Advances in predictive in vitro models of drug-induced nephrotoxicity

Abstract

In vitro screens for nephrotoxicity are currently poorly predictive of toxicity in humans. Although the functional proteins that are expressed by nephron tubules and mediate drug susceptibility are well known, current in vitro cellular models poorly replicate both the morphology and the function of kidney tubules and therefore fail to demonstrate injury responses to drugs that would be nephrotoxic in vivo. Advances in protocols to enable the directed differentiation of pluripotent stem cells into multiple renal cell types and the development of microfluidic and 3D culture systems have opened a range of potential new platforms for evaluating drug nephrotoxicity. Many of the new in vitro culture systems have been characterized by the expression and function of transporters, enzymes, and other functional proteins that are expressed by the kidney and have been implicated in drug-induced renal injury. In vitro platforms that express these proteins and exhibit molecular biomarkers that have been used as readouts of injury demonstrate improved functional maturity compared with static 2D cultures and represent an opportunity to model injury to renal cell types that have hitherto received little attention. As nephrotoxicity screening platforms become more physiologically relevant, they will facilitate the development of safer drugs and improved clinical management of nephrotoxicants.

Fig. 1. Renal transporters and targets of nephrotoxicants

Different segments of the nephron express various transporters and receptors that affect the susceptibility of the segments to the nephrotoxic effects of different drugs. a | In addition to the specific nephrotoxic effects of agents on different transporters in the tubule (discussed below), drugs such as nonsteroidal anti-inflammatory drugs (NSAIDs) can cause nephrotic syndrome by inducing immunoglobulin deposition on the glomerular basement membrane (GBM), damaging the membrane and podocytes. b | The proximal tubule expresses many transporters and receptors that are affected by pharmaceutical agents. For example, tenofovir, cisplatin, and gentamicin have affinity for organic anion transporters (OATs), organic cation transporters (OCTs), and endocytic receptors, respectively, allowing them to accumulate within the cell and cause toxic injury. c | The loop of Henle expresses aquaporins (AQPs) and ion transporters in different segments. d | The distal tubule expresses unique ion transporters. Drugs such as ciclosporin can affect the expression of these transporters and cause adverse effects such as Mg²⁺ and Na⁺ loss. e | The collecting duct is composed of principal and intercalated cells. The principal cells express epithelial sodium channel (ENaC), which can transport lithium, contributing to lithium-induced diabetes insipidus. In addition, pharmaceutical agents can cause nonspecific nephrotoxic injury by inducing ischaemia, interstitial nephritis, or microangiopathy (not shown). αKG, α-ketoglutarate; ACE, angiotensin-converting enzyme; AKI, acute kidney injury ; ARB, angiotensin receptor blocker; BCRP, breast cancer resistance protein; CLCK2, H⁺/Cl⁻ exchange transporter 5 (also known as CLCN5); ClC-Kb, chloride channel protein ClC-Kb (also known as CLCNKB); CTR1, copper transporter 1; DC, dicarboxylate cotransporter; KIR4.1, ATP-dependent inwardly rectifying potassium channel KIR4.1 (also known as KCNJ10); MATE, multidrug and toxin extrusion protein; MDR1, multidrug resistance protein 1; MRP, multidrug resistance-associated protein; NaDC3, Na⁺/dicarboxylate cotransporter 3; NCC, Na⁺/Cl⁻ cotransporter; NCX1, Na⁺/Ca²⁺-exchange protein 1 (also known as SLC8A1); NKCC2, solute carrier family 12 member 1 (also known as SLC12A1); OA, organic anion; OATP4C1, solute carrier organic anion transporter family member 4C1 (also known as SLCO4C1); OC, organic cation; OCTN1, organic cation/carnitine transporter 1 (also known as SLC22A4); ROMK, ATP-sensitive inward rectifier potassium channel 1 (also known as KCNJ1); SGLT, sodium/glucose cotransporter; TNF, tumour necrosis factor; TRPM6, transient receptor potential cation channel subfamily M member 6; TRPV5, transient receptor potential cation channel subfamily V member 5; URAT1, urate anion exchanger 1 (also known as SLC22A12).

Fig. 2. Novel culture platforms for modelling nephrotoxicity in vitro

a | Organoids consist of multiple immature nephrons and interstitial cells that self-organize in response to developmental cues and overcome the cellular simplicity of 2D cultures. b | A simple kidney-on-a-chip model allows media containing the compound of interest to flow across a cell monolayer. c | A kidney-on-a-chip that comprises a perfusable, convoluted 3D tubule within an extracellular matrix (ECM) enables fluid flow and the administration of test compounds to the apical surface of the cells. d | A kidney-on-a-chip with parallel 3D channels enables multiple cell types (for example, vasculature) to be modelled on a single chip with tubules. e | A biofunctionalized hollow fibre is coated with ECM and seeded with proximal tubule cells on its external surface, rendering both the basolateral and apical surfaces of the cells accessible for testing compounds. f | A 3D engineered renal tissue array consists of a monolayer of proximal tubule cells with an interstitial layer (comprising human umbilical vein endothelial cells (HUVECs) and fibroblasts) on their basolateral side, arranged on a Transwell. This model enables control over the spatial arrangement of cell types and media access to the basolateral and apical surfaces of the cells. PDMS, poly(dimethylsiloxane); PTEC, proximal tubule epithelial cell. Part b is reproduced with permission from REF., Royal Society of Chemistry. Part c is reproduced from REF., Macmillan Publishers Limited. Part d is reproduced with permission from REF., Elsevier.