Placental STAT3 signaling is activated in women with polycystic ovary syndrome

Study question: Does polycystic ovary syndrome (PCOS) in women without pregnancy complications affect placental signal transducer and activator of transcription 3 (STAT3) and mechanistic target of rapamycin (mTOR) signaling?

Summary answer: Placental STAT3 signaling is activated but mTOR signaling is unaffected in PCOS.

What is known already: Women with PCOS have increased risk of poor pregnancy outcomes (e.g. restricted or accelerated fetal growth), indicating placental dysfunction. Placental STAT3 and mTOR pathways regulate placental function and indirectly affect fetal growth.

Study design, size, duration: In a case-control study, placental tissue and maternal blood were collected at delivery from 40 control pregnant women and 38 PCOS women with uncomplicated pregnancy.

Participants/materials, setting, methods: Women with PCOS were recruited at two medical centers and pregnant controls were recruited at one of these centers. Placental mRNA expression of genes encoding proteins related to steroid action, metabolic pathways and cytokines was analyzed by quantitative RT-PCR. Phosphorylated placental STAT3 (P-STAT3) and mTOR targets was measured by western blot. Levels of sex steroids in serum were determined by mass spectrometry.

Main results and the role of chance: Placental P-STAT3 (Tyr-705) was increased in women with PCOS (P < 0.05) versus controls. Placental mTOR signaling was not affected in PCOS women when compared with controls. Circulating levels of androstenedione, androst-5-ene-3β, 17β-diol, testosterone, 5α-dihydrotestosterone and etiocholanolone glucuronide were higher and estradiol lower in women with PCOS than in controls (all P < 0.05). No correlation between sex steroid levels in serum and P-STAT3 was observed.

Limitations, reasons for caution: Women with PCOS and pregnancy complications were excluded to avoid the confounding effects of placental pathologies, which could modify STAT3 and mTOR signaling. Moreover, 97.4% of women with PCOS in the study displayed oligoamenorrhea at diagnosis. Thus, the current findings could be restricted to PCOS women with the oligo-anovulatory phenotype without pregnancy complications.

Wider implications of the findings: Phosphorylation of STAT3 is increased in the placenta from women with PCOS and uncomplicated pregnancies, indicating that specific metabolic placental pathways are activated in the absence of obstetric and perinatal complications.

Study funding/competing interests: The work was supported by the Swedish Medical Research Council (Project No. 2011-2732 and 2014-2775); Jane and Dan Olsson Foundation, Wilhelm and Martina Lundgrens's Science Fund; Hjalmar Svensson Foundation (E.S.-V and M.M.); Adlerbert Research Foundation; Swedish federal government under the LUA/ALF agreement ALFFGBG-136481 and 429501 and the Regional Research and Development agreement (VGFOUREG-5171, -11296 and -7861). MM thanks the Becas Chile Programme (Chile) and University of Chile for financial support through a postdoctoral fellowship. There are no competing interests.