2025 年 30 巻 1 号 p. 3-10
Drugs taken up by hepatocytes are excreted into the bile canaliculi via transporters such as bile salt export pump (BSEP). Here, human hepatocyte cell line PLC/PRF/5, which were reported to express BSEP, were cultured in three-dimensional (3D) culture using a scaffold called Cellbed and compared with that of two-dimensional (2D) monolayer culture. The results showed that the expression of sodium taurocholate co-transporting polypeptide (NTCP), the bile acid uptake system, did not change in both culture systems at the protein or gene level, whereas the expression of BSEP, the excretion system, was significantly enhanced in 3D culture at the protein and gene levels. The uptake and excretion activities of tauro-nor-THCA-24DBD, a model fluorescent substance for bile acids, by NTCP and BSEP were inhibited by Cyclosporin A, which is known to inhibit the activities by NTCP and BSEP in both culture systems, and the excretion activity of BSEP by 3D culture was approximately 70 times higher than that of 2D culture. The high expression of BSEP in this Cellbed 3D culture was accompanied by high expression of the hypoxia-induced transcription factor HIF-1α and HIF-1α-related genes, and the nuclear receptor for bile acids, FXR, which was reported to induce BSEP expression. These results suggest that in Cellbed cultured PLC/PRF/5 cells, the expression of BSEP is increased in accordance with the increased expression of HIF-1α, and is a promising evaluation system for drug efflux in vitro.
