Satyan Kalkunte

Vascular endothelial growth factor C facilitates immune tolerance and endovascular activity of human uterine NK cells at the maternal-fetal interface.

Although replete with cytotoxic machinery, uterine NK (uNK) cells remain tolerant at the maternal-fetal interface. The mechanisms that facilitate the uNK cell tolerance are largely unknown. In this study, we demonstrate that vascular endothelial growth factor (VEGF) C, a proangiogenic factor produced by uNK cells, is responsible for their noncytotoxic activity. VEGF C-producing uNK cells support endovascular processes as demonstrated in a three-dimensional coculture model of capillary tube formation on Matrigel. Peripheral blood NK cells fail to produce VEGF C and remain cytotoxic. This response can be reversed by exogenous VEGF C. We show that cytoprotection by VEGF C can be related to induction of the TAP-1 expression and MHC class I assembly in target cells. Small interfering RNA-mediated silencing of TAP-1 expression abolished the VEGF C-imparted protection. Overall, these results demonstrate that empowerment of uNK cells with angiogenic factors keeps them noncytotoxic. This phenotype is critical to their pregnancy-compatible immunovascular role during placentation and fetal development.

A Critical Role of Interleukin-10 in Modulating Hypoxia-Induced Preeclampsia-Like Disease in Mice

Hypoxia has been implicated in the pathogenesis of preeclampsia, a hypertensive disorder of pregnancy. However, in vivo evidence and mechanistic understanding remain elusive. Preeclampsia is associated with impaired placental angiogenesis. We have recently shown that interleukin (IL)-10 can support trophoblast-driven endovascular crosstalk. Accordingly, we hypothesize that pathological levels of oxygen coupled with IL-10 deficiency induce severe preeclampsia-like features coupled with elevated production of antiangiogenic factors, apoptotic pathways, and placental injury. Exposure of pregnant wild-type and IL-10−/− mice to 9.5% oxygen resulted in graded placental injury and systemic symptoms of renal pathology, proteinuria (wild-type 645.15±115.73 versus 198.09±93.45; IL-10−/− 819.31±127.85 versus 221.45±82.73 &mgr;g/mg/24 hours) and hypertension (wild-type 118.37±14.45 versus 78.67±14.07; IL-10−/− 136.03±22.59 versus 83.97±18.25 mm Hg). Recombinant IL-10 reversed hypoxia-induced features in pregnant IL-10−/− mice confirming the protective role of IL-10 in preeclampsia. Hypoxic exposure caused marked elevation of soluble fms-like tyrosine kinase 1 (110.8±20.1 versus 44.7±11.9 ng/mL) in IL-10−/− mice compared with their wild-type counterparts (81.6±13.1 versus 41.2±8.9 ng/mL), whereas soluble endoglin was induced to similar levels in both strains (approximately 380±50 versus 180±31 ng/mL). Hypoxia-induced elevation of p53 was associated with marked induction of proapoptotic protein Bax, downregulation of Bcl-2, and trophoblast-specific apoptosis in utero-placental tissue. Collectively, we conclude that severe preeclampsia pathology could be triggered under certain threshold oxygen levels coupled with intrinsic IL-10 deficiency, which lead to excessive activation of antiangiogenic and apoptotic pathways.

Evolution of non-cytotoxic uterine natural killer cells.

