Cellular aspects of corpus luteum function in the primate

Time interval between hCG administration and oocyte retrieval and ART outcomes: an updated systematic review and meta-analysis

RESEARCH QUESTION

To explore whether prolonged hCG-ovum pickup interval improves assisted reproductive technology outcomes.

DESIGN

CENTRAL, CNKI, Cochrane Systematic Reviews, EMBASE, MEDLINE, PUBMED, and Web of Science up to May 13 2023 were searched for studies reporting associations between hCG-ovum pickup intervals and assisted reproductive technology outcomes. Intervention types included short (≤ 36 h) and long (> 36 h) hCG-ovum pickup intervals in assisted reproductive technology cycles. All outcomes were based upon only fresh embryo transfers. Primary outcome is defined as the clinical pregnancy rate. Data were pooled using random-effects models. Heterogeneity was assessed using the I 2 statistics.

RESULTS

Twelve studies were included in the meta-analysis, including five retrospective cohort studies, one prospective cohort study, and six randomized or quasi-randomized controlled trials. The short and long interval groups had similar oocyte maturation rates, fertilization rate and high-quality embryo rate (OR, 0.69; 95% CI, 0.45-1.06; I 2 = 91.1%, OR, 0.88; 95% CI, 0.77-1.0; I 2 = 44.4% and OR, 1.05; 95% CI, 0.95-1.17; I 2 = 8.6%, respectively). The clinical pregnancy rates in the long retrieval group were significantly higher than in the short retrieval group (OR, 0.66; 95% CI, 0.45-0.95; I 2 = 35.4%). The groups had similar miscarriage and live birth rates (OR, 1.92; 95% CI, 0.66-5.60; I 2 = 0.0% and OR, 0.50; 95% CI, 0.24-1.04; I 2 = 0.0%, respectively).

CONCLUSIONS

The clinical pregnancy rates can be increased by prolonging the hCG-ovum pickup interval, which would help us develop more reasonable time schedules for fertility centers and patients.

META-ANALYSIS REGISTRATION

PROSPERO CRD42022310006 (28 Apr 2022).

PreImplantation factor (PIF*) promotes embryotrophic and neuroprotective decidual genes: effect negated by epidermal growth factor

Background

Intimate embryo-maternal interaction is paramount for pregnancy success post-implantation. The embryo follows a specific developmental timeline starting with neural system, dependent on endogenous and decidual factors. Beyond altered genetics/epigenetics, post-natal diseases may initiate at prenatal/neonatal, post-natal period, or through a continuum. Preimplantation factor (PIF) secreted by viable embryos promotes implantation and trophoblast invasion. Synthetic PIF reverses neuroinflammation in non-pregnant models. PIF targets embryo proteins that protect against oxidative stress and protein misfolding. We report of PIF’s embryotrophic role and potential to prevent developmental disorders by regulating uterine milieu at implantation and first trimester.

Methods

PIF’s effect on human implantation (human endometrial stromal cells (HESC)) and first-trimester decidua cultures (FTDC) was examined, by global gene expression (Affymetrix), disease-biomarkers ranking (GeneGo), neuro-specific genes (Ingenuity) and proteins (mass-spectrometry). PIF co-cultured epidermal growth factor (EGF) in both HESC and FTDC (Affymetrix) was evaluated.

Results

In HESC, PIF promotes neural differentiation and transmission genes (TLX2, EPHA10) while inhibiting retinoic acid receptor gene, which arrests growth. PIF promotes axon guidance and downregulates EGF-dependent neuroregulin signaling. In FTDC, PIF promotes bone morphogenetic protein pathway (SMAD1, 53-fold) and axonal guidance genes (EPH5) while inhibiting PPP2R2C, negative cell-growth regulator, involved in Alzheimer’s and amyotrophic lateral sclerosis. In HESC, PIF affects angiotensin via beta-arrestin, transforming growth factor-beta (TGF-β), notch, BMP, and wingless-int (WNT) signaling pathways that promote neurogenesis involved in childhood neurodevelopmental diseases—autism and also affected epithelial-mesenchymal transition involved in neuromuscular disorders. In FTDC, PIF upregulates neural development and hormone signaling, while downregulating genes protecting against xenobiotic response leading to connective tissue disorders.

In both HESC and FTDC, PIF affects neural development and transmission pathways. In HESC interactome, PIF promotes FUS gene, which controls genome integrity, while in FTDC, PIF upregulates STAT3 critical transcription signal. EGF abolished PIF’s effect on HESC, decreasing metalloproteinase and prolactin receptor genes, thereby interfering with decidualization, while in FTDC, EGF co-cultured with PIF reduced ZHX2, gene that regulates neural AFP secretion.

Conclusions

PIF promotes decidual trophic genes and proteins to regulate neural development. By regulating the uterine milieu, PIF may decrease embryo vulnerability to post-natal neurodevelopmental disorders. Examination of PIF-based intervention strategies used during embryogenesis to improve pregnancy prognosis and reduce post-natal vulnerability is clearly in order.

