•Allometric scaling is suitable for prediction of human renal drug clearance (CLr).•The average CLr of a diverse set of 20 drugs scales to the ¾ power of body mass.•Rat models should be used with ...caution for drug disposition studies.•Meta-analyses of (pre)clinical data can reduce pharmacokinetic animal experiments.
Various animal models are used to study pharmacokinetics (PK) of drugs in development. Human renal clearance (CLr) should be predictable through interpolation from animal data by allometric scaling. Based on this premise, we quantified interspecies differences in CLr, and related them to drug properties. Using PubMed and EMBASE, we systematically reviewed literature on human and animal CLr measures for 20 renally excreted drugs, calculated average fold errors, and quantified mean differences between animals and humans. Our results show that animal models are generally good predictors for human drug clearance using simple allometry, except for rats, with which human CLr is significantly overestimated.
For predictions of human renal drug clearance, we rely on nonhuman animal models and allometric scaling, but are these models reliable enough? Are nonhuman animal- and/or drug-specific differences significant obstacles for the determination of first-in-human doses?
Single-cell RNA sequencing has recently led to the identification of a flurry of rare, new cell types, such as the CFTR-high ionocytes in the airway epithelium. Ionocytes appear to be specifically ...responsible for fluid osmolarity and pH regulation. Similar cells exist in multiple other organs and have received various names, including intercalated cell in the kidney, mitochondria-rich cell in the inner ear, clear cell in the epididymis, and ionocyte in the salivary gland. Here, we compare the previously published transcriptomic profile of cells expressing FOXI1, the signature transcription factor expressed in airway ionocytes. Such FOXI1+ cells were found in datasets representing human and/or murine kidney, airway, epididymis, thymus, skin, inner ear, salivary gland, and prostate. This allowed us to assess the similarities between these cells and identify the core transcriptomic signature of this ionocyte 'family'. Our results demonstrate that, across all these organs, ionocytes maintain the expression of a characteristic set of genes, including FOXI1, KRT7, and ATP6V1B1. We conclude that the ionocyte signature defines a class of closely related cell types across multiple mammalian organs.
Over the course of more than 500 million years, the kidneys have undergone a remarkable evolution from primitive nephric tubes to intricate filtration-reabsorption systems that maintain homeostasis ...and remove metabolic end products from the body. The evolutionarily conserved solute carriers organic cation transporter 2 (OCT2) and organic anion transporters 1 and 3 (OAT1/3) coordinate the active secretion of a broad range of endogenous and exogenous substances, many of which accumulate in the blood of patients with kidney failure despite dialysis. Harnessing OCT2 and OAT1/3 through functional preservation or regeneration could alleviate the progression of kidney disease. Additionally, it would improve current in vitro test models that lose their expression in culture. With this review, we explore OCT2 and OAT1/3 regulation from different perspectives: phylogenetic, ontogenetic, and cell dynamic. Our aim is to identify possible molecular targets both to help prevent or compensate for the loss of transport activity in patients with kidney disease and to enable endogenous OCT2 and OAT1/3 induction in vitro in order to develop better models for drug development.
Nephropathic cystinosis is a severe monogenic kidney disorder caused by mutations in CTNS, encoding the lysosomal transporter cystinosin, resulting in lysosomal cystine accumulation. The sole ...treatment, cysteamine, slows down the disease progression, but does not correct the established renal proximal tubulopathy. Here, we developed a new therapeutic strategy by applying omics to expand our knowledge on the complexity of the disease and prioritize drug targets in cystinosis. We identified alpha‐ketoglutarate as a potential metabolite to bridge cystinosin loss to autophagy, apoptosis and kidney proximal tubule impairment in cystinosis. This insight combined with a drug screen revealed a bicalutamide–cysteamine combination treatment as a novel dual‐target pharmacological approach for the phenotypical correction of cystinotic kidney proximal tubule cells, patient‐derived kidney tubuloids and cystinotic zebrafish.
SYNOPSIS
Nephropathic cystinosis is a severe genetic disorder caused by mutations in the lysosomal cystine transporter, cystinosin. Although several cellular defects have been associated with cystinosis, the mechanism linking cystinosin loss, and epithelial dysfunction remains largely unknown.
CRISPR‐generated isogenic cystinotic renal proximal tubule cells recapitulate the disease pathology and allow direct evaluation of the effect of cystinosin loss, independent of chronic exposure to disease‐related changes in the body.
Alpha‐ketoglutarate (αKG), an important intermediate of the tricarboxylic acid cycle, is a part of a unifying mechanism linking cystinosin loss, lysosomal autophagy disruption and proximal tubule impairment in cystinotic renal proximal tubule cells.
Cysteamine‐bicalutamide combination therapy restores proximal tubule function in advanced in vitro models and corrects cystinosis related defects in cystinotic zebrafish. Our findings demonstrate that the combination therapy is a novel potential treatment for patients with nephropathic cystinosis.
