Leukemia inhibitory factor antisense oligonucleotide inhibits the development of murine embryos at preimplantation stages

Editorial: Advances in genomic and genetic tools, and their applications for understanding embryonic development and human diseases

Significant advances have been recently made in the development of the genetic and genomic platforms. This has greatly contributed to a better understanding of gene expression and regulation machinery. Consequently, this led to considerable progress in unraveling evidence of the genotype-phenotype correlation between normal/abnormal embryonic development and human disease complexity. For example, advanced genomic tools such as next-generation sequencing, and microarray-based CGH have substantially helped in the identification of gene and copy number variants associated with diseases as well as in the discovery of causal gene mutations. In addition, bioinformatic analysis tools of genome annotation and comparison have greatly aided in data analysis for the interpretation of the genetic variants at the individual level. This has unlocked potential possibilities for real advances toward new therapies in personalized medicine for the targeted treatment of human diseases. However, each of these genomic and bioinformatics tools has its limitations and hence further efforts are required to implement novel approaches to overcome these limitations. It could be possible that the use of more than one platform for genotype-phenotype deep analysis is an effective approach to disentangling the cause and treatment of the disease complexities. Our research topic aimed at deciphering these complexities by shedding some light on the recent applications of the basic and advanced genetic/genomic and bioinformatics approaches. These include studying gene-gene, protein-protein, and gene-environment interactions. We, in addition, aimed at a better understanding of the link between normal/abnormal embryonic development and the cause of human disease induction.

Effects of Bisphenol A and 4-tert-Octylphenol on Embryo Implantation Failure in Mouse

Miscarriage due to blastocyst implantation failure occurs in up to two-thirds of all human miscarriage cases. Calcium ion has been shown to be involved in many cellular signal transduction pathways as well as in the regulation of cell adhesion, which is necessary for the embryo implantation process. Exposure to endocrine-disrupting chemicals (EDs) during early gestation results in disruption of intrauterine implantation and uterine reception, leading to implantation failure. In this study, ovarian estrogen (E2), bisphenol A (BPA), or 4-tert-octylphenol (OP), with or without ICI 182,780 (ICI) were injected subcutaneously from gestation day 1 to gestation day 3 post-coitus. The expression levels of the calcium transport genes were assessed in maternal uteri and implantation sites. The number of implantation sites was significantly low in the OP group, and implantation sites were absent in the E2, ICI and EDs + ICI groups. There were different calcium transient transport channel expression levels in uterus and implantation site samples. The levels of TRPV5 and TRPV6 gene expression were significantly increased by EDs with/without ICI treatment in utero. Meanwhile, TRPV5 and TRPV6 gene expression were significantly lower in implantation sites samples. NCX1 and PMCA1 mRNA levels were significantly decreased by OP and BPA in the implantation site samples. Compared to vehicle treatment in the uterus, both the MUC1 mRNA and protein levels were markedly high in all but the BPA group. Taken together, these results suggest that both BPA and OP can impair embryo implantation through alteration of calcium transport gene expressions and by affecting uterine receptivity.

Requirement of Leukemia Inhibitory Factor or Epidermal Growth Factor for Pre-Implantation Embryogenesis via JAK/STAT3 Signaling Pathways

Leukemia inhibitory factor (LIF) plays a key role in the survivability of mouse embryos during pre-implantation. In this study, we verified the role of LIF by detecting gene expression in morula stage embryos through DNA microarray. Our results showed that LIF knockdown affected expression of 369 genes. After LIF supplementation, the epidermal growth factor (EGF) is most affected by LIF expression. To observe the correlation between LIF and EGF, the LIF knockdown embryos were supplemented with various growth factors, including LIF, EGF, GM-CSF, TGF, and IGF II. Only LIF and EGF caused the rate of blastocyst development to recover significantly from 52% of control to 83% and 93%, respectively. All of the variables, including the diameter of blastocysts, the number of blastomeres, and cells in ICM and TE, were almost restored. Moreover, EGF knockdown also impaired blastocyst development, which was reversed by LIF or EGF supplementation. The treatment with various signaling suppressors revealed that both EGF and LIF promoted embryonic development through the JAK/STAT3 signaling pathway. These data suggest that the EGF and LIF can be compensatory to each other during early embryonic development, and at least one of them is necessary for sustaining the normal development of pre-implantation embryos.

