Investigating the effects of obesity on kidney tubuloids and toward combining them with liver and adipoids in a multi-organ-on-a-chip model

Abstract

Obesity is a major health concern that increases the risk of various health complications, including acute kidney injury (AKI), a sudden decline in kidney function that can become fatal without treatment. This association has been studied suboptimal in vitro, and animal models fail to replicate complex human physiological interactions adequately. Therefore, this study employed human multi-organ-on-a-chip (MOC) models of kidney tubuloids, liver organoids, and adipoids under obesity-inducing culture conditions. This experimental setup raises the question of how we can investigate the effects of obesity on kidney tubuloids in a kidney-liver-adipoids MOC model. To eventually study obesity-related effects on kidney tubuloids in the chip, static culture conditions for tubuloids were optimized, and potential readouts have been examined. We found that 20,000 single-cell tubuloids resulted in a confluent monolayer and demonstrated that fibroblast growth factor 10 from different suppliers performed comparably. This was due to the new supplier’s growth factor offering advantages such as cost reduction and the absence of animal-derived components. Four kidney donors had stable barrier integrity for an extended period of time, measuring trans-epithelial electric resistance (TEER). However, trans-epithelial MRP2/4 transporter activity using a CDFDA assay could not be confirmed. Microscopic analysis confirmed the presence of the efflux transporter P-glycoprotein, showed leak-tightness of the tubuloid monolayer, and displayed lipid accumulation in tubuloids cultured in palmitic acid supplemented medium. Furthermore, hydrogen peroxide-induced AKI resulted in inconsistent outcomes. In the second part of this study, functional kidney–liver and kidney–liver–adipoids MOC models were performed, both demonstrating stable barrier integrity in the kidney tubuloids. To address the research question, effective approaches include measuring barrier integrity with TEER, assessing leak-tightness through tight junction staining, and evaluating lipid accumulation in 2D tubuloids via a lipid staining. This study helps understand obesity-associated kidney diseases, which could support the development of more effective therapies.