Single-Cell RNA sequencing highlights the regulatory role of T cell marker genes Ctla4, Ccl5 and Tcf7 in corneal allograft rejection of mouse model.

BACKGROUND: A mouse corneal allograft model was induced and single-cell RNA sequencing (scRNA-seq) data of corneal tissues and T cells were analyzed to reveal a T cell-mediated mechanism for corneal allograft rejection in mice. METHODS: Corneal tissue samples from a mouse model of corneal allograft were collected for scRNA-seq analysis, followed by quality control, dimensionality reduction, cluster analysis and enrichment analysis. A large number of highly variable genes were identified in mice with corneal allograft. Significant difference existed in immune T cells, especially in CD4 + T cells. RESULTS: It was found that T cell marker genes Ctla4, Ccl5, Tcf7, Lgals1, and Itgb1 may play key roles in the corneal allograft rejection. Mice with allograft rejection showed a significant increase in the proportion of CD4 + T cells in the corneal tissues. Besides, Ccl5 and Tcf7 expression was increased in mice with allograft rejection and positively linked to the proportion of CD4 + T cells. Whereas, Ctla4 expression was downregulated and negatively associated with the proportion of CD4 + T cells. CONCLUSION: Collectively, Ctla4, Ccl5 and Tcf7 may participate in the rejection of corneal allograft in mice by affecting CD4 + T cell activation.

Combined use of gap-PCR and next-generation sequencing improves thalassaemia carrier screening among premarital adults in China.

AIMS: Thalassaemia is one of the most common genetics disorders in the world, especially in southern China. The aim of the present study was to investigate the feasibility of combining the gap-PCR and next-generation sequencing (NGS) for thalassaemia carrier screening in the Chinese population. METHODS: Blood samples were obtained from 944 prepregnancy couples; thalassaemia carrier screening was performed by using a routine haematological method and a combination of gap-PCR and NGS method. RESULTS: We found that the α thalassaemia carrier rate was 11% (207/1888); the ß thalassaemia carrier rate was 3.7% (70/1888); the composite α thalassaemia and ß thalassaemia carrier rate was 0.4% (8/1888). We also identified seven novel mutations, including HBA1: c.412A>G, -50 (G>A), HBB: c.*+129T>A, HBB: c.-64G>C, HBB: c.-180G>C, HBB: c.*+5G>A and HBB: c.-113A>G. By comparing the combined gap-PCR and NGS method, the MCV+MCH and HbA2 detection strategy showed a lower sensitivity of 61.05% (105/172) and a higher missed diagnosis ratio of 38.95% (67/172) for α thalassaemia mutations. The sensitivity was improved with the MCV+MCH and HbA2 detection screen when compared with MCV+MCH detection for ß thalassaemia (98.51% vs 85.90%). CONCLUSIONS: Our study suggests the combined gap-PCR and NGS method is a cost-effective method for the thalassaemia carrier screening, particularly for the α thalassaemia mutation carriers.

MiRNA-99a can regulate proliferation and apoptosis of human granulosa cells via targeting IGF-1R in polycystic ovary syndrome.

PURPOSE: We aimed to evaluate the regulation of miR-99a to the biological functions of granulosa cells in polycystic ovary syndrome (PCOS) via targeting IGF-1R. METHODS: We collected aspirated follicular fluid in both patients with and without PCOS. Granulosa cells (GCs) were isolated through Percoll differential centrifugation to detect both miR-99a and IGF-1R expressions. We further transfected COV434 cells with miR-99a mimics to establish a miRNA-99a (miR-99a) overexpression model. We explored the regulation of miR-99a to the proliferation and apoptosis of human GCs via IGF-1R in COV434. The effect of different insulin concentrations on miR-99a expression was also evaluated. RESULTS: MiR-99a was significantly downregulated while IGF-1R was upregulated in patients with PCOS. MiR-99a can regulate IGF-1R on a post-transcriptional level. After transfection of miR-99a mimics, the proliferation rate was decreased and apoptosis rate was increased significantly in COV434. Exogenous insulin-like growth factor 1 (IGF-1) treatment could reverse the effect of miR-99a. MiR-99a was negatively and dose-dependently regulated by insulin in vitro. CONCLUSIONS: MiR-99a expression was downregulated in patients with PCOS, the degree of which may be closely related to insulin resistance and hyperinsulinemia. MiR-99a could attenuate proliferation and promote apoptosis of human GCs through targeting IGF-1R, which could partly explain the abnormal folliculogenesis in PCOS.