Rescue effects: irradiated cells helped by unirradiated bystander cells

The rescue effect describes the phenomenon where irradiated cells or organisms derive benefits from the feedback signals sent from the bystander unirradiated cells or organisms. An example of the benefit is the mitigation of radiation-induced DNA damages in the irradiated cells. The rescue effect can compromise the efficacy of radioimmunotherapy (RIT) (and actually all radiotherapy). In this paper, the discovery and subsequent confirmation studies on the rescue effect were reviewed. The mechanisms and the chemical messengers responsible for the rescue effect studied to date were summarized. The rescue effect between irradiated and bystander unirradiated zebrafish embryos in vivo sharing the same medium was also described. In the discussion section, the mechanism proposed for the rescue effect involving activation of the nuclear factor κB (NF-κB) pathway was scrutinized. This mechanism could explain the promotion of cellular survival and correct repair of DNA damage, dependence on cyclic adenosine monophosphate (cAMP) and modulation of intracellular reactive oxygen species (ROS) level in irradiated cells. Exploitation of the NF-κB pathway to improve the effectiveness of RIT was proposed. Finally, the possibility of using zebrafish embryos as the model to study the efficacy of RIT in treating solid tumors was also discussed.

Germ-cell culture conditions facilitate the production of mouse embryonic stem cells

The derivation of embryonic stem-cell (ESC) lines from blastocysts is a very inefficient process. Murine ESCs are thought to arise from epiblast cells that are already predisposed to a primordial-germ-cell fate. During the process of ESC derivation from B6D2 F1 hybrid mice, if we first culture the embryo from the two-cell stage in medium supplemented with LIF, we improve the quality of the blastocyst. When the blastocyst is then cultured in a germ-line stem-cell culture medium (GSCm), we are able to more efficiently (28.3%) obtain quality ESC lines that have a normal karyotype, proper degree of chimerism, and exhibit germ-line transmission when microinjected into blastocysts. Although germ-cell-specific genes were expressed in all culture medium conditions, GSCm did not shift the transcriptome towards germ-cell specification. A correlation was further observed between ESC derivation efficiency and the expression of some imprinted genes and retrotransposable elements. In conclusion, the combination of LIF supplementation followed by culture in GSCm establishes a higher efficiency method for ESC derivation.

Leukemia inhibitory factor enhances bovine oocyte maturation and early embryo development

The present study was conducted to examine the effects of leukemia inhibitory factor (LIF) on bovine oocyte maturation and early embryo development in vitro. Results showed that LIF supplementation (25 ng/ml) enhanced nuclear maturation of intact cumulus-oocyte complexes (COCs) compared to the vehicle control. Similar results were observed in denuded oocytes, indicating that LIF directly influences oocyte development. LIF-treated oocytes showed a higher cortical-granule-migration rate and increased expression of CD9, a tetraspanin transmembrane protein essential for fertilization. After in vitro fertilization, oocytes receiving LIF supplementation exhibited a higher cleavage rate and yielded a significantly higher number of blastocysts. To further dissect the molecular mechanism underlying this LIF-induced bovine oocyte maturation phenotype, we examined the involvement of two signaling cascades, mitogen-activated protein kinases (MAPK3/1)- and the signal transducer and activator of transcription 3 (STAT3)-dependent pathways. Western blot results revealed that LIF phosphorylated MAPK3/1 and STAT3. Inhibition of MAPK3/1 activation with MEK inhibitor U0126 only partially blocked LIF-induced nuclear maturation, although it attenuated oocyte cytoplasmic maturation. Inhibition of JAK/STAT3 activation with a specific pharmacological inhibitor completely abolished the LIF-response in bovine oocyte. In summary, these data revealed a novel role for LIF in bovine oocyte maturation subsequent embryonic development.

