FROM CHIP TO CHICK - Novel models to bridge in vitro and in vivo kidney research

Abstract

Chronic kidney disease affects up to 15% of the global population, imposing significant health and economic burdens. Progress in understanding kidney physiology and pathology—and in developing effective therapeutics—remains constrained by the lack of translational experimental models. Conventional in vitro systems fail to recapitulate the kidney’s multicellular, vascular, and dynamic nature, while animal models often diverge physiologically from humans and raise ethical and logistical concerns. This thesis addresses these challenges by developing complementary in vitro and in vivo experimental platforms that bridge this translational gap—ranging “from chip to chick.” In Chapter 2, a human distal tubuloid-on-a-chip model was developed using adult stem cell–derived kidney tubuloids cultured within a 3D microfluidic OrganoPlate®. The model reproduced key features of distal nephron segments, including epithelial polarization, tight barrier integrity, and physiological expression of sodium and water transporters. Functional assays demonstrated ENaC-mediated sodium reabsorption, water movement, and pharmacological responsiveness to amiloride and trimethoprim. This system represents the first human-derived distal nephron-on-chip platform suitable for investigating tubular transport, drug responses, and donor-specific variability, highlighting its promise for nephrotoxicity testing and personalized medicine. Chapter 3 presents a systematic review of cell macroencapsulation devices (CMDs), which integrate living cells within semi-permeable biomaterial membranes for therapeutic applications. By synthesizing four decades of fragmented research, this review identified dominant design trends, such as the shift from inert PTFE membranes to bioactive hydrogels, and underscored key parameters—vascularization, foreign-body response, and functional protein release—essential for successful CMD performance. These insights provided a conceptual framework for experimental CMD development in subsequent chapters. In Chapter 4, the chorioallantoic membrane (CAM) of the chicken embryo was introduced as a novel, vascularized platform for evaluating CMDs. By integrating semi-permeable inserts onto the CAM and modulating vascular density with VEGF and extracellular matrix components, this model enabled rapid assessment of epithelial viability, polarization, and selective permeability. Functional assays confirmed controlled molecular diffusion across membranes, validating the CAM’s utility as a biologically active interface for CMD optimization. Building on this, Chapter 5 advanced the CAM platform by integrating it with a microfluidic biofluidic device, achieving a dynamic, vascularized, and perfused environment. The setup sustained kidney tubuloids under flow, allowing real-time diffusion monitoring and demonstrating epithelial–vascular cross-talk. This hybrid system bridges static culture and whole-organ models, offering a new avenue for studying transport physiology and bioartificial kidney design. Chapter 6 extended the use of the chicken embryo model to establish a whole-organism system for nephrotoxicity testing. Using gentamicin as a reference compound, dose- and time-dependent renal injury was observed, with histological evidence of tubular dilation and recovery consistent with mammalian profiles. The model combines physiological relevance, scalability, and ethical advantages, aligning with the 3Rs principles and providing a cost-effective platform for preclinical toxicity assessment. Together, these studies form an integrated preclinical pipeline linking organ-on-chip precision with organism-level context. The approaches developed herein enhance translational relevance while reducing animal use, setting the stage for more predictive, ethical, and accessible kidney research. Collectively, this work redefines experimental nephrology by offering complementary platforms that bridge mechanistic insight and clinical application.