Increased Krüppel-like factor 12 impairs embryo attachment via downregulation of leukemia inhibitory factor in women with recurrent implantation failure

Innate and adaptive immune dysregulation in women with recurrent implantation failure

Recurrent implantation failure (RIF) is a condition where a woman fails to obtain pregnancy after multiple embryo transfer cycles, even with superior-quality blastocysts. There are various factors that can contribute to RIF, including immunologic disturbances. The immune system is extremely important during pregnancy. Immune cells such as T cells, B cells, natural killer (NK) cells, and macrophages (MQ) are present in the female reproductive tract and are accountable for regulating the immune response to invading pathogens and maintaining tissue homeostasis. Dysregulation of these immune cells can lead to inflammation, which can impair fertility. One of the most common immunological disturbances observed in RIF is an altered Th1/Th2 ratio, along with changes in NK cell and macrophage numbers. In addition, the presence of some antibodies, such as anti-ovarian antibodies, can also contribute to RIF. Interleukins have been implicated in the development of an inflammatory response that can interfere with successful embryo implantation. As a result, a comprehensive understanding of immunological compartments in RIF women could assist us in determining the immunological origins of this disease. We will discuss immunological factors that might contribute to RIF etiology, including cellular and molecular components.

Bioinformatic analysis of endometrial miRNA expression profile at day 26-28 of pregnancy in the mare

The establishment of the fetomaternal interface depends on precisely regulated communication between the conceptus and the uterine environment. Recent evidence suggests that microRNAs (miRNAs) may play an important role in embryo-maternal dialogue. This study aimed to determine the expression profile of endometrial miRNAs during days 26-28 of equine pregnancy. Additionally, the study aimed to predict target genes for differentially expressed miRNAs (DEmiRs) and their potential role in embryo attachment, adhesion, and implantation. Using next-generation sequencing, we identified 81 DEmiRs between equine endometrium during the pre-attachment period of pregnancy (day 26-28) and endometrium during the mid-luteal phase of the estrous cycle (day 10-12). The identified DEmiRs appear to have a significant role in regulating the expression of genes that influence cell fate and properties, as well as endometrial receptivity formation. These miRNAs include eca-miR-21, eca-miR-126-3p, eca-miR-145, eca-miR-451, eca-miR-491-5p, members of the miR-200 family, and the miRNA-17-92 cluster. The target genes predicted for the identified DEmiRs are associated with ion channel activity and sphingolipid metabolism. Furthermore, it was noted that the expression of mucin 1 and leukemia inhibitory factor, genes potentially regulated by the identified DEmiRs, was up-regulated at day 26-28 of pregnancy. This suggests that miRNAs may play a role in regulating specific genes to create a favorable uterine environment that is necessary for proper attachment, adhesion, and implantation of the embryo in mares.

Non-coding RNAs in Recurrent implantation failure

Recurrent implantation failure (RIF), defined as the inability to achieve conception following multiple consecutive in-vitro fertilization (IVF) attempts, represents a complex and multifaceted challenge in reproductive medicine. The emerging role of non-coding RNAs in RIF etiopathogenesis has only gained prominence over the last decade, illustrating a new dimension to our understanding of the intricate network underlying RIF. Successful embryo implantation demands a harmonious synchronization between an adequately decidualized endometrium, a competent blastocyst, and effective maternal-embryonic interactions. Emerging evidence has clarified the involvement of a sophisticated network of non-coding RNAs, including microRNAs, circular RNAs, and long non-coding RNAs, in orchestrating these pivotal processes. Disconcerted expression of these molecules can disrupt the delicate equilibrium required for implantation, amplifying the risk of RIF. This comprehensive review presents an in-depth investigation of the complex role played by non-coding RNAs in the pathogenesis of RIF. Furthermore, it underscores the vast potential of non-coding RNAs as diagnostic biomarkers and therapeutic targets, with the ultimate goal of enhancing implantation success rates in IVF cycles. As ongoing research continues to unravel the intercalated web of molecular interactions, exploiting the power of non-coding RNAs may offer promising avenues for mitigating the challenges posed by RIF and improving the outcomes of assisted reproduction.

