Alignment of Micrometer-Scale Electrospun Fibers Does Not Enhance Performance of Primary Human Renal Proximal Tubular...

Renal failure remains a leading cause of morbidity and mortality, as current renal replacement therapies restore filtration but fail to replicate the kidney's transport, metabolic, and endocrine functions. Bioengineered systems using primary renal epithelial cells show promise in recapitulating these processes, and integration into synthetic tubular platforms may further enhance biological mimicry, advancing drug discovery, and next-generation bioartificial kidneys. The native proximal tubule basement membrane contains aligned ridges (~200 nm), suggesting that scaffold fiber alignment could improve epithelial cell function. We therefore hypothesized that aligned electrospun fibers would promote proximal tubule epithelial cell organization and enhance functional performance compared to random fibers. Polycaprolactone scaffolds with random or aligned fibers were fabricated in both flat and tubular configurations using solution electrospinning (SES). Human renal proximal tubule epithelial cells (HRPTEpiC) were cultured for up to 11 days and assessed for morphology, barrier function, polarization, and transporter expression. Aligned fibers induced cytoskeletal organization but did not affect tight junction formation, polarization, or monolayer formation. Barrier function was significantly reduced on aligned scaffolds at Day 11, attributed to larger pore sizes (15.3 vs. 7.5 μm²). Transporter expression showed transient differences, with ATP1A1 and AQP1 reduced on aligned scaffolds at Day 7 but equalized by Day 11. Functional transport assays revealed significant ABC transporter inhibition only on random scaffolds (p = 0.048 vs. p = 0.058 for aligned). Overall, these findings show that at the tested diameters (1.2-1.6 μm), fiber alignment influenced cell morphology but offered limited functional benefit compared to random fibers.