Abstract
In the kidney, the renal proximal tubule (PT) reabsorbs solutes into the peritubular capillaries through active transport. Here, we replicate this reabsorptive function in vitro by engineering a microfluidic PT. The microfluidic PT architecture comprises a porous membrane with user-defined submicron surface topography separating two microchannels representing a PT filtrate lumen and a peritubular capillary lumen. Human PT epithelial cells and microvascular endothelial cells in respective microchannels created a PT-like reabsorptive barrier. Co-culturing epithelial and endothelial cells in the microfluidic architecture enhanced viability, metabolic activity, and compactness of the epithelial layer. The resulting tissue expressed tight junctions, kidney-specific morphology, and polarized expression of kidney markers. The microfluidic PT actively performed sodium-coupled glucose transport, which could be modulated by administration of a sodium-transport inhibiting drug. The microfluidic PT reproduces human physiology at the cellular and tissue levels, and measurable tissue function which can quantify kidney pharmaceutical efficacy and toxicity.
Highlights
We developed a co-culture of an human renal proximal tubule epithelial cells (hRPTEC) layer opposing a human microvascular endothelial cell layer in a microfluidic PT, mimicking the architectural design of the renal proximal tubule (Fig 1A and 1B)
Human renal proximal epithelial cells (ScienCell, #4100) were characterized according to ScienCell Quality Control and demonstrated expression of cytokeratin-18, -19 and vimentin and were negative for mycoplasma DNA measured by PCR. hRPTEC were passaged once prior to seeding them in the device and were maintained in hRPTEC complete media, a DMEM-F12 base supplemented with 0.5% FBS, 10ng/ml human epithelial growth factor (hEGF), 5 μg/ml insulin, 0.5 μg/ml hydrocortisone, 0.5 μg/ml epinephrine, 6.5 ng/ml Tri-idothyronine, 10 μg/ml transferrin, 100 U/ml penicillin, and 100 μg/ml streptomycin
Topographically-patterned polycarbonate membrane into the microfluidic PT, with 750 nm wide grooves that are within an order of magnitude of the sub-micron feature sizes observed in renal basement membrane (BM) [16,17]
Summary
We developed a co-culture of an hRPTEC layer opposing a human microvascular endothelial cell (hMVEC) layer in a microfluidic PT, mimicking the architectural design of the renal proximal tubule (Fig 1A and 1B). Reabsorption of the fluorescent glucose analog, 2-NBDG, served as a metric to monitor the transport function of the PT co-culture model in our device.
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