Molecular Determinants of Uterine Receptivity: Comparison of Successful Implantation, Recurrent Miscarriage, and Recurrent Implantation Failure

Embryo implantation is one of the most remarkable phenomena in human reproduction and is not yet fully understood. Proper endometrial function as well as a dynamic interaction between the endometrium itself and the blastocyst-the so-called embryo-maternal dialog-are necessary for successful implantation. Several physiological and molecular processes are involved in the success of implantation. This review describes estrogen, progesterone and their receptors, as well as the role of the cytokines interleukin (IL)-6, IL-8, leukemia inhibitory factor (LIF), IL-11, IL-1, and the glycoprotein glycodelin in successful implantation, in cases of recurrent implantation failure (RIF) and in cases of recurrent pregnancy loss (RPL). Are there differences at the molecular level underlying RIF or RPL? Since implantation has already taken place in the case of RPL, it is conceivable that different molecular biological baseline situations underlie the respective problems.

Personalized embryo transfer based on RNA sequencing endometrial receptivity test in repeated implantation failure patients: artificial cycle versus natural cycle

INTRODUCTION

Embryo implantation provides an efficient way for patients with repeated implantation failure (RIF) to achieve pregnancy. The aim of this study is to compare the implantation outcomes of RIF patients in artificial cycle to those in natural cycle, both were treated with RNA sequencing endometrial receptivity test (rsERT) based personalized embryo implantation.

METHODS

The endometrial receptivity (ER) analysis was performed using rsERT followed by personalized embryo transfer at optimal window of implantation (WOI). The implantation rate (IR), clinical pregnancy rate (CPR) and live birth rate (LBR) were calculated. The expression levels of biomarkers involved in pregnancy process in the patients detected as in receptivity status were also analyzed.

RESULTS

The rsERT shown that 44.8% (natural cycle) and 47.8% (artificial cycle) patients were in non-receptive status, which indicated a WOI displacement. After personalized embryo transfer, the IR of patients in artificial cycle was higher than those in natural cycle (52.2% vs 27.6%). The expressions of FKBP52, MUC1 and LPAR3 were significantly lower in artificial cycle than in natural cycle.

CONCLUSION

Using artificial cycle for personalized embryo transfer based on rsERT may yield better pregnancy outcomes for RIF patients. A gene expression analysis of FKBP52, MUC1 and LPAR3 provided a potential way to increase implantation outcomes for RIF patients.

Decreased Krüppel-like factor 4 in adenomyosis impairs decidualization by repressing autophagy in human endometrial stromal cells

Background

Poor decidualization and abnormal autophagy conditions in the endometria of adenomyosis patients have been reported previously. However, the specific regulatory mechanism of decidualization in adenomyosis and its relationship with autophagy levels have not been clarified.

Methods

Endometrial tissues from adenomyosis patients and uteri from an adenomyosis mouse model were collected for the detection of different expression patterns of KLF4 and autophagy markers (LC3-B/LC3-A and Beclin-1) compared with control groups. Human endometrial stromal cells (hESCs) isolated from adenomyosis and control endometrial tissues were employed to elucidate the biological functions of KLF4 in autophagy and decidualization. Gene expression regulation was examined by quantitative real-time PCR (qRT-PCR), western blotting and luciferase reporter assays. In addition, DNA promoter-protein interactions were examined by chromatin immunoprecipitation (ChIP)/PCR assay and avidin–biotin conjugate DNA precipitation (ABCD) assay.

Results

KLF4 expression was decreased in endometrial tissues from adenomyosis patients compared with those from fertile controls, especially in stromal compartments. The opposite results were observed for autophagy marker (LC3-B/LC3-A and Beclin-1) expression. At the same time, KLF4 reversed the poor decidualization of hESCs from adenomyosis patients. In addition, KLF4 could induce hESC decidualization by promoting the autophagy level. Mechanistically, KLF4 bound to a conserved site in the autophagy-related 5 (ATG5) promoter region and promoted ATG5 expression. Similar expression patterns of KLF4 and autophagy markers were detected in adenomyotic mice.

Conclusions

KLF4 overexpression increases the autophagy level of hESCs by transcriptionally promoting ATG5 expression, and abnormally decreased KLF4 in adenomyosis impairs hESC decidualization by repressing autophagy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12860-022-00425-6.

The Molecular Basis and Therapeutic Potential of Leukemia Inhibitory Factor in Cancer Cachexia

Simple Summary

The mechanism of cancer cachexia is linked to a variety of factors, and inflammatory factors are thought to play a key role. We summarize the main roles of LIF in the development of cancer cachexia, including promoting fat loss, inducing skeletal muscle atrophy and causing anorexia nervosa. The main aim of this review is to increase the understanding of the effects of LIF in cachexia and to provide new insights into the treatment of cancer cachexia.

