Drucilla J. Roberts

Soluble endoglin contributes to the pathogenesis of preeclampsia.

Preeclampsia is a pregnancy-specific hypertensive syndrome that causes substantial maternal and fetal morbidity and mortality. Maternal endothelial dysfunction mediated by excess placenta-derived soluble VEGF receptor 1 (sVEGFR1 or sFlt1) is emerging as a prominent component in disease pathogenesis. We report a novel placenta-derived soluble TGF-β coreceptor, endoglin (sEng), which is elevated in the sera of preeclamptic individuals, correlates with disease severity and falls after delivery. sEng inhibits formation of capillary tubes in vitro and induces vascular permeability and hypertension in vivo. Its effects in pregnant rats are amplified by coadministration of sFlt1, leading to severe preeclampsia including the HELLP (hemolysis, elevated liver enzymes, low platelets) syndrome and restriction of fetal growth. sEng impairs binding of TGF-β1 to its receptors and downstream signaling including effects on activation of eNOS and vasodilation, suggesting that sEng leads to dysregulated TGF-β signaling in the vasculature. Our results suggest that sEng may act in concert with sFlt1 to induce severe preeclampsia.

Hedgehog is an early and late mediator of pancreatic cancer tumorigenesis

Hedgehog signalling—an essential pathway during embryonic pancreatic development, the misregulation of which has been implicated in several forms of cancer—may also be an important mediator in human pancreatic carcinoma. Here we report that sonic hedgehog, a secreted hedgehog ligand, is abnormally expressed in pancreatic adenocarcinoma and its precursor lesions: pancreatic intraepithelial neoplasia (PanIN). Pancreata of Pdx–Shh mice (in which Shh is misexpressed in the pancreatic endoderm) develop abnormal tubular structures, a phenocopy of human PanIN-1 and -2. Moreover, these PanIN-like lesions also contain mutations in K-ras and overexpress HER-2/neu, which are genetic mutations found early in the progression of human pancreatic cancer. Furthermore, hedgehog signalling remains active in cell lines established from primary and metastatic pancreatic adenocarcinomas. Notably, inhibition of hedgehog signalling by cyclopamine induced apoptosis and blocked proliferation in a subset of the pancreatic cancer cell lines both in vitro and in vivo. These data suggest that this pathway may have an early and critical role in the genesis of this cancer, and that maintenance of hedgehog signalling is important for aberrant proliferation and tumorigenesis.

Human ISL1 heart progenitors generate diverse multipotent cardiovascular cell lineages

The generation and expansion of diverse cardiovascular cell lineages is a critical step during human cardiogenesis, with major implications for congenital heart disease. Unravelling the mechanisms for the diversification of human heart cell lineages has been hampered by the lack of genetic tools to purify early cardiac progenitors and define their developmental potential. Recent studies in the mouse embryo have identified a multipotent cardiac progenitor that contributes to all of the major cell types in the murine heart. In contrast to murine development, human cardiogenesis has a much longer onset of heart cell lineage diversification and expansion, suggesting divergent pathways. Here we identify a diverse set of human fetal ISL1+ cardiovascular progenitors that give rise to the cardiomyocyte, smooth muscle and endothelial cell lineages. Using two independent transgenic and gene-targeting approaches in human embryonic stem cell lines, we show that purified ISL1+ primordial progenitors are capable of self-renewal and expansion before differentiation into the three major cell types in the heart. These results lay the foundation for the generation of human model systems for cardiovascular disease and novel approaches for human regenerative cardiovascular medicine.

CD133 Expression Defines a Tumor Initiating Cell Population in Primary Human Ovarian Cancer

Evidence is accumulating that solid tumors contain a rare phenotypically distinct population of cells, termed cancer stem cells (CSC), which give rise to and maintain the bulk of the tumor. These CSC are thought to be resistant to current chemotherapeutic strategies due to their intrinsic stem‐like properties and thus may provide the principal driving force behind recurrent tumor growth. Given the high frequency of recurrent metastasis associated with human ovarian cancer, we sought to determine whether primary human ovarian tumors contain populations of cells with enhanced tumor‐initiating capacity, a characteristic of CSC. Using an in vivo serial transplantation model, we show that primary uncultured human ovarian tumors can be reliably propagated in NOD/SCID mice, generating heterogeneous tumors that maintain the histological integrity of the parental tumor. The observed frequency of tumor engraftment suggests only certain subpopulations of ovarian tumor cells have the capacity to recapitulate tumor growth. Further profiling of human ovarian tumors for expression of candidate CSC surface markers indicated consistent expression of CD133. To determine whether CD133 expression could define a tumor‐initiating cell population in primary human ovarian tumors, fluorescence‐activated cell sorting (FACS) methods were employed. Injection of sorted CD133+ and CD133− cell populations into NOD/SCID mice established that tumor‐derived CD133+ cells have an increased tumorigenic capacity and are capable of recapitulating the original heterogeneous tumor. Our data indicate that CD133 expression defines a NOD/SCID tumor initiating subpopulation of cells in human ovarian cancer that may be an important target for new chemotherapeutic strategies aimed at eliminating ovarian cancer. STEM CELLS 2009;27:2875–2883