The immune tolerance and de novo vascularization are two highly intriguing processes at the maternal–fetal interface that appear to be central to normal pregnancy outcome. Immune tolerance occurs despite the local presence of an active maternal immune system including macrophages, dendritic cells and specialized CD56brightCD16− uterine natural killer (uNK) cells (65–70%). Recent observations indicate that the phenotypic and functional repertoire of uNK cells is distinct from peripheral blood NK and endometrial NK cells, challenging the understanding of their temporal occurrence and function. Origin and specialized programming of uNK cells continue to be debated. uNK cells, replete with an armamentarium to kill the foreign, tolerate the conceptus and facilitate pregnancy. Why do these uNK cells remain non‐cytotoxic? Are these NK cells ‘multitasking’ in nature harboring beneficial and detrimental roles in pregnancy? Are there distinct subpopulations of NK cells that may populate the decidua? We propose that the endometrium/decidua functions as an ‘inducible tertiary lymphoid tissue’ that supports the recruitment and expansion of CD56brightCD16− NK cells and induces transcriptional up‐regulation of angiogenic machinery in response to exposure to local hormonal factors, cytokine milieu and perhaps hypoxia. The angiogenic features of uNK cells could further result in a ‘multitasking’ phenotype that still remains to be characterized. This article discusses the factors and pathways that bridge the angiogenic and non‐cytotoxic response machineries at the maternal–fetal interface.

Vascular IL-10: a protective role in preeclampsia

IL-10 is a pregnancy compatible cytokine that plays a vital role in maintaining the balance of anti-inflammatory and pro-inflammatory milieu at the maternal-fetal interface. Recent evidence now suggests that IL-10 is a potent vascular cytokine that can blunt hypertension and inflammation-mediated vascular dysfunction. Thus, a re-evaluation of IL-10 as a cytokine supporting endovascular interactions and angiogenesis as well as blunting hypoxic-injury and preeclampsia-like features is warranted. In this review, we highlight these novel functions of IL-10 and propose that its immune-modulating and vascular functions are mutually inclusive, particularly in the context of normal gestation.

Multiple pregnancy failures: an immunological paradigm.

Recurrent spontaneous abortion (RSA), three or more pregnancy losses prior to 20 weeks, occurs in about 1% of all pregnancies, 50% of RSA cases remain unexplained and unresolved. Recently, immune pathways have been implicated in the pathophysiology of RSA. Immune tolerance of the fetal–placental unit and placental angiogenesis are mandatory for a successful pregnancy outcome. Unscheduled dysregulation of the placental vasculature is thought to be the pathophysiologic mechanisms underlying an array of pregnancy complications like infertility, miscarriage, pre‐eclampsia, and fetal growth restriction and death. Investigations on mechanisms and management of RSA are mired by substandard design and lack of optimal randomized clinical trials and have resulted in disagreement on guidelines for evaluation and treatments for patients with multiple pregnancy losses of unknown etiology. The present review focuses on evidence‐based research discussion with immunologic causes, and immune‐regulatory therapies recommended for helping patients with a history of RSA. We highlight data that might support revalidation of low molecular weight heparin as a protective therapy in RSA. Newly launched growth factors, GM‐CSF, and potentially novel agents to suppress inflammatory rejection, including regulatory T cells, human chorionic gonadotropin, and M‐CSF/IL‐10, may work in concert with tender‐loving‐care therapy and give hope to couples with multiple pregnancy losses.

Review: hCG, preeclampsia and regulatory T cells

Human chorionic gonadotropin (hCG) is crucial for successful pregnancy. Its many functions include angiogenesis and immune regulation. Despite years of research, the etiology of preeclampsia remains unknown. Marked by insufficient trophoblast invasion and poor spiral artery remodeling, preeclampsia has also been linked to immune dysregulation. Here we discuss the roles of hCG in the context of endovascular cross-talk between trophoblasts and endothelial cells and immune tolerance. We propose that functional and glycosylation modifications of hCG may contribute to the pathogenesis of preeclampsia.

In vitro and in vivo evidence for lack of endovascular remodeling by third trimester trophoblasts.