GnRH antagonist versus follicular-phase single-dose GnRH agonist protocol in patients of normal ovarian responses during controlled ovarian stimulation.

OBJECTIVE: This study aims to explore the differences of the ovarian stimulation (OS) characteristics, laboratory, and clinical outcomes between follicular-phase single-dose gonadotropin-releasing hormone (GnRH) agonist protocol and GnRH antagonist protocol during controlled ovarian hyperstimulation (COH). METHODS: About 1883 consecutive IVF/ICSI fresh cycles of normal ovarian responders were retrospectively analyzed, with 1229 in the single-dose GnRH agonist protocol group and 654 in the GnRH antagonist protocol group at Reproductive Medical Center of Tongji Hospital from 1 January 2014 to 31 December 2017. RESULTS: The follicular-phase single-dose GnRH agonist group showed significantly more oocytes obtained, higher implantation rate and pregnancy rate, as well as lower luteinizing hormone (LH) level and estradiol (E2)/oocyte ratio on the day of human chorionic gonadotropin (hCG) administration. However, differences were not significant in meiosis II (MII) oocyte rate, two pronuclear zygote (2PN) embryo rate, viable embryo rate or high-quality embryo rate, compared with the GnRH antagonist group. Further comparison of clinical outcomes in the first frozen-thawed cycles did not show significant difference in either implantation or clinical pregnancy rate between the two protocol groups. CONCLUSIONS: Follicular-phase single-dose GnRH agonist protocol may achieve better clinical outcomes in normal ovarian responders, which could be explained more by positive effect on endometrial receptivity rather than embryo quality.

Open versus closed vitrification system of human oocytes and embryos: a systematic review and meta-analysis of embryologic and clinical outcomes.

BACKGROUND: The objective of this study was to carry out a systematic review and meta-analysis of embryologic and clinical outcomes following open versus closed vitrification of human oocytes and embryos. METHODS: An electronic literature search was conducted in main electronic databases up to June 30, 2018 using the following key terms: 'oocyte', 'embryo', 'blastocyst', 'vitrification', 'cryopreservation', 'device', 'survival rate', 'pregnancy rate', etc. A meta-analysis was performed using a random effect model to estimate the value of risk ratios (RRs) and 95% confidence interval (CI). Subgroup analyses and sensitivity analyses were carried out to further confirm the results. RESULTS: Twelve (Eight prospective and four retrospective) studies comparing open versus closed vitrification of human oocytes or embryos were included. For prospective studies on oocytes, no evidence for a significant difference in cryosurvival rate (RR = 0.91, 95% CI: 0.80-1.03, P = 0.14; n = 2048) or clinical pregnancy rate (RR = 1.29, 95% CI: 0.80-2.06, P = 0.30; n = 150) was observed. Additionally, there were no significant differences between the two methods concerning secondary endpoints included positive ßHCG rate, implantation rate, miscarriage rate, ongoing pregnancy rate, live birth rate, cancellation rate, babies born per transferred blastocysts, or multiple birth rate (P > 0.05). The results of the retrospective studies were similar as the prospective studies. CONCLUSIONS: It is still impossible to conclude that closed vitrification system could be a substitution for open system in human oocyte and embryo cryopreservation based on current evidence. Therefore, more well-designed prospective studies addressing these issues are still warranted.

The effect of premature luteinizing hormone increases among high ovarian responders undergoing a gonadotropin-releasing hormone antagonist ovarian stimulation protocol.

OBJECTIVE: To explore factors causing a premature rise in luteinizing hormone among high ovarian responders undergoing the gonadotropin-releasing hormone (GnRH) antagonist ovarian stimulation protocol. METHODS: The present retrospective study included healthy women undergoing fresh cycles using a fixed GnRH antagonist protocol with a predicted high response and antral follicle count (AFC) of at least 15 at the Reproductive Medicine Center of Tongji Hospital, China, between January 1 and December 31, 2016. Treatment-related characteristics, hormone changes, and pregnancy outcomes were compared between patients who did or did not experience a premature luteinizing hormone rise. RESULTS: There were 314 patients included; 49 experienced premature luteinizing hormone increases. Among patients who experienced a premature rise in luteinizing hormone, a lower two pronuclear embryo rate (P=0.038); fewer high-quality embryos (P=0.020); higher serum luteinizing hormone (P=0.006), progesterone (P=0.013), and estradiol (E2) levels (P=0.003) on the day of human chorionic gonadotropin administration; a lower clinical pregnancy rate (P=0.031); and a higher cancellation rate (P=0.006) were observed. AFC of at least 22 (P=0.001) and E2 of 669 pg/mL or higher at the start of GnRH antagonist administration were predictive of early (P=0.036) and late (P=0.033) premature luteinizing hormone increases. CONCLUSION: Earlier administration of GnRH antagonist could avoid premature luteinizing hormone increases among high ovarian responders, especially those with a starting AFC of 22 or more.

