The RhoA guanine exchange factor ABR: a glucose-sensitive mediator of actin reorganization in feto-placental arterial endothelial cells altered by gestational diabetes mellitus.

In utero exposure to gestational diabetes mellitus (GDM) programs the fetus, increasing offspring risk for endothelial dysfunction and cardiovascular disease later in life. Hyperglycaemia is widely recognized as the driving force of diabetes-induced programming. We have previously shown that GDM exposure alters DNA methylation and gene expression associated with actin remodelling in primary feto-placental arterial endothelial cells (fpEC). Thus, we hypothesized that hyperglycaemic insults underlie programmed changes in fpEC morphology and actin organization by GDM. Therefore, arterial fpECs isolated after normal and GDM pregnancy, as well as normal fpECs that were exposed to hyperglycaemia in vitro, were analysed for the effect of GDM and hyperglycaemia on actin organization and network formation. Integration of gene expression and DNA methylation data identified the RhoA activator active BCR-related (ABR) as programmed by GDM and altered by in vitro hyperglycaemia. ABR silencing in GDM-exposed cells reduced RhoA activity by 34 ± 26% (P = 0.033) and restored normal fpEC phenotype. In fact, in vitro hyperglycaemia induced a similar fpEC phenotype as intrauterine exposure to GDM, i.e. round morphology and increased network formation on Matrigel by 34 ± 33% (P = 0.022) vs. 22 ± 20% for GDM (P = 0.004). Thus, we identified ABR as a novel glucose sensitive regulator of actin organization and cell shape, programmed by GDM and upregulated by hyperglycaemia. Identification of mechanisms induced by hyperglycaemia and affecting endothelial function in the long term will contribute to understanding GDM-induced programming of offspring endothelial dysfunction and cardiovascular disease. Future studies could focus on investigating the prevention or reversal of such malprogramming. KEY POINTS: In utero exposure to gestational diabetes mellitus (GDM) affects future health of the offspring, with an increased risk for endothelial dysfunction and cardiovascular disease in later life. GDM alters DNA methylation and expression of ABR in feto-placental arterial endothelial cells (fpEC), a model for endothelial cells exposed to the intrauterine environment of the fetus. GDM phenotype of fpECs is also induced by hyperglycaemia in vitro, and is characterized by altered actin organization and cell shape, which can be restored by ABR silencing. Revealing the cellular mechanisms induced by GDM and hyperglycaemia is important for understanding the mechanisms of how these conditions disturb endothelial function in the offspring.

Human Placental Hofbauer Cells Maintain an Anti-inflammatory M2 Phenotype despite the Presence of Gestational Diabetes Mellitus.

BACKGROUND: Hofbauer cells (HBCs) are macrophages of the feto-placental unit. Despite the general view that these cells have an anti-inflammatory M2 phenotype, recent studies have claimed that pregnancy pathologies-e.g., gestational diabetes mellitus (GDM)-cause a switch from an M2 to an M1 pro-inflammatory phenotype in HBCs. The pilot-study presented here challenges this claim, showing that HBCs maintain anti-inflammatory properties in spite of the hyperglycemic, low-grade inflammatory environment of GDM. METHODS: HBCs were isolated from placentae of healthy women (N = 5) and women with GDM (N = 6) diagnosed in the second trimester. FACS was used to measure surface markers associated with either M1 or M2 phenotype on the cells. In addition, placental tissue sections were subjected to immune histochemical imaging to assess the phenotype within the tissue context. Supernatant from control and GDM HBCs was collected at defined time points and used in a multiplex ELISA-on-beads approach to assess secretion of cytokines, chemokines, and growth factors. The effect of HBC cell culture supernatant on placental endothelial activation was investigated. RESULTS: FACS and immune staining showed that, indeed, M2 markers, such as CD206 and CD209, are increased in HBCs isolated from GDM placentae. Also, the M1 marker CD86 was increased, but only by trend. Secretion of numerous cytokines, chemokines and growth factors was not changed; pro-inflammatory interleukin (IL)-1ß and IL-6 release form GDM HBC was increased but not significant. Exposure to GDM HBC supernatant did not induce cell adhesion molecules (VCAM-1, selectins, vascular endothelial-cadherin) in placental endothelial cells compared to supernatant from control HBCs, an induction of intracellular adhesion molecule 1 was observed however. CONCLUSION: Our study-although performed in a small set of patients-shows that placental macrophages maintain their anti-inflammatory, tissue remodeling M2 phenotype even in pregnancies affected by gestational diabetes. This consistent phenotype might be important for propagation of maternal tolerance toward the fetus and for protection of the fetus from a low-grade inflammatory environment.

Post-transcriptional down regulation of ICAM-1 in feto-placental endothelium in GDM.

Maternal gestational diabetes (GDM) is associated with hyperglycaemia and hyperinsulinemia in the fetal circulation which consequently may induce endothelial dysfunction in the feto-placental vasculature. In fact, feto-placental vasculature reveals various morphological changes in response to GDM. The cell adhesion molecules (CAMs) ICAM-1, VCAM-1 and E-selectin promote attachment and trans-endothelial migration of leukocytes, and are up regulated in inflammation and endothelial dysfunction. Thus, we hypothesized that the GDM environment upregulates ICAM-1, VCAM-1 and E-selectin in the feto-placental endothelium. We isolated primary feto-placental endothelial cells (fpEC) after normal (n=18) and GDM pregnancy (n=11) and analyzed mRNA (RT-qPCR) and protein expression (Immunoblot) of ICAM-1, VCAM-1 and E-selectin. While other CAMs were unchanged on mRNA and protein levels, ICAM-1 protein was decreased by GDM. Further analysis revealed also a decrease in the release of soluble ICAM-1 (sICAM-1), whose levels correlated negatively with maternal BMI. We conclude that this reduction of ICAM-1 protein species is the result of post-translational regulation, since ICAM-1 mRNA expression was unchanged. In fact, miRNAs targeting ICAM-1 were upregulated in GDM fpEC. Immunohistochemistry showed weaker ICAM-1 staining in the placental endothelium after GDM pregnancies, and demonstrated ICAM-1 binding partners CD11a and CD18 expressed on leukocytes in fetal circulation and on placental tissue macrophages. This study identified reduction of ICAM-1 protein in fpEC in GDM pregnancy, which was regulated post-transcriptionally. Low ICAM-1 protein production may represent a protective, placenta-specific mechanism to avoid leukocyte transmigration into the placenta in response to GDM.