Maternal tract factors contribute to paternal seminal fluid impact on metabolic phenotype in offspring

Paternal characteristics and exposures influence physiology and disease risks in progeny, but the mechanisms are mostly unknown. Seminal fluid, which affects female reproductive tract gene expression as well as sperm survival and integrity, provides one potential pathway. We evaluated in mice the consequences for offspring of ablating the plasma fraction of seminal fluid by surgical excision of the seminal vesicle gland. Conception was substantially impaired and, when pregnancy did occur, placental hypertrophy was evident in late gestation. After birth, the growth trajectory and metabolic parameters of progeny were altered, most profoundly in males, which exhibited obesity, distorted metabolic hormones, reduced glucose tolerance, and hypertension. Altered offspring phenotype was partly attributable to sperm damage and partly to an effect of seminal fluid deficiency on the female tract, because increased adiposity was also evident in adult male progeny when normal two-cell embryos were transferred to females mated with seminal vesicle-excised males. Moreover, embryos developed in female tracts not exposed to seminal plasma were abnormal from the early cleavage stages, but culture in vitro partly alleviated this. Absence of seminal plasma was accompanied by down-regulation of the embryotrophic factors Lif, Csf2, Il6, and Egf and up-regulation of the apoptosis-inducing factor Trail in the oviduct. These findings show that paternal seminal fluid composition affects the growth and health of male offspring, and reveal that its impact on the periconception environment involves not only sperm protection but also indirect effects on preimplantation embryos via oviduct expression of embryotrophic cytokines.

Leukemia inhibitory factor promotes porcine oocyte maturation and is accompanied by activation of signal transducer and activator of transcription 3

We produced recombinant porcine leukemia inhibitory factor (pLIF) and examined its effect on in vitro maturation (IVM) of porcine oocytes and their developmental competence after in vitro fertilization. Porcine cumulus-oocyte complexes (COCs) were matured in a medium supplemented with pLIF during the first 22 hr, last 22 hr, or entire 44 hr duration of IVM. Oocytes in all groups tended to show enhanced nuclear maturation rates by the metaphase II (MII) stage (76.1%, 82.1%, and 86.6%, respectively) compared to the without-pLIF treatment group (69.6%, control). A significant increase in MII rate (P < 0.05) and obvious induction of cumulus expansion were observed over the whole time span (44 hr) in the IVM group. When cumulus cells were removed at 22 hr and denuded oocytes were further cultured, pLIF showed no effect on maturation rate. Oocytes matured in pLIF-supplemented medium showed a tendency for more rapid blastocyst development (21.1% vs. 16.2%, P = 0.0715). Examination of transcripts and proteins of the LIF signaling pathway in COCs revealed that LIF, LIF receptors, and signal transducer and activator of transcription 3 (STAT3) are present in both cumulus cells and oocytes. The amount of phosphorylated STAT3 (p-STAT3) markedly increased in both cumulus cells and oocytes cultured in pLIF-supplemented media, although oocyte p-STAT3 disappeared after 44 hr of IVM. These results suggest that the LIF/STAT3 pathway is functional during IVM of porcine oocytes, and supplementing pLIF in the IVM medium can improve oocyte maturation by activating this pathway.