Both conditional ablation and overexpression of E2 SUMO-conjugating enzyme (UBC9) in mouse pancreatic beta cells result in impaired beta cell function.

AIMS/HYPOTHESIS: Post-translational attachment of a small ubiquitin-like modifier (SUMO) to the lysine (K) residue(s) of target proteins (SUMOylation) is an evolutionary conserved regulatory mechanism. This modification has previously been demonstrated to be implicated in the control of a remarkably versatile regulatory mechanism of cellular processes. However, the exact regulatory role and biological actions of the E2 SUMO-conjugating enzyme (UBC9)-mediated SUMOylation function in pancreatic beta cells has remained elusive. METHODS: Inducible beta cell-specific Ubc9 (also known as Ube2i) knockout (KO; Ubc9Δbeta) and transgenic (Ubc9Tg) mice were employed to address the impact of SUMOylation on beta cell viability and functionality. Ubc9 deficiency or overexpression was induced at 8 weeks of age using tamoxifen. To study the mechanism involved, we closely examined the regulation of the transcription factor nuclear factor erythroid 2-related factor 2 (NRF2) through SUMOylation in beta cells. RESULTS: Upon induction of Ubc9 deficiency, Ubc9Δbeta islets exhibited a 3.5-fold higher accumulation of reactive oxygen species (ROS) than Ubc9f/f control islets. Islets from Ubc9Δbeta mice also had decreased insulin content and loss of beta cell mass after tamoxifen treatment. Specifically, at day 45 after Ubc9 deletion only 40% of beta cell mass remained in Ubc9Δbeta mice, while 90% of beta cell mass was lost by day 75. Diabetes onset was noted in some Ubc9Δbeta mice 8 weeks after induction of Ubc9 deficiency and all mice developed diabetes by 10 weeks following tamoxifen treatment. In contrast, Ubc9Tg beta cells displayed an increased antioxidant ability but impaired insulin secretion. Unlike Ubc9Δbeta mice, which spontaneously developed diabetes, Ubc9Tg mice preserved normal non-fasting blood glucose levels without developing diabetes. It was noted that SUMOylation of NRF2 promoted its nuclear expression along with enhanced transcriptional activity, thereby preventing ROS accumulation in beta cells. CONCLUSIONS/INTERPRETATION: SUMOylation function is required to protect against oxidative stress in beta cells; this mechanism is, at least in part, carried out by the regulation of NRF2 activity to enhance ROS detoxification. Homeostatic SUMOylation is also likely to be essential for maintaining beta cell functionality.

Oxidative stress in granulosa cells contributes to poor oocyte quality and IVF-ET outcomes in women with polycystic ovary syndrome.

The increased levels of intracellular reactive oxygen species (ROS) in granulosa cells (GCs) may affect the pregnancy results in women with polycystic ovary syndrome (PCOS). In this study, we compared the in vitro fertilization and embryo transfer (IVF-ET) results of 22 patients with PCOS and 25 patients with tubal factor infertility and detected the ROS levels in the GCs of these two groups. Results showed that the PCOS group had significantly larger follicles on the administration day for human chorionic gonadotropin than the tubal factor group (P < 0.05); however, the number of retrieved oocytes was not significantly different between the two groups (P > 0.05). PCOS group had slightly lower fertilization, cleavage, grade I/II embryo, clinical pregnancy, and implantation rates and higher miscarriage rate than the tubal factor group (P > 0.05). We further found a significantly higher ROS level of GCs in the PCOS group than in the tubal factor group (P < 0.05). The increased ROS levels in GCs caused GC apoptosis, whereas NADPH oxidase 2 (NOX2) specific inhibitors (diphenyleneiodonium and apocynin) significantly reduced the ROS production in the PCOS group. In conclusion, the increased ROS expression levels in PCOS GCs greatly induced cell apoptosis, which further affected the oocyte quality and reduced the positive IVF-ET pregnancy results of women with PCOS. NADPH oxidase pathway may be involved in the mechanism of ROS production in GCs of women with PCOS.

