***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Background : Implantation failure is one of the most important factors limiting success in IVF treatment . The majority of trials have demonstrated favorable effect of endometrial injury on implantation success rate especially in women with recurrent implantation failure , while some studies failed to detect any benefit . Objective : The purpose of our trial was to explore whether endometrial injury in luteal phase prior to frozen-thawed embryo transfer cycles would improve pregnancy outcomes ? Material s and Methods : We conducted a prospect i ve controlled trial of 93 consecutive subjects at a research and clinical center for infertility . All women were undergone frozen-thawed embryo transfer ( FTE ) cycles . Women in the experimental group underwent endometrial biopsy with a Pipelle catheter in luteal phase proceeding FET cycle . Primary outcomes were implantation and clinical pregnancy rates and secondary outcomes were chemical , ongoing and multiple pregnancy and miscarriage rates . Results : 45 subjects who underwent endometrial injury ( EI ) were compared with 48 control group which did not include any uterine manipulation . There were no significant differences in baseline and cycle characteristics between two groups . The difference in implantation rate was trend to statistically significance , 11.8 % in EI group vs. 20.5 % in control group ( p=0.091 ) . The chemical , clinical and ongoing pregnancy rates were lower in EI group compared with control group but not statistically significant . The multiple pregnancy rate and miscarriage rate also were lower in EI group compared with control group . Conclusion : Based on results of this study , local injury to endometrium in luteal phase prior to FET cycle had a negative impact on implantation and clinical pregnancy rates Purpose Endometrial biopsy preceding implantation in in vitro fertilization ( IVF ) treatment causes a type of injury which facilitates implantation . Pre-treatment hysteroscopic evaluation of uterine cavity also raises the success in IVF . This study investigates whether office hysteroscopy and concurrent endometrial biopsy performed in the luteal phase , on the day of GnRH agonist initiation for long protocol , improves subsequent IVF outcome . Methods A prospect i ve , nonr and omized , controlled study of 128 normoresponder women was performed : In 70 women ( study group ) , office hysteroscopy and concurrent endometrial biopsy were performed on the day of GnRH agonist initiation preceding ET cycle and in 58 women ( control group ) , GnRH agonist was initiated without any intervention . However , uterine cavity was shown to be normal with hysteroscopy within the previous 6 months in those women . Implantation and pregnancy rates were compared between the groups . Results Intrauterine pathologies were observed in 28 % of women in the study group . Implantation rate ( 38 vs. 25 % ; p = 0.04 ) and pregnancy rate per ET ( 67 vs. 45 % ; p = 0.01 ) were found to be significantly higher in the study group compared to the control group . Conclusion Office hysteroscopy and concurrent endometrial biopsy performed in the luteal phase , on the day of GnRH agonist initiation for long protocol , provide direct evaluation of the uterine cavity immediately before ET cycle and also significantly improve the implantation and IVF outcome OBJECTIVE To explore the possibility that endometrial injury modulates the expression of specific genes that may increase uterine receptivity . DESIGN Controlled clinical study . SETTING Clinical IVF unit and academic research center . PATIENT(S ) IVF patients with 28- to 30-day menstrual cycles . INTERVENTION(S ) Endometrial biopsies from two groups of patients were collected on days 20 - 21 of their spontaneous menstrual cycle . The experimental , but not the control , group underwent biopsies on days 11 - 13 and 21 - 24 of their preceding cycle . MAIN OUTCOME MEASURE(S ) Global endometrial gene expression and specific analysis of uroplakin Ib ( UPIb ) mRNA level throughout the menstrual cycle . RESULT ( S ) Local injury modulated the expression of a wide variety of genes . One of the prominently up-regulated genes was the bladder transmembranal protein , UPIb , whose expression by the endometrium is shown here for the first time . Endometrial UPIb mRNA increases after biopsy in the same cycle wct 2with an additional