Bridging population and cell: modelling complex diseases with human induced pluripotent stem cells.

Induced pluripotent stem cells (iPSCs) have emerged as a powerful tool in biomedical research, enabling the study of cellular function and early disease mechanisms within patient-specific genetic contexts. Traditionally, iPSCs have been used to model monogenic diseases, where highly penetrant variants produce robust cellular phenotypes detectable in few cell lines. Recent advances in scalability and standardisation now enable systematic comparisons across many donors. This development is particularly relevant for complex diseases, which are driven by numerous genetic variants with small individual effects and therefore require population-scale designs to resolve genotype-phenotype relationships. However, several limitations of iPSC technology continue to challenge the reliability and reproducibility of such studies, constraining their translational relevance. Here, we review the challenges and opportunities of using iPSCs to model complex diseases, structured around three key themes: detecting subtle effects, modelling environmental context, and expanding genetic diversity.