P-522 Impact of TGFß/BMP/SMAD Pathway on Premature Ovarian Insuffiency (POI)
Authors: Philipp J , Vilkaite A , Bender U , Hinderhofer K , Dietrich J , Strowitzki T , Rehnitz J 
Published: July 2024

Abstract

Study question
Is TGFß/BMP/SMAD pathway altered in women with POI and can results be detected from peripheral blood samples?

Summary answer
The TGFß/BMP/SMAD pathway mRNA-expression-alterations are detectable in leukocytes of women with Premature Ovarian Insufficiency (POI) paving the way to use it as predictive tool.

What is known already
A proper ovarian function relies on a complex system of signalling molecules including several BMP/TGFß-superfamily-members expressed in the ovary at different stages of folliculogenesis acting via two types of Serine/Threonine Kinase receptors. The downstream located SMAD proteins are classified into three subclasses according to their function as activated R-SMADs1,2,3,4,9, common-partner SMAD4 or inhibitory SMADs6,7. Mutations in BMPR2 and its ligands have been shown to be related to POI. Recently neurologic studies demonstrated that FMRP(Fragile-X-Mental-Retardation-1-Protein) represses BMPR2 and its gene FMR1(Fragile X Mental-Retardation-1) is one major regulator of follicular development and the most frequent genetic cause of POI if premutated.

Study design, size, duration
RT-q-PCR was performed to measure the mRNA-levels of SMAD 1,3,4,5, BMPR2 and FMR1. cDNA was synthesized using RNA obtained from leucocytes of patients with POI and of the control group with a normal ovarian reserve. 163 patients diagnosed with POI and 51 women in the control group were recruited between 2008 and 2022 at Heidelberg University’s Women’s Hospital.

Participants/materials, setting, methods
Blood samples were drawn from every participant to extract leucocyte-RNA and synthesize non-specific cDNA. RT-q-PCR was performed with TaqMan reagents to quantify relative mRNA-expression levels of SMAD 1,3,4, 5, BMPR2 and FMR1. Statistical analysis was performed with Microsoft Excel and GraphPad Prism 10 using the 2–ΔΔCt method and Mann-Whitney-Test. Statistical significance was set to p = 0.05.

Main results and the role of chance
In our investigation, we observed a consistent and statistically significant decrease in the expression levels of all tested SMADs—SMAD1, SMAD3, SMAD4, and SMAD5—in leukocytes of women diagnosed with POI compared to unaffected controls. The p-values amounted to p &lt; 0.0001 for SMAD1, p = 0.0340 for SMAD3, p &lt; 0.0001 for SMAD4, and p = 0.0076 for SMAD5. However, we did not identify notable differences in the expression levels of FMR1 and BMPR2 between the two groups.
These results suggest an alteration in the regulation of the activated downstream elements SMAD 1, 3, and 5 and their common partner SMAD4 in women with POI, emphasizing its potential role as a contributing factor to diminished ovarian function. These effects seem to be independent of BMPR2 and FMR1 and regulated by other receptors and or ligands.

Limitations, reasons for caution
Our data are limited to mRNA-levels. So further experiments including protein-level and their phosphorylation-status are needed to receive an overall assessment of its impact on ovarian damage. It’s worth noting that the study is concentrated on leukocytes as potential diagnostic tool and results should be cross-checked in ovarian-tissue and cells.

Wider implications of the findings
The identified alteration in TGFß/BMP/SMAD pathway gene expression in women with POI suggest a role in ovarian damage. Lower expression levels in the aforementioned mRNAs could serve as a potential predictive biomarker for POI risks and putatively used in consultations of women prior to fertility treatment and/or preservation.

Trial registration number
not applicable