal antibodies, we have determined the distribution of Ia+ cells in the non-pregnant rat uterus. In cycling animals, Ia+ cells, most of dendritic shape and non-specific esterase negative, were abundant in the connective tissue of the myometrium and throughout the endometrium, especially adjacent to the luminal and glandular epithelia. In contrast, the number of T lymphocytes was very much less and few of these cells expressed Ia antigen. Stromal Ia+ cells were more numerous during estrus than in any other phase of the cycle. Only a few Ia+ cells were seen in neonatal uterine samples, but the numbers increased to approximately adult levels by 32 days of age. Prepubertal glands were consistently negative, but epithelial expression of Ia antigens in adult uteri showed interesting variations. The luminal epithelium was always negative, whereas the glandular epithelial cells often were positive. Glandular staining was quite heterogeneous in individual samples, but most gland profiles were negative or weakly positive during proestrus and estrus and positive during diestrus. Ovariectomized females given different steroid supplements revealed significant hormonal effects. Estrogen alone dramatically increased the numbers of Ia+ stromal cells compared with control samples, but progesterone alone had no effect. However, progesterone given with estrogen abrogated the estrogenic influence. Progesterone alone caused decreased expression of Ia antigens by the glandular epithelium. If the highly-Ia/ cells in the stroma are capable of antigen presentation, these results indicate a significant potential for local antigen processing with the uterine endometrium.

Characterization of hematogenous cellular constituents of the murine decidua: a surface marker study

Decidual tissue, which includes typical (stromal type) decidual cells as well as infiltrating leukocytes, appears to play a local immunoregulatory role in the maintenance of pregnancy in nature. The present study evaluated the contribution of numerous leukocyte subsets characterized on the basis of morphology combined with cell surface markers to the development of murine decidua during syngeneic (CBA female X CBA male) and allogeneic (CBA female X C57BL/6 male) pregnancy. Collagenase dispersed decidua were subjected to total and differential counts and cell surface labeling for a radioautographic identification of various markers: S-IgM on B cells, Thy-1 on T cells, neither marker on null lymphocytes, Lyt- (1 or 2 or 1,2) antigens on T cell subsets, Mac-1 and I-A on macrophages, using 125I-labeled monoclonal antibodies or a sandwich labeling with 125I-protein A. The total cellularity of decidua basalis showed a biphasic rise in both pregnancies, with peaks on day 11 and days 15 and 16, but the allopregnant decidua showed a higher accumulation of all cell types indicating that an allogeneic conceptus causes an augmented deciduogenesis. The number of decidual cells, the most frequent cell class, rose to a peak on day 11 followed by a decline possibly due to cell death. The number of lymphocytes, the next frequent cell class, showed a parallel pattern initially, followed by a sharp secondary rise on day 16. This rise may be due to a withdrawal of progesterone, an antiinflammatory hormone. Null cells predominated amongst decidual lymphocytes (45-80%), as well as in the progestational endometrium (53%), indicating a hormonal control of their accumulation. The frequency of B cells was low (10-13%) and T cells (25-45%) comparable to that in the blood, with Lyt-1 only class being the most common T cell subset. Allopregnant decidua also showed a late rise in the total number of Lyt-2 only cells which may have a suppressor function. Macrophages, the next common leukocyte class, all expressed Mac-1. Their number rose to a plateau by day 12, but at a higher level in allopregnancy. I-A (needed for antigen presentation) was expressed by an increasing proportion (5-60%) of macrophages with advancing gestation. These findings provide a basis for further functional studies.

Phagocytotic and iron-storing capacities of stromal cells in the rat endometrium. A histochemical and ultrastructural study

Cytoplasmic pigment inclusions of rat endometrial stromal cells were studied by histology, histochemistry, fluorescence microscopy, electron microscopy and X-ray microprobe analysis. It is shown that a number of endometrial perivascular stromal cells contain numerous free cytoplasmic ferritin particles as well as hemosiderin vacuoles. The larger pigment inclusions reveal also positive PAS- and Schmorl reactions indicating that they contain polysaccharide and lipofuscin material, respectively. These pigment-storing stromal cells also display acid phosphatase activity; they avidly phagocytose instillated latex particles. No pigment-storing cells occur within the surface or glandular epithelium, either in the basal endometrium or in the myometrium. It is demonstrated that the endometrial iron-storing cells function as iron depots; they take part in the phagocytosis and endocytosis of extracellular tissue components and therefore can be named phagocytes. Our data show that "fibroblastoid" endometrial stromal cells may differentiate into endometrial resident phagocytes, which ensure interstitial proteolysis and hence facilitate the drainage of extracellular fluid into the venous blood capillaries.

Rat uterine tissue and cell responses to the presence of plain and indomethacin-delivering IUDs

Plain silastic intrauterine devices or those containing 270 micrograms of indomethacin were inserted into the caudal portion of one uterine horn of mature Wistar rats. After a 3-week period animals were fixed by perfusion on the morning of day 2 after estrus. Segments of uterine tissue corresponding to regions adjacent to and cranial to the devices as well as an equivalent portion of the contralateral horn were embedded in glycol methacrylate. A group of control animals without any form of device were treated in an identical manner. Sections cut from these segments were evaluated by grid-point stereology to ascertain changes in tissue volumes and cell populations. It was found that the presence of plain devices induced hypertrophy in the stroma and myometrium of the portion of the uterus adjacent to the device. The presence of indomethacin in such devices prevented stromal hypertrophy. No changes in populations of fibroblasts or areas of glandular or vascular tissue were evident in any treatment group. Cell populations of neutrophils, eosinophils, and mononuclear cells, however, were elevated in the superficial stroma of the horns bearing either type of device; this feature was more pronounced for neutrophils in the presence of the indomethacin devices. Neutrophils, rather than eosinophils, predominated in the epithelia of the uterus bearing either type of IUD. Conversely, eosinophil populations were reduced in the superficial tissues cranial to the devices delivering indomethacin. Neutrophils and mononuclear cells were also found to be elevated in the deep stroma of tissues adjacent to both the plain and medicated device.

