Hunting Down Aging Factors in Distal Tubular Cell-derived Exosomes to Rejuvenate Kidneys

Background and hypothesis: Senescent cells release exosomes that drive aging and disease in neighboring cells via a paracrine mechanism. Given that renal distal convoluted tubule (DCT) cells have the highest mitochondrial concentration per unit, we hypothesized that they play a key role in renal aging. Objectives: To identify key aging and rejuvenation factors in DCT-derived exosomes and explore the molecular mechanisms by which they influence kidney aging. Methods and Results: Our data show that aged DCT cells (aDCTs) have reduced telomerase reverse transcriptase (TERT) activity and release more exosomes than young DCT cells (yDCTs). Injecting exosomes from yDCTs (yDCT-Exo) into aged kidneys improved glomerular filtration rate (GFR), increased urinary creatinine and ion excretion, and prevented aging-related hypertension. In contrast, injecting exosomes from aDCTs (aDCT-Exo) into young kidneys resulted in a significant decrease in GFR, reduced urinary ion excretion, and elevated systolic blood pressure, demonstrating the harmful effects of aDCT-Exo. Proteomic analysis revealed distinct protein profiles in yDCT-Exo and aDCT-Exo. Notably, proteins enriched in aDCT-Exo, including Ddx3x and Psmd3, were linked to aging and longevity regulation pathways, while Fbln7 and Rarres1 were more abundant in yDCT-Exo. Knocking down Ddx3x and Psmd3 in aDCTs using siRNAs significantly reduced senescence markers, such as p53 and β-galactosidase. Additionally, lowering Ddx3x levels in aDCT-Exo abolished their negative impacts on kidney function and blood pressure. Interestingly, while aDCT-Exo reduced telomerase activity and increased senescence markers in yDCTs, these effects were eliminated when Ddx3x was absent in aDCT-Exo, underscoring Ddx3x as a key driver of the aging effects of aDCT-derived exosomes. Conclusions: These findings suggest promising potential for exosome-based therapies to restore kidney function and counteract aging-related damage. We identify Ddx3x as a key senescence-accelerating factor carried by aDCT-derived exosomes, revealing a novel mechanistic pathway in which Ddx3x significantly contributes to kidney aging by affecting telomerase activity. Future research that aims to uncover the detailed molecular mechanisms of Ddx3x in kidney aging would offer new therapeutic interventions for cellular senescence and kidney rejuvenation. This work is supported by NIH research grants R01 DK138872 and AG062375. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.