K⁺channel inhibition modulates the biochemical and morphological differentiation of human placental cytotrophoblast cells in vitro

Abstract

Maintaining placental syncytiotrophoblast, a specialized multinucleated transport epithelium, is essential for normal human pregnancy. Syncytiotrophoblast continuously renews through differentiation and fusion of cytotrophoblast cells, under paracrine control by syncytiotrophoblast production of human chorionic gonadotropin (hCG). We hypothesized that K+ channels participate in trophoblast syncytialization and hCG secretion in vitro. Two models of normal-term placenta were used: 1) isolated cytotrophoblast cells and 2) villous tissue in explant culture. Cells and explants were treated with K+ channel modulators from 18 h, and day 3, onward, respectively. Culture medium was analyzed for hCG, to assess secretion, as well as for lactate dehydrogenase (LDH), to indicate cell/tissue integrity. hCG was also measured in cytotrophoblast cell lysates, indicating cellular production. Syncytialization of cytotrophoblast cells was assessed by immunofluorescent staining of desmosomes and nuclei. Over 18–66 h, mononucleate cells fused to form multinucleated syncytia, accompanied by a 28-fold rise in hCG secretion. 1 mM Ba2+ stimulated cytotrophoblast cell hCG secretion at 66 h compared with control, whereas 5 mM tetraethylammonium (TEA) inhibited hCG secretion by >90%. 0.1–1 mM 4-aminopyridine (4-AP) reduced cytotrophoblast cell hCG secretion and elevated cellular hCG; without altering cellular integrity or syncytialization. In villous explants, hCG secretion was not altered by 1 mM Ba2+ but inhibited by 5 mM 4-AP and 5/10 mM TEA, without affecting LDH release. Anandamide, pinacidil, and cromakalim were without effect in either model. In conclusion, 4-AP- and TEA-sensitive K+ channels (e.g., voltage-gated and Ca2+-activated) regulate trophoblast hCG secretion in culture. If these K+ channels participate in hCG secretion in situ, they may regulate trophoblast turnover in health and disease.

Regulation of amino acid transporters by glucose and growth factors in cultured primary human trophoblast cells is mediated by mTOR signaling

“…LDH release from cells incubated with low glucose media [median ϭ 0.038, IQ range ϭ 0.025, optical density (OD) 490 nm, n ϭ 6] or low glucose media containing rapamycin (median ϭ 0.052, IQ range ϭ 0.046, OD 490 nm, n ϭ 6) was not different from the LDH release from cells grown with control medium (median ϭ 0.031, IQ range ϭ 0.014, OD 490 nm, n ϭ 6, P ϭ 0.091). In line with previous reports (58), LDH release fell significantly from 18 h (median ϭ 0.40, IQ range ϭ 0.12) to 42 h (median ϭ 0.036, IQ range ϭ 0.035) but remained unchanged thereafter (66 h, median ϭ 0.021, IQ range ϭ 0.018; 90 h, median ϭ 0.031, IQ range ϭ 0.014, OD 490 nm, n ϭ 3-6).…”

Transient receptor potential vanilloid 1 is expressed in human cytotrophoblasts: Induction of cell apoptosis and impairment of syncytialization

“…Contrary to CPS, the endovanniloid AEA decreased pALP activity via a TRPV1-independent mechanism and had no significant effects on hCG secretion, which is in agreement with a previous work (Williams et al, 2008). These data suggest that AEA may not impair hCT differentiation.…”

Differential Expression of Potassium Channels in Placentas from Normal and Pathological Pregnancies: Targeting of the Kir 2.1 Channel to Lipid Rafts

“…The four potassium channels examined (K ir 2.1, K v 2.1, TREK-1, and TASK-1) were previously characterized in multiple placenta studies (Clarson et al 2001;Bai et al 2005Bai et al , 2006Williams et al 2008). In addition, this study is the first to demonstrate that K ir 2.1 is a Graphical quantification and representative image of western blot for K ir 2.1 in the flotation gradient fractions of LMVM and MVM subdomains from normal placenta before (control) and after the apical fractions were preincubated with 2% mb-CD (n = 2).…”

“…channels (K2p), in the villous tissue from human placenta and in cultured human cytotrophoblast cells. Williams et al (2008) suggest the presence of potassium channels sensitive to K v channel blockers 4-AP and TEA in cytotrophoblast cells and human placental villous explants.…”