Downregulation of E-cadherin in pluripotent stem cells triggers partial EMT.

Epithelial to mesenchymal transition (EMT) is a critical cellular process that has been well characterized during embryonic development and cancer metastasis and it also is implicated in several physiological and pathological events including embryonic stem cell differentiation. During early stages of differentiation, human embryonic stem cells pass through EMT where deeper morphological, molecular and biochemical changes occur. Though initially considered as a decision between two states, EMT process is now regarded as a fluid transition where cells exist on a spectrum of intermediate states. In this work, using a CRISPR interference system in human embryonic stem cells, we describe a molecular characterization of the effects of downregulation of E-cadherin, one of the main initiation events of EMT, as a unique start signal. Our results suggest that the decrease and delocalization of E-cadherin causes an incomplete EMT where cells retain their undifferentiated state while expressing several characteristics of a mesenchymal-like phenotype. Namely, we found that E-cadherin downregulation induces SNAI1 and SNAI2 upregulation, promotes MALAT1 and LINC-ROR downregulation, modulates the expression of tight junction occludin 1 and gap junction connexin 43, increases human embryonic stem cells migratory capacity and delocalize ß-catenin. Altogether, we believe our results provide a useful tool to model the molecular events of an unstable intermediate state and further identify multiple layers of molecular changes that occur during partial EMT.

Endocannabinoids participate in placental apoptosis induced by hypoxia inducible factor-1.

During pregnancy, apoptosis is a physiological event critical in the remodeling and aging of the placenta. Increasing evidence has pointed towards the relevance of endocannabinoids (ECs) and hypoxia as modulators of trophoblast cell death. However, the relation between these factors is still unknown. In this report, we evaluated the participation of ECs in placental apoptosis induced by cobalt chloride (CoCl2), a hypoxia mimicking agent that stabilizes the expression of hypoxia inducible factor-1 alpha (HIF-1α). We found that HIF-1α stabilization decreased FAAH mRNA and protein levels, suggesting an increase in ECs tone. Additionally, CoCl2 incubation and Met-AEA treatment reduced cell viability and increased TUNEL-positive staining in syncytiotrophoblast layer. Immunohistochemical analysis demonstrated Bax and Bcl-2 protein expression in the cytoplasm of syncytiotrophoblast. Finally, HIF-1α stabilization produced an increase in Bax/Bcl-2 ratio, activation of caspase 3 and PARP cleavage. All these changes in apoptotic parameters were reversed with AM251, a CB1 antagonist. These results demonstrate that HIF-1α may induce apoptosis in human placenta via intrinsic pathway by a mechanism that involves activation of CB1 receptor suggesting a role of the ECs in this process.

Oxygen tension modulates AQP9 expression in human placenta.

UNLABELLED: Placental hypoxia has been implicated in pregnancy pathologies such as preeclampsia. We have previously reported that AQP9 is highly expressed in syncytiotrophoblast from normal placentas and shows an overexpression in preeclamptic placentas, with a lack of functionality for water transport. Up to now, the response of AQP9 to changes in the oxygen tension in trophoblast cells is still unknown. OBJECTIVE: Our aim was to establish whether alterations in oxygen levels may modulate AQP9 expression in human placenta. METHODS: A theoretical analysis of the human AQP9 gene to find conserved DNA regions that could serve as putative HIF-1 binding sites. Then, explants from normal placentas were cultured at different concentrations of oxygen or with 250 µM CoCl2. AQP9 molecular expression and water uptake was determined. RESULTS: Fourteen consensus HIF-1 binding sites were found in the human AQP9 gene, but none of them in the promoter region. However, placental AQP9 decreased abruptly when HIF-1α is expressed by deprivation of oxygen or CoCl2 stabilization. In contrast, after reoxygenation, HIF-1α was undetectable while AQP9 increased significantly and changed its cellular distribution, showing the same pattern as that previously described in preeclamptic placentas. Accordingly with the decrease in AQP9 expression, water uptake decreased in explants exposed to hypoxia or treated with CoCl2. Conversely as we expected, after reoxygenation, water uptake decreased dramatically compared to the control and was not sensitive to HgCl2. CONCLUSION: Our findings suggest that oxygen tension may modulate AQP9 expression in human placenta. However, the role of AQP9 still remains uncertain.

Differential expression of endocannabinoid system in normal and preeclamptic placentas: effects on nitric oxide synthesis.

Anandamide (AEA) is a lipid mediator that participates in the regulation of several reproductive functions. This study investigated the endocannabinoid system in normal (NP) and preeclamptic (PE) placentas, and analyzed the potential functional role of AEA in the regulation of nitric oxide synthesis. The protein expression and localization of NAPE-PLD, FAAH and CB1 receptor were analyzed in normal and preeclamptic pregnancies using immunoblotting and immunohistochemistry. NAPE-PLD expression was shown to be significantly higher (p < 0.05) in PE tissues than in NP. In contrast, a decrease in FAAH protein (p < 0.001) was detected in placentas collected from women with preeclampsia. Both enzymes were mainly located in the syncytiotrophoblasts from normal and preeclamptic tissues. No differences were seen in CB1 receptor from both groups of placental villous. Exogenous and endogenous AEA significantly increased NOS activity. Although pre-incubation with AM251 (CB1 antagonist) had no effect, co-incubation with both AEA and AM251 diminished NOS activity from normal term placentas. We observed increased NOS activity in placental villous from women with preeclampsia compared with normotensive pregnant women. Furthermore, NOS activity from preeclamptic tissues was diminished by co-treatment with AM251, illustrating that the NO levels could be modulated by AEA. These data suggest that AEA may be one of the factors involved in the regulation of NOS activity in normal and preeclamptic placental villous. Interestingly, the differential expression of NAPE-PLD and FAAH suggests that AEA could play an important role in the pathophysiology of PE.

Evidence for insulin-mediated control of AQP9 expression in human placenta.

UNLABELLED: The AQP9 gene contains a negative insulin response element, suggesting that it may be modulated by insulin. Previously, we reported AQP9 overexpression in preeclamptic placentas but a lack of functionality of AQP9 in water and mannitol transport. We also observed high serum levels of insulin and TNF-α in preeclamptic women. OBJECTIVE: To evaluate whether AQP9 expression is regulated by insulin in the human placenta, and whether the dysregulation of AQP9 observed in preeclamptic placentas may be related to the inability to respond to insulin stimuli. METHODS: Explants from normal and preeclamptic placentas were cultured at different concentrations of insulin. Treatment with TNF-α was used to induce phosphorylation of insulin receptor substrate (IRS), which may desensitize insulin action. AQP9 molecular expression and water uptake was determined. RESULTS: Insulin decreased the molecular expression of AQP9 exclusively in explants from normal placentas in a concentration-dependent manner. Treatment with TNF-α previous to insulin addition prevented these changes. Moreover, insulin treatment did not modify water uptake neither its sensitivity to HgCl(2.) CONCLUSION: AQP9 water permeability seems to be independent of its molecular expression, strongly suggesting that AQP9 might not have a key role in water transport in human placenta. We also propose another mechanism of down-regulation of AQP9 molecular expression mediated by insulin in a concentration-dependent manner in human placenta and provide new evidence that in preeclamptic placentas the mechanisms of insulin signaling may be altered, producing an overexpression of AQP9 that does not correlate with an increase in its functionality.