Investigating the sex-specific legacy of excessive fetal androgen exposure on immune function and hepatic health

Background: It is well established that there are sex-specific differences in immune competence, with females considered more immunologically robust that males; and androgens are considered a major factor in these differences. Insults during pregnancy such as excessive exposure to sex steroid hormones (androgens or estrogens), can alter cellular function, and disrupt the physiological processes of a developing fetus; ultimately impacting upon an individual’s health potential. Polycystic ovary syndrome (PCOS), a highly prevalent metabolic and reproductive condition affecting around 10% of women, is characterised by excessive androgen production, and the fetus in a PCOS pregnancy is exposed to these androgens. Androgens are known immunomodulators, posited to have a suppressive effect on the immune system. The liver is a major site of androgen metabolism and reception, but also an important immune organ. Critically, adaptations made by fetal livers in response to the intrauterine environment can persist into adulthood. Hepatic outcomes of excessive androgen exposure during fetal development have been shown in males, such as dyslipidaemia and potential cholestasis in adolescence, but immune consequences of excessive fetal exposure were unknown.Methods: Using an established animal model to recreate the uterine conditions a fetus would be exposed to during a PCOS pregnancy, this thesis examines the sex-specific legacy of prenatal androgen exposure on immune potential and liver health utilising RNA sequencing, qRT-PCR, proteomics, plasma proteomics and histology.Results/discussion: In males, in response to excessive prenatal androgen exposure, expression of numerous transcripts associated with natural killer cell deficiency and cytotoxicity were reduced. Additionally, elements of the proteasomal complex were reduced, potentially suppressing T cell activation and Th1 differentiation. As the peptides degraded by the proteasome are presented with MHC-1 molecules, units of the genes encoding the MHC-1 chains were analysed and had decreased expression, but the same was not observed in such exposed females. In keeping with this, adolescent males, but not females, exposed to prenatal androgen excess had decreased hepatic transcript expression of vital components of T cell receptor signalling, indicative of decreased potential for T cell signalling, in addition to decreased expression of general T cell and CD8 type T cell markers. Factors associated with T cell differentiation were also differentially expressed in postnatal life in male animals exposed to prenatal androgen excess, with decreased expression of unique Th1 gene repertoires and transcriptomic features, whilst Th2 features increased, indicative of a shift away from Th1 type responses which can lead to decreased cell-mediated immunity. Transcriptomic expression of chemokines and their receptors involved in both adaptive and innate immunity were also decreased in prenatally androgenised males. Increased expression of collagen transcripts and other fibrosis-promoting genes was observed, coupled with increased circulating COL1a1 and APOA4. Histological examination confirmed the presence of increased total collagen, collagen IV and a-SMA, a marker of activated hepatic stellate cells, in the livers of these males, indicative of early liver disease.Conclusions: Male offspring subjected to excessive prenatal androgen exposure are vulnerable to immune dysfunction, perhaps as an exaggeration of natural sex-specific differences, which can result in liver damage as early as puberty, potentially attenuated cell-mediated immunity, and thereby increased hepatic disease susceptibility