elevation in the following cycle . Immunohistochemical analysis localized the UPIb protein to the gl and ular-epithelial cells . Genes encoding other membrane proteins such as adipose differentiation-related protein and mucin 1 , transmembrane , were also up-regulated . CONCLUSION ( S ) The biopsy-induced increase in the expression of UPIb and other genes encoding membrane proteins supports the possible importance of the membrane structure and stability during implantation . The specific role of UPIb in uterine receptivity should be eluci date Background Mechanical endometrial injury prior to IVF has been suggested as a means to increase implantation rates by improving endometrial receptivity . However , the effects of endometrial injury in proliferative vs. luteal phase have not been studied before . This study aim ed to explore whether endometrial injury in the proliferative phase of the preceding cycle before in vitro fertilization/embryo transfer ( IVF-ET ) improves the clinical outcomes in unselected subfertile women compared with injury in luteal phase . Methods A group of 142 patients who were good responders to hormonal stimulation were r and omized into four groups : injury group ( group A : endometrial injury in proliferative phase , n = 38 ; group B : endometrium injury in luteal phase , n = 32 ) , and non-injury group as control ( group C : non-injury in proliferative phase , n = 36 ; group D : non-injury in luteal phase , n = 36 ) . Patients in injury groups underwent endometrial injury in either proliferative phase or luteal phase in the preceding cycle before IVF treatment . Clinical outcomes including implantation , pregnancy , and live birth rates were analyzed among the four groups . Results The baseline characteristics of the four groups including age , body mass index , duration , type and causes of infertility were similar . There were no significant differences in implantation , clinical pregnancy or live birth rates between injury group and non-injury group . Moreover , there were also no significant differences in implantation , clinical pregnancy , or live birth rates in injury in proliferative phase compared with luteal phase . Conclusions Endometrial injury in the cycle preceding IVF of unselected subfertile women does not increase implantation , clinical pregnancy , or live birth rates . Furthermore , there is no significant difference in clinical outcomes between endometrial injury in the proliferative phase and injury in the luteal phase . Trial registration This study was retrospectively registered on May 26th , 2017 ( ChiCTR-IOR-17011506 ) OBJECTIVE To evaluate the effectiveness of local endometrial injury in women undergoing in vitro fertilization ( IVF ) with at least one previous unsuccessful attempt . STUDY DESIGN R and omized controlled trial . Recruited women were r and omized into two groups . In group A ( pipelle group ) , women underwent pipelle biopsy twice in the luteal phase in the cycle prior to IVF . In group B ( control ) , women did not undergo any intervention prior to IVF . The primary outcome was clinical pregnancy rate . The secondary outcomes included live birth , miscarriage , multiple pregnancy and preterm delivery rates . RESULTS One hundred and eleven women were included in the study with 55 in the pipelle group and 56 in the control arm . The baseline clinical characteristics were similar in both groups . The clinical pregnancy rates were not significantly different between pipelle and control group ( 34.09 % vs. 27.65 % ; Odds ratio , OR 1.35 , 95 % confidence interval , CI 0.55 - 3.30 ) . The live birth ( 31.81 % vs. 25.53 % ; OR 1.36 , 95 % CI 0.55 - 3.39 ) , multiple pregnancy ( 33.33 % vs. 61.54 % ; OR 0.31 , 95 % CI 0.07 - 1.47 ) , miscarriage ( 6.66 % vs. 7.69 % ; OR 0.86 , 95 % CI 0.05 - 15.23 ) and preterm delivery rates ( 35.71 % vs. 66.66 % ; OR 0.28 , 95 % CI 0.05 - 1.4 ) were also not significantly different between the two groups . CONCLUSION Current study did not find any improvement in IVF success rates following endometrial injury in woman undergoing IVF after previous failed attempt STUDY QUESTION Is recurrent implantation failure ( RIF ) associated with decreased expression of platelet and endothelial cell adhesion molecule 1 ( PECAM1 ) and transforming growth factor β1 ( TGF-β1 ) in the endometrium during the implantation window ? SUMMARY ANSWER The present study demonstrates that the