Altered Expression of C4BPA and CXCL1 Genes in the Endometrium of Patients with Recurrent Implantation Failure after In Vitro Fertilization and Thin Endometrium

Currently, recurrent implantation failure (RIF) after in vitro fertilization is a problem that is commonly faced by reproductive specialists. The phenomenon of a thin endometrium in RIF patients is not yet completely understood or sufficiently treated. This study aimed to reveal the dysregulated expression of selected genes between RIF patients with a thin endometrium and fertile women. Endometrial samples were collected in the implantation window (21-24 days of the natural menstrual cycle) from RIF patients (<i>n</i> = 20) and fertile women (<i>n</i> = 14). Ten genes were chosen as target genes regarding their possible relations with the implantation process. The endometrial gene expression levels showed differences in RIF samples compared to fertile samples. Significant downregulation was observed for the <i>CXCL1</i> (<i>p</i> = 0.005) and <i>C4BPA</i> (<i>p</i> = 0.03) genes. There was no statistically significant difference between the RIF group and the fertile group in the expression of eight genes: <i>CXCL8</i>, <i>HPRT1</i>, <i>MMP10</i>, <i>INFG</i>, <i>VEGFB</i>, <i>HAND2</i>, <i>IL-15</i>, and <i>TNC</i> (<i>p</i> > 0.05). The use of a combination of two markers (<i>C4BPA + CXCL1</i>) allows for the good discrimination of RIF patients from fertile women (AUC 0.806).