AAL exacerbates pro-inflammatory response in macrophages by regulating Mincle/Syk/Card9 signaling along with the Nlrp3 inflammasome assembly.

Previously, we demonstrated that Agrocybe aegerita lectin (AAL), a galectin isolated from edible mushroom Agrocybe aegerita, exerts potent anti-tumor activity, while the mechanisms by which AAL suppresses tumor growth are yet to be elucidated. Here, we conducted studies with focus for its impact on the cecal ligation and puncture (CLP)-induced innate immune response. Administration of AAL significantly exacerbated the severity of CLP-induced septic shock as manifested the increased lethality. AAL promoted inflammatory cytokine production by preferentially regulating macrophage activation and recruitment. Mechanistic studies revealed that AAL likely targets macrophages through receptor Mincle to activate Syk/Card9 signaling, which then couples to the Nlrp3 inflammasome assembly. It was further noted that AAL markedly promotes H3K4 di- and trimethylation, by which it enhances Hmgb1 expression. Specifically, AAL induced macrophages secretion of copious amount of Hmgb1 as manifested the Hmgb1 cytoplasmic translocation along with the detection of extracellular Hmgb1. AAL also stimulated a significant increase for nuclear Hmgb1, which then formed a complex with RelA, and thereby enhancing NF-κB transcriptional activity. Together, our data suggest that AAL may possess important pharmaceutical properties in the regulation of innate immune response.

Senile cataract and genetic polymorphisms of APE1, XRCC1 and OGG1.

Polymorphisms of DNA repair enzymes which may influence their repair efficiency lead to diseases, for example, senile cataract. In this study, we aimed to analyze the association of single nucleotide polymorphisms in AP endonuclease-1 (APE1), 8-oxoguanine glycosylase-1 (OGG1) and X-ray repair cross-complementing-1 (XRCC1) genes with the risk of age-related cataract in a Chinese population. Genotyping was carried out by the polymerase chain reaction and DNA sequencing on 402 cataract patients and 813 controls in this study. Differences in the frequencies were estimated by the chi-square test, and risk was estimated using unconditional logistic regression after adjusting for age and gender. Our results demonstrated there was a significant difference between the case and control groups in the APE1-141 G/G genotype (P=0.002). This difference still existed after adjusting for age and gender (P*=0.003). The APE1-141 T/T genotype and T allele frequencies were significantly higher in cataract patients, while the G/G genotype and G allele frequencies in patients were significantly lower than in controls (P < 0.05). The APE1-141 G/G genotype (OR, 0.49; 95% CI, 0.31-0.77) seems to have a protective role against cataract, and the T allele seems to have a deleterious role in the development of cataract. In OGG1 Ser326Cys and XRCC1 Arg399Gln polymorphisms, there were no significant differences in frequencies of the variant homozygous in patients compared with controls.

Assessment of type 2 diabetes risk conferred by SNPs rs2241766 and rs1501299 in the ADIPOQ gene, a case/control study combined with meta-analyses.

We conducted a case/control study to assess the impact of two SNPs, rs2241766 and rs1501299 within the ADIPOQ gene, on type 2 diabetes (T2D) susceptibility in a Chinese Han dataset (741 cases and 902 controls). SNP rs2241766 was found significantly associated with T2D risk in the additive model, dominant model and recessive model. A marginal association was detected for SNP rs1501299 in the additive model and recessive model after Bonferroni correction, and haplotype analysis provided additional evidence supporting the association between these two SNPs and T2D risk. A meta-analysis including 29 published datasets along with current dataset was next carried out to further confirm the association. In consistent with our case/control results, rs2241766 showed a significant association with T2D in the dominant model and additive model, and the association between rs1501299 and T2D was also characterized in the homozygote model, dominant model, recessive model, and additive model. Of note, the association became much stronger in East Asians after exclusion of ethnic stratification. Together, our data support that the rs2241766 and rs1501299 polymorphisms within the ADIPOQ gene confer genetic susceptibility for type 2 diabetes, especially in the Chinese Han population.

MBD2 regulates TH17 differentiation and experimental autoimmune encephalomyelitis by controlling the homeostasis of T-bet/Hlx axis.

