Regulation of matrix metalloproteinases (MMPS) and their inhibitors (TIMPS) during mouse peri-implantation: role of nitric oxide

Follicular Fluid Growth Factors and Interleukin Profiling as Potential Predictors of IVF Outcomes

Growth hormone (GH) has gained attention as an anti-aging compound enhancing oocyte quality. In fact, GH is known to activate intrafollicular metabolic events for oocyte maturation. Insulin growth factor I (IGF1) is another ovarian growth factor that mediates the FSH and GH actions. Cytokines could also increase IVF outcomes. Indeed, IL-6 is a pleiotropic cytokine with multiple cellular effects that can vary based on the physiological environment. IL-6 may also play an important role in follicular development (Yang et al., J Assist Reprod Genet, 2020, 37 (5), 1171–1176). Clinical studies have been performed to explore the potential role of IL-6 in human oocyte maturation and subsequent embryonic development. To date, the answers are not conclusive. During peri-implantation, many cytokines balances are regulated like pro-inflammatory and anti-inflammatory interleukins. The pro-inflammatory properties of IL-17 and its impact on the tumor microenvironment or autoimmune diseases are characterized, but new dimensions of IL-17 activity that promotes embryo implantation are not well explored. In the search for answers, our study compared concentrations of growth factors IGF1, GH, and interleukins IL-6 and IL-17 in the follicular fluid (FF) from 140 women divided into two groups depending on bad (G1) or good prognosis (G2) and investigated the relationships between these FF components’ levels and the main parameters of IVF. GH, IGF1, and IL-6 were significantly higher for G2. For GH, it was negatively correlated to patient age and positively correlated to maturity rate and IGF1. Moreover, GH and IGF1 were correlated to the top embryo rate and cumulative pregnancy rate. Regarding IL-6, it was correlated to IGF1 level, endometrium thickness, and implantation rate. As for IL-17, it was only correlated to IL-6. Consequently, all these FF components were predictive of oocyte quality except IL-17. GH seemed to be the best biomarker of this quality.

The effects of hyaluronate-containing medium on human embryo attachment to endometrial epithelial cells in vitro

STUDY QUESTION

Does embryo transfer medium containing hyaluronate (HA) promote the attachment phase of human embryo implantation?

SUMMARY ANSWER

HA-containing medium does not promote human blastocyst attachment to endometrial epithelial cells in vitro.

WHAT IS KNOWN ALREADY

Embryo transfer media containing high concentrations of HA are being used to increase implantation and live birth rates in IVF treatment, although the mechanism of action is unknown.

STUDY DESIGN, SIZE, DURATION

Expression of HA-interacting genes in frozen-thawed oocytes/embryos was assessed by microarray analysis (n = 21). Fresh and frozen human blastocysts (n = 98) were co-cultured with human endometrial epithelial Ishikawa cell layers. Blastocyst attachment and the effects of a widely used HA-containing medium were measured.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Human embryos surplus to treatment requirements were donated with informed consent from several ART centres. Blastocyst-stage embryos were transferred at day 6 to confluent Ishikawa cell layers; some blastocysts were artificially hatched. Blastocyst attachment was monitored from 1 to 48 h, and the effects of blastocyst pre-treatment for 10 min with HA-containing medium were determined.

MAIN RESULTS AND THE ROLE OF CHANCE

Human embryos expressed the HA receptor genes CD44 and HMMR, hyaluronan synthase genes HAS1–3, and hyaluronidase genes HYAL1–3, at all stages of preimplantation development. Attachment of partially hatched blastocysts to Ishikawa cells at 24 and 48 h was related to trophectoderm grade (P = 0.0004 and 0.007, respectively, n = 34). Blastocysts of varying clinical grades that had been artificially hatched were all attached within 48 h (n = 21). Treatment of artificially hatched blastocysts with HA-containing medium did not significantly affect attachment at early (1–6 h) or late (24 and 48 h) time points, compared with control blastocysts (n = 43).

LIMITATIONS, REASONS FOR CAUTION

Using an adenocarcinoma-derived cell line to model embryo-endometrium attachment may not fully recapitulate in vivo interactions. The high levels of blastocyst attachment seen with this in vitro model may limit the sensitivity with which the effects of HA can be observed.