Migration of leucocytes into the uterus after acute removal of ovarian progesterone during early pregnancy in the sheep

The effects of acute deprivation of progesterone during early pregnancy on the occurrence of maternal leucocytes in uterine tissues was studied in sheep. Ovariectomy on day 21 of pregnancy resulted in a rapid influx of polymorphonuclear (PM) leucocytes into both caruncular and intercaruncular (glandular) endometrium but not into the myometrium. The infiltration had commenced by 24 hours after ovariectomy when the fetal membranes appeared histologically normal. By 72 hours after ovariectomy infiltration of PM leucocytes and degradation of the fetal syncytium were severe and extensive. The effect was specifically due to progesterone deprivation in pregnant animals since it was not seen in progesterone-treated ovariectomized pregnant animals or in non-pregnant animals ovariectomized in the mid luteal phase of the oestrous cycle. The PM leucocyte influx was not associated with changes in the number of intra-epithelial lymphocytes, the occurrence of which was only slightly reduced at the time of attachment. The results implicate maternal progesterone as a local anti-inflammatory agent within the gravid uterus and also show that total expulsion of lymphocytes from uterine epithelia at implantation is not a mechanism for immunoprotection of the sheep fetal allograft.

Steroids as immunosuppressants in pregnancy

In considering the potential of known reproductive hormones to act as immunoregulatory substances during pregnancy, progesterone clearly is an attractive candidate for the following reasons: 1) progesterone is a primitive hormone occurring in virtually all species; 2) it is the only hormone which has been shown to be absolutely essential for maintenance of pregnancy in a variety of mammals, including the human; 3) it has demonstrable in vivo and in vitro immunosuppressive effects when present in concentrations known to be present in the human placenta; 4) it has weak systemic effects compared to cortisol; 5) in many species including primates, it is produced by trophoblastic cells: potential targets of the maternal immune system. Inhibitory effects of progesterone on immune cells have been demonstrated despite the absence of classical steroid receptors for progesterone (Lippman 1979). Specific functions of human T-lymphocytes and macrophages are inhibited by concentrations of progesterone known to occur in the placenta (10(-6)-10(-5) M). Although similar effects are produced by cortisol, clear-cut differences exist in the mechanisms by which cortisol and progesterone act on immune cells. The results suggest, but do not prove, that progesterone does not act on immune cells by binding to the glucocorticoid receptor. This can be considered to be advantageous, for otherwise pregnancy could be associated with glucocorticoid toxicity. Remarkable local anti-inflammatory activity of progesterone has been observed in vivo, although the mechanism of this effect is poorly understood. The striking absence of inflammatory cells in the pregnant uterus until a few days before birth is consistent with known effects of progesterone from animal studies. Whether this regulatory effect on cell traffic is exerted directly by progesterone or by secondary mediators produced within the uterus remains to be determined. In either case, appropriate timing of the removal of progesterone's influence may constitute an integral part of the process of parturition. Post-partum resolution of the placental attachment-site has many of the cellular characteristics of transplant rejection. Furthermore, it has recently been proposed that inflammatory cells which invade the cervix may generate prostaglandins which mediate the biochemical changes that are essential for its dilation to allow escape of the fetus (Liggins 1981). If the processes begin prior to delivery as a consequence either of progesterone withdrawal or inhibition of its activity, parturition may in fact be considered as a delayed rejection process.(ABSTRACT TRUNCATED AT 400 WORDS)

Phagocytosis in the uterus: A review

Phagocytosis is an important non-specific defense mechanism. Uterine phagocytosis is reviewed emphasizing factors which may alter the uterine phagocytic responses including the estrous cycle, pregnancy and the puerperium, and the presence of an intrauterine device. Implications of phagocytosis in therapy of and recovery from intrauterine infections are considered.

Bone marrow origin of decidual cell precursors in the pseudopregnant mouse uterus

Decidual cells are considered to be the endproduct of a hormonally induced transformation of endometrial stromal cells of the uterus. However, the source of these precursors remains unknown. This study of evaluated the possibility of their bone marrow origin by an examination of the H-2 phenotype of decidual cells in pseudopregnant bone marrow chimeras. These chimeras were produced by repopulating lethally irradiated CBA/J female (H-2k) mice with bone marrow from (CBA/J x C57BL/6J) F1 female (H-2kb) mice. Pseudopregnancy was produced with a hormonal regimen followed by an oil-induced decidual stimulus. Chimerism was evaluated radioautographically by an identification of the donor-specific Kb phenotype on cells with an immunolabeling technique with monospecific anti-H-2 serum followed by radioiodinated protein A. The extent of chimerism as indicated by the degree of Kb labeling on decidual cells as well as macrophages contained within the decidual nodules was quantitatively compared with that seen on splenic lymphocytes. Fair to good chimerism, as reflected by labeling for the donor-specific marker (Kb), was seen on splenic lymphocytes and macrophages within the decidual nodules in 6 out of 11 animals. A similar level of chimerism was detected on decidual cells in all but one of these six, in which case this was low. One animal showed low chimerism in the spleen but good chimerism on the decidual cells. The remaining four mice were nonchimeric for all three cell types. These results indicate that decidual cells and macrophages appearing within the decidual nodules of pseudopregnant mice are ultimate descendants of bone marrow cells.