expression of PECAM1 and TGF-β1 is significantly decreased in the mid-secretory endometrium in women with RIF , which may account for embryo implantation failure . WHAT IS KNOWN ALREADY RIF has become a bottleneck issue that hampers the improvement of pregnancy rates in IVF-embryo transfer ( IVF-ET ) . The causes of RIF are complex and may involve the dysregulation of various growth factors , metabolites , and inflammatory cytokines . At present , the precise pathogenesis of RIF has not been eluci date d. STUDY DESIGN , SIZE , DURATION This was a prospect i ve case-control study . Endometrial tissue sample s were obtained from January 2014 to December 2016 from two groups of women who had undergone IVF ( RIF group , 22 women who underwent ≥3 ETs including a total of ≥4 good- quality embryos without pregnancy , control group , 18 women who conceived in their first treatment cycle ) . At the same time , sample s were obtained from 18 women with infertility secondary to tubal factor in the early proliferative , late proliferative and mid-secretory phases of the menstrual cycle ( n = 6 per group ) . Sample s used for isolation of primary human endometrial epithelial cells and stromal cells ( HEECs and HESCs ) were collected in December 2017 from six women with infertility secondary to tubal factor . PARTICIPANTS / MATERIAL S , SETTING , METHODS We investigated gene expression using integrative whole genome expression microarray analysis , including differentially expressed gene screening , principal component analysis , and functional enrichment analysis . RT-qPCR , western blotting , immunohistochemistry , immunofluorescence co-localization analysis and short hairpin RNA ( shRNA ) plasmid transfection in Ishikawa cell line , HEECs and HESCs were used to investigate the expression of PECAM1 and TGF-β1 . MAIN RESULTS AND THE ROLE OF CHANCE Integrative data mining of whole-genome expression profiles identified cell adhesion as a key regulator in RIF . Data base retrieval and literature review screened several novel cell adhesion-related genes that might participate in embryo implantation , which include PECAM1 , intercellular adhesion molecule 2 ( ICAM2 ) , integrin subunit β2 ( ITGB2 ) , selectin P ( SELP ) and TEK receptor tyrosine kinase ( TEK ) . Among these targets , the mRNA and protein levels of PECAM1 were significantly lower in the RIF group than those in the control group . During the menstrual cycles of women with secondary infertility , the protein expression level of PECAM1 was the lowest in early proliferative phase , slightly increased in late proliferative phase and was the highest in mid-secretory phase . While the expression level of HOXA10 , an endometrial receptivity marker , kept at a low level in early proliferative phase and increased in late proliferative phase , then maintained at a high level in the mid-secretory phase . Furthermore , TGF-β1 , mediated by PECAM1 , was also decreased significantly in the RIF group . Using shRNA-based approach , we demonstrated that the depletion of PECAM1 significantly decreased the expression of TGF-β1 in Ishikawa cells , as well as in primary HEECs and HESCs . These results indicated that PECAM1 and TGF-β1 might play a pivotal role in modulating endometrial receptivity . LIMITATIONS REASONS FOR CAUTION Although we have shown that PECAM1 and TGF-β1 were down-regulated in the women with RIF , the molecular mechanism of the effect of the factors on the endometrial receptivity remain unclear . WIDER IMPLICATION S OF THE FINDINGS Our findings provide insight into the contribution of PECAM1 and TGF-β1 in regulating implantation , which could be used to develop potential therapeutic methods for RIF . STUDY FUNDING /COMPETING INTEREST(S ) This work was supported by grants from the National Natural Science Foundation of China ( Nos. 81771656 and 81370763 ) , Special fund for clinical research of the Chinese Medical Association ( No. 16020480664 ) , and the Merck Serono China Research Fund for Fertility Agreement . The authors have no competing interests BACKGROUND The success rate of in-vitro fertilisation ( IVF ) remains low and many women undergo multiple treatment cycles . A previous meta- analysis suggested hysteroscopy could improve outcomes in women who have had recurrent implantation 
    Output:
    
There is still insufficient evidence to support the use of endometrial injury in women with implantation failure .