WIDER IMPLICATIONS OF THE FINDINGS

Morphological trophectoderm grade can be correlated with blastocyst attachment in vitro. HA-containing medium may increase pregnancy rates by mechanisms other than promoting blastocyst attachment to endometrium.

STUDY FUNDING/COMPETING INTEREST(S)

This work was funded by a grant from the Wellbeing of Women, the NIHR Local Comprehensive Research Network and NIHR Manchester Clinical Research Facility, the Department of Health Scientist Practitioner Training Scheme, and the Ministry of Higher Education, The State of Libya. None of the authors has any conflict of interest to declare.

Modification of endothelial nitric oxide synthase by 4-oxo-2(E)-nonenal(ONE) in preeclamptic placentas

Preeclampsia (PE) is a leading cause of pregnancy complications, affecting 3-7% of pregnant women worldwide. The pathophysiology of preeclampsia involves a redox imbalance, oxidative stress and a reduced nitric oxide (NO) bioavailability. The molecular and cellular mechanisms leading to the dysfunction of the placental endothelial NO synthase (eNOS) are not clarified. This study was designed to investigate whether aldehydes generated by lipid peroxidation products (LPP), may contribute to placental eNOS dysfunction in PE. The analysis of placentas from PE-affected patients and normal pregnancies, showed a significant increase in protein carbonyl content, indicative of oxidative stress-induced protein modification, as shown by the accumulation of acrolein, 4-hydroxynonenal (HNE), and 4-oxo-2(E)-nonenal (ONE) adducts in PE placentas. In contrast, the levels of these LPP-adducts were low in placentas from normal pregnancies. Immunofluorescence and confocal experiments pointed out a colocalization of eNOS with ONE-Lys adducts, whereas eNOS was not modified in normal placentas. LC-MS/MS analysis of recombinant eNOS preincubated with ONE, allowed to identify several ONE-modified Lys-containing peptides, confirming that eNOS may undergo post-translational modification by LPP. The preincubation of HTR-8/SVneo human trophoblasts (HTR8) with ONE, resulted in ONE-Lys modification of eNOS and a reduced generation of NO. ONE inhibited the migration of HTR8 trophoblasts in the wound closure model, and this was partly restored by the NO donor, NOC-18, which confirmed the important role of NO in the invasive potential of trophoblasts. In conclusion, placental eNOS is modified by ONE in PE placentas, which emphasizes the sensitivity of this protein to oxidative stress in the disturbed redox environment of preeclamptic pregnancies.

The MMP-9/TIMP-1 System is Involved in Fluoride-Induced Reproductive Dysfunctions in Female Mice

A total of 84 healthy female mice were kept with various concentrations of sodium fluoride (F) (0, 50, 100, 150 mg F^-/L in drinking water for 90 days) and were then mated with healthy male mice for 1 week to study the effect of excessive fluoride on female reproductive function, particularly in embryo implantation. The rate of pregnancy, litter size, and the birth weight of female mice were evaluated. Ultrastructural changes of uteri tissues were observed by transmission electron microscopy (TEM). The mRNA expression levels of MMP-9 and TIMP-1 were determined by quantitative real-time PCR. The protein expression levels of MMP-9 and TIMP-1 were analyzed by western blotting. Results showed a significant decrease of litter size in mice exposed to fluoride. TEM images of uteri tissue of mice that underwent a 150 mg/L F^- treatment for 90 days showed a vague nucleus, reduced microvilli, increased lysosomes, a dilated endoplasmic reticulum, and a vacuolization mitochondrion when compared with the control group. Following the damage of the structure, the expression levels of MMP-9 and TIMP-1 in uteri tissues were significantly unregulated in the F 150 group. These results show that MMP-9/TIMP-1 system disturbance and changes of histological structure in uteri tissue are involved in fluoride-induced reproductive dysfunctions.