Embryos of the zebrafish Danio rerio in studies of non-targeted effects of ionizing radiation

The use of embryos of the zebrafish Danio rerio as an in vivo tumor model for studying non-targeted effects of ionizing radiation was reviewed. The zebrafish embryo is an animal model, which enables convenient studies on non-targeted effects of both high-linear-energy-transfer (LET) and low-LET radiation by making use of both broad-beam and microbeam radiation. Zebrafish is also a convenient embryo model for studying radiobiological effects of ionizing radiation on tumors. The embryonic origin of tumors has been gaining ground in the past decades, and efforts to fight cancer from the perspective of developmental biology are underway. Evidence for the involvement of radiation-induced genomic instability (RIGI) and the radiation-induced bystander effect (RIBE) in zebrafish embryos were subsequently given. The results of RIGI were obtained for the irradiation of all two-cell stage cells, as well as 1.5 hpf zebrafish embryos by microbeam protons and broad-beam alpha particles, respectively. In contrast, the RIBE was observed through the radioadaptive response (RAR), which was developed against a subsequent challenging dose that was applied at 10 hpf when <0.2% and <0.3% of the cells of 5 hpf zebrafish embryos were exposed to a priming dose, which was provided by microbeam protons and broad-beam alpha particles, respectively. Finally, a perspective on the field, the need for future studies and the significance of such studies were discussed.

Characterization of microRNA expression profiles and the discovery of novel microRNAs involved in cancer during human embryonic development

MicroRNAs (miRNAs), approximately 22-nucleotide non-coding RNA molecules, regulate a variety of pivotal physiological or pathological processes, including embryonic development and tumorigenesis. To obtain comprehensive expression profiles of miRNAs in human embryos, we characterized miRNA expression in weeks 4-6 of human embryonic development using miRNA microarrays and identified 50 human-embryo-specific miRNAs (HES-miRNAs). Furthermore, we selected three non-conserved or primate-specific miRNAs, hsa-miR-638, -720, and -1280, and examined their expression levels in various normal and tumor tissues. The results show that expression of most miRNAs is extremely low during early human embryonic development. In addition, the expression of some non-conserved or primate-specific miRNAs is significantly different between tumor and the corresponding normal tissue samples, suggesting that the miRNAs are closely related to the pathological processes of various tumors. This study presents the first comprehensive overview of miRNA expression during human embryonic development and offers immediate evidence of the relationship between human early embryonic development and tumorigenesis.

[The new function of p53 family and its pathway related proteins in female reproduction]

p53 is an important tumor suppressor gene and one of the key genes in sensing and regulating responses to the environmental stress. Recent study showed that cold winter temperature naturally selected p53 Arg72 in eastern Asian population, suggesting that p53 plays a role in reproduction. It has also been reported that some SNPs of p53, Mdm2(Murine double minute 2), MdmX and Hausp (Herpes virus-associated ubiquitin-specific protease) in p53 pathway are associated with the risk of the women's reproduction disorder. p53 regulates the LIF (leukaemia inhibitory factor) expression level by its DBD domain, and thus contributes to female reproduction by affecting the embryo implantation process. The MDM2, MDMX, and HAUSP proteins regulates the level and activity of p53 protein, which are critical for the appropriate p53 response in the embryo implantation process. The members of p53 family, p63 and p73, also play roles in female reproduction through other pathways. p63 has been implicated as a major regulator of oocyte death following treatment with irradiation and chemotherapeutic drugs, which prevents fetal malformation. p73 regulates the formation of spindle assembly complex(SAC). The dysfunction of SAC results in poor blastocyst quality and defects in kinetochore-microtubule associations, which leads to aneuploidy. This review summarized the function of p53 family and its pathway related proteins in female reproduction, pointed out a new method in improving the success rate in IVF-ET, and provided a new diagnosis idea for unexplained infertile women. It will facilitate personalized strategies in the infertility therapy.

The relationship between early embryo development and tumourigenesis

With the recent substantial progress in developmental biology and cancer biology, the similarities between early embryo development and tumourigenesis, as well as the important interaction between tumours and embryos become better appreciated. In this paper, we review in detail the embryonic origin of tumour, and the similarities between early embryo development and tumourigenesis with respect to cell invasive behaviours, epigenetic regulation, gene expression, protein profiling and other important biological behaviours. Given an improved understanding of the relationship between early embryo development and tumourigenesis, now we have better and broader resources to attack cancer from the perspective of developmental biology and develop next generation of prognostic and therapeutic approaches for this devastating disease.