Dynamic changes in gene expression that occur during the period of spontaneous functional regression in the rhesus macaque corpus luteum

Luteolysis of the corpus luteum (CL) during nonfertile cycles involves a cessation of progesterone (P4) synthesis (functional regression) and subsequent structural remodeling. The molecular processes responsible for initiation of luteal regression in the primate CL are poorly defined. Therefore, a genomic approach was used to systematically identify differentially expressed genes in the rhesus macaque CL during spontaneous luteolysis. CL were collected before [d 10-11 after LH surge, mid-late (ML) stage] or during (d 14-16, late stage) functional regression. Based on P4 levels, late-stage CL were subdivided into functional-late (serum P4 > 1.5 ng/ml) and functionally regressed late (FRL) (serum P4 < 0.5 ng/ml) groups (n = 4 CL per group). Total RNA was isolated, labeled, and hybridized to Affymetrix genome microarrays that contain elements representing the entire rhesus macaque transcriptome. With the ML stage serving as the baseline, there were 681 differentially expressed transcripts (>2-fold change; P < 0.05) that could be categorized into three primary patterns of expression: 1) increasing from ML through FRL; 2) decreasing from ML through FRL; and 3) increasing ML to functional late, followed by a decrease in FRL. Ontology analysis revealed potential mechanisms and pathways associated with functional and/or structural regression of the macaque CL. Quantitative real-time PCR was used to validate microarray expression patterns of 13 genes with the results being consistent between the two methodologies. Protein levels were found to parallel mRNA profiles in four of five differentially expressed genes analyzed by Western blot. Thus, this database will facilitate the identification of mechanisms involved in primate luteal regression.

Characterization of cAMP/PKA/CREB signaling cascade in the bonnet monkey corpus luteum: expressions of inhibin-alpha and StAR during different functional status

Luteinizing hormone mediates its nuclear action primarily by activating cAMP/Protein kinase A (PKA) pathway leading to phosphorylation of cAMP response element binding (CREB) family of transcription factors. Earlier studies have documented altered cAMP responsiveness of luteal cells during maturation, and in the rhesus monkey, extinction of CREB expression following luteinization and ovulation. In the course of studies aimed at characterizing LH-cAMP signaling pathway, we serendipitously discovered that CREB is after all present in the monkey corpus luteum (CL). The present experiments were carried out to examine the PKA activity, CREB expression and RT-PCR expression of inhibin-alpha (Inh-alpha) subunit and steroidogenic acute regulatory protein (StAR) in CL obtained from a variety of model systems. PKA activity in the CL was maintained throughout the luteal phase. Messenger RNA expression by RT-PCR and Northern analyses and protein levels employing antibodies specific to total- and phospho-forms demonstrated presence of CREB in the CL. Additionally, immuno-histo/cytochemical analyses, Electrophoretic mobility shift assays and chromatin immunoprecipitation assays for Inh-alpha and StAR genes further confirmed the presence of CREB in the CL. The present study, contrary to an earlier report, demonstrates the presence of CREB (both transcript and protein) in the monkey CL. Also, analysis of expression of Inh-alpha and StAR genes (considered to be cAMP responsive), during different functional status of CL suggests that LH regulates their expression perhaps by cAMP/PKA/CREB pathway.

Effects of the insecticide amitraz, an α2-adrenergic receptor agonist, on human luteinized granulosa cells

BACKGROUND

Amitraz, an insecticide used to prevent tick and mite infestation of cattle, crops and dogs, is an alpha2-adrenergic receptor agonist that inhibits GnRH release and the ovulatory LH surge in rats. Noradrenalin, the physiological ligand for adrenergic receptors, inhibits progesterone production by IVF-derived granulosa cells, but the effects of amitraz are unknown.

METHODS

Luteinized granulosa cells obtained from women undergoing ovarian stimulation were exposed to amitraz (1, 10, 50, 100 microg/ml) for 2-72 h, and to amitraz (50 microg/ml) +/- hCG or the specific alpha2-adrenergic receptor antagonist yohimbine, for 6 h. Cell numbers were determined by 3-(4, 5-dimethylthiazol-(2)-yl)-2, 5-diphenyl tetrazolium bromide(MTT) assay and hormone production by radioimmunoassay.

RESULTS

Amitraz 10 microg/ml did not affect cell numbers or estrogen production, but reduced progesterone production to 58 +/- 8% (p < 0.01, 24 h, n = 6) of control values. Amitraz (100 microg/ml) was cytotoxic and caused a corresponding reduction in hormone production. Amitraz 50 microg/ml did not affect cell numbers or estrogen production, but reduced progesterone per cell production to 82 +/- 6% of control values after 6 h. This was prevented by 0.2 mmol/l yohimbine. Exposure to amitraz 50 microg/ml for 6 h exposure abolished hCG-stimulated progesterone production but not estrogen production.

CONCLUSIONS

Amitraz inhibited basal and hCG-stimulated progesterone but not estrogen production. The inhibitory action of amitraz and its antagonism by yohimbine suggest that alpha2-adrenergic receptors are expressed by luteinized human granulosa cells.