Reduced NO signaling during pregnancy attenuates outward uterine artery remodeling by altering MMP expression and collagen and elastin deposition

Recent findings indicate that endothelial nitric oxide (NO) plays a key role in uterine artery outward circumferential remodeling during pregnancy. Although the underlying mechanisms are not known, they likely involve matrix metalloproteinases (MMPs). The goal of this study was to examine the linkage among NO inhibition, expansive remodeling, and MMP expression within the uterine vascular wall. Adult female rats were treated with N(G)-nitro-L-arginine methyl ester [L-NAME (LPLN)] beginning on day 10 of pregnancy and until death at day 20 and compared with age-matched controls [late pregnant (LP)]. Mean arterial pressure of LPLN rats was significantly higher than controls. LPLN fetal and placental weights were significantly reduced compared with controls. Main uterine arteries (mUA) were collected to determine dimensional properties (lumen area and wall thickness), collagen and elastin content, and levels of endothelial nitric oxide synthase (eNOS) and MMP expression. Circumferential remodeling was attenuated, as evidenced by significantly smaller lumen diameters. eNOS RNA and protein were significantly (>90%) decreased in the LPLN mUA compared with LP. Collagen and elastin contents were significantly increased in LPLN rats by ∼10 and 25%, respectively, compared with LP (P < 0.05). Both MMP-2 and tissue inhibitors of metalloproteinase-2 as assessed by immunofluorescence were lower in the endothelium (reduction of 60%) and adventitia (reduction of 50%) of LPLN compared with LP mUA. Membrane bound MMP-1 (MT1-MMP) as assessed by immunoblot was significantly decreased in LPLN. These data suggest a novel contribution of MMPs to gestational uterine vascular remodeling and substantiate the linkage between NO signaling and gestational remodeling of the uterine circulation via altered MMP, TIMP-2, and MT1-MMP expression and activity.

Potential role of intermedin/adrenomedullin 2 in early embryonic development in rats

Adrenomedullin2 (ADM2), also referred to as Intermedin (IMD) is expressed in trophoblast cells in human placenta and enhances the invasion and migration of first trimester HTR-8/SV-neo cells. Recently we demonstrated that infusion of IMD antagonist in pregnant rats causes feto-placental growth restriction suggesting a role for IMD in maintaining a successful pregnancy. Therefore, this study was undertaken to assess if IMD has a functional role in embryo implantation in a rat model. We show that IMD mRNA is expressed in rat implantation sites and its expression is significantly higher on day 15 in placenta compared to days 18-22. Infusion of IMD antagonist IMD₁₇₋₄₇ from day 3 of pregnancy causes a significant decrease in the weights of day 9 implantation sites as well as serum levels of 17β-estradiol, progesterone, nitric oxide and serum MMP2 and MMP9 gelatinase activity. Further, expression of MMP2, MMP9, VEGF and PLGF protein levels are significantly downregulated in the implantation sites of IMD antagonist treated rats. This study suggests a potential involvement of IMD in regulating the factors that are critical for implantation and growth of the embryo and thus in establishment of normal rat pregnancy.

Protein phosphatase 1A (PPM1A) is involved in human cytotrophoblast cell invasion and migration

Trophoblast invasion is crucial for embryo implantation and placentation. Excessive trophoblast invasion leads to hydatidiform moles and choriocarcinoma. PPM1A is a phosphatase which dephosphorylates and inactivates a broad range of substrates, including TGF-beta, MAP kinases, p38 and JNK kinase cascades, and is involved in tumor suppression. The objective of this study was to investigate the expression of PPM1A in normal and malignant human placenta and its role in trophoblast invasion, which shares many similarities with invasion of tumor cells. By Western blotting and immunocytochemistry, significantly higher expression of PPM1A in human placental villi at term was found as compared with that during the first trimester. Furthermore, the expression level of PPM1A protein in hydatidiform moles was lower compared with that during normal pregnancy. We further investigated the function of PPM1A in extravillous trophoblast cell line HTR8/SVneo. Transwell migration and Matrigel invasion assays demonstrated that PPM1A siRNA significantly promoted the motility and invasiveness of the cells. Gelatin zymography showed that knockdown of PPM1A with siRNA elevated the expression of pro-matrix metalloproteinase pro-(MMP)-9, but down-regulated tissue inhibitors of metalloproteinases (TIMP)-2. The present data indicate that PPM1A plays a critical role in the regulation of normal placentation by inhibiting trophoblast migration and invasion.

