Oral Presentation Australian Epigenetics Alliance Conference 2022

Investigating epigenetic and immunological changes across gender-affirming hormone therapy (#20)

Rebecca Shepherd 1 2 , Ingrid Bretherton 3 4 , Ken Pang 5 6 7 , Toby Mansell 1 8 , Anna Czajko 1 , Bowon Kim 1 , Amanda Vlahos 1 , Jeffrey Zajac 3 9 , Richard Saffery 1 8 , Ada Cheung 3 10 , Boris Novakovic 1 8
  1. Molecular Immunity, Murdoch Children's Research Institute, Parkville, VIC, Australia
  2. Murdoch Children's Research Institute, Parkville, VIC, Australia
  3. Department of Medicine (Austin Health), University of Melbourne, Parkville, VIC, Australia
  4. Department of Endocrinology, Austin Health, Heidelberg, VIC, Australia
  5. Brain and Mitochondrial Research, Murdoch Children's Research Institute, Parkville, VIC, Australia
  6. Inflammation Division, Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, Australia
  7. Adolescent Medicine, Royal Children's Hospital, Parkville, VIC, Australia
  8. Paediatrics, University of Melbourne, Parkville, VIC, Australia
  9. Endocrinology, Austin Health, Heidelberg, VIC, Australia
  10. Medicine (Austin Health), University of Melbourne, Parkville, VIC, Australia

Sexual dimorphism exists in many aspects of immunity and epigenetics, with females having a higher risk of many autoimmune disorders and heightened immunogenicity to several pathogens and vaccines. Sex-specific DNA methylation patterns are widespread across autosomal chromosomes and can be present from birth or arise over the lifespan. Periods of hormonal change including puberty, pregnancy, and menopause, can affect blood DNA methylation and immune cell proportions. In individuals where gender identity and sex assigned at birth are incongruent, as in the case of transgender people, feminisation or masculinisation may be sought through gender affirming hormone therapy (GAHT). Despite GAHT being a cornerstone of transgender healthcare, its effects on the immune system and epigenome have not been characterised.

We profiled genome-wide DNA methylation in the blood of transgender women (n=13) and transgender men (n=13) prior to and after 6 and 12 months of GAHT. In transgender women and transgender men on GAHT, we identified regions of hypomethylation in VMP1 and PRR4, respectively. Loss of methylation in these regions occurs in a sex-specific manner in cisgender females and males (respectively) across adolescence, highlighting that GAHT induces some puberty-associated epigenetic changes. We also identified thousands of differentially methylated CpGs (DMPs) across masculinizing and feminizing GAHT, showing that GAHT induces changes to the blood methylome.

To address the effects of GAHT on the immune system, we have developed a workflow for blood samples from transgender women blood samples (n=70) (baseline, 3 months, and 6 months). We combine in-depth immunophenotyping, transcriptome analysis and histone post-translational modification profiling in immune cell subsets, and functional assays of cytokine production following in vitro stimulation. The characterisation of the immune system of across GAHT is important in the context of transgender healthcare and will advance our understanding of the complex interplay between sex hormones, sex chromosomes, immunology, and epigenetics.