Modeling kidney fibrosis and tubular regeneration in iPSC-derived kidney organoids.

BACKGROUND

Kidney fibrosis is one of the pathological hallmarks of chronic kidney disease, likely contributing to the loss of kidney function. The mechanisms leading to kidney fibrosis and its reversibility is only partially understood, which hampers the development of therapeutic targets. Therefore, it is crucial to establish a robust human in vitro model that can be used to study kidney fibrosis and potential regeneration.

METHODS

Human induced pluripotent stem cells (iPSC) were differentiated into kidney organoids. Fibrotic injury was induced by mimicking hypoxia (1% O2 48 h), inflammation (interleukin-1 beta (IL-1β) 96 h) or a combination (hypoxia and IL-1β). Organoids were harvested at injury onset and up to 2 weeks post-injury. Fibrosis was assessed by mRNA and protein expression of fibronectin (FN1) and collagen type I, regeneration was evaluated through the presence of CD133+ and CD24+ progenitor cells and markers for differentiated kidney cell types.

RESULTS

The combination of hypoxia and IL-1β induced the strongest fibrotic response with significant upregulation of FN1 and collagen type I, and loss of tubular and glomerular markers. Over time, FN1 levels realigned with the control group, whereas collagen type I remained elevated. Tubular markers (Villin and ECAD) recovered to near-control levels, coinciding with increased CD133+ and CD24+ cell population and Ki67 expression. In contrast, PODXL+ glomerular structures showed limited recovery.

CONCLUSIONS

We present a reproducible human kidney organoid model that captures both fibrotic remodeling and tubular regeneration following clinically relevant injury. This platform offers a valuable tool for studying kidney-specific fibrosis dynamics and testing anti-fibrotic or pro-regenerative strategies.