Study on reproductive endocrinology of human placenta (II)--Hormone secreting activity of cytotrophoblast cells.
ABSTRACT The capability of cytotrophoblast cells to produce hCG, progesterone, estrogen, cGnRH and beta-endorphin in vitro has been demonstrated in serum-free culture medium. Before experiment, a 24-h preculture was carried out in order to remove the endogenous hormones of the tissue. During a period of 8 days' culture, the cytotrophoblast cells could constantly produce a small amount of hCG. The production of progesterone rose rapidly and became doubled within six days. The estrogen secretion showed a similar pattern in the presence of androstenedione, a precursor of estrogen, indicating the elevation of aromatase activity in the cells. The elevation of the enzyme activity has been further demonstrated not to be induced by androstenedione. In both cytotrophoblast and syncytiotrophoblast cell cultures, cGnRH was only detected in the culture of cytotrophoblast cells, with a value up to 4 pg/10(5) cells/24 h. However, beta-endorphin was identified both in cytotrophoblast and syncytiotrophoblast cells. Its content increased significantly in the medium of cytotrophoblast cell culture from the 4th to 6th days, but declined in the medium of syncytiotrophoblast cell culture. The results demonstrate clearly that the cytotrophoblast cells are the sole origin of GnRH in human placenta and are also able to synthesize beta-endorphin and steroid hormones. The findings indicate that there is no such a sharp functional demarcation existing between these two kinds of trophoblast cells as suggested before. The data are of significance for a better understanding of the mechanism of hormonal regulation in placenta.
- SourceAvailable from: Craig S AtwoodEmbryonic Stem Cells: The Hormonal Regulation of Pluripotency and Embryogenesis, 04/2011; , ISBN: 978-953-307-196-1
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ABSTRACT: Division of the human zygote leads to the formation of the blastocyst that contains human embryonic stem cells (hESC) which develop into the embryo. Little is known about the physiological signals that direct hESC division and differentiation during early embryogenesis. A number of growth factors, including the pregnancy-associated hormone human chorionic gonadotropin (hCG), are secreted by trophoblasts^1-3^ that lie adjacent to the embryoblast in the blastocyst, but it is not known whether these growth factors directly signal the epiblast. Here we show that hCG promotes the division of embryoblast-derived inner mass cells (hESC), and their differentiation during blastulation and neurulation. Inhibition of LH/hCG receptor (LHCGR) signaling with P-antisense oligonucleotides suppresses hESC proliferation. Similarly, hESC proliferation can be blocked using an antibody against the extracellular activation site of LHCGR, an effect that is reversed by treatment with hCG. hCG treatment rapidly upregulates steroidogenic acute regulatory protein-mediated cholesterol transport and the synthesis of progesterone, a neurogenic steroid^4,5^. Treatment of hESC colonies with progesterone induces neurulation as demonstrated by the expression of nestin and the formation of columnar neuroectodermal cells that organize into neural tube-like rosettes. Suppression of progesterone signaling by withdrawing progesterone or treating with the progesterone receptor antagonist RU-486 inhibits the differentiation of hESC colonies into embryoid bodies (blastulation) and rosettes (neurulation). These results explain the default pathway of hESC differentiation towards a neural stem cell fate in vitro. Collectively, our findings implicate trophoblastic hCG secretion and signaling via LHCGR on the adjacent embryoblast in the induction of hESC proliferation and differentiation into blastocysts and neurula. This paracrine/juxtacrine signaling by extraembryonic tissues is the commencement of trophic support by placental tissues in the growth and development of the human embryo.Nature Precedings
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ABSTRACT: The growth factors that drive the division and differentiation of stem cells during early human embryogenesis are unknown. The secretion of endorphins, progesterone (P(4)), human chorionic gonadotropin, 17beta-estradiol, and gonadotropin-releasing hormone by trophoblasts that lie adjacent to the embryoblast in the blastocyst suggests that these pregnancy-associated factors may directly signal the growth and development of the embryoblast. To test this hypothesis, we treated embryoblast-derived human embryonic stem cells (hESCs) with ICI 174,864, a delta-opioid receptor antagonist, and RU-486 (mifepristone), a P(4) receptor competitive antagonist. Both antagonists potently inhibited the differentiation of hESC into embryoid bodies, an in vitro structure akin to the blastocyst containing all three germ layers. Furthermore, these agents prevented the differentiation of hESC aggregates into columnar neuroectodermal cells and their organization into neural tube-like rosettes as determined morphologically. Immunoblot analyses confirmed the obligatory role of these hormones; both antagonists inhibited nestin expression, an early marker of neural precursor cells normally detected during rosette formation. Conversely, addition of P(4) to hESC aggregates induced nestin expression and the formation of neuroectodermal rosettes. These results demonstrate that trophoblast-associated hormones induce blastulation and neurulation during early human embryogenesis.Stem cells and development 10/2008; 18(5):737-40. DOI:10.1089/scd.2008.0190 · 4.20 Impact Factor