RESUMO
INTRODUCTION: Placental DNA methylation is thought to be influenced by environmental exposure. Decidual natural killer cells (dNKs) directly contact with cytotrophoblasts in the early stage of pregnancy. dNKs may affect DNA methylation of extravillous cytotrophoblasts (EVTs) directly or indirectly through their secreted soluble factors. OBJECTIVES: Previously, we showed that EVT outgrowth and migration on collagen gel were restricted by exposure to dNK or dNK-derived conditioned medium (dNK-CM) (ref [1]). The aim of this study was to determine if EVT DNA methylation was altered by treating with dNK or dNK-CM. METHODS: Placental explants collected from 6 first-trimester healthy pregnancy terminations were cultured on a rat collagen gel model. Outgrowth EVTs from each subject were treated with medium or concordant dNK (trapped inside of hollow fibers) or dNK-CM. EVTs were harvested after 96-hour co-culturing and underwent DNA extraction. DNA methylation was quantified using the Infinium Human Methylation 450 BeadChip, which targets over 450,000 CpG sites in the human genome. Differential methylation was defined by having p<0.05 (Student's t-test) and average DNA methylation change >10% before and after treatments. Functional enrichment was assessed by gene ontology analysis with False Discovery Rate <10% defined as significantly enriched. RESULTS: Increased DNA methylation was observed for 360 loci and 572 loci by dNK or dNK-CM respectively, and decreased DNA methylation was shown for 62 loci and 188 loci by dNK or dNK-CM respectively. DNA methylation at 44 loci was altered by both dNK and dNK-CM. The common loci were overrepresented for associations with EVT differentiation, adhesion and migration. Examples of the relevant overlapped loci with increased DNA methylations were MYO15A and PRDM16 (PR domain zinc finger protein 16); and the overlapped loci with reduced DNA methylation were CDH9 and USP29 (ubiquitin specific protein 29). dNK but not dNK-CM reduced IL18 methylation and increased methylation on ITGAL (integrin, alpha L) and ITGB7. dNK-CM but not dNK reduced methylation of ITGAD and PCDH8 (protocadherin 8) and increased methylation of CDH4 and CDH6. CONCLUSION: DNA methylation of EVT was altered by exposure to surrounding dNK and their secreted soluble molecules. These results serve as a basis for further investigations on whether DNA methylation can mediate the changes in protein expression that influence EVT differentiation, adhesion and migration.
RESUMO
Extravillous cytotrophoblast (EVT) migration, invasion and endovascular differentiation are regulated by a variety of growth factors, cytokines and adhesion molecules. Decidual natural killer cells (dNK) and their secreted cytokines probably modulate these processes. In this study, we used dNK-derived conditioned medium (dNK-CM) to investigate whether or not (i) dNK-CM was able to enhance capillary tube and network formation of an EVT cell line, HTR8/SVneo, on Matrigel, (ii) PI3K/AKT pathway and p38 MAPK pathway activation were involved, and (iii) HTR8/SVneo surface ICAM-1 played a role in the process of HTR8/SVneo endovascular differentiation. The results demonstrated that HTR8/SVneo constitutively form 'vascular' tubes and networks after culture on Matrigel. dNK-CM enhanced and maintained tube and network formation, acquiring an endothelium-like angiogenic morphology followed by increased VEGF-C production. HTR8/SVneo cell expression level of VE-cadherin, PECAM-1, VCAM-1 and alphavbeta3 was unaltered by dNK-CM, whereas ICAM-1 expression level was increased. Anti-human ICAM-1 blocking antibody inhibited HTR8/SVneo migration and partially reversed dNK-CM-mediated enhancement of HTR8/SVneo tube and network formation. PI3K/AKT and p38 MAPK pathways were activated in dNK-CM-mediated enhancement of HTR8/SVneo tube and network formation. The PI3K/AKT and p38 MAPK pathway inhibitors (LY294002 and SB202190, respectively) decreased dNK-CM-stimulated ICAM-1 induction, HTR8/SVneo migration, and reversed tube and network formation. The results suggest that dNK cell-secreted growth factors and cytokines participate in the regulation of HTR8/SVneo endothelium-like tube formation. Adhesion molecules, particularly ICAM-1, expressed on EVT may participate in the process. To our knowledge, this is the first report of a role for ICAM-1 in EVT angiogenesis, as previously reported for endothelial cells.