Unlike genetic alterations, epigenetic modifications are reversible and amenable to pharmacological interventions, which make them appealing targets for clinical therapy. However, little is known about epigenetic regulation in experimental autoimmune encephalomyelitis (EAE). Here we demonstrated that methyl-CpG-binding domain protein 2 (MBD2), an epigenetic regulator, controls autoimmunity and EAE through T-bet/Hlx. Tbx21 and Hlx underwent a DNA methylation turnover upon polarizations and a unique methylation pattern was essential for TH17 development. Loss of Mbd2 resulted in a defect for reading the information encoded by this methylation turnover, which disrupted the homeostasis of T-bet/Hlx axis and suppressed TH17 differentiation. DNA demethylation induced similar effect on helper T cell differentiation. Therefore, Mbd2(-/-) mice were completely protected from EAE. Pathogenic splenocytes isolated from wild-type mice challenged with MOG35-55 could adoptively transfer disease to Mbd2(-/-) mice. In addition, Mbd2(-/-) mice reconstituted with unstimulated wild-type splenocytes developed EAE as wild-type mice did. These data would provide novel insights into epigenetic regulation of EAE.

Assessing the optimal dose for Cetrorelix in Chinese women undergoing ovarian stimulation during the course of IVF-ET treatment.

We conducted a prospective, randomized, and controlled trial to assess the optimal dose for GnRH antagonist, cetrorelix, for Chinese women during the course of ovarian stimulation. The patients were randomly divided into two groups, in which 48 patients were advised to inject 0.25 mg Cetrorelix daily (the 0.25 mg group), while 39 patients were instructed to receive a daily dose of 0.125 mg cetrorelix (the 0.125 mg group). In general, a daily dose of 0.125 mg cetrorelix could be more optimal for Chinese women as manifested by the lower cancellation rate, higher implantation rate and clinical pregnancy rate. Specifically, daily administration of 0.125 mg cetrorelix for patients under 35 years old is associated with a 3-fold higher implantation rate and a 5-fold higher clinical pregnancy rate as compared with that of those patients ≥ 35 years old. On the contrary, higher rates for implantation and clinical pregnancy were noted by daily injection of 0.25 mg cetrorelix in elder patients (≥ 35 years old) as compared with that of young patients (< 35 years old). Together, our data suggest that a daily dose of 0.125 mg cetrorelix could be more optimal for patients < 35 years old, while 0.25 mg/day of cetrorelix are likely conducive to higher implantation and clinical pregnancy rate for those patients ≥ 35 years old. These data could be important for preventing LH surge while maintaining optimal LH levels necessary for embryo implantation for Chinese women during the course of IVF-ET treatment.

Comparison of the GnRH agonist and antagonist protocol on the same patients in assisted reproduction during controlled ovarian stimulation cycles.

Despite the fact that both gonadotropin-releasing hormone (GnRH) agonist and antagonist protocol are effective in suppressing the incidence of premature luteinizing hormone (LH) surges through reversibly blocking the secretion of pituitary gonadotropins, the exact impact of these two distinctive protocols on the clinical setting of patients for in vitro fertilization and embryo transfer (IVF-ET) treatment, however, remained controversial. We thus in the present report conducted a retrospective study to compare the impact of GnRH agonist and antagonist protocol on the same patients during controlled ovarian stimulation cycles. A total of 81 patients undergoing 105 agonist and 88 antagonist protocol were analyzed. We failed to detect a significant difference between two protocols for the difference in duration of ovarian stimulation, number of recombinant FSH (Gonal-F) ampoules used, number of oocytes retrieved, serum levels for estradiol (E2) and progestone (P), thickness of endometrium, and the zygote- and blastocyst-development rate. It is seemly that high quality embryo rate was higher in the antagonist protocol, but the data did not reach a statistical significance. Nevertheless, Implantation rate and clinical pregnancy rate were significantly higher in the antagonist protocol (10.64% and 30.26%, respectively) than that of the agonist protocol (5.26% and 15.82%, respectively). Our data also suggest that the GnRH antagonist protocol is likely to have the advantage for improving the outcome of pregnancy in those patients with a history of multiple failures for the IVF-ET treatment.

The significance of antral follicle size prior to stimulation in predicting ovarian response in a multiple dose GnRH antagonist protocol.

