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2471 Tmprss6 siRNA Treatment in Mice Stops Hepcidin Reduction across Pregnancy

Program: Oral and Poster Abstracts
Session: 102. Iron Homeostasis and Biology: Poster II
Hematology Disease Topics & Pathways:
Research, Fundamental Science
Sunday, December 10, 2023, 6:00 PM-8:00 PM

Katherine Fielding, FRACP FRCPA MBBS1, Ricardo Ataide, PhD2*, Cavan Bennett, PhD2*, Anne Pettikiriarachchi, PhD2*, Danielle Clucas, MBBS2*, Ute Schaeper, PhD3* and Sant-Rayn Pasricha, MD, PhD4,5,6

1The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, Australia
2The Walter and Eliza Hall Institute of Medical Research, Parkville, Australia
3Silence Therapeutics GmbH, Berlin, Germany
4Population Health and Immunity, Walter and Eliza Hall Institute of Medical Research, Fitzroy North, VIC, Australia
5Diagnostic Haematology, Royal Melbourne Hospital, Parkville, VIC, Australia
6Clinical Haematology, Royal Melbourne Hospital & Peter MacCallum Cancer Centre, Parkville, Australia

Aim: Hepcidin levels are suppressed during human and murine pregnancy. It is unknown whether hepcidin levels are primarily the result of iron deficiency/utilisation or whether there is a pregnancy-specific mechanism for hepcidin suppression. We reasoned that Tmprss6 inhibition would cause constitutive BMP-SMAD signalling and help determine the mechanism of antenatal hepcidin suppression.

Method: Female wildtype C57BL/6 mice were treated subcutaneously every 21 days with a GalNAc-siRNA conjugate targeting Tmprss6 (Silence Therapeutics GmbH, Berlin, Germany) or a non-targeting control (NTC) siRNA conjugate. Mice were mated and monitored for pregnancy. Samples were collected from pregnant mice humanely euthanised at E8.5 or E14.5, and unmated controls.

Results: Treatment with Tmprss6 siRNA inhibited hepatic Tmprss6 mRNA expression (unmated fold change 0.077, p<0.0001).

qPCR Hamp expression was significantly increased in Tmprss6 siRNA-treated mice, compared to NTC-treated mice, at all timepoints. Serum hepcidin, by ELISA, was higher in Tmprss6 siRNA-treated mice than in NTC-treated mice at E14.5 (1126ng/ml vs 178.5, p<0.0001). In unmated mice, serum hepcidin was not significantly elevated (640.9 vs 980.1ng/ml, p=0.224).

Across NTC treated pregnancy, Hamp expression and serum hepcidin were reduced at E14.5 compared to unmated (Hamp fold change E14.5 0.293, p=0.0367; serum hepcidin E14.5 178.5 vs 640.9, p=0.0247). In contrast, Tmprss6 siRNA treatment caused elevated hepcidin through pregnancy (E14.5 1126 vs unmated 980ng/ml, p=0.99); Fig 1a.

Maternal liver iron was unchanged between groups. Tmprss6 siRNA reduced placental iron, fetal liver iron, and fetal weight (0.189 vs 0.226g, p<0.0001), Fig 1b. At E8.5/E14.5, Tmprss6 siRNA reduced Mean Cell Volume (E14.5: 41.42 vs 51.72fL, p<0.0001) and Mean Cell Haemoglobin (E14.5: 11.20 vs 15.68pg, p<0.0001); at E14.5 only, maternal anaemia was seen with Tmprss6 siRNA (haemoglobin 9.4 vs 13.85g/L, p=0.0004).

Conclusion: Disruption of Tmprss6 increased hepcidin and ablated the hepcidin fall over pregnancy. This may suggest that any pregnancy-related factor which directly suppresses hepcidin cannot overcome Tmprss6 knockdown. Tmprss6 siRNA treatment resulted in iron-restricted erythropoiesis, reduced placental iron and impacted fetal development, despite unchanged liver iron stores.

Disclosures: Schaeper: Silence Therapeutics GmbH: Current Employment. Pasricha: ITL Biomedical: Consultancy; Vifor Pharmaceuticals: Consultancy, Other: Speaking Fees.

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