Grant, R.; Giselbrecht, S.

Bioengineers strive to recreate in vivo microenvironments in vitro to reduce our use of animal models and provide insights into human biology. While liver models show promise, sex differences in liver biology remain largely neglected in preclinical studies. Despite the 2014 EU mandate for the inclusion of women in clinical trials, decoupling of research data by sex is historically rare, with only 11% of papers disaggregating data by sex. This gap contributes to women being more susceptible to drug-induced liver injury (DILI) and being underserved in drug development, as well as to costly drug attrition levels. Here we present a novel approach to modelling sex differences in vitro. Human induced pluripotent stem cells (iPSCs) from both male (XY) and female (XX) donors, were differentiated into hepatocyte liver spheroids and exposed to in vivo-mimicking levels of testosterone, progesterone, and oestrogen in high-throughput microwell format. We successfully recapitulated sex-specific metabolic profiles and demonstrated significant differences in CYP1A2 and CYP3A4 drug metabolism and gene expression patterns consistent with reported in vivo observations, without compromising cell viability. These findings validate the utility of sex-differentiated microenvironments in early-stage research, offering a pathway to refine animal and clinical trials and improve therapeutic outcomes for all sexes.