Abstract
In the field of cosmetic research, there is a growing interest in alternatives to animal experiments, such as in vitro models using cultured cells. The trend is spreading to the field of food and drugs. Although various types of cells are used as in vitro models, the effect of cellular senescence on the expression and function of transporters in these models is unclear. In the present study, we examined the effect of replicative senescence (by passage culture) on the expression and function of transporters in renal proximal tubular epithelial cells (RPTECs). The increase in senescence-associated-β-galactosidase (SA-β-gal)-positive cells, cell cycle arrest markers, and senescence-associated secretory phenotype (SASP) markers was associated with an increase in passage numbers of RPTECs. Gene expression of various transporters in RPTEC was also altered. The mRNA level of organic cation transporter 2 decreased most rapidly with passage numbers among the transporters. The uptake of fluorescent cationic substrates in SA-β-gal-positive RPTECs was less than that in SA-β-gal-negative RPTECs. However, these changes in the expression of transporters seem to be significantly different from those observed in rodents and human kidneys in many aspects. As cellular senescence is observed in various situations, especially in RPTECs, it may be necessary to exclude it from toxicological and pharmacokinetic evaluations using in vitro models as much as possible. Additionally, when discussing cellular senescence, it is important to note the differences between aging in cells and aging and senescence in individuals.
