Endometrial gene expression profiling of recurrent implantation failure after in vitro fertilization

Embryo implantation is one of the most important stages of the female reproductive process. Synchronous interaction between a receptive endometrium and embryo is crucial for the success of implantation. In addition, implantation occurs only when this interaction takes place over a certain period of time. This time interval covering the 20-24 days of the regular menstrual cycle was named as window of implantation in the 1970s. Recurrent implantation failure (RIF) is diagnosed when good-quality embryos repeatedly fail to implant after transfer in several in vitro fertilization (IVF) treatment cycles. There are many genes that regulate the implantation process. Differences in the expression of these genes can cause implantation failure. Expression differences in maternal mRNAs could be referring to so many diseases including RIF. The aim of this thesis study was to identify different expression levels of several mRNAs in the maternal endometrium tissue and determine their associated pathways. In this study, the endometrial biopsy samples were collected in secretory phase (cycle day 20-24) from healthy fertile controls (n=34) and patients with RIF (n=34). After "Pathway and network-oriented GWAS analysis" (PANOGA) and KEGG pathway analysis "Membrane Metalloendopeptidase" (MME), "WW and C2 Domain Containing 1" (WWC1) and "Tenascin C" (TNC) genes were chosen as target genes by regarding to their possible relation with implantation process. Detection of differences in mRNA expression between control group and RIF patients was performed with droplet digital PCR (ddPCR) method. The obtained results were evaluated using "Graphpad Prism 8.3.0" software. Significance tests were performed using non-parametric "Mann Whitney Test". Sensitivity and specificity tests were performed using ROC ("Receiver Operating Characteristic") analysis. The data obtained from ddPCR application showed that MME gene expression increased 4.9 times (p < 0.05), WWC1 gene expression increased 5.2 times (p < 0.05) and TNC gene expression decreased 9 times (p < 0.05) in the patient group compared to the control group. Changes are observed in the expression of the renin angiotensin system pathway in which the MME gene is involved in the implantation process. The increase in Angiotensin II gene expression, which is as a result of increased MME gene expression, can be thought to cause implantation failure by restricting the invasion of trophoblast cells. Increasing WWC1 gene expression in the Hippo signaling pathway inhibits "Yes-associated protein 1" (YAP) expression, which is a transcriptional cofactor. Inhibition of YAP protein expression may have resulted in failure of the implantation process by causing the failure of endometrial decidualization. The TNC gene is located in the focal adhesion pathway and this pathway reduces cell adhesion on the endometrial surface to facilitate the attachment of the embryo to the endometrium. The reason for implantation failure might be that the intercellular connections are not suitable for implantation as a result of decreased expression of the focal adhesion pathway in which the TNC gene is effective. Considering the relations between the pathways of the target genes and the implantation process, changes in the expression of target genes might be a cause RIF.