Factor XII gene expression in endometrial stromal cells during decidualisation

Decidualisation of endometrial stromal cells (ESC) is a prerequisite for the implantation of human embryos. Identification of genes that are upregulated or downregulated during decidualisation could lead to a better understanding of the molecular mechanisms involved in this process. In the present study, we examined differences in gene expression between decidualised and non-decidualised cells using microarray analysis and found that Factor XII (FXII) gene expression was upregulated during decidualisation. Furthermore, we also examined the expression of FXII by human ESC before and during pregnancy, as well as its expression by cells that had undergone decidualisation in vitro. Weak expression of FXII mRNA was detected in the non-pregnant endometrium that increased gradually from the proliferative to the secretory endometrium. During pregnancy, FXII mRNA expression was markedly increased in decidualised endometrium. When sex steroids (200 pg mL–1 of 17β-oestradiol and 100 ng mL–1 of progesterone) were used to induce in vitro decidualisation of ESC, the expression of FXII mRNA increased by approximately 25.3-fold compared with that in non-decidualised ESC. Using western blotting, we confirmed the presence of FXII protein (80 kDa) in ESC after in vitro decidualisation. Increased expression of FXII in ESC during decidualisation suggests that the kallikrein–kininogen–kinin system may be activated during the implantation of human embryos.

Expression of tissue inhibitor of metalloproteinase-4 (TIMP-4) in endometrium and placenta of rhesus monkey (Macaca mulatta) during early pregnancy

The tissue inhibitors of metalloproteinases (TIMPs) are secreted as important regulators of the matrix metalloproteinases (MMPs). TIMP-4 is the most recently characterized member of the TIMPs family. In the present study, we examined the expression and localization of the TIMP-4 transcript and protein in endometrium and placenta of rhesus monkey (Macaca mulatta) on days 12, 18 and 26 of pregnancy using RT-PCR, in situ hybridization, and immunohistochemistry. The fragment of TIMP-4 gene from rhesus monkey uterine samples shared 95% identity with the corresponding region of human homologue. On day 12 of pregnancy, TIMP-4 mRNA was mainly expressed in the glandular and luminal epithelium. On days 18 and 26 of pregnancy, the expression of TIMP-4 mRNA tended to decline in glandular epithelium and there were strong staining in the placental villi. Furthermore, TIMP-4 mRNA was very faint or undetectable in the stromal cells, endothelial cells of arterioles and myometrium at any stages of pregnancy. The results of immunohistochemical analysis were similar to that of its mRNA. These findings indicate that TIMP-4 might play an important role in glandular secretion, endometrial tissue remodeling and invasion of the trophoblast cells by regulating MMPs in a localized manner in the uteri of rhesus monkey during early pregnancy.

Effects of E-cadherin on mouse embryo implantation and expression of matrix metalloproteinase-2 and -9

E-cadherin is a cell surface glycoprotein, which is responsible for adhesion between epithelial cells. Whether it is involved in embryo implantation is still unknown. In a mouse intrauterine horn injection model, one uterine horn in each mouse was injected with different doses of E-cadherin antibody on day 3 of pregnancy. The results showed that embryo implantation was significantly inhibited in the mice injected with 3 microg E-cadherin antibody. The mouse uteri in this group were collected on days 5, 6, and 7 of pregnancy and expressions of MMP-2 and -9 were studied. In situ hybridization and RT-PCR results showed that the expression of MMP-2 and -9 mRNAs in uteri of E-cadherin antibody treated group was increased on days 5-7. The results of gelatin zymography of MMPs showed that the activities of pro-MMP-2, MMP-2, and pro-MMP-9 were increased significantly on days 5 and 6, and pro-MMP-9 activity was increased on day 7. The present study suggested that E-cadherin was involved in embryo implantation through decreasing the expressions and activities of MMP-2 and -9.

