- Organoids are three-dimensional, multicellular structures derived from stem cells that recapitulate aspects of organ-specific biology, but definitions remain imprecise and vary between pluripotent stem cell (PSC) and tissue stem cell (TSC) derived systems.
- Reproducibility is a critical problem due to variability in Matrigel (a heterogeneous protein mix from mouse sarcoma cells) and upstream cell sources, leading to large differences in gene expression even when protocols and materials are standardized.
- Organoids lack vascularization, causing necrotic cores and limiting drug pharmacokinetic modeling; partial solutions include co-culture with endothelial cells or transplantation into animals, but these are not high-throughput.
- Integrating immune cells is difficult because culture media for organoids and immune cells are incompatible, and HLA mismatches cause rejection, restricting the study of immune-mediated drug effects.
- Organoids are developmentally and chronologically fetal, which hinders modeling of age-related diseases; some maturation can be induced over long cultures or by modulating metabolism, but full adult maturity remains unproven.
- Despite their limitations, organoids provide a more human-relevant platform than animal models for cell-autonomous drug effects, and ongoing innovations (e.g., microfluidics, organ-on-a-chip) aim to address key deficiencies.