ESPE Abstracts

Introduction: Sex differences associated with inflammation have been observed across numerous autoimmune and cardiometabolic conditions. We aim ed to explore the differential impact of sex hormones/sex chromosomes on molecular pathways potentially relevant for immune cell functions using a unique post-pubertal transgender cohort.

Methods: RNA-sequencing was performed on peripheral blood mononuclear cells (PBMCs) from a healthy transgender cohort, including post-pubertal individuals: a) pre-treatment (n = 5 trans-male [XX]/ n = 5 trans-female [XY], mean age=15.9/16.6 years, respectively); b) on GnRHa ‘puberty blockers’ (n = 7 trans-male/ n = 5 trans-female, mean age= 17.1/18.3 years, respectively); or c) on gender-affirming hormone therapy (GAHT) (n = 5 trans-male on testosterone/ n = 5 trans-female on oestradiol, mean age= 18.2/19.4 years, respectively). Differentially expressed gene (DEG) (log2fold change >1.5, unadjusted p-value <0.01) and pathway enrichment analyses were performed using DEseq2 and Metascape to explore transcriptomic differences between groups.

Results: This exploratory pilot analysis demonstrated significant transcriptomic changes (DEGs) between the six groups, uniquely driven by both sex hormones and chromosomes, as well as disrupted biological pathways with immunological relevance. GAHT was associated with the greatest number of DEGs when compared to GnRHa: 72 DEGs, involving upregulated macrophage differentiation and lipid metabolism pathways (in trans-females, XY); and 83 DEGs, involving upregulated metabolism-related compounds/pathways related to digestion (in trans-males, XX). Blocking natal sex hormones significantly dysregulated genes, such as SYT5 (P = 0.00048) in trans-females (XY) and PLCD4 (P = 0.000325), CPT1A (P = 0.00042) and DHFRP1 (P = 0.00024) in trans-males (XX). Genes linked to inflammation/metabolism were distinctly regulated by sex hormones: in trans-females (XY), IL-15 (P = 0.0020) was downregulated by blocking testosterone, while TLR2 (P = 0.0077) was upregulated by oestradiol. Genes involved in lipid/cholesterol metabolism such as SCARB1 (P = 0.0075) and HMGCR (P = 0.0180) were upregulated by testosterone vs. GnRHa in trans-males (XX). Interestingly, oestrogen receptor 1 (ESR1), was only downregulated by blocking physiological testosterone in post-pubertal trans-females (XY; P = 0.0037), suggesting sex chromosome background-specific signalling feedback mechanisms.

Conclusion: To our knowledge, this is the first exploration of the impact of GnRHa and GAHT on the PBMC transcriptome of post-pubertal transgender individuals. Oestrogens upregulated inflammatory signals (TLR-2) in trans-females (XY), while testosterone upregulated genes related to cholesterol synthesis in trans-males (XX), in keeping with their recognised role in promoting pro-inflammatory responses, and increasing cholesterol levels, respectively. Future research is needed to explore the relevance of sex hormone-sex chromosome interactions with relevance to cardio-metabolic functions and immune responses in transgender populations.