Indian Hedgehog is an antagonist of Wnt signaling in colonic epithelial cell differentiation

Wnt signaling defines the colonic epithelial progenitor cell phenotype, and mutations in the gene adenomatous polyposis coli (APC) that activate the Wnt pathway cause the familial adenomatous polyposis coli (FAP) syndrome and most sporadic colon cancers. The mechanisms that regulate the transition of epithelial precursor cells into their differentiated derivatives are poorly characterized. We report that Indian hedgehog (Ihh) is expressed by mature colonocytes and regulates their differentiation in vitro and in vivo. Hedgehog (Hh) signaling restricts the expression of Wnt targets to the base of the colonic crypt in vivo, and transfection of Ihh into colon cancer cells leads to a downregulation of both components of the nuclear TCF4–β-catenin complex and abrogates endogenous Wnt signaling in vitro. In turn, expression of Ihh is downregulated in polyps of individuals with FAP and expression of doxycycline-inducible dominant negative TCF4 (dnTCF4) restores Ihh expression in APC mutant DLD-1 colon cancer cells. These data identify a new Wnt-Hh axis in colonic epithelial renewal.

Fetal Vascular Obstructive Lesions: Nosology and Reproducibility of Placental Reaction Patterns

The purpose of this study was to assemble and test the reliability of a complete set of the placental reaction patterns seen with chronic fetal vascular obstruction in the hope that this might provide a standardized diagnostic framework useful for practicing pathologists. Study cases (14 with fetal vascular obstructive lesions, 6 controls) were reviewed blindly by seven pathologists after agreement on a standard set of diagnostic criteria. Majority vote served as the gold standard and 80% of the 180 diagnoses rendered (9 diagnoses each for 20 cases) were agreed upon by at least six of the seven scores. The sensitivity of individual diagnosis relative to the group consensus averaged 83% (range, 69–100%) and specificity averaged 91% (range, 86–100%). Reproducibility was measured by unweighted kappa-values and interpreted as follows: < 0.2, poor; 0.2–0.6, fair/moderate; > 0.6, substantial. Kappa values for lesions of distal villi were generally superior to those for lesions involving large fetal vessels: avascular villi (0.49), villous stromal-vascular karyorrhexis (0.58), and villitis of unknown etiology (VUE) with stem villitis and avascular villi (0.65) versus large vessel thrombi (any vessel, 0.34; chorionic plate vessel, 0.40) and intimal fibrin cushions (recent, 0.47; remote, 0.78). Reproducibility for a global impression of any villous change consistent with chronic fetal vascular obstruction was substantial (0.63), while that for a more severe subgroup was moderate (0.44). Three points are worthy of emphasis. Our system separately recognizes, but later combines, uniformly avascular villi and villous stromal-vascular karyorrhexis as manifestations of the same underlying process. We propose that this combined group of villous lesions be dichotomized with the terms fetal thrombotic vasculopathy or extensive avascular villi (and/or villous stromal-vascular karyorrhexis) being reserved for the group with 15 or more affected terminal villi per section. Scattered foci of avascular villi (and/or villous stromal-vascular karyorrhexis) could be used to describe less severe cases. Finally, we distinguish VUE with stem villitis and avascular villi (obliterative fetal vasculopathy) as a distinct process with substantial perinatal morbidity.

Molecular mechanisms of development of the gastrointestinal tract

The gut offers a complex but rich organ system to study visceral pattern formation. The gut is an early evolutionary advance. Data supports that the molecular controls of gut pattern formation are be conserved across species. The gut develops in a stereotyped manner in many different species, by using a basic mechanism of development, the epithelial‐mesenchymal interaction. Signaling between the endoderm and mesoderm is essential for normal gut development. The signaling molecules involved are just being described and include factors known to be critical in embryonic development of other systems. The gut has four major patterned axes: anterior‐posterior (AP), dorsal‐ventral (DV), left‐right (LR), and radial (RAD). The molecular pathways used to control pattern in each of these axes are the subject of this review. Major advances in the understanding of AP and LR axis formation in the gut have been described within the past few years. RAD and DV axes are now hot topics for investigation. Despite advances in these areas of gut development, basic events remain poorly understood. Discovery of specific factors that control gut pattern formation may provide a template for the study of pattern formation in other visceral/organ systems.

