The sex-chromosomes related cellular dimorphism in physiology and pathology

Sex-based biological differences have a profound impact on health and disease. Historically, these disparities were primarily attributed to differences in gonadal hormones. Recent advances in biochemistry and molecular biology, however, have revealed additional contributing mechanisms-most notably, the critical role of genes located on the X and Y chromosomes. The expression of Y-linked genes, increased dosage of X-linked genes in XX compared to XY cells due to incomplete X-chromosome inactivation, genomic imprinting, and the presence of non-coding and micro-RNAs on the X chromosome are all factors that require consideration in the development of in vitro models addressing sex dimorphism. In the present narrative review, we propose studies showing sex differences in vascular and cardiac cells, skeletal muscle cells, adipose tissue, liver, immune cells, cancer tissues and brain tissues. Given the absence of appropriate experimental methodologies for reproducing in vitro the sex differences observed in vivo and the limited research conducted at the cellular and molecular level to elucidate the mechanisms responsible for the observed dimorphism, the present review has two objectives. Firstly, it aims to emphasize the necessity of incorporating sex as a variable in preclinical research. Secondly, it highlights the importance of sex chromosome differences as a biological variable that can influence cell physiology and biological responses, which is crucial when conducting in vitro studies.