Abstract

Cachexia is a chronic metabolic syndrome that is characterized by sustained weight and muscle mass loss and anorexia. Cachexia can be secondary to a variety of diseases and affects the prognosis of patients significantly. The increase in inflammatory cytokines in plasma is deeply related to the occurrence of cachexia. As a member of the IL-6 cytokine family, leukemia inhibitory factor (LIF) exerts multiple biological functions. LIF is over-expressed in the cancer cells and stromal cells of various tumors, promoting the malignant development of tumors via the autocrine and paracrine systems. Intriguingly, increasing studies have confirmed that LIF contributes to the progression of cachexia, especially in patients with metastatic tumors. This review combines all of the evidence to summarize the mechanism of LIF-induced cachexia from the following four aspects: (i) LIF and cancer-associated cachexia, (ii) LIF and alterations of adipose tissue in cachexia, (iii) LIF and anorexia nervosa in cachexia, and (iv) LIF and muscle atrophy in cachexia. Considering the complex mechanisms in cachexia, we also focus on the interactions between LIF and other key cytokines in cachexia and existing therapeutics targeting LIF.

Production of biologically active recombinant buffalo leukemia inhibitory factor (BuLIF) in Escherichia Coli

Background

Leukemia inhibitory factor (LIF) is a multifunctional cytokine which plays multiple roles in different biological processes such as implantation, bone remodeling, and hematopoiesis. The buESCs are difficult to culture due to lack of proper understanding of the culture conditions. LIF is one of the important factors which maintain the pluripotency in embryonic stem cells and commercial LIF from murine and human origin is used in the establishment of buffalo embryonic stem cells (buESCs). The LIF from a foreign origin is not able to maintain pluripotency and proliferation in buESCs for a long term which is contributed by difference in the binding sites on LIF; therefore, culture medium supplemented with buffalo-specific LIF may enhance the efficiency of buESCs by improving the environment of culture conditions. The high cost of LIF is another major drawback which restricts buESCs research, thus limits the scope of buffalo stem cell use. Various methods have been developed to produce human and murine LIF in prokaryotic system. However, Buffalo leukemia inhibitory factor (BuLIF) has not been yet produced in prokaryotic system. Here, we describe a simple strategy for the expression and purification of biologically active BuLIF in Escherichia coli (E. coli).

Results

The BuLIF cDNA from buffalo (Bubalus bubalis) was cloned into pET22b(+) and expressed in E. coli Lemo-21(DE3). The expression of BuLIF was directed into periplasmic space of E. coli which resulted in the formation of soluble recombinant protein. One step immobilized metal affinity chromatography (IMAC chromatography) was performed for purification of BuLIF with ≥ 95% of homogeneity. The recombinant protein was confirmed by western blot and identified by mass spectroscopy. The biological activity of recombinant BuLIF was determined on murine myeloid leukemic cells (M1 cells) by MTT proliferation assay. The addition of BuLIF increased the reduction of MTT by stimulated M1 cells in a dose-dependent manner. The BuLIF induced the formation of macrophage like structures from M1 cells where they engulfed fluorescent latex beads. The recombinant BuLIF successfully maintained pluripotency in buffalo embryonic stem cells (buESCs) and were positive for stem cells markers such as Oct-4, Sox-2, Nanog, and alkaline phosphatase activity.

Conclusions

The present study demonstrated a simple method for the production of bioactive BuLIF in E. coli through single step purification. BuLIF effectively maintained buffalo embryonic stem cells pluripotency. Thus, this purified BuLIF can be used in stem cell study, biomedical, and agricultural research.

Supplementary Information

The online version contains supplementary material available at 10.1186/s43141-022-00328-1.

The Role of Interleukins in Recurrent Implantation Failure: A Comprehensive Review of the Literature

Recurrent implantation failure (RIF) is a multifactorial condition affecting 10-15% of in vitro fertilization (IVF) couples. Data suggest that functional dysregulation of the endometrial immune system constitutes one of the main pathophysiological mechanisms leading to RIF. The aim of this article is to provide a thorough presentation and evaluation of the role of interleukins (ILs) in the pathogenesis of RIF. A comprehensive literature screening was performed summarizing current evidence. During implantation, several classes of ILs are secreted by epithelial and stromal endometrial cells, including IL-6, IL-10, IL-12, IL-15, IL-18, and the leukemia inhibitory factor. These ILs create a perplexing network that orchestrates both proliferation and maturation of uterine natural killer cells, controls the function of regulatory T and B cells inhibiting the secretion of antifetal antibodies, and supports trophoblast invasion and decidua formation. The existing data indicate associations between ILs and RIF. The extensive analysis performed herein concludes that the dysregulation of the ILs network indeed jeopardizes implantation leading to RIF. This review further proposes a mapping of future research on how to move forward from mere associations to robust molecular data that will allow an accurate profiling of ILs in turn enabling evidence-based consultancy and decision making when addressing RIF patients.