The placental-decidual interaction through invading trophoblasts determines whether a physiological transformation of the uterine spiral arteries is established or not. Trophoblast-orchestrated artery remodeling is central to normal placentation. Dysregulated uteroplacental interaction and vascular remodeling are thought to be associated with the molecular events underlying the pathology of late pregnancy anomalies including preeclampsia. Although the exact gestational age at which trophoblast invasion ceases is not known, it remains unclear whether late pregnancy trophoblasts retain the ability to transform the uterine arteries. Here, we have developed a dual cell, in vitro culture system that mimics the vascular remodeling events during normal pregnancy. We demonstrate that first and third trimester trophoblasts respond differentially to interactive signals from endothelial cells when cultured on matrigel. Term primary trophoblasts or immortalized third trimester extravillous TCL1 trophoblasts not only fail to respond to signals from endothelial cells but also inhibit endothelial cell tube formation. In contrast, HTR8 cells, representing a first trimester trophoblast cell line with invasive properties, undergo spontaneous migration and synchronize with the endothelial cells in a capillary network. This disparity in behavior was confirmed in vivo using a matrigel plug assay. Poor expression of VEGF C and VEGF receptors coupled with high E-cadherin expression by term primary trophoblasts and TCL1 cells contributed to their restricted interactive and migratory properties. We further show that the kinase activity of VEGF R2 is essential for proactive crosstalk by HTR8 cells. This unique behavior of first trimester trophoblasts in the presence of endothelial cells offers a potential approach to study cell-cell interactions and to decipher modulatory components in the serum samples from adverse pregnancy outcomes.

Transthyretin Is Dysregulated in Preeclampsia, and Its Native Form Prevents the Onset of Disease in a Preclinical Mouse Model

Preeclampsia is a major pregnancy complication with potential short- and long-term consequences for both mother and fetus. Understanding its pathogenesis and causative biomarkers is likely to yield insights for prediction and treatment. Herein, we provide evidence that transthyretin, a transporter of thyroxine and retinol, is aggregated in preeclampsia and is present at reduced levels in sera of preeclamptic women, as detected by proteomic screen. We demonstrate that transthyretin aggregates form deposits in preeclampsia placental tissue and cause apoptosis. By using in vitro approaches and a humanized mouse model, we provide evidence for a causal link between dysregulated transthyretin and preeclampsia. Native transthyretin inhibits all preeclampsia-like features in the humanized mouse model, including new-onset proteinuria, increased blood pressure, glomerular endotheliosis, and production of anti-angiogenic factors. Our findings suggest that a focus on transthyretin structure and function is a novel strategy to understand and combat preeclampsia.

The Water Channel Aquaporin 1 Is a Novel Molecular Target of Polychlorinated Biphenyls for in Utero Anomalies

Despite serious health risks in humans and wild life, the underlying mechanisms that explain the gene-environment effects of chemical toxicants are largely unknown. Polychlorinated biphenyls (PCBs) are one of the most ubiquitous environmental toxicants worldwide, with reported epidemiological evidence for reproductive and neurocognitive anomalies in humans. Here, we show that Aroclor 1254, a mixture of structurally distinct PCBs, causes preterm birth in interleukin (IL)-10-/- mice at a dose that does not show any adverse effects in wild type mice, highlighting the significance of IL-10 as an anti-toxicant cytokine. Aroclor 1254-treated IL-10-/- mice demonstrated increased amniotic fluid, intrauterine growth restriction, and reduced litter size with postnatal neuromotor defects. Further, our results identify aquaporin 1 (AQP1), a potent effector of fluid volume regulation and angiogenic activity, as a novel placental target of PCBs. In vivo or in vitro exposure to Aroclor 1254 coupled with IL-10 deficiency significantly reduced the protein content of AQP1. Reduced uterine AQP1 levels were associated with defective spiral artery transformation. Importantly, recombinant IL-10 reversed PCB-induced in vivo and in vitro effects. These data demonstrate for the first time that the IL-10-AQP1 axis is a novel regulator of PCB-induced in utero effects.

Uterine Regulatory T cells, IL-10 and Hypertension

Citation Nevers T, Kalkunte S, Sharma S. Uterine Regulatory T Cells, IL‐10 and hypertension. Am J Reprod Immunol 2011; 66 (Suppl. 1): 88–92