Nephropathic cystinosis is a severe genetic disorder caused by mutations in the lysosomal cystine transporter, cystinosin. Although several cellular defects have been associated with cystinosis, the mechanism linking cystinosin loss, and epithelial dysfunction remains largely unknown.
Kidney organoids generated from induced pluripotent stem cells (iPSC) have proven valuable for studies of kidney development, disease, and therapeutic screening. However, specific applications have ...been hampered by limited expansion capacity, immaturity, off-target cells, and inability to access the apical side. Here, we apply recently developed tubuloid protocols to purify and propagate kidney epithelium from d7+18 (post nephrogenesis) iPSC-derived organoids. The resulting 'iPSC organoid-derived (iPSCod)' tubuloids can be exponentially expanded for at least 2.5 mo, while retaining expression of important tubular transporters and segment-specific markers. This approach allows for selective propagation of the mature tubular epithelium, as immature cells, stroma, and undesirable off-target cells rapidly disappeared. iPSCod tubuloids provide easy apical access, which enabled functional evaluation and demonstration of essential secretion and electrolyte reabsorption processes. In conclusion, iPSCod tubuloids provide a different, complementary human kidney model that unlocks opportunities for functional characterization, disease modeling, and regenerative nephrology.
Organoid technology is rapidly gaining ground for studies on organ (patho)physiology. Tubuloids are long-term expanding organoids grown from adult kidney tissue or urine. The progenitor state of ...expanding tubuloids comes at the expense of differentiation. Here, we differentiate tubuloids to model the distal nephron and collecting ducts, essential functional parts of the kidney. Differentiation suppresses progenitor traits and upregulates genes required for function. A single-cell atlas reveals that differentiation predominantly generates thick ascending limb and principal cells. Differentiated human tubuloids express luminal NKCC2 and ENaC capable of diuretic-inhibitable electrolyte uptake and enable disease modeling as demonstrated by a lithium-induced tubulopathy model. Lithium causes hallmark AQP2 loss, induces proliferation, and upregulates inflammatory mediators, as seen in vivo. Lithium also suppresses electrolyte transport in multiple segments. In conclusion, this tubuloid model enables modeling of the human distal nephron and collecting duct in health and disease and provides opportunities to develop improved therapies.
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•Human tubuloid differentiation introduces distal nephron and collecting duct cells•Differentiated tubuloids demonstrate electrolyte reabsorption, a key renal function•A single-cell atlas shows differentiated tubuloid cells resemble in vivo equivalents•Differentiated tubuloids enable modeling of human lithium tubulopathy in vitro
Tubuloid differentiation introduces distal nephron and collecting duct cell types that resemble their counterparts in human in vivo kidney tissue. Differentiated tubuloids demonstrate electrolyte reabsorption, a key renal function, and enable modeling of diseases of the human distal nephron and collecting duct in vitro.
Given the increasing prevalence of end-stage kidney disease, the high morbidity and mortality of dialysis treatment, and the shortage of donor kidneys, the field of nephrology is progressively ...shifting its focus to regenerative medicine. In particular, both the development of a bioartificial kidney and the improvement of kidney-mimicking systems developed in vitro (e.g. organoids or tubuloids) for implantation purposes are attractive therapeutic strategies. However, a major hurdle to overcome with the current kidney cell models available is the limited control over cellular plasticity to augment cell-type-specific functionality. In this review, we summarize the main knowledge on important factors known to drive or affect maturation of kidney epithelial cells. This might aid in the advancement of in vitro kidney models to enable their use in regenerative medicine.
Nephropathic cystinosis is characterized by abnormal intralysosomal accumulation of cystine throughout the body, causing irreversible damage to various organs, particularly the kidneys. Cysteamine, ...the currently available treatment, can reduce lysosomal cystine and postpone disease progression. However, cysteamine poses serious side effects and does not address all of the symptoms of cystinosis. To screen for new treatment options, a rapid and reliable high‐performance liquid chromatography–tandem mass spectrometry (HPLC‐MS/MS) method was developed to quantify cystine in conditionally immortalized human proximal tubular epithelial cells (ciPTEC). The ciPTEC were treated with N‐ethylmaleimide, lysed and deproteinized with 15% (w/v) sulfosalicylic acid. Subsequently, cystine was measured using deuterium‐labeled cystine‐D4, as the internal standard. The assay developed demonstrated linearity to at least 20 μmol/L with a good precision. Accuracies were between 97.3 and 102.9% for both cell extracts and whole cell samples. Cystine was sufficiently stable under all relevant analytical conditions. The assay was successfully applied to determine cystine levels in both healthy and cystinotic ciPTEC. Control cells showed clearly distinguishable cystine levels compared with cystinotic cells treated with or without cysteamine. The method developed provides a fast and reliable quantification of cystine, and is applicable to screen for potential drugs that could reverse cystinotic symptoms in human kidney cells.
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