Single-Cell Transcriptomics of the Renal Tubule Reveals Cell Type-Specific Ferroptosis in Aging

Background: Aging markedly impairs kidney function and increases the risk of chronic kidney disease (CKD) and other age-related disorders (such as cardiovascular disease and end-stage renal disease) with millions worldwide. Ferroptosis, an iron-dependent programmed cell death involving iron accumulation and lipid peroxidation, is a newly identified factor in aging and cellular senescence. In kidney aging, senescent cells are highly susceptible to ferroptosis and drive functional decline. However, the specific changes and molecular mechanisms of ferroptosis in renal aging need further investigation. Methods: To address how age influences ferroptosis in kidney renal tubules, our study utilized Drosophila as a model to construct a single-cell atlas of the renal tubules (Malpighian tubules) at young and old ages to identify cell clusters. We also evaluated the role of ferroptosis in renal aging by examining iron levels and lipid peroxidation in the intracellular and mitochondria. Furthermore, the study investigated the role of the iron transporter Malvolio (Mvl), homolog of DMT1 in humans, in ferroptosis through cell type-specific knockdown experiments that analyze its effects on mitochondrial and intracellular ferroptosis. Results: Our snRNA-seq analysis annotated 8 cell clusters corresponding to distinct cell types and functions. Importantly, we identify that ferroptosis was activated in kidney aging by differentially expressed ferroptosis genes, intracellular and mitochondrial iron markers and lipid peroxidation assays. Our analysis also reveals an unexpected cell-specific signature of aging-induced ferroptosis. We show that ferroptosis is strongly induced in aged main segment of Malpighian tubules, homolog of the proximal tubule in mammalian kidney, rather than the initial segment. This difference may be due to segment-specific variations in ion transport and lipid metabolism. The iron transport protein Malvolio (Mvl) shows strong enrichment for main segment-specific expression, which implies a key role in ferroptosis. Intriguingly, Mvl knockdown reduces ferroptosis by blocking the accumulation of mitochondrial labile iron rather than intracellular ones. Conclusion: These findings highlight the cell-specific ferroptosis induction in aging kidney renal tubules, and inhibiting mitochondrial ferroptosis in kidney proximal tubules could represent a novel therapeutic target to combat kidney aging.