Proangiogenic immature myeloid cells populate the human placenta and their presence correlates with placental and birthweight

The effects of progesterone on immune cellular function at the maternal-fetal interface and in maternal circulation

Progesterone is a sex steroid hormone that plays a critical role in the establishment and maintenance of pregnancy. This hormone drives numerous maternal physiological adaptations to ensure the continuation of pregnancy and to facilitate fetal growth, including broad and potent modulation of the maternal immune system to promote maternal-fetal tolerance. In this brief review, we provide an overview of the immunomodulatory functions of progesterone in the decidua, placenta, myometrium, and maternal circulation during pregnancy. Specifically, we summarize current evidence of the regulated functions of innate and adaptive immune cells induced by progesterone and its downstream effector molecules in these compartments, including observations in human pregnancy and in animal models. Our review highlights the gaps in knowledge of interactions between progesterone and maternal cellular immunity that may direct future research.

CD11b+Ly6G+ myeloid-derived suppressor cells promote liver regeneration in a murine model of major hepatectomy

Liver regeneration depends on sequential activation of pathways and cells involving the remaining organ in recovery of mass. Proliferation of parenchyma is dependent on angiogenesis. Understanding liver regeneration-associated neovascularization may be useful for development of clinical interventions. Myeloid-derived suppressor cells (MDSCs) promote tumor angiogenesis and play a role in developmental processes that necessitate rapid vascularization. We therefore hypothesized that the MDSCs could play a role in liver regeneration. Following partial hepatectomy, MDSCs were enriched within regenerating livers, and their depletion led to increased liver injury and postoperative mortality, reduced liver weights, decreased hepatic vascularization, reduced hepatocyte hypertrophy and proliferation, and aberrant liver function. Gene expression profiling of regenerating liver-derived MDSCs demonstrated a large-scale transcriptional response involving key pathways related to angiogenesis. Functionally, enhanced reactive oxygen species production and angiogenic capacities of regenerating liver-derived MDSCs were confirmed. A comparative analysis revealed that the transcriptional response of MDSCs during liver regeneration resembled that of peripheral blood MDSCs during progression of abdominal tumors, suggesting a common MDSC gene expression profile promoting angiogenesis. In summary, our study shows that MDSCs contribute to early stages of liver regeneration possibly by exerting proangiogenic functions using a unique transcriptional program.-Nachmany, I., Bogoch, Y., Sivan, A., Amar, O., Bondar, E., Zohar, N., Yakubovsky, O., Fainaru, O., Klausner, J. M., Pencovich, N. CD11b⁺Ly6G⁺ myeloid-derived suppressor cells promote liver regeneration in a murine model of major hepatectomy.

CD33(+) /HLA-DR(neg) and CD33(+) /HLA-DR(+/-) Cells: Rare Populations in the Human Decidua with Characteristics of MDSC

PROBLEM

Human pregnancy needs a remarkable local immune tolerance toward the conceptus. Myeloid-derived suppressor cells (MDSC) are important players promoting cancer initiation and progression by suppressing T-cell functions and thus inducing immune tolerance. Therefore, MDSC were expected within decidua.

METHODS

Subpopulations of CD33(+) immune cells were isolated from human early pregnancy decidua and characterized phenotypically and functionally by microscopy, FACS analysis, RT-PCR, Western blotting and in the coculture with T cells.

RESULTS

Decidua harbors CD33(+) /HLA-DR(neg) and CD33(+) /HLA-DR(+/-) cells which both express arginase, iNOS and IDO and a typical cytokine profile. Both subtypes potently suppress T-cell proliferation and therefore fulfill the criteria of MDSC.

CONCLUSION

We characterized a new population of CD33(+) /HLA-DR(neg) and CD33(+) /HLA-DR(+/-) cells in human early pregnancy decidua with properties of classical MDSC and thus potentially being an important player in immune tolerance in pregnancy.

Inflammation and preterm birth

Preterm birth is the leading cause of neonatal morbidity and mortality. Although the underlying causes of pregnancy-associated complication are numerous, it is well established that infection and inflammation represent a highly significant risk factor in preterm birth. However, despite the clinical and public health significance, infectious agents, molecular trigger(s), and immune pathways underlying the pathogenesis of preterm birth remain underdefined and represent a major gap in knowledge. Here, we provide an overview of recent clinical and animal model data focused on the interplay between infection-driven inflammation and induction of preterm birth. Furthermore, here, we highlight the critical gaps in knowledge that warrant future investigations into the interplay between immune responses and induction of preterm birth.

Reduced Myeloid-derived Suppressor Cells in the Blood and Endometrium is Associated with Early Miscarriage

PROBLEM

The contribution of myeloid-derived suppressor cells (MDSC) in patients suffering from early or recurrent miscarriage is unknown. MDSC are implicated in modulation of T-cell response in healthy pregnancies; however, the role of MDSC in patients suffering from miscarriage has not been studied. We hypothesized that MDSC play major role in inducing maternal-fetal tolerance and this tolerance is compromised in patients suffering from miscarriage.

METHOD OF STUDY

MDSC level was assessed by flow cytometry and immunostaining in blood and endometrial decidua, respectively. Activation of T cells was determined by MTT proliferation and IL-2 ELISA assays.

