Bioengineered Cystinotic Kidney Tubules Recapitulate a Nephropathic Phenotype

Thermoforming for Small Feature Replication in Melt Electrowritten Membranes to Model Kidney Proximal Tubule

A novel approach merging melt electrowriting (MEW) with matched die thermoforming to achieve scaffolds with micron-sized curvatures (200 - 800 µm versus 1000 µm of mandrel printing) for in vitro modeling of the kidney proximal tubule (PT) is proposed. Recent advances in this field emphasize the relevance of accurately replicating the intricate tissue microenvironment, particularly the curvature of the nephrons' tubular segments. While MEW offers promising capabilities for fabricating highly and porous precise 3D structures mimicking the PT, challenges persist in approximating the diameter of tubular scaffolds to match the actual PT. The thermoformed MEW membranes retain the initial MEW printing design parameters (rhombus geometry, porosity > 45%) while accurately following the imprinted curvature (ratios between 0.67-0.95). PT epithelial cells cultured on these membranes demonstrate the ability to fill in the large pores of the membrane by secreting their own collagen IV-rich extracellular matrix and form an organized, functional, and tight monolayer expressing characteristic PT markers. Besides approximating PT architecture, this setup maximizes the usable surface area for cell culture and molecular readouts. By closely mimicking the structural intricacies of native tissue architecture, this approach enhances the biomimetic fidelity of engineered scaffolds, offering potential applications beyond kidney tissue engineering.

Advances in metabolomics profiling of pediatric kidney diseases: A review

Pediatric renal diseases encompass a diverse array of pathological conditions, often engendering enduring ramifications. Metabolomics, an emergent branch of omics sciences, endeavors to holistically delineate alterations in metabolite compositions through the amalgamation of sophisticated analytical chemistry techniques and robust statistical methodologies. Recent advancements in metabolomics research within the realm of pediatric nephrology have been substantial, offering promising avenues for the identification of robust biomarkers, the elaboration of novel therapeutic targets, and the intricate elucidation of molecular mechanisms. The present discourse aims to critically review the progress in metabolomics profiling pertinent to pediatric renal disorders over the previous 12 years.

Evaluation of the efficacy of cystinosin supplementation through CTNS mRNA delivery in experimental models for cystinosis

Messenger RNA (mRNA) therapies are emerging in different disease areas, but have not yet reached the kidney field. Our aim was to study the feasibility to treat the genetic defect in cystinosis using synthetic mRNA in cell models and ctns-/- zebrafish embryos. Cystinosis is a prototype lysosomal storage disorder caused by mutations in the CTNS gene, encoding the lysosomal cystine-H+ symporter cystinosin, and leading to cystine accumulation in all cells of the body. The kidneys are the first and the most severely affected organs, presenting glomerular and proximal tubular dysfunction, progressing to end-stage kidney failure. The current therapeutic standard cysteamine, reduces cystine levels, but has many side effects and does not restore kidney function. Here, we show that synthetic mRNA can restore lysosomal cystinosin expression following lipofection into CTNS-/- kidney cells and injection into ctns-/- zebrafish. A single CTNS mRNA administration decreases cellular cystine accumulation for up to 14 days in vitro. In the ctns-/- zebrafish, CTNS mRNA therapy improves proximal tubular reabsorption, reduces proteinuria, and restores brush border expression of the multi-ligand receptor megalin. Therefore, this proof-of-principle study takes the first steps in establishing an mRNA-based therapy to restore cystinosin expression, resulting in cystine reduction in vitro and in the ctns-/- larvae, and restoration of the zebrafish pronephros function.

Co-axial Printing of Convoluted Proximal Tubule for Kidney Disease Modeling

Despite the increasing incidence of kidney-related diseases, we are still far from understanding the underlying mechanisms of these diseases and their progression. This lack of understanding is partly because of a poor replication of the diseases in vitro, limited to planar culture. Advancing towards three-dimensional models, hereby we propose coaxial printing to obtain microfibers containing a helical hollow microchannel. These recapitulate the architecture of the proximal tubule (PT), an important nephron segment often affected in kidney disorders. A stable gelatin/alginate-based ink was formulated to allow printability while maintaining structural properties. Fine tuning of the composition, printing temperature and extrusion rate allowed for optimal ink viscosity that led to coiling of the microfiber's inner channel. The printed microfibers exhibited prolonged structural stability (42 days) and cytocompatibility in culture. Healthy conditionally immortalized PT epithelial cells and a knockout cell model for cystinosis (CTNS^-/-) were seeded to mimic two genotypes of PT. Upon culturing for 14 days, engineered PT showed homogenous cytoskeleton organization as indicated by staining for filamentous actin, barrier-formation and polarization with apical marker α-tubulin and basolateral marker Na⁺/K⁺-ATPase. Cell viability was slightly decreased upon prolonged culturing for 14 days, which was more pronounced inCTNS^-/-microfibers. Finally, cystinosis cells showed reduced apical transport activity in the microfibers compared to healthy PT epithelial cells when looking at breast cancer resistance protein and multidrug resistance-associated protein 4. Engineered PT incorporated in a custom-designed microfluidic chip allowed to assess leak-tightness of the epithelium, which appeared less tight in cystinosis PT compared to healthy PT, in agreement with its in vivo phenotype. While we are still on the verge of patient-oriented medicine, this system holds great promise for further research in establishing advanced in vitro disease models.