3 minute lightning oral presentation (and poster) ESA-SRB 2023 in conjunction with ENSA

Cystatin 6 (CST6) expression is increased in preeclamptic pregnancies (#200)

Stefan M Botha 1 2 3 4 5 , Ping Cannon 1 2 , Anna Nguyen 1 2 , Tuong-Vi Nguyen 1 2 , Natasha Pritchard 2 , Catherine A Cluver 1 2 6 , Lina Bergman 6 7 8 , Ralf Dechend 3 4 5 9 10 , Olivia Nonn 3 4 5 9 10 11 , Stephen Tong 1 2 , Tu'uhevaha J Kaitu'u-Lino 1 2
  1. Translational Obstetrics Group, The Department of Obstetrics and Gynaecology, Mercy Hospital for Women, University of Melbourne, Melbourne, Victoria 3084, Australia
  2. Mercy Perinatal, Mercy Hospital for Women, Melbourne, Victoria 3084, Australia
  3. Experimental and Clinical Research Center, a cooperation between the Max-Delbrück-Center for Molecular Medicine in the Helmholtz Association and the Charité-Universitätsmedizin Berlin, Berlin, Germany
  4. Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
  5. Max-Delbrück-Center for Molecular Medicine in the Helmholtz Association (MDC), Berlin, Germany
  6. Department of Obstetrics and Gynaecology, Stellenbosch University, Cape Town 7505, South Africa
  7. Department of Women’s and Children’s Health, Uppsala University, Uppsala 751 85, Sweden
  8. Department of Obstetrics and Gynaecology, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg 405 30, Sweden
  9. DZHK (German Center for Cardiovascular Research), partner site Berlin, Berlin, Germany
  10. Department of Cardiology and Nephrology, HELIOS Clinic, Berlin, Germany
  11. Division of Cell Biology, Histology and Embryology, Gottfried Schatz Research Center, Medical University of Graz, Graz, Austria

Preeclampsia results from placental insufficiency, causing maternal endothelial dysfunction and multi-organ damage. In the search for preeclampsia biomarkers, our in silico analysis identified Cystatin 6 (CST6), a cysteine protease inhibitor, as located on the placental surface where it might be released from into maternal circulation. Therefore, we aimed to characterise CST6 in preeclampsia and assess its biomarker potential.

CST6 mRNA expression was significantly increased (~6.07-fold) in placentas from patients with early onset preeclampsia (<34 weeks’ gestation, n=78) relative to gestation matched controls (n=30, p<0.0001). Plasma CST6 significantly increased (~23.45%) preceding diagnosis of term preeclampsia (36 weeks’ gestation, n=23) compared to controls delivering without preeclampsia (n=181, p=0.0084).

To determine the placental cell type producing CST6, human trophoblast stem cells (hTSCs) were differentiated into syncytiotrophoblast or extravillous trophoblast (EVT). Differentiation was confirmed by significantly reduced cytotrophoblast markers TEAD4 (p=0.0018) and CDH2 (p=0.0096) and significantly increased syncytiotrophoblast marker, SDC1 (p=0.0013), and EVT marker, HLA-G (p=0.0005). CST6 significantly increased across 96 hours, in syncytiotrophoblast (~2.97-fold, p=0.0066) and EVT differentiation (~1.52-fold, p=0.0618 at 96 hours), confirming highest expression in syncytiotrophoblast. As preeclampsia is associated with placental hypoxia and inflammation, we next measured CST6 in syncytiotrophoblast exposed to these conditions. CST6 significantly increased in hypoxia exposed syncytiotrophoblast (1% O2 vs 8% O2) (~2-fold, p=0.0079). No significant change was observed in syncytiotrophoblast treated with inflammatory cytokines TNF-α or IL-6.

Another potential source of circulating CST6 in preeclampsia is dysfunctional endothelium. We induced endothelial dysfunction by treating human umbilical vein endothelial cells with TNF-α. This induced markers of endothelial dysfunction, ICAM-1 (p=0.0250), VCAM-1 (p=0.0250) and ET-1 (p=0.0464). Interestingly, this caused a significant reduction in CST6 (~0.5-fold, p=0.0036).

We provide the first data characterising CST6 in preeclampsia. We show it is increased in the placenta and circulation and suggest elevated circulating levels may be induced by placental hypoxia.