RESULTS AND CONCLUSION

The miscarriage patients harbor reduced level of functionally suppressive MDSC in blood and endometrium as compared to healthy control women with successful pregnancies. These results suggest MDSC regulate maternal tolerance in healthy pregnancies and that drug inducing MDSC could have therapeutic implication in the miscarriage patients.

Transient CD15-positive endothelial phenotype in the human placenta correlates with physiological and pathological fetoplacental immaturity

OBJECTIVE

Placental growth and villous maturation are critical parameters of placental function at the end of pregnancy. A failure in these processes leads to the development of placental dysfunction, as well as fetal and neonatal mortality and morbidity. The aim of the study was to determine the relevant diagnostic markers associated with pathological placental development.

STUDY DESIGN

Forty tissue samples from normal placentas of different gestational age and 68 pathological term placentas with defective villous maturation (GDM, idiopathic IUFD, preeclamsia, HELLP syndrome) comprised the comparative immunohistochemical study (CD15, CD45 and CD34). Positive immunohistochemical reactions were quantitatively assessed in the chorionic plate and vessels of the villi of different histological type.

RESULTS

Physiologically immature placentas of the first and second trimester and pathologically immature term placentas were characterized by marked endothelial CD15-immunostaining. A significant loss of CD15-positive endothelium of the placentas was associated with a physiological and accelerated villous maturity. A spatio-temporal correlation was shown for CD15+ endothelial cells (ECs) and the number of CD45+ stromal cells (SCs). A negative temporal correlation was shown for CD15+ ECs and CD15+ myelomonocytes in the fetal blood. CD34 expression in the ECs was stable during the pregnancy.

CONCLUSION

A correlation between a transient CD15-positive endothelial phenotype and a physiological and pathological fetoplacental immaturity was demonstrated. Physiological and accelerated placental maturation was accompanied by a significant disappearance of CD15-positive endothelium. We propose that "immature" CD15+ endothelium is an important diagnostic marker of the physiological and pathological fetoplacental immaturity.

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.

Myeloid cell alterations in the mouse placenta precede the onset of labor and delivery

OBJECTIVE

Immature myeloid cells (IMCs) are bone marrow-derived cells that normally differentiate into granulocytes, macrophages, and dendritic cells (DCs) but expand in pathological conditions such as malignancy. DCs are antigen-presenting cells that regulate the immune response. Both IMCs and DCs were shown to take part in angiogenesis; however, little is known of their function in the placenta. We sought to determine whether alterations in DC and IMC populations in the placenta precede the onset of delivery.

STUDY DESIGN

Experiments were performed on 6-8 week old C57Bl/6 female mice. Placentas from pregnant mice that were killed on designated days, immunostained using fluorescently labeled anti-CD11b, Gr-1, CD11c, major histocompatibility II (MHCII), and CD45, and analyzed by flow cytometry and immunofluorescent microscopy.

RESULTS

Throughout the latter part of pregnancy toward labor and delivery, the CD45(+)CD11b(+)Gr1(+)-IMC population decreased 29 ± 9.1% (day 12) and 30 ± 9.9% (day 15), vs 21 ± 8.1% (day18, n = 21, 15, and 27; P = .006 and P = .004, respectively), whereas the CD45(+)CD11c(+)MHCII(+)-DC population increased 0.87 ± 0.3% (day 12) and 0.70 ± 0.3% (day 15) vs 1.81 ± 1.3% (day 18, n = 21, 15, and 27, P = .002 and P = .001, respectively). Both myeloid cell populations were localized adjacent to CD31(+) endothelial cells in sites of placental angiogenesis.

CONCLUSION

Labor and delivery are preceded by proangiogenic-myeloid cell alterations, reflected by a decrease in IMCs and an increase in DCs populating the mouse placenta. The intriguing possibility that delivery is preceded by the maturation of IMCs in part into DCs warrants further studies.

Lack of activation of peripheral blood dendritic cells in human pregnancies complicated by intrauterine growth restriction

INTRODUCTION

The state of activation of dendritic cells (DCs) at the feto-maternal interface critically contributes to optimal decidual immune responses needed to support fetal-placental development. We recently demonstrated that during healthy pregnancy also peripheral blood DCs (PBDCs), which are easily accessible, are activated as well. In this study, to investigate a possible involvement of DCs in intrauterine growth restriction (IUGR), we evaluated whether PBDCs in pregnancy complicated by IUGR may be altered compared with PBDCs in healthy pregnancy.

METHODS

PBDCs from 12 pregnant women with primary IUGR, 21 healthy pregnant and 19 nonpregnant women were analyzed by flow cytometric analysis of whole-blood samples collected at a single time point.

RESULTS

The number of plasmacytoid PBDCs was significantly reduced in women with IUGR pregnancy. Myeloid and plasmacytoid PBDCs in IUGR lacked the state of activation (assessed as CD80, CD86, CD40 expression) and the shift to a proinflammatory pattern of cytokine production occurring during healthy pregnancy.

DISCUSSION

To our knowledge, this is the first study investigating the state of PBDC activation in IUGR pregnancy. Our results are in accordance with a previous study reporting a lower expression of activation and maturation markers by decidual DCs in IUGR placentas.

CONCLUSIONS

The reduced activation of PBDCs in IUGR pregnancy may possibly reflect a reduced activation of decidual DCs. If confirmed at the feto-maternal interface, the alterations of DCs described in IUGR pregnancy have the potential to negatively impact on vascular development during gestation. These observations may therefore broaden our understanding of IUGR pathogenesis.