ATF3 deficiency impairs the proliferative-secretory phase transition and decidualization in RIF patients

Decidualization is a complex process involving cellular proliferation and differentiation of the endometrial stroma and is required to establish and support pregnancy. Dysregulated decidualization has been reported to be a critical cause of recurrent implantation failure (RIF). In this study, we found that Activating transcription factor 3 (ATF3) expression was significantly downregulated in the endometrium of RIF patients. Knockdown of ATF3 in human endometrium stromal cells (hESCs) hampers decidualization, while overexpression could trigger the expression of decidual marker genes, and ameliorate the decidualization of hESCs from RIF patients. Mechanistically, ATF3 promotes decidualization by upregulating FOXO1 via suppressing miR-135b expression. In addition, the endometrium of RIF patients was hyperproliferative, while overexpression of ATF3 inhibited the proliferation of hESCs through CDKN1A. These data demonstrate the critical roles of endometrial ATF3 in regulating decidualization and proliferation, and dysregulation of ATF3 in the endometrium may be a novel cause of RIF and therefore represent a potential therapeutic target for RIF.

The emerging role of leukemia inhibitory factor in cancer and therapy

Leukemia inhibitory factor (LIF) is a multi-functional cytokine of the interleukin-6 (IL-6) superfamily. Initially identified as a factor that inhibits the proliferation of murine myeloid leukemia cells, LIF displays a wide variety of important functions in a cell-, tissue- and context-dependent manner in many physiological and pathological processes, including regulating cell proliferation, pluripotent stem cell self-renewal, tissue/organ development and regeneration, neurogenesis and neural regeneration, maternal reproduction, inflammation, infection, immune response, and metabolism. Emerging evidence has shown that LIF plays an important but complex role in human cancers; while LIF displays a tumor suppressive function in some types of cancers, including leukemia, LIF is overexpressed and exerts an oncogenic function in many more types of cancers. Further, targeting LIF has been actively investigated as a novel strategy for cancer therapy. This review summarizes the recent advances in the studies on LIF in human cancers and its potential application in cancer therapy. A better understanding of the role of LIF in different types of cancers and its underlying mechanisms will help to develop more effective strategies for cancer therapy.

Meta-Analysis of Transcriptome Data Detected New Potential Players in Response to Dioxin Exposure in Humans

Dioxins are one of the most potent anthropogenic poisons, causing systemic disorders in embryonic development and pathologies in adults. The mechanism of dioxin action requires an aryl hydrocarbon receptor (AhR), but the downstream mechanisms are not yet precisely clear. Here, we performed a meta-analysis of all available transcriptome datasets taken from human cell cultures exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Differentially expressed genes from different experiments overlapped partially, but there were a number of those genes that were systematically affected by TCDD. Some of them have been linked to toxic dioxin effects, but we also identified other attractive targets. Among the genes that were affected by TCDD, there are functionally related gene groups that suggest an interplay between retinoic acid, AhR, and Wnt signaling pathways. Next, we analyzed the upstream regions of differentially expressed genes and identified potential transcription factor (TF) binding sites overrepresented in the genes responding to TCDD. Intriguingly, the dioxin-responsive element (DRE), the binding site of AhR, was not overrepresented as much as other cis-elements were. Bioinformatics analysis of the AhR binding profile unveils potential cooperation of AhR with E2F2, CTCFL, and ZBT14 TFs in the dioxin response. We discuss the potential implication of these predictions for further dioxin studies.

Identification of single nucleotide polymorphisms of PIK3R1 and DUSP1 genes and their genetic associations with milk production traits in dairy cows

Background

Previously, phosphoinositide-3-kinase regulatory subunit 1 (PIK3R1) and dual specificity phosphatase 1 (DUSP1) were identified as promising candidate genes for milk production traits due to their being differentially expressed between the dry period and the peak of lactation in livers of dairy cows. Hence, in this study, the single nucleotide polymorphisms (SNPs) of PIK3R1 and DUSP1 genes were identified and their genetic associations with milk yield, fat yield, fat percentage, protein yield, and protein percentage, were investigated using 1067 Chinese Holstein cows from 40 sire families.

