Development of a compartmentalized silk fibroin-reinforced GelMA hydrogel platform for kidney-inspired tissue engineering.

Chronic kidney disease (CKD) and the limited availability of donor organs continue to drive the need for advanced biomaterial systems for renal tissue engineering and in vitro kidney modeling. However, reproducing the spatial complexity and compartmentalized organization of native renal tissue remains a significant challenge. In this study, a compartmentalized silk fibroin (SF)-reinforced gelatin methacrylate (GelMA) hydrogel platform with spatially defined architectures inspired by renal tissue organization was developed. Initially, SF-reinforced GelMA hydrogels with tunable stiffness were fabricated by varying the concentration of the hydroxyethyl methacrylate (HEMA) crosslinker, while SF was incorporated at concentrations of 25 mg/mL and 50 mg/mL to systematically modulate the physicochemical properties of the hydrogels. The resulting formulations were characterized through degradation and swelling analyses, along with preliminary in vitro cytocompatibility studies. Degradation studies demonstrated that low-stiffness hydrogels exhibited more controlled degradation behavior compared to high-stiffness formulations, particularly at higher SF concentrations, indicating improved structural stability. Swelling analysis revealed that all hydrogel groups supported fluid uptake, with hydrogels containing 25 mg/mL SF exhibiting comparatively stable swelling and degradation profiles. In vitro studies confirmed that all scaffold formulations supported cellular attachment and exhibited non-toxic behavior. Based on the optimized hydrogel formulation, a two-zone compartmentalized platform was subsequently developed consisting of a central triangular-patterned region inspired by the renal medulla and a surrounding honeycomb-patterned region representing the renal cortex. Confocal imaging demonstrated spatial organization of L929 fibroblasts within the patterned hydrogel architecture, while depth-coded three-dimensional confocal imaging of nuclei-stained renal proximal tubular epithelial cells (RPTECs) at days 1, 3, and 5 enabled visualization of cell localization within the engineered patterned regions. Collectively, this study demonstrates the feasibility of developing a compartmentalized SF-GelMA hydrogel platform with tunable material properties and spatially organized architectures inspired by renal tissue organization. The platform provides a promising foundation for future studies involving kidney-specific cell populations and region-specific renal tissue engineering applications.