Preeclampsia is a persistent hypertensive gestational disease characterized by high blood pressure and proteinuria, which presents from the second trimester of pregnancy. At the cellular level, preeclampsia has largely been associated with the release of free radicals by the placenta. Placenta-borne oxidative and nitrosative stresses are even sometimes considered as the major molecular determinants of the maternal disease. In this review, we present the recent literature evaluating free radical production in both normal and pathological placentas (including preeclampsia and other major pregnancy diseases), in humans and animal models. We then assess the putative effects of these free radicals on the placenta and maternal endothelium. This analysis was conducted with regard to recent papers and possible therapeutic avenues.

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Islets of Langerhans are microorgans scattered throughout the pancreas, and are responsible for synthesizing and secreting pancreatic hormones. While progress has recently been made concerning cell differentiation of the islets of Langerhans, the mechanism controlling islet morphogenesis is not known. It is thought that these islets are formed by mature cell association, first differentiating in the primitive pancreatic epithelium, then migrating in the extracellular matrix, and finally associating into islets of Langerhans. This mechanism suggests that the extracellular matrix has to be degraded for proper islet morphogenesis. We demonstrated in the present study that during rat pancreatic development, matrix metalloproteinase 2 (MMP-2) is activated in vivo between E17 and E19 when islet morphogenesis occurs. We next demonstrated that when E12.5 pancreatic epithelia develop in vitro, MMP-2 is activated in an in vitro model that recapitulates endocrine pancreas development (Miralles, F., P. Czernichow, and R. Scharfmann. 1998. Development. 125: 1017–1024). On the other hand, islet morphogenesis was impaired when MMP-2 activity was inhibited. We next demonstrated that exogenous TGF-β1 positively controls both islet morphogenesis and MMP-2 activity. Finally, we demonstrated that both islet morphogenesis and MMP-2 activation were abolished in the presence of a pan-specific TGF-β neutralizing antibody. Taken together, these observations demonstrate that in vitro, TGF-β is a key activator of pancreatic MMP-2, and that MMP-2 activity is necessary for islet morphogenesis.

In this review, we comprehensively present the function of epigenetic regulations in normal placental development as well as in a prominent disease of placental origin, preeclampsia (PE). We describe current progress concerning the impact of DNA methylation, non-coding RNA (with a special emphasis on long non-coding RNA (lncRNA) and microRNA (miRNA)) and more marginally histone post-translational modifications, in the processes leading to normal and abnormal placental function. We also explore the potential use of epigenetic marks circulating in the maternal blood flow as putative biomarkers able to prognosticate the onset of PE, as well as classifying it according to its severity. The correlation between epigenetic marks and impacts on gene expression is systematically evaluated for the different epigenetic marks analyzed.

Preeclampsia is a pregnancy disease affecting 5 to 8% of pregnant women and a leading cause of both maternal and fetal mortality and morbidity. Because of a default in the process of implantation, the placenta of preeclamptic women undergoes insufficient vascularization. This results in placental ischemia, inflammation and subsequent release of placental debris and vasoactive factors in the maternal circulation causing a systemic endothelial activation. Several microarray studies have analyzed the transcriptome of the preeclamptic placentas to identify genes which could be involved in placental dysfunction. In this study, we compared the data from publicly available microarray analyses to obtain a consensus list of modified genes. This allowed to identify consistently modified genes in the preeclamptic placenta. Of these, 67 were up-regulated and 31 down-regulated. Assuming that changes in the transcription level of co-expressed genes may result from the coordinated action of a limited number of transcription factors, we looked for over-represented putative transcription factor binding sites in the promoters of these genes. Indeed, we found that the promoters of up-regulated genes are enriched in putative binding sites for NFkB, CREB, ANRT, REEB1, SP1, and AP-2. In the promoters of down-regulated genes, the most prevalent putative binding sites are those of MZF-1, NFYA, E2F1 and MEF2A. These transcriptions factors are known to regulate specific biological pathways such as cell responses to inflammation, hypoxia, DNA damage and proliferation. We discuss here the molecular mechanisms of action of these transcription factors and how they can be related to the placental dysfunction in the context of preeclampsia.