Abnormal development and increased 3-nitrotyrosine in copper-deficient mouse embryos

Copper-deficient rat embryos are characterized by brain and heart anomalies, low superoxide dismutase activity, and high superoxide anion concentrations. One consequence of increased superoxide anions can be the formation of peroxynitrite, a strong biological oxidant. To investigate developmentally important features of copper deficiency, GD 8.5 mouse embryos from copper-adequate and copper-deficient dams were cultured in media that were adequate or deficient in copper. After 48 h, copper-deficient embryos exhibited brain and heart anomalies, and a high incidence of yolk sac vasculature abnormalities compared to controls. Immunohistochemistry of 4-hydroxynonenal and 8-hydroxy-2'-deoxyguanosine for lipid and DNA damage, respectively, was similar between groups. In contrast, 3-nitrotyrosine, taken as a measure of protein nitration, was markedly higher in the neuroepithelium of the anterior neural tube of copper-deficient embryos than in controls. Repletion of copper-deficient media with copper, or supplementation with copper-zinc superoxide dismutase, Tiron, or glutathione peroxidase did not ameliorate the abnormal development, but did decrease 3-nitrotyrosine in neuroepithelium of copper-deficient embryos. These data support the concept that while copper deficiency compromises oxidant defense and increases protein nitration, additional mechanisms, e.g., altered nitric oxide metabolism may contribute to copper-deficiency-induced teratogenesis.

Failure of decidual arteriolar remodeling in the CBA/J x DBA/2 murine model of recurrent pregnancy loss is linked to increased expression of tissue inhibitor of metalloproteinase 2 (TIMP-2)

OBJECTIVE

Uterine vascular remodeling at mid gestation includes the thinning of the vessel walls and, typically, an increase in lumen diameter. This study aimed to elucidate any differences in structural remodeling in normal murine pregnancies versus those differences that resulted from the crossing of CBA/J female mice by DBA/2 male mice, a combination that is known to exhibit recurrent resorption/pregnancy loss.

STUDY DESIGN

CBA/J female mice that were pregnant by DBA/2 male mice (abnormals) and DBA/2 female mice that were pregnant by CBA/J male mice (normals) were killed at mid gestation, which is a time when fetal resorption can be identified. Tissues were collected for permanent fixation and gene expression studies with complementary DNA macroarrays that were specific for extracellular matrix proteins. A 2-fold increase in expression or a 50% decline was considered significant. Expression changes were confirmed by real-time reverse transcriptase-polymerase chain reaction.

RESULTS

The vessel-to-lumen diameter ratios were found to be significantly greater for the CBA/J implantation sites (1.50 +/- 0.05 vs 1.22 +/- 0.02, respectively; P < .0001), which indicates a lack of vascular remodeling. There was also a trend towards smaller lumen diameters for the CBA/J vessels, but this was not statistically significant (78.2 +/- 4.4 microm vs 93.5 +/- 6.8 microm, respectively; P = .22). The mean coefficient of variation for lumen measurements was 0.8% and for vessel diameter was 0.3%. The ranges were 0 to 3.2% and 0 to 1.4%, respectively. Tissue inhibitor of metalloproteinase 2 expression was up-regulated in the placentas of the group with higher resorption rates when compared with normals. This was confirmed with reverse transcriptase-polymerase chain reaction, where abnormals exhibited 2.6-fold greater tissue inhibitor of metalloproteinase 2 protein quantities when compared with normal controls (P = .03).

CONCLUSION

The expansive vascular remodeling of decidual vessels that is characteristic of normal murine pregnancy is attenuated significantly in the CBA/J x DBA/2 mating combination, which is known for its tendency to recurrent fetal resorption. This has been correlated with a relative overexpression of tissue inhibitor of metalloproteinase 2 protein in placentas of this strain combination and compared with normals.

Protein S-nitrosation: Biochemistry and characterization of protein thiol–NO interactions as cellular signals

The interaction of nitric oxide with thiols is complex and still an active area of research. Herein, we provide an overview of the ways in which nitric oxide can be biologically transformed into species capable of adding an NO moiety to protein sulfhydryls, emphasizing how protein S-nitrosation differs from nitrosation of low molecular weight thiols. Protein S-nitrosation is being revealed as a post-translational means of chemically modifying and functionally altering proteins. Changes in protein function, which persist on a physiologically relevant time scale, effectively transmit biological signals and thus provide a framework for elucidating signaling networks. A description of recently developed methodology facilitating inquiry into this area is provided, along with a sketch of various proteins reported to be targets for nitrosation and the functional consequences therein. Protein denitrosation appears to be an active and perhaps enzymatically catalyzed process. Here, we summarize the evidence that suggests this and proffer a précis of proteins possessing denitrosation activity.