HCG--A new kid on the block in prematurity prevention.

Human chorionic gonadotropin (HCG) is a molecule with multiple endocrine, paracrine, and immunoregulatory actions. Its importance for the enhancement of fertility, successful implantation, and survival of the conceptus in early gestation is recognized. However, studies conducted worldwide in recent years indicate that HCG may also play a significant role in maintaining pregnancy well after the first trimester. Emerging evidence suggests that different biomolecular and physiologic effects of HCG are concordantly directed toward inhibition of myometrial contractility to maintain pregnancy. These studies have prompted preliminary animal and human testing of HCG for the prevention of preterm birth. This article reviews the current knowledge as well as the future perspectives on HCG as a useful new tool in prematurity prevention.

Feto-placental communication system with the myometrium inpregnancy and parturition: the role of hormones, neurohormones, inflammatory mediators, and locally active factors.

Pregnancy is a unique condition in which the conceptus is allowed to implant, survive, develop, and reach a considerable organ growth and maturation within the maternal body despite the fact that it is half genetically different from the mother. Moreover, it deeply influences the overall endocrine, metabolic, and immunological functions of the recipient mother. These objectives are accomplished through the establishment of several communication systems in which a large array of substances produced by the feto-placental unit reach specific maternal target organs and/or systems and modulate their function. The myometrium is a fundamental reproductive tissue involved in pregnancy maintenance as well as in labor onset and progression and is a potential target organ for such a communication system. An appropriate regulation of myometrial function is a key condition required for pregnancy to develop physiologically until full term is reached and for labor to start. Emerging experimental and clinical evidence suggests that a very complex feto-placental biomolecular communication system exists with the myometrium and is actively operative in the control of myometrial contractility in pregnancy and parturition through the production of a continuously increasing number of substances with endocrine, paracrine, and immunoregulatory actions.

Subcellular localization and regulation of type-1C and type-5 phosphodiesterases.

We investigated the subcellular localization of PDE5 in in vitro human myometrial cells. We demonstrated for the first time that PDE5 is localized in discrete cytoplasmic foci and vesicular compartments corresponding to centrosomes. We also found that PDE5 intracellular localization is not cell- or species-specific, as it is conserved in different animal and human cells. PDE5 protein levels are strongly regulated by the mitotic activity of the smooth muscle cells (SMCs), as they were increased in quiescent, contractile myometrial cultures, and conditions in which proliferation was inhibited. In contrast, PDE1C levels decreased in all conditions that inhibited proliferation. This mirrored the enzymatic activity of both PDE5 and PDE1C. Increasing cGMP intracellular levels by dbcGMP or sildenafil treatments did not block proliferation, while dbcAMP inhibited myometrial cell proliferation. Together, these results suggest that PDE5 regulation of cGMP intracellular levels is not involved in the control of SMC cycle progression, but may represent one of the markers of the contractile phenotype.

Macrophage migration inhibitory factor-nitric oxide interaction in human fetal membranes at term pregnancy.

OBJECTIVES: Macrophage migration inhibitory factor (MIF), a multifunctional proinflammatory cytokine, has been recently involved in many aspects of reproduction including pregnancy. However, no evidence is available on the role of MIF in gestational tissues nor on factors regulating MIF production. This study, conducted on explants of human fetal membranes at term gestation, has been undertaken to investigate whether: (1) MIF is produced by fetal membranes; (2) nitric oxide (NO) can regulate local MIF production; and (3) MIF, in turn, can influence NO release in these tissues. METHODS: Tissues were obtained from 56 healthy women who underwent elective cesarean delivery. Fetal membranes have been incubated with either sodium nitroprusside (NP), a NO donor, or recombinant MIF (r-MIF), or a specific anti-MIF antibody (MIF-Ab). Reverse transcriptase-polymerase chain reaction (RT-PCR), Western blot, enzyme-linked immunosorbent assay (ELISA), and colorimetric assay have been used to detect MIF mRNA and protein, inducible nitric oxide synthase (iNOS), and NO metabolites. RESULTS: Fetal membranes basally express MIF mRNA and protein and release MIF. Exposing tissues to NP results in an increase of MIF mRNA expression and protein release. Conversely, treatment of tissues with MIF is followed by a reduction in iNOS mRNA and protein expression as well as in NO release. These effects are reversed by adding MIF-Ab. CONCLUSIONS: MIF is generated and released by human fetal membranes at term. MIF mRNA and protein expression and release are modulated by NO. MIF, in turn, can reduce iNOS expression and NO release by these tissues. NO could be a regulator of MIF production in pregnancy and labor.

Regulation of phosphodiesterase 5 expression and activity in human pregnant and non-pregnant myometrial cells by human chorionic gonadotropin.

OBJECTIVES: This study has a twofold aim: 1) to investigate whether protein expression and enzyme activity of phosphodiesterase 5 (PDE5) can be detected in human myometrium and undergo changes in relation to the presence of pregnancy and/or labor; 2) to evaluate whether PDE5 expression and activity in myometrial cells can be influenced by human chorionic gonadotropin (HCG). METHODS: Primary cultures of myometrial cells, obtained from non-pregnant women and from pregnant women at term, either before or during labor, were carried out in the presence of HCG or dibutyryl-cyclic AMP (db-cAMP), the non-hydrolizable analogue of cAMP. PDE5 expression in cultures of myometrial cells was detected by immunocytochemistry and western blot. PDE5 activity was detected in cell extracts by enzyme assay. RESULTS: PDE5 is expressed and is functionally active in smooth muscle cells. Treatment of cell cultures with HCG and db-cAMP results in a reduction of PDE5 expression and activity. The effects of HCG and db-cAMP are exerted irrespective of the functional status of the myometrium (non-pregnant, pregnant not in labor, pregnant in labor). CONCLUSIONS: PDE5 protein is expressed in human non-pregnant and pregnant myometrium. HCG reduces PDE5 expression and enzyme activity in smooth muscle cells, possibly through a pathway involving cAMP.