Fetal cell microchimerism in tissue from multiple sites in women with systemic sclerosis.

OBJECTIVE The realization that fetal cells pass into the maternal circulation and can survive for many years has raised the question of whether fetal microchimerism can cause subsequent disease in the mother. Available data suggest that fetal-maternal transfusion may be related to some autoimmune diseases, notably systemic sclerosis (SSc). The goal of the current work was to identify and quantify tissue-specific fetal microchimerism in women with SSc. METHODS We analyzed multiple tissue specimens obtained at autopsy from women with SSc as well as women who had died of causes unrelated to autoimmunity, using fluorescence in situ hybridization to detect the presence of male cells in women with sons. Tissues analyzed included adrenal gland, heart, intestine, kidney, liver, lung, lymph node, pancreas, parathyroid, skin, and spleen. RESULTS Male cells were observed in tissue from at least 1 site in each woman with SSc and were found most frequently in spleen sections. After spleen, male cells were observed most frequently in lymph node, lung, adrenal gland, and skin tissue. The only tissue type in which male cells were not seen in any patient was pancreatic tissue. Male cells were not observed in tissue from women who had died of causes unrelated to autoimmunity. CONCLUSION The results of this study suggest that fetal cells migrate from the peripheral circulation into multiple organs in women with SSc. All of the women studied had previously given birth to sons, so it is likely that these cells are of fetal origin. While the relevance of this finding to the pathogenesis of SSc remains to be elucidated, the presence of fetal cells in internal organs suggests that they could play a role in disease pathogenesis and that they may preferentially sequester in the spleen. The presence of these male cells may also be a result of disease, possibly through the migration of terminally differentiated and/or progenitor cells to areas of tissue damage.

BMP signaling is necessary for neural crest cell migration and ganglion formation in the enteric nervous system

The enteric nervous system (ENS) is derived from neural crest cells that migrate along the gastrointestinal tract to form a network of neurons and glia that are essential for regulating intestinal motility. Despite the number of genes known to play essential roles in ENS development, the molecular etiology of congenital disorders affecting this process remains largely unknown. To determine the role of bone morphogenetic protein (BMP) signaling in ENS development, we first examined the expression of bmp2, bmp4, and bmprII during hindgut development and find these strongly expressed in the ENS. Moreover, functional BMP signaling, demonstrated by the expression of phosphorylated Smad1/5/8, is present in the enteric ganglia. Inhibition of BMP activity by noggin misexpression within the developing gut, both in ovo and in vitro, inhibits normal migration of enteric neural crest cells. BMP inhibition also leads to hypoganglionosis and failure of enteric ganglion formation, with crest cells unable to cluster into aggregates. Abnormalities of migration and ganglion formation are the hallmarks of two human intestinal disorders, Hirschsprungs disease and intestinal neuronal dysplasia. Our results support an essential role for BMP signaling in these aspects of ENS development and provide a basis for further investigation of these proteins in the etiology of neuro-intestinal disorders.

A flow cytometric study of 137 fresh hydropic placentas : correlation between types of hydatidiform moles and nuclear DNA ploidy

Hydropic placentas may be classified by histopathology into hydropic abortus, partial hydatidiform mole, and complete hydatidiform mole. We studied 142 hydropic placentas: 39% were complete hydatidiform moles, 35% partial hydatidiform moles, and 26% hydropic abortuses. Villous vesicle size was predictive of histologic diagnosis. We determined DNA ploidy in 137 cases. Seventy-three percent of hydropic abortuses were diploid and 11% were triploid. Ninety percent of partial moles were triploid or near-triploid; one partial mole was haploid and one diploid. Of the complete moles, 50% were diploid, 43% were tetraploid, 3.6% polyploid, and 1.7% triploid. Partial moles had lower pre-evacuation beta-hCG levels than complete moles. Persistent tumor followed 33% of complete moles and 12% of partial moles. Although the numbers were small, no patient with a diploid, tetraploid, aneuploid, or haploid partial mole developed persistent disease. Among complete moles, the pre-evacuation beta-hCG level was not predictive of persistence (P = .15). Subdividing complete moles by ploidy, we found that tetraploid moles were associated with higher pre-evacuation beta-hCG levels than were diploid moles. However, tetraploidy was not associated with increased persistent tumor among complete moles. Although most partial moles were triploid and most complete moles were diploid or tetraploid, there was wider DNA heterogeneity among molar gestations than previously reported. In this series, DNA ploidy was not an independent predictor of persistence in complete moles.