Aging is a major risk factor for drug-induced kidney injury, yet the specific impact of age on the susceptibility of human primary kidney stem cells to mitochondrial toxicity (MtT) remains largely uncharacterized.

To address this gap, this study in Genes & Diseases by researchers from Capital Medical University and Wake Forest University Health Sciences employed an in vitro 3D silk fiber matrix model to culture human primary urine-derived stem cells (USCs) obtained from both young (yUSCs) and older (oUSCs) donors. The authors used tenofovir (TFV), a widely prescribed antiretroviral medication associated with renal adverse effects, to evaluate age-related, drug-induced mitochondrial toxicity in comparison with other antiretroviral agents such as emtricitabine (FTC) and raltegravir (RAL).

Compared with yUSCs, oUSCs exhibited greater baseline mitochondrial vulnerability, including lower mitochondrial mass and mitochondrial DNA (mtDNA) content, increased oxidative stress, enhanced apoptotic signaling, greater cellular senescence, and reduced telomerase activity. The authors observed that these age-related differences became more pronounced upon antiretroviral exposure. TFV reduced mitochondrial mass and mtDNA content even at clinically relevant concentrations during prolonged 3D culture, highlighting the sensitivity of primary USCs to chronic mitochondrial injury.

TFV also impaired mitochondrial respiratory function, causing dose-dependent reductions in electron transport chain (ETC) complexes I–V in oUSCs, with mitochondrial damage being more pronounced in older cells than in younger cells. Furthermore, increased oxidative stress was evident from elevated SOD2 expression, while mitochondrial dysfunction was accompanied by reduced ATP production and compromised renal cell function. The greater TFV-associated impairment of mitochondrial parameters in oUSCs is consistent with the authors' conclusion that aging increases susceptibility to drug-induced MtT.

Importantly, TFV promoted apoptosis in renal stem cells. The higher baseline cleaved caspase-3/caspase-3 ratio in oUSCs than in yUSCs indicated greater age-associated apoptotic susceptibility, while exposure to TFV further increased this ratio in a dose-dependent manner. Thus, chronic TFV-induced mitochondrial injury was accompanied not only by functional mitochondrial impairment but also by increased apoptotic stress, particularly in older cells.

TFV additionally accelerated cellular senescence. Older USCs exhibited higher β-galactosidase activity and increased expression of the senescence-associated genes p53, p21, and Rb, while TFV further increased these markers and reduced telomerase activity, with stronger effects in oUSCs. Renal injury was also reflected by increased KIM-1 expression, while alterations in CYP2E1 reflected changes in renal drug-metabolic function. Other tested antiretroviral agents, FTC and RAL, also induced oxidative stress, ETC dysfunction, apoptosis, and renal cellular injury, although they did not reproduce the broader effects of TFV on mitochondrial mass, mtDNA, senescence, and stem-cell properties.

Mechanistically, the findings implicated disruption of the telomere–mitochondrial axis involving PGC-1α. Older USCs exhibited reduced TRF1, telomerase activity, and PGC-1α expression, while TFV exposure was associated with decreased mtTFA and Nrf2 expression and reduced Nrf1 expression in oUSCs relative to baseline. The authors propose that telomere dysfunction and increased p53 signaling suppress PGC-1α, thereby impairing mitochondrial homeostasis and contributing to oxidative stress, senescence, apoptosis, and renal progenitor-cell dysfunction.

Importantly, the 3D USC–SFM system detected chronic mitochondrial toxicity more sensitively than conventional HEK293 and HepG2 cell models and maintained primary USCs over prolonged exposure, supporting its potential as an age-specific preclinical platform for evaluating renal drug toxicity.

In conclusion, the study demonstrates that aging markedly increases renal stem-cell susceptibility to TFV-induced telomere–mitochondrial dysfunction, oxidative stress, senescence, apoptosis, and functional injury, while highlighting the 3D silk matrix model as a promising platform for evaluating age-specific nephrotoxicity.

Reference
Title of the original paper: Age-dependent mitochondrial toxicity in renal stem cells: A precise 3D silk matrix model
Journal: Genes & Diseases
Genes & Diseases is a journal for molecular and translational medicine. The journal primarily focuses on publishing investigations on the molecular bases and experimental therapeutics of human diseases. Publication formats include full length research article, review article, short communication, correspondence, perspectives, commentary, views on news, and research watch.
DOI: https://doi.org/10.1016/j.gendis.2026.102108

Funding Information:
National Institute of Allergy and Infectious Diseases, National Institutes of Health, under Contract No. Funding Sources: NIAID, R21 AI152832, R03 AI165170; NEI, R21 EY0358332024
2024 Translational Team Science Pilot Award, Translational Eye and Vision Research Center (TrEVR), Wake Forest School of Medicine (WFSOM)
2024 Pilot Research Grant, Eye Bank Association of America (EBAA)

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Genes & Diseases publishes rigorously peer-reviewed and high quality original articles and authoritative reviews that focus on the molecular bases of human diseases. Emphasis is placed on hypothesis-driven, mechanistic studies relevant to pathogenesis and/or experimental therapeutics of human diseases. The journal has worldwide authorship, and a broad scope in basic and translational biomedical research of molecular biology, molecular genetics, and cell biology, including but not limited to cell proliferation and apoptosis, signal transduction, stem cell biology, developmental biology, gene regulation and epigenetics, cancer biology, immunity and infection, neuroscience, disease-specific animal models, gene and cell-based therapies, and regenerative medicine.

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