Design and Optimization of a Bioactive Composite Hydrogel for Sustained Ex Vivo Maintenance of Kidney Slices in Preclinical Applications

The kidney is a heterogeneous organ composed of more than 23 specialized cell types whose coordinated interactions are essential for physiological function. Conventional in vitro models of isolated renal cell types lack this complexity and native extracellular matrix (ECM) support, limiting their translational relevance. To address these limitations, we developed a composite hydrogel comprising hydroxypropyl methylcellulose (HPMC), chitosan, and collagen for encapsulating rat kidney slices, combining ECM-like mechanical cues with preserved tissue heterogeneity. Thirteen formulations were evaluated for chemical composition, rheological properties, swelling, degradation, and cytocompatibility. Also, the Design of Experiments (DoE) approach was employed to analyze the role of various components in hydrogel properties. Two optimal candidates were identified: H10C30 (1:1 HPMC:chitosan/collagen, 10% citric acid, 30% β-glycerophosphate) and H20C50 (7:3 ratio, 20% citric acid, 50% β-glycerophosphate). Both supported renal architecture for 14 days, with H10C30 demonstrating superior preservation of glomerular and tubular structures. The platform enabled oxidative stress modeling via lipopolysaccharide/interferon-γ-induced reactive oxygen species and demonstrated structural recovery following mesenchymal stromal cell treatment. This cost-effective, tunable system bridges the gap between 2D cultures and native tissue, providing a physiologically relevant ex vivo platform for drug screening, disease modeling, and regenerative therapy evaluation.