Repeated implantation failure (RIF) occurs in a condition when good quality embryos fail to implant in the endometrium following several in vitro fertilization (IVF) cycles. Suboptimal endometrial receptivity is one of the main underlying factors that causes this failure. Progesterone is the key regulator of endometrial receptivity which regulates gene expression through binding to its receptors in the endometrial stromal cells (eSC). The aim of this study was to evaluate the effect of 1,25(OH)2-vitamin D3 on progesterone receptor (PR) expression level and its phosphorylation on Ser294 residues in eSC of RIF patients and healthy fertile women. After isolation of the eSC from biopsy samples of RIF patients and healthy fertile women and their characterization, the cells were incubated with vitamin D3 and the expression level of PR mRNA, PR protein and phospho-Ser294 PR protein were evaluated after treatment. The results showed that vitamin D3 treatment increases PR mRNA and protein level and phospho-Ser294 PR protein level in the isolated eSC of both RIF patients and the control group. These results suggest that vitamin D3 may possibly play a key role during the embryo implantation process by affecting the expression pattern and regulatory modifications of the PR in the eSC.

中文翻译：

---

1,25（OH）2-维生素D3对反复植入失败患者子宫内膜基质细胞中孕酮受体表达和磷酸化的影响。

多次体外受精（IVF）周期后，优质胚胎无法植入子宫内膜时，会发生重复植入失败（RIF）。子宫内膜的可接受性不佳是导致此失败的主要潜在因素之一。孕酮是子宫内膜容受性的关键调节剂，它通过与子宫内膜基质细胞（eSC）中的受体结合来调节基因表达。这项研究的目的是评估1,25（OH）2-维生素D3对RIF患者和健康可育妇女的eSC中孕激素受体（PR）表达水平及其磷酸化对Ser294残留的影响。从RIF患者和健康可育妇女的活检样品中分离出eSC并对其特征进行了表征后，将细胞与维生素D3和PR mRNA的表达水平进行了温育，处理后评估PR蛋白和磷酸化Ser294 PR蛋白。结果表明，维生素D3治疗可提高RIF患者和对照组分离的eSC中PR mRNA和蛋白水平以及磷酸Ser294 PR蛋白水平。这些结果表明，维生素D3可能通过影响eSC中PR的表达模式和调节修饰而在胚胎着床过程中发挥关键作用。