Prediction of ovarian responses prior to stimulation is not only useful for patient counseling, but also important in tailoring the optimal dosage of gonadotrophin for individual patients. By prospectively study of 214 women undergoing in vitro fertilization and embryo transfer (IVF-ET) treatment, we obtained data supporting that antral follicle size could be an additional valuable predictive marker other than the antral follicle count (AFC) in predicting ovarian response. Our studies revealed that AFC achieved the best predictive value in relation to the number of oocyte obtained, followed by antral follicle size, basal follicle stimulating hormone (FSH) and body mass index (BMI). Unlike AFC, antral follicle size was noted to be negatively correlated with the dosage (R = -0.493) and duration (R = -0.465) of rFSH stimulation. Antral follicle size was also found with higher negative regression coefficient (B = -0.661) as compared with that of basal FSH concentration (B = -0.326) and BMI (b = -0.281). More importantly, women with antral follicle size 6-7 mm showed significantly higher AFC, oocytes retrieved, fertilized oocytes and grade I/II embryos along with much lower transfer cycle cancellation rate (7.5% vs. 16-17%). Together, our data suggest that basal antral follicle size could be a valued predictive marker in women with IVF-ET treatment, in which women with antral follicle size 6-7 mm are likely predisposed to better IVF-ET outcomes.

Comparison between a GnRH agonist and a GnRH antagonist protocol for the same patient undergoing IVF.

In order to compare GnRH agonist with antagonist protocol for the same patient during controlled ovarian stimulation cycles, the in vitro fertilization and embryo transfer (IVF-ET) outcome was retrospectively studied in 81 patients undergoing 105 agonist protocols and 88 antagonist protocols. The results showed that there was no statistically significant difference in duration of ovarian stimulation, number of ampoules, oocytes retrieved, serum estradiol (E(2)) and progesterone (P) levels, thickness of endometrium, the zygote-and blastocyst-development rate between GnRH agonist and antagonist protocols (P>0.05). High quality embryo rate was higher in antagonist protocols, but there was no significant difference between two protocols. Implantation rate and clinical pregnant rate were significantly higher in antagonist protocol (15.82% and 30.26%, respectively) than in agonist protocol (5.26% and 10.64% respectively (P<0.05). It was concluded GnRH antagonist protocol probably improved the outcome of pregnancy of older patients with a history of multiple failure of IVF-ET in a GnRH protocol.

Comparison between a GnRH Agonist and a GnRH Antagonist Protocol for the Same Patient Undergoing IVF / 华中科技大学学报（医学）（英德文版）

Summary: In order to compare GnRH agonist with antagonist protocol for the same patient during controlled ovarian stimulation cycles, the in vitro fertilization and embryo transfer (IVF-ET) outcome was retrospectively studied in 81 patients undergoing 105 agonist protocols and 88 antagonist protocols. The results showed that there was no statistically significant difference in duration of ovarian stimulation, number of ampoules, oocytes retrieved, serum estradiol (E2) and progesterone (P) levels,thickness of endometrium, the zygote-and blastocyst-developmcnt rate between GnRH agonist and antagonist protocols (P>0.05). High quality embryo rate was higher in antagonist protocols, but there was no significant difference between two protocols. Implantation rate and clinical pregnant rate were significantly higher in antagonist protocol (15.82% and 30.26%, respectively) than in agonist protocol (5.26% and 10.64% respectively (P<0.05). It was concluded GnRH antagonist protocol probably improved the outcome of pregnancy of older patients with a history of multiple failure of IVF-ET in a GnRH protocol.

Transcription and translation of Dickkopf-1 in endometrium of pregnant mice during the peri-implantation period.

To study the expression of Dickkopf-1 (DKK-1) in endometrium of pregnant mice during the peri-implantation period and the role of DKK-1 during the embryo implantation in mice. Immunohistochemical technique was employed to determine the location of DKK-1 protein in endometrium, and semiquantitative reverse transcriptase polymerase chain reaction (RT-PCR) was utilized to determine the levels of DKK-1 mRNA. Our results showed that the expressions of DKK1 mRNA and protein were higher in experimental groups than in control group (P<0.01) and it increased significantly on day 3 and reached its peak on day 4, and then decreased gradually on day 5-7. The levels of DKK-1 mRNA and protein on day 4 was significantly higher than those of other groups (P<0.01). It is concluded that DKK-1 probably plays an important role in signal transudation of embryo implantation and its high expression indicates the opening of implantation window.