Results

By re-sequencing the entire coding region and 2000 bp of the 5′ and 3′ flanking regions of the two genes, one SNP in the 5′ untranslated region (UTR), three in the 3′ UTR, and two in the 3′ flanking region of PIK3R1 were identified, and one in the 5′ flanking region, one in the 3′ UTR, and two in the 3′ flanking region of DUSP1 were found. Subsequent single-locus association analyses showed that five SNPs in PIK3R1, rs42590258, rs210389799, rs208819656, rs41255622, rs133655926, and rs211408208, and four SNPs in DUSP1, rs207593520, rs208460068, rs209154772, and rs210000760, were significantly associated with milk, fat and protein yields in the first or second lactation (P values ≤ 0.0001 and 0.0461). In addition, by the Haploview 4.2 software, the six and four SNPs in PIK3R1 and DUSP1 respectively formed one haplotype block, and the haplotype-based association analyses showed significant associations between their haplotype combinations and the milk traits in both two lactations (P values ≤ 0.0001 and 0.0364). One SNP, rs207593520(T/G), was predicted to alter the transcription factor binding sites (TFBSs) in the 5′ flanking region of DUSP1. Further, the dual-luciferase assay showed that the transcription activity of allele T in rs207593520 was significantly higher than that of allele G, suggesting the activation of transcriptional activity of DUSP1 gene by allele T of rs207593520. Thus, the rs207593520 SNP was highlighted as a potential causal mutation that should be further verified.

Conclusions

We demonstrated novel and significant genetic effects of the PIK3R1 and DUSP1 genes on milk production traits in dairy cows, and our findings provide information for use in dairy cattle breeding.

The role of IL-10-producing B cells in repeated implantation failure patients with cellular immune abnormalities

There are a few data of the role of B cells in RIF pathogenesis. Accordingly, the objective of the current study was to determine the role of IL-10-producing B cells in RIF. Twenty-three RIF women with cellular immune abnormalities and 25 normal controls were enrolled in this experiment. Isolated naïve B cells from peripheral blood of the subjects were cultured in vitro, divided into two parts and activated by CpG ODN and imiquimod as TLR agonists. Afterwards, the number of CD19⁺ IL-10⁺ B cells was evaluated by flow cytometry and their related IL-10 cytokine level was assessed by ELISA. The mRNA expression levels of related genes in just CPG stimulated B cell population were also analyzed using real-time PCR. RIF patients exhibited a decreased level of the cells (P = 0.014, P = 0.023, respectively) and IL-10 cytokine (P = 0.009, P = 0.045, respectively) in both CPG and imiquimod stimulated B cell groups. IL-10 serum level was also lower in these patients (P = 0.0014). Additionally, we found a negative relationship between the frequency of these cells with the number of failed ET and total IgG titers in RIF patients. The mRNA levels of IL-10-producing B cells related genes (IL-10 and PD-L1) was also significantly lower in RIF women, whereas the expression of plasma cells-associated transcriptional factors (BLIMP1, IRF4, and XBP1) was higher. Summing up the obtained results, we concluded that peripheral blood IL-10-producing B cells down-regulation might result in RIF pathogenesis. It is further suggested that these cells can suppress autoantibody generation and contribute to a successful implantation.

KLF12 Regulates Mouse NK Cell Proliferation

NK cells are innate lymphocytes that play an integral role in tumor rejection and viral clearance. Unlike their other lymphocyte counterparts, NK cells have the unique ability to recognize and lyse target cells without prior exposure. However, there are no known NK cell-specific genes that are exclusively expressed by all NK cells. Therefore, identification of NK cell-specific genes would allow a better understanding of why NK cells are unique cytotoxic lymphocytes. From the Immunological Genome (ImmGen) Consortium studies, we identified kruppel-like factor 12 (Klf12), encoding a novel transcription factor, preferentially expressed in C57BL/6 mouse NK cells. KLF12 was dispensable for NK cell development, IFN-γ production, degranulation, and proliferation in Klf12 knockout mice. RNA-sequencing analysis revealed increased expression of Btg3, an antiproliferative gene, in KLF12-deficient NK cells compared with wild-type NK cells. Interestingly, competitive mixed bone marrow chimeric mice exhibited reduced development of KLF12-deficient NK cells, altered IFN-γ production and degranulation, and impairment of NK cell proliferation in vitro and in vivo in response to mouse CMV infection. KLF12-deficient NK cells from bone marrow chimeric mice also expressed higher levels of the IL-21R, which resulted in increased IL-21R signaling and correlated with greater inhibition of NK cell proliferation. Furthermore, IL-21 induced Btg3 expression, which correlated with arrested NK cell maturation and proliferation. In summary, we found that KLF12 regulates mouse NK cell proliferation potentially by regulating expression of Btg3 via IL-21.