Cathepsin D, a lysosomal proteinase, is induced by estrogens in mammary cancer cells where its concentration is correlated with a higher risk of metastasis. Its gene expression is stimulated by estrogens in MCF7 cells, and we have shown that a short proximal promoter fragment from -365 to -122 is required for this induction. We now characterize, at -261, a nonconsensus estrogen-responsive element (ERE) (E2) with two differences in the distal half of its palindrome, which confers estradiol responsiveness to the heterologous Herpes simplex virus thymidine kinase promoter in transient transfection experiments. This ERE is located in a 21-base pair sequence: 5'GGGCCGGGCTGACCCCGC GGG3', containing a GC-rich region in its 3'-part, which is almost perfectly repeated at -362 (the E1 site). The E2 site was necessary but not sufficient to mediate an estrogen response and required cooperation with the homologous E1 element and/or with general transcription sites located downstream. In vitro, the E2 site but not the E1 site was protected by estrogen receptor (ER) against DNAse I digestion, and gel shift experiments suggested an interaction with the ER as a dimer. Moreover, we showed in vivo that ER DNA binding domain was required to mediate estrogen induction from the cathepsin D ERE. We conclude that estradiol induction of cathepsin D is mediated by interaction of the ER with a nonconsensus ERE that requires synergy with other elements located upstream and/or downstream of this central ERE.

The Goto-Kakisaki (GK) rat is a genetic model of type 2 diabetes obtained by selective inbreeding of mildly glucose-intolerant Wistar rats. Previous studies have shown that at birth, the ␤-cell mass of the GK rat is severely reduced compared with that of the Wistar rat. Therefore, ␤-cell deficit could be the primary defect leading to type 2 diabetes in this model. To identify the abnormality at the origin of the ␤-cell mass deficit, we compared the fetal development of GK and Wistar rats. Our study reveals that during early development (embryonic day 12-14 [E12-14]), GK fetuses present a delayed global growth that progressively recovers: at birth, no size or weight difference persists. However, from E18 onward, the weight and DNA content of the pancreas and liver are reduced by 30% in the GK fetuses. Cell proliferation is reduced in the GK pancreas from E16 to E20. Whereas apoptotic cells are scarce in the Wistar fetal pancreas, a wave of apoptosis from E16 to E18 was detected in the GK pancreas. Analysis of pancreas differentiation revealed that from E12 to E14, there are no significant differences in the number of ␣-and ␤-cells between the GK and Wistar pancreas. However, by E16, the average number of ␤-cells in the GK pancreas represents only 50% that of the Wistar pancreas, and this difference persists until birth. The number of ␣-cells was reduced by 25% from E18 to E21. S ome studies suggest that total ␤-cell mass is decreased in type 2 diabetic patients compared with weight-matched control subjects (1-3). This supports the notion that a ␤-cell mass inadequate to compensate for insulin resistance and/or ␤-cell secretory defects results in insufficient insulin production and leads to overt diabetes. However, prospective data on the evolution of ␤-cell mass during the course of type 2 diabetes are not available in humans, and hence it is unknown whether the ␤-cell mass deficit results from ␤-cell death and/or inadequate ␤-cell expansion. This has been addressed in different animal models of type 2 diabetes, although with conflicting conclusions. Thus, in the ZDF rat, the failure of ␤-cell mass expansion to compensate for insulin resistance is due to increased ␤-cell apoptosis (4), whereas in the OLEFT rat, it seems to be due to impaired ␤-cell proliferation (5).The Goto-Kakisaki (GK) rat is a genetic model of type 2 diabetes without obesity (6). The adult GK rat displays decreased ␤-cell mass (7) together with mild hyperglycemia, glucose intolerance, impaired glucose-induced insulin secretion (8), hepatic glucose overproduction, and moderate peripheral insulin resistance in muscle and adipose tissue (9). Previous studies in our laboratory have shown that newborn GK rats have normal fasting glucose levels compared with Wistar rats and a drastically reduced ␤-cell mass (7). Thus, the ␤-cell mass deficit precedes other manifestations of the disease and could represent the primary defect leading to type 2 diabetes in the adult. This result prompted us to investigate the fetal development of the GK pancreas to cl...

Recent studies have shown that persistent expression of FGF10 in the developing pancreas of transgenic mice results in enhanced and prolonged proliferation of pancreatic progenitors, pancreatic hyperplasia and impaired pancreatic differentiation. These studies have also suggested that FGF10 prevents the differentiation of pancreatic progenitors by maintaining persistent Notch signalling. Here, we provide experimental evidence sustaining the capacity of FGF10 to induce the proliferation of pancreatic precursors, while preventing their differentiation. Using explant cultures of E10.5 isolated dorsal pancreatic epithelium, we found that FGF10 maintained Notch activation and induced the expansion of pancreatic precursors while blocking their differentiation. In addition, by using a γ-secretase inhibitor, we were able to down-regulate the expression of Hes1, a target gene of the Notch pathway in explant cultures of pancreatic epithelium treated with FGF10. In such explants, the effect of FGF10 on the proliferation and maintenance of pancreatic progenitors was suppressed. These results demonstrate that activation of the Notch pathway is required as a downstream mediator of FGF10 signalling in pancreatic precursor cells.