Caco2

Caco-2 is a human epithelial colorectal adenocarcinoma cell line derived from a metastatic site. Under appropriate culture conditions, it differentiates into enterocyte-like cells and is widely used as an in vitro model of the intestinal barrier.

When grown as confluent monolayers on permeable supports, Caco-2 cells differentiate over two to three weeks to form tight junctions, brush border microvilli, and apical membrane enzymes. They express a range of transporters and metabolic enzymes, and transepithelial electrical resistance (TEER) values are used to assess barrier integrity.

Caco-2 monolayers are employed to evaluate intestinal drug absorption and transport. By measuring apparent permeability (Papp) across the monolayer and efflux ratios, researchers study passive diffusion and transporter-mediated processes. The cell line expresses efflux transporters such as P-glycoprotein, BCRP, and MRP2, as well as uptake transporters including PEPT1 and OATP family members.

Limitations include incomplete representation of the in vivo intestine: absence of mucus-secreting goblet cells and M cells, variable transporter expression across cell lines and passages, and dependence on culture conditions. To address these gaps, researchers use co-culture systems with mucus-secreting cells (for example, HT29-MTX) or more advanced models like gut-on-a-chip to enhance physiological relevance.

Typical culture conditions involve growing Caco-2 cells in glucose-rich DMEM with serum and antibiotics on collagen-coated Transwell inserts, with maturation over several weeks. While widely used, results should be interpreted with awareness of the model’s limitations when predicting human oral absorption.