Immunohistological localization and expression of alpha-actin in the baboon (Papio anubis) corpus luteum

We have recently shown the presence of E-cadherin and of alpha- and gamma-catenins in human and baboon corpora lutea. These are components of adherens junctions between cells. The cytoplasmic catenins link the cell membrane-associated cadherins to the actin-based cytoskeleton. This interaction is necessary for the functional activity of the E-cadherins. Our aim therefore was to determine the presence of alpha-actin in the baboon corpus luteum, to further establish whether the necessary components for E-cadherin activity are present in this tissue. An antibody specific for the smooth muscle isoform of actin, alpha-actin, was used for these studies. The results using immunohistochemistry show that (a) alpha-actin is present in steroidogenic cells of the active corpus luteum, theca externa of the corpus luteum, cells of the vasculature, and the tunica albuginea surrounding the ovary. The intensity of immunoreactivity for alpha-actin varied, with the cells of the vasculature reacting more intensely than the luteal cells. A difference in intensity of immunoreactivity was also observed among the luteal cells, with the inner granulosa cells showing stronger immunoreactivity than the peripheral theca lutein cells. There was no detectable immunoreactivity in the steroidogenic cells of the atretic corpus luteum. However, in both the active and atretic corpora lutea, alpha-actin-positive vascular cells were dispersed within the tissue. (b) Total alpha-actin (luteal and non-luteal), as determined by Western blot analyses, does not change during the luteal phase and subsequent corpus luteum demise (atretic corpora lutea). (c) hCG stimulated the expression of alpha-actin and progesterone secretion by the early luteal phase (LH surge + 1-5 days) and mid-luteal phase (LH surge + 6-10 days) cells in culture, but only progesterone in the late luteal phase (LH surge + 11-15 days). The data show that alpha-actin is present in luteal cells and that its expression is regulated by hCG, thus suggesting that E-cadherin may form functional adherens junctions in the corpus luteum.

Is irregular regression of corpora lutea in climacteric women caused by age-induced alterations in the "tissue control system"?

PROBLEM

We have recently observed that the regression of corpora lutea (CL) in women during the reproductive period of life is accompanied by a diminution of Thy-1 differentiation protein release from vascular pericytes and an accumulation of T lymphocytes and activated macrophages among both degenerating granulosa lutein cells (GLC) and theca lutein cells. These data suggest that the immune system and other stromal factors, representing components of the "tissue control system," may play a role in regression of the CL. We investigated degenerating CL from climacteric women to address the possibility that the decline of immune functions with advancing age may result in incomplete regression of luteal tissue. This could contribute to the altered hormonal profiles and abnormal uterine bleeding that frequently occur during the climacteric.

METHOD

Immunoperoxidase staining and image analysis were used to localize Thy-1 differentiation protein of vascular pericytes, cytokeratin staining of GLC, neural cell adhesion molecule expression by theca lutein cells, CD15 of neutrophils, CD4, CD14, CD68, and leukocyte common antigens of macrophages, and CD3 and CD8 determinants of T lymphocytes. We also investigated the expression of luteinizing hormone receptor (LH receptor) and mitogen activated protein kinases (MAP kinases) in luteal cells. Samples of regressing luteal tissue were obtained during the follicular phase from perimenopausal women (age 45-50) who exhibited prolonged or irregular cycles. For comparison, luteal tissues from women with regular cycles (age 29-45) and CL of pregnancy were also investigated.

RESULTS

Corpora lutea of the climacteric women exhibited irregular regression of luteal tissue characterized by a lack of cytoplasmic vacuolization and nuclear pyknosis in GLC, and by a persistence of theca lutein cells exhibiting hyperplasia and adjacent theca externa layers. This was accompanied by a continuing release of Thy-1 differentiation protein from vascular pericytes. Persisting GLC lacked surface expression of macrophage markers (CD4, CD14, CD68 and leukocyte common antigen) as well as nuclear granules exhibiting CD15 of neutrophils, detected in regularly regressing GLC. In addition, such persisting GLC showed weak or no LH receptor expression, and retained the expression of cytokeratin. They also exhibited enhanced staining for MAP kinases. Strong cytoplasmic MAP kinase expression with occasional nuclear translocation was also detected in persisting theca lutein cells, indicating high metabolic activity of these cells. T lymphocytes, although occasionally present in luteal stroma within luteal convolutions, did not invade among persisting GLC and were virtually absent from layers of theca externa and theca lutein cells.

CONCLUSIONS

These data indicate that the regressing CL in climacteric women may exhibit persistence of luteal cells, perhaps because of age-induced alterations of the immune system and other local stromal homeostatic mechanisms involved in the elimination of luteal cells. Persisting GLC and/or theca lutein cells may exhibit abnormal hormonal secretion that contributes to the alteration of target tissues, such as the endometrium, resulting in abnormal uterine bleeding, hyperplasia, and neoplasia.