The polarised expression of specific transporters in proximal tubular epithelial cells is important for the renal clearance of many endogenous and exogenous compounds. Thus, ideally, the in vitro tools utilised for predictions would have a similar expression of apical and basolateral xenobiotic transporters as in vivo. Here, we assessed the functionality of organic cation and anion transporters in proximal tubular-like cells (PTL) differentiated from human induced pluripotent stem cells (iPSC), primary human proximal tubular epithelial cells (PTEC), and telomerase-immortalised human renal proximal tubular epithelial cells (RPTEC/TERT1). Organic cation and anion transport were studied using the fluorescent substrates 4-(4-(dimethylamino)styryl)-N-methylpyridinium iodide (ASP) and 6-carboxyfluorescein (6-CF), respectively. The level and rate of intracellular ASP accumulation in PTL following basolateral application were slightly lower but within a 3-fold range compared to primary PTEC and RPTEC/TERT1 cells. The basolateral uptake of ASP and its subsequent apical efflux could be inhibited by basolateral exposure to quinidine in all models. Of the three models, only PTL showed a modest preferential basolateral-to-apical 6-CF transfer. These results show that organic cation transport could be demonstrated in all three models, but more research is needed to improve and optimise organic anion transporter expression and functionality.

Cyclodextrins (CDs) are widely used as pharmaceutical excipients, yet their systemic use is constrained by cytotoxic effects that remain incompletely understood. While β-cyclodextrins are commonly associated with cholesterol extraction, it remains unclear whether this mechanism alone explains their biological activity. Here, we investigate the effects of native and modified CDs in human renal proximal tubule cells using complementary imaging, flow cytometry, and MALDI-TOF mass spectrometry. Distinct, host-dependent responses were observed. α-Cyclodextrin induced rapid membrane disruption at elevated concentrations, whereas methylated β-cyclodextrin (Meβ-CD) produced a progressive phenotype characterized by increased membrane permeability, impaired lipid internalization, and reduced cell proliferation under sub-lethal conditions. Despite these differences, both Meβ-CD and γ-cyclodextrin enhanced cholesterol internalization without evidence of immediate depletion, indicating modulation of endogenous transport processes. In contrast, Meβ-CD selectively disrupted membrane lipid uptake and altered extracellular lipid composition, yielding vesicle fractions enriched in cholesterol esters and ceramides but depleted in phosphoinositides. These findings support a model in which cyclodextrins perturb phosphoinositide-dependent lipid trafficking pathways, providing a mechanistic link between altered lipid distribution and cytotoxic response, and informing the design of safer CD-based therapeutics.