Optimization of embryo culture conditions for increasing efficiency of cloning in buffalo (Bubalus bubalis) and generation of transgenic embryos via cloning

Cloning in bovine species is marred by low efficiency of blastocyst formation. Any increase in the efficiency of blastocyst formation upon nuclear transfer will greatly enhance the efficiency of cloning. In the present study, the effect of various media, protein sources, and growth factors on the development of cloned buffalo embryos was evaluated. Among various combinations tested, culture of cloned embryos in TCM-199 media on the feeder layer of Buffalo Oviductal Epithelial Cells (BOEC) in the presence of bovine serum albumin-free fatty acid (BSA-FFA) and leukemia inhibitory factor (LIF) provided most suitable environment for efficient development of cloned blastocysts. Under these conditions, we achieved a blastocyst formation rate of 43%, which is better than those reported previously. Because preimplantation embryonic development, in vivo, occurs in an environment of oviductal cells, the blastocysts generated by this method may presumably be more suitable for implantation and further development. Additionally, we generated green blastocysts from enucleated oocytes by transfer of nuclei from cells transfected with EGFP transgene, showing possibility of transgenesis via cloning in this species. To our knowledge, this is the first report regarding the production of transgenic cloned buffalo embryos and their developmental competence with respect to various media, cocultures, and supplements.

Research progress in correlation between early embryo development and tumorigenesis

With the increased cognition in developmental biology, researchers have discovered the similarity of biological behaviors between early embryo development and tumorigenesis, as well as the important interaction between tumors and embryos. Therefore, it enlightens us to study tumors from the view of developmental biology, which may provide a new clue for tumor therapy. In this article, we review in detail the embryonic origin of tumors, the similarity between early embryo development and tumorigenesis at the level of gene and protein expression, their important biological behaviors, and moreover, the interaction between tumors and embryos from the angle of developmental biology.

Leukemia inhibitory factor induces cumulus expansion in immature human and mouse oocytes and improves mouse two-cell rate and delivery rates when it is present during mouse in vitro oocyte maturation

OBJECTIVE

To examine the role of leukemia inhibitory factor (LIF) during in vitro maturation (IVM) on human and mice cumulus expansion and mice oocyte competence by in vitro fertilization (IVF), culture, and embryo transfer (ET).

DESIGN

Prospective animal and human study.

SETTING

Serono laboratories and IVF clinic.

PATIENT(S)

Healthy women volunteers and 8-week-old female mice.

INTERVENTION(S)

Cumulus compacted human and mice oocytes were matured in IVM media with and without recombinant follicle-stimulating hormone (FSH) and with and without LIF. Mice IVM oocytes with and without 0.2 IU/mL of recombinant FSH; or with and without recombinant FSH + LIF (0.1, 1.0, 1000.0 ng/mL) and ovulated oocytes were in vitro fertilized and cultured. We transferred 395 blastocysts to the uterine horn of 2.5-day pseudopregnant female mice.

MAIN OUTCOME MEASURE(S)

Cumulus expansion in human and mice oocytes, and two-cell rate, blastocyst rate, and delivered rate of live pups in mice.

RESULT(S)

In human and mouse oocytes, LIF induced cumulus expansion. When 1000 ng/mL of LIF was added in combination with recombinant FSH, a statistically significant increase in cleavage rate, embryo development rate, and birth rate was observed when compared with oocytes matured with FSH alone.

CONCLUSION(S)

Leukemia inhibitory factor induced cumulus expansion similarly in human and mouse cumulus-oocyte complexes, and recombinant FSH plus LIF supplementation during mouse IVM significantly improved oocyte competence as measured by cleavage rate, blastocyst development, and birth rate.

