Vascularization of Human iPSC-Derived Kidney Organoids Using Perfusion Culture, Pre-Vascularized Collagen Scaffolds, and Decellularized Extracellular Matrix.

Human induced pluripotent stem cell-derived kidney organoids represent promising in vitro models for studying kidney development and drug-induced toxicity, yet their lack of vasculature limits maturation and translational use. Here, we present a proof-of-concept co-culture platform to promote vascularization of kidney organoids by integrating stromal vascular fraction cells, collagen sponge scaffolds, porcine kidney decellularized extracellular matrix (dECM), and dynamic culture in a perfusion-based U-CUP bioreactor. We systematically evaluated the effects of serum supplementation, scaffold pre-vascularization, dECM encapsulation, and flow conditions on organoid-vascular integration. Low-level serum supplementation (1.5% FBS) sustained vascular networks without compromising organoid morphology. Perfusion supported vascular expansion; however, while a low flow rate comparable to interstitial tissue flow (0.01 mL/min) preserved organoid morphology and glomerular-like structures, a higher flow rate optimized for vascularization (0.47 mL/min) disrupted overall organoid architecture. Encapsulation within dECM preserved glomerular morphology and supported vascular infiltration, whereas co-culture with stromal vascular fraction cells enabled putative podocyte-endothelial interactions. Finally, exposure to the calcineurin inhibitor tacrolimus revealed dose-dependent cytotoxicity and characteristic nephron and vascular injury, demonstrating the model's utility for nephrotoxicity screening. The established modular platform enables the engineering of vascularized kidney organoids, establishing foundations for physiologically relevant models for disease modeling and pre-clinical drug testing.