P-760 Effect of relaxin on human endometrial stromal cell characteristics
Authors: Meier S , Springer C , Richter K , Schröder-Heurich B , Von Versen-Höynck F 
Published: June 2023

Abstract

Study question
Does relaxin (RLX) regulate decidualization and pro- and antiangiogenic factors in primary human endometrial stromal cells (hESC), primary decidual cells (pD) and hTERT-immortalized hESC (T hESC)?

Summary answer
RLX treatment enhances decidualization and affects the mRNA expression levels of pro- and antiangiogenic factors.

What is known already
Patients undergoing frozen embryo transfer in an artificial cycle (AC-FET) are at a 2-fold increased risk for preeclampsia compared to embryo transfer in a natural cycle. This may be related to the absence of the corpus luteum in an artificial FET cycle, which produces important hormones such as estrogen and progesterone in early pregnancy. These hormones are supplied during AC-FET, whereas other products of the corpus luteum, such as RLX, are not. Low maternal RLX levels were found in women who developed preeclampsia, but the direct relationship between RLX and the occurrence of preeclampsia remains to be elucidated.

Study design, size, duration
Primary hESC were isolated from biopsies of women without endometrial pathology, pD cells from biopsies of the maternal side of the placenta of uncomplicated pregnancies and T hESC purchased from American Type Culture Collection. Cells were decidualized with either 0.5 mM cyclic adenosine monophosphate (cAMP) or a cocktail of 10 nM estradiol, 1 µM progesterone and 0.5 mM cAMP (EPC) and additionally treated with 0, 0.3 or 1 ng/ml RLX for twelve days.

Participants/materials, setting, methods
RNA was isolated on day zero and day twelve from all three cell types. mRNA expression level of decidualization markers (prolactin (PRL), insulin like growth factor binding protein 1 (IGFBP1)) as well as pro- and antiangiogenic factors (vascular endothelial growth factor (VEGF); placenta like growth factor (PlGF); soluble Fms-like tyrosine kinase-1 (sFlt-1); and endoglin (ENG)) were evaluated by quantitative real time polymerase chain reaction (qRT-PCR), N = 3 biological replicates.

Main results and the role of chance
Decidualization treatment of hESC with cAMP caused more noticeable changes to cell morphology than treatment with EPC. While there was no rise of decidualization markers PRL (p = 0.99) and IGFBP1 (p = 0.95) in the cAMP treatment group, hESC after EPC treatment showed a significant increase in both PRL (p = 0.0003) and IGFBP1 (p = 0.0001). RLX treatment in the EPC treated hESC and pD significantly increased the mRNA expression levels of PRL and IGFBP1 (both p &lt; 0.05, respectively), as well as the expression of the proangiogenic marker VEGF (P = 0.05). A comparative analysis with T hESC showed a moderate effect on VEGF and PlGF. No effect of RLX was detected for IGFBP1 and PRL mRNA expression levels. The mRNA expression level of the antiangiogenic marker ENG increased in the EPC group in both, primary hESC (P = 0.04) and T hESC (P = 0.01) after treatment with 0.3 ng/ml RLX compared to control. ENG mRNA expression level increased in a dose dependent manner in pD but not in hESC and T hESC. RLX treatment with 1ng/ml of cAMP decidualized hESC significantly enhanced mRNA expression levels of VEGF (P = 0.002) and PlGF (P = 0.02) only in hESC but not in T hESC or pD.

Limitations, reasons for caution
Our pilot study indicates that RLX treatment improves decidualization and affects pro- and antiangiogenic factors in three different human endometrial stromal cell models. A wider approach is needed to investigate the effects of RLX in the decidualization process and pro- and antiangiogenic factors.

Wider implications of the findings
Our results provide the basis for further studies elucidating the relationship between low maternal RLX levels and the occurrence of preeclampsia. This could lead to the development of improved prediction models and new treatment options in assisted reproduction that reduce the risk of preeclampsia, e.g. in AC-FET.

Trial registration number
Not applicable