Embryo-endometrial expression of leukemia inhibitory factor in the golden hamster (Mesocricetus auratus): increased expression during proestrous and window of implantation stages

Leukemia inhibitory factor (LIF) is a pleiotropic IL-6 family cytokine and its maternal uterine expression is critical for mouse blastocyst implantation. In the golden hamster (Mesocricetus auratus), although the blastocyst hatching phenomenon is quite interesting and LIF is shown to regulate hatching, information is not available on the embryonic and uterine expression of LIF and hormonal regulation of LIF expression during the peri-implantation period. The present investigation is aimed at studying embryonic and uterine expression of LIF during preimplantation hamster development. We observed embryonic expression of LIF mRNA and protein in the 8-cell, morula and blastocyst stages. In cycling females, uterine LIF mRNA expression was maximal during the oestrogen-dominant phase of the oestrous cycle, i.e. proestrous stage. Interestingly, during pregnancy, both LIF mRNA and protein were highly upregulated on Days 3.5 and 4 (‘window of implantation’), implying a role for this cytokine in blastocyst hatching and implantation. Cell type-specific localisation of LIF mRNA and protein was observed predominantly in luminal epithelium and uterine glands with faint staining being detected in the stroma. The hamster uterus encoded a ~4.2 kb LIF transcript whose coding region, when cloned and sequenced, showed a high degree of identity to the murine cDNA counterpart. These data demonstrate that: (1) hamster preimplantation embryos show LIF mRNA and protein expression; (2) uterine expression of LIF mRNA and protein was dependent on elevated levels of circulating oestrogen, and (3) there is a possible functional association of LIF with the peri-implantation development in the golden hamster.

Cytokine knockouts in reproduction: the use of gene ablation to dissect roles of cytokines in reproductive biology

Cytokines play many diverse and important roles in reproductive biology, and dissecting the complex interactions between these proteins and the different reproductive organs is a difficult task. One approach is to use gene ablation, or 'knockout', to analyse the effect of deletion of a single cytokine on mouse reproductive function. This review summarizes the essential roles of cytokines in reproductive biology that have been revealed by gene knockout studies, including development and regulation of the hypothalamo-pituitary-gondal axis, ovarian folliculogenesis, implantation and immune system modulation during pregnancy. However, successful utilization of this approach must consider the caveats associated with gene ablation studies, e.g. embryonic lethality, systemic effects of cytokine ablation on local reproductive processes and the limited exposure to pathogens in mice housed in laboratory conditions. New sophisticated technology that temporally or spatially regulates gene ablation can overcome some of these limitations. Discoveries on the roles of cytokines in reproductive function uncovered by gene ablation studies can now be applied to improve in vitro fertilization for infertile couples and in the development of contraceptive therapies.

Effects of human versus mouse leukemia inhibitory factor on the in vitro development of bovine embryos

Leukemia inhibitory factor (LIF) is a cytokine that shows conflicting effects on in vitro produced (IVP) bovine embryos. Bovine LIF (bLIF) has been cloned and used in culture, but there is no commercially available bLIF. Thus, researchers use human LIF (hLIF) to supplement the culture medium for bovine embryos because of its greater sequence homology compared to murine LIF (mLIF). We compared the effects of mLIF and hLIF on the development of bovine embryos in culture with the effects described for bLIF. Oocytes were matured and fertilized in vitro and cultured in modified synthetic oviduct fluid with BSA. On Day 6 post-insemination, morulae were cultured for 48h in the presence of: (1) mLIF, 100ngml(-1); (2) hLIF, 100ngml(-1); or (3) no LIF. Reduced blastocyst rates were observed on Day 8 for hLIF at the middle and expanded stages, while mLIF had no effect. In contrast, Day 8 blastocysts showed decreased cell counts both in terms of inner cell mass (ICM) and ICM/total cell proportions in the presence of mLIF, while hLIF had no effect. No changes were seen in trophectoderm (TE) and total cell counts. The increased hatching rates and TE cell counts previously described for bLIF, together with the disparate effects exhibited by hLIF and mLIF during blastocyst formation indicate these compounds are inappropriate to replace bLIF. We recommend that heterospecific LIF should not be used to supplement the culture medium for bovine embryo or embryonic stem cells.

Inhibition of Oct4 expression in mouse preimplantation embryos using morpholino antisense oligonucleotides

Morpholino oligonucleotides (MO) can induce gene silencing by binding to a target mRNA and inhibiting its translation, and this technique has been especially successful in studies of embryonic development in various vertebrates. But in mice MO-induced downregulation of target genes has not been widely reported. In this study, we examined whether MO delivery using ethoxylated polyethylenimine (EPEI) delivery reagent is useful for silencing gene expression in the mouse preimplantation embryo, by targeting endogenous gene Oct4. To optimize the conditions for MO delivery, we examined the MO concentration, the EPEI concentration, the treatment time, and the number of MO treatments. The MO treatment was performed at the 2-cell, the morula, the blastocyst, and the hatched blastocyst stage. We first determined the optimal conditions for MO delivery into the nucleus using fluorescein isothiocyanate (FITC)-labeled MO, and demonstrated that treatment with a combination of 20 microM MO and 0.56 microM EPEI for 3 hrs produced effective MO delivery. MO-induced downregulation of Oct4 was then examined. Two-step MO treatment at the 2-cell and blastocyst stages successfully suppressed Oct4 expression. This MO treatment resulted in marked reduction of Oct4 protein at the blastocyst stage. After cultivation of blastocysts for further 4 days, derivatives of embryos either differentiated to trophoblastic cells or showed developmental arrest at the blastocyst. This phenocopy is similar to Oct4-deficient embryos. Overall, our results indicate that MO delivery with EPEI is an effective tool for analyzing gene function in mouse preimplantation embryos.

Leukaemia inhibitory factor in implantation and uterine biology

Leukaemia inhibitory factor (LIF) is one of the most important cytokines in the reproductive tract. Without expression of LIF in the uterus, implantation of a blastocyst cannot begin. Yet, 13 years after publication of the phenotype of the LIF knockout mouse we are only just beginning to understand how LIF functions in the uterus. This review addresses our knowledge of the role of LIF in regulating implantation through its influence on the luminal epithelium and stromal decidualization, but also its influence on reproductive tract cells such as leukocytes and glandular epithelium, during the pre-implantation phase of pregnancy.

Inhibiting Uterine PC6 Blocks Embryo Implantation: An Obligatory Role for a Proprotein Convertase in Fertility1

Successful embryo implantation involves complex interactions between the embryo and the uterus and is critical in establishing pregnancy. Proprotein convertase (PC) 6 (PC6) is one of the PC endoproteases regulating protein function through posttranslational activation of precursor proteins, including growth and differentiation factors. Here we show that PC6 protein is induced in the uterine stromal cells specifically at the site of embryo attachment during early pregnancy in mice. In vivo blocking of uterine production of PC6 protein using morpholino antisense oligonucleotides in mice resulted in total inhibition of implantation, revealing a vital role for PC6 in modulating the uterus for embryo implantation. Studies in primates (rhesus monkey and human) showed a dramatic upregulation of endometrial PC6 during the phase of uterine receptivity and at implantation, particularly during a critical uterine cell differentiation process termed decidualization. Thus, the current studies have demonstrated that PC6 is an essential molecule in modulating uterine function to support the establishment of embryo implantation. Interestingly, PC6 is one of the PCs identified to be important in processing the coat protein of HIV; inhibition of PCs has been suggested to be an effective approach to reduce HIV transmission. We therefore propose the novel concept that PC6 could be a potential nonhormonal target in the female reproductive tract for dual protection for women, both